rustc_resolve/
late.rs

1// ignore-tidy-filelength
2//! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
3//! It runs when the crate is fully expanded and its module structure is fully built.
4//! So it just walks through the crate and resolves all the expressions, types, etc.
5//!
6//! If you wonder why there's no `early.rs`, that's because it's split into three files -
7//! `build_reduced_graph.rs`, `macros.rs` and `imports.rs`.
8
9use std::assert_matches::debug_assert_matches;
10use std::borrow::Cow;
11use std::collections::BTreeSet;
12use std::collections::hash_map::Entry;
13use std::mem::{replace, swap, take};
14
15use rustc_ast::ptr::P;
16use rustc_ast::visit::{
17    AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor, try_visit, visit_opt, walk_list,
18};
19use rustc_ast::*;
20use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
21use rustc_data_structures::unord::{UnordMap, UnordSet};
22use rustc_errors::codes::*;
23use rustc_errors::{
24    Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, StashKey, Suggestions,
25};
26use rustc_hir::def::Namespace::{self, *};
27use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS};
28use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LOCAL_CRATE, LocalDefId};
29use rustc_hir::{MissingLifetimeKind, PrimTy, TraitCandidate};
30use rustc_middle::middle::resolve_bound_vars::Set1;
31use rustc_middle::ty::DelegationFnSig;
32use rustc_middle::{bug, span_bug};
33use rustc_session::config::{CrateType, ResolveDocLinks};
34use rustc_session::lint::{self, BuiltinLintDiag};
35use rustc_session::parse::feature_err;
36use rustc_span::source_map::{Spanned, respan};
37use rustc_span::{BytePos, Ident, Span, Symbol, SyntaxContext, kw, sym};
38use smallvec::{SmallVec, smallvec};
39use thin_vec::ThinVec;
40use tracing::{debug, instrument, trace};
41
42use crate::{
43    BindingError, BindingKey, Finalize, LexicalScopeBinding, Module, ModuleOrUniformRoot,
44    NameBinding, ParentScope, PathResult, ResolutionError, Resolver, Segment, TyCtxt, UseError,
45    Used, errors, path_names_to_string, rustdoc,
46};
47
48mod diagnostics;
49
50type Res = def::Res<NodeId>;
51
52use diagnostics::{ElisionFnParameter, LifetimeElisionCandidate, MissingLifetime};
53
54#[derive(Copy, Clone, Debug)]
55struct BindingInfo {
56    span: Span,
57    annotation: BindingMode,
58}
59
60#[derive(Copy, Clone, PartialEq, Eq, Debug)]
61pub(crate) enum PatternSource {
62    Match,
63    Let,
64    For,
65    FnParam,
66}
67
68#[derive(Copy, Clone, Debug, PartialEq, Eq)]
69enum IsRepeatExpr {
70    No,
71    Yes,
72}
73
74struct IsNeverPattern;
75
76/// Describes whether an `AnonConst` is a type level const arg or
77/// some other form of anon const (i.e. inline consts or enum discriminants)
78#[derive(Copy, Clone, Debug, PartialEq, Eq)]
79enum AnonConstKind {
80    EnumDiscriminant,
81    FieldDefaultValue,
82    InlineConst,
83    ConstArg(IsRepeatExpr),
84}
85
86impl PatternSource {
87    fn descr(self) -> &'static str {
88        match self {
89            PatternSource::Match => "match binding",
90            PatternSource::Let => "let binding",
91            PatternSource::For => "for binding",
92            PatternSource::FnParam => "function parameter",
93        }
94    }
95}
96
97impl IntoDiagArg for PatternSource {
98    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
99        DiagArgValue::Str(Cow::Borrowed(self.descr()))
100    }
101}
102
103/// Denotes whether the context for the set of already bound bindings is a `Product`
104/// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
105/// See those functions for more information.
106#[derive(PartialEq)]
107enum PatBoundCtx {
108    /// A product pattern context, e.g., `Variant(a, b)`.
109    Product,
110    /// An or-pattern context, e.g., `p_0 | ... | p_n`.
111    Or,
112}
113
114/// Tracks bindings resolved within a pattern. This serves two purposes:
115///
116/// - This tracks when identifiers are bound multiple times within a pattern. In a product context,
117///   this is an error. In an or-pattern, this lets us reuse the same resolution for each instance.
118///   See `fresh_binding` and `resolve_pattern_inner` for more information.
119///
120/// - The guard expression of a guard pattern may use bindings from within the guard pattern, but
121///   not from elsewhere in the pattern containing it. This allows us to isolate the bindings in the
122///   subpattern to construct the scope for the guard.
123///
124/// Each identifier must map to at most one distinct [`Res`].
125type PatternBindings = SmallVec<[(PatBoundCtx, FxIndexMap<Ident, Res>); 1]>;
126
127/// Does this the item (from the item rib scope) allow generic parameters?
128#[derive(Copy, Clone, Debug)]
129pub(crate) enum HasGenericParams {
130    Yes(Span),
131    No,
132}
133
134/// May this constant have generics?
135#[derive(Copy, Clone, Debug, Eq, PartialEq)]
136pub(crate) enum ConstantHasGenerics {
137    Yes,
138    No(NoConstantGenericsReason),
139}
140
141impl ConstantHasGenerics {
142    fn force_yes_if(self, b: bool) -> Self {
143        if b { Self::Yes } else { self }
144    }
145}
146
147/// Reason for why an anon const is not allowed to reference generic parameters
148#[derive(Copy, Clone, Debug, Eq, PartialEq)]
149pub(crate) enum NoConstantGenericsReason {
150    /// Const arguments are only allowed to use generic parameters when:
151    /// - `feature(generic_const_exprs)` is enabled
152    /// or
153    /// - the const argument is a sole const generic parameter, i.e. `foo::<{ N }>()`
154    ///
155    /// If neither of the above are true then this is used as the cause.
156    NonTrivialConstArg,
157    /// Enum discriminants are not allowed to reference generic parameters ever, this
158    /// is used when an anon const is in the following position:
159    ///
160    /// ```rust,compile_fail
161    /// enum Foo<const N: isize> {
162    ///     Variant = { N }, // this anon const is not allowed to use generics
163    /// }
164    /// ```
165    IsEnumDiscriminant,
166}
167
168#[derive(Copy, Clone, Debug, Eq, PartialEq)]
169pub(crate) enum ConstantItemKind {
170    Const,
171    Static,
172}
173
174impl ConstantItemKind {
175    pub(crate) fn as_str(&self) -> &'static str {
176        match self {
177            Self::Const => "const",
178            Self::Static => "static",
179        }
180    }
181}
182
183#[derive(Debug, Copy, Clone, PartialEq, Eq)]
184enum RecordPartialRes {
185    Yes,
186    No,
187}
188
189/// The rib kind restricts certain accesses,
190/// e.g. to a `Res::Local` of an outer item.
191#[derive(Copy, Clone, Debug)]
192pub(crate) enum RibKind<'ra> {
193    /// No restriction needs to be applied.
194    Normal,
195
196    /// We passed through an impl or trait and are now in one of its
197    /// methods or associated types. Allow references to ty params that impl or trait
198    /// binds. Disallow any other upvars (including other ty params that are
199    /// upvars).
200    AssocItem,
201
202    /// We passed through a function, closure or coroutine signature. Disallow labels.
203    FnOrCoroutine,
204
205    /// We passed through an item scope. Disallow upvars.
206    Item(HasGenericParams, DefKind),
207
208    /// We're in a constant item. Can't refer to dynamic stuff.
209    ///
210    /// The item may reference generic parameters in trivial constant expressions.
211    /// All other constants aren't allowed to use generic params at all.
212    ConstantItem(ConstantHasGenerics, Option<(Ident, ConstantItemKind)>),
213
214    /// We passed through a module.
215    Module(Module<'ra>),
216
217    /// We passed through a `macro_rules!` statement
218    MacroDefinition(DefId),
219
220    /// All bindings in this rib are generic parameters that can't be used
221    /// from the default of a generic parameter because they're not declared
222    /// before said generic parameter. Also see the `visit_generics` override.
223    ForwardGenericParamBan(ForwardGenericParamBanReason),
224
225    /// We are inside of the type of a const parameter. Can't refer to any
226    /// parameters.
227    ConstParamTy,
228
229    /// We are inside a `sym` inline assembly operand. Can only refer to
230    /// globals.
231    InlineAsmSym,
232}
233
234#[derive(Copy, Clone, PartialEq, Eq, Debug)]
235pub(crate) enum ForwardGenericParamBanReason {
236    Default,
237    ConstParamTy,
238}
239
240impl RibKind<'_> {
241    /// Whether this rib kind contains generic parameters, as opposed to local
242    /// variables.
243    pub(crate) fn contains_params(&self) -> bool {
244        match self {
245            RibKind::Normal
246            | RibKind::FnOrCoroutine
247            | RibKind::ConstantItem(..)
248            | RibKind::Module(_)
249            | RibKind::MacroDefinition(_)
250            | RibKind::InlineAsmSym => false,
251            RibKind::ConstParamTy
252            | RibKind::AssocItem
253            | RibKind::Item(..)
254            | RibKind::ForwardGenericParamBan(_) => true,
255        }
256    }
257
258    /// This rib forbids referring to labels defined in upwards ribs.
259    fn is_label_barrier(self) -> bool {
260        match self {
261            RibKind::Normal | RibKind::MacroDefinition(..) => false,
262
263            RibKind::AssocItem
264            | RibKind::FnOrCoroutine
265            | RibKind::Item(..)
266            | RibKind::ConstantItem(..)
267            | RibKind::Module(..)
268            | RibKind::ForwardGenericParamBan(_)
269            | RibKind::ConstParamTy
270            | RibKind::InlineAsmSym => true,
271        }
272    }
273}
274
275/// A single local scope.
276///
277/// A rib represents a scope names can live in. Note that these appear in many places, not just
278/// around braces. At any place where the list of accessible names (of the given namespace)
279/// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a
280/// stack. This may be, for example, a `let` statement (because it introduces variables), a macro,
281/// etc.
282///
283/// Different [rib kinds](enum@RibKind) are transparent for different names.
284///
285/// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
286/// resolving, the name is looked up from inside out.
287#[derive(Debug)]
288pub(crate) struct Rib<'ra, R = Res> {
289    pub bindings: FxIndexMap<Ident, R>,
290    pub patterns_with_skipped_bindings: UnordMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
291    pub kind: RibKind<'ra>,
292}
293
294impl<'ra, R> Rib<'ra, R> {
295    fn new(kind: RibKind<'ra>) -> Rib<'ra, R> {
296        Rib {
297            bindings: Default::default(),
298            patterns_with_skipped_bindings: Default::default(),
299            kind,
300        }
301    }
302}
303
304#[derive(Clone, Copy, Debug)]
305enum LifetimeUseSet {
306    One { use_span: Span, use_ctxt: visit::LifetimeCtxt },
307    Many,
308}
309
310#[derive(Copy, Clone, Debug)]
311enum LifetimeRibKind {
312    // -- Ribs introducing named lifetimes
313    //
314    /// This rib declares generic parameters.
315    /// Only for this kind the `LifetimeRib::bindings` field can be non-empty.
316    Generics { binder: NodeId, span: Span, kind: LifetimeBinderKind },
317
318    // -- Ribs introducing unnamed lifetimes
319    //
320    /// Create a new anonymous lifetime parameter and reference it.
321    ///
322    /// If `report_in_path`, report an error when encountering lifetime elision in a path:
323    /// ```compile_fail
324    /// struct Foo<'a> { x: &'a () }
325    /// async fn foo(x: Foo) {}
326    /// ```
327    ///
328    /// Note: the error should not trigger when the elided lifetime is in a pattern or
329    /// expression-position path:
330    /// ```
331    /// struct Foo<'a> { x: &'a () }
332    /// async fn foo(Foo { x: _ }: Foo<'_>) {}
333    /// ```
334    AnonymousCreateParameter { binder: NodeId, report_in_path: bool },
335
336    /// Replace all anonymous lifetimes by provided lifetime.
337    Elided(LifetimeRes),
338
339    // -- Barrier ribs that stop lifetime lookup, or continue it but produce an error later.
340    //
341    /// Give a hard error when either `&` or `'_` is written. Used to
342    /// rule out things like `where T: Foo<'_>`. Does not imply an
343    /// error on default object bounds (e.g., `Box<dyn Foo>`).
344    AnonymousReportError,
345
346    /// Resolves elided lifetimes to `'static` if there are no other lifetimes in scope,
347    /// otherwise give a warning that the previous behavior of introducing a new early-bound
348    /// lifetime is a bug and will be removed (if `emit_lint` is enabled).
349    StaticIfNoLifetimeInScope { lint_id: NodeId, emit_lint: bool },
350
351    /// Signal we cannot find which should be the anonymous lifetime.
352    ElisionFailure,
353
354    /// This rib forbids usage of generic parameters inside of const parameter types.
355    ///
356    /// While this is desirable to support eventually, it is difficult to do and so is
357    /// currently forbidden. See rust-lang/project-const-generics#28 for more info.
358    ConstParamTy,
359
360    /// Usage of generic parameters is forbidden in various positions for anon consts:
361    /// - const arguments when `generic_const_exprs` is not enabled
362    /// - enum discriminant values
363    ///
364    /// This rib emits an error when a lifetime would resolve to a lifetime parameter.
365    ConcreteAnonConst(NoConstantGenericsReason),
366
367    /// This rib acts as a barrier to forbid reference to lifetimes of a parent item.
368    Item,
369}
370
371#[derive(Copy, Clone, Debug)]
372enum LifetimeBinderKind {
373    BareFnType,
374    PolyTrait,
375    WhereBound,
376    Item,
377    ConstItem,
378    Function,
379    Closure,
380    ImplBlock,
381}
382
383impl LifetimeBinderKind {
384    fn descr(self) -> &'static str {
385        use LifetimeBinderKind::*;
386        match self {
387            BareFnType => "type",
388            PolyTrait => "bound",
389            WhereBound => "bound",
390            Item | ConstItem => "item",
391            ImplBlock => "impl block",
392            Function => "function",
393            Closure => "closure",
394        }
395    }
396}
397
398#[derive(Debug)]
399struct LifetimeRib {
400    kind: LifetimeRibKind,
401    // We need to preserve insertion order for async fns.
402    bindings: FxIndexMap<Ident, (NodeId, LifetimeRes)>,
403}
404
405impl LifetimeRib {
406    fn new(kind: LifetimeRibKind) -> LifetimeRib {
407        LifetimeRib { bindings: Default::default(), kind }
408    }
409}
410
411#[derive(Copy, Clone, PartialEq, Eq, Debug)]
412pub(crate) enum AliasPossibility {
413    No,
414    Maybe,
415}
416
417#[derive(Copy, Clone, Debug)]
418pub(crate) enum PathSource<'a, 'ast, 'ra> {
419    /// Type paths `Path`.
420    Type,
421    /// Trait paths in bounds or impls.
422    Trait(AliasPossibility),
423    /// Expression paths `path`, with optional parent context.
424    Expr(Option<&'ast Expr>),
425    /// Paths in path patterns `Path`.
426    Pat,
427    /// Paths in struct expressions and patterns `Path { .. }`.
428    Struct,
429    /// Paths in tuple struct patterns `Path(..)`.
430    TupleStruct(Span, &'ra [Span]),
431    /// `m::A::B` in `<T as m::A>::B::C`.
432    ///
433    /// Second field holds the "cause" of this one, i.e. the context within
434    /// which the trait item is resolved. Used for diagnostics.
435    TraitItem(Namespace, &'a PathSource<'a, 'ast, 'ra>),
436    /// Paths in delegation item
437    Delegation,
438    /// An arg in a `use<'a, N>` precise-capturing bound.
439    PreciseCapturingArg(Namespace),
440    /// Paths that end with `(..)`, for return type notation.
441    ReturnTypeNotation,
442    /// Paths from `#[define_opaque]` attributes
443    DefineOpaques,
444}
445
446impl PathSource<'_, '_, '_> {
447    fn namespace(self) -> Namespace {
448        match self {
449            PathSource::Type
450            | PathSource::Trait(_)
451            | PathSource::Struct
452            | PathSource::DefineOpaques => TypeNS,
453            PathSource::Expr(..)
454            | PathSource::Pat
455            | PathSource::TupleStruct(..)
456            | PathSource::Delegation
457            | PathSource::ReturnTypeNotation => ValueNS,
458            PathSource::TraitItem(ns, _) => ns,
459            PathSource::PreciseCapturingArg(ns) => ns,
460        }
461    }
462
463    fn defer_to_typeck(self) -> bool {
464        match self {
465            PathSource::Type
466            | PathSource::Expr(..)
467            | PathSource::Pat
468            | PathSource::Struct
469            | PathSource::TupleStruct(..)
470            | PathSource::ReturnTypeNotation => true,
471            PathSource::Trait(_)
472            | PathSource::TraitItem(..)
473            | PathSource::DefineOpaques
474            | PathSource::Delegation
475            | PathSource::PreciseCapturingArg(..) => false,
476        }
477    }
478
479    fn descr_expected(self) -> &'static str {
480        match &self {
481            PathSource::DefineOpaques => "type alias or associated type with opaqaue types",
482            PathSource::Type => "type",
483            PathSource::Trait(_) => "trait",
484            PathSource::Pat => "unit struct, unit variant or constant",
485            PathSource::Struct => "struct, variant or union type",
486            PathSource::TraitItem(ValueNS, PathSource::TupleStruct(..))
487            | PathSource::TupleStruct(..) => "tuple struct or tuple variant",
488            PathSource::TraitItem(ns, _) => match ns {
489                TypeNS => "associated type",
490                ValueNS => "method or associated constant",
491                MacroNS => bug!("associated macro"),
492            },
493            PathSource::Expr(parent) => match parent.as_ref().map(|p| &p.kind) {
494                // "function" here means "anything callable" rather than `DefKind::Fn`,
495                // this is not precise but usually more helpful than just "value".
496                Some(ExprKind::Call(call_expr, _)) => match &call_expr.kind {
497                    // the case of `::some_crate()`
498                    ExprKind::Path(_, path)
499                        if let [segment, _] = path.segments.as_slice()
500                            && segment.ident.name == kw::PathRoot =>
501                    {
502                        "external crate"
503                    }
504                    ExprKind::Path(_, path)
505                        if let Some(segment) = path.segments.last()
506                            && let Some(c) = segment.ident.to_string().chars().next()
507                            && c.is_uppercase() =>
508                    {
509                        "function, tuple struct or tuple variant"
510                    }
511                    _ => "function",
512                },
513                _ => "value",
514            },
515            PathSource::ReturnTypeNotation | PathSource::Delegation => "function",
516            PathSource::PreciseCapturingArg(..) => "type or const parameter",
517        }
518    }
519
520    fn is_call(self) -> bool {
521        matches!(self, PathSource::Expr(Some(&Expr { kind: ExprKind::Call(..), .. })))
522    }
523
524    pub(crate) fn is_expected(self, res: Res) -> bool {
525        match self {
526            PathSource::DefineOpaques => {
527                matches!(
528                    res,
529                    Res::Def(
530                        DefKind::Struct
531                            | DefKind::Union
532                            | DefKind::Enum
533                            | DefKind::TyAlias
534                            | DefKind::AssocTy,
535                        _
536                    ) | Res::SelfTyAlias { .. }
537                )
538            }
539            PathSource::Type => matches!(
540                res,
541                Res::Def(
542                    DefKind::Struct
543                        | DefKind::Union
544                        | DefKind::Enum
545                        | DefKind::Trait
546                        | DefKind::TraitAlias
547                        | DefKind::TyAlias
548                        | DefKind::AssocTy
549                        | DefKind::TyParam
550                        | DefKind::OpaqueTy
551                        | DefKind::ForeignTy,
552                    _,
553                ) | Res::PrimTy(..)
554                    | Res::SelfTyParam { .. }
555                    | Res::SelfTyAlias { .. }
556            ),
557            PathSource::Trait(AliasPossibility::No) => matches!(res, Res::Def(DefKind::Trait, _)),
558            PathSource::Trait(AliasPossibility::Maybe) => {
559                matches!(res, Res::Def(DefKind::Trait | DefKind::TraitAlias, _))
560            }
561            PathSource::Expr(..) => matches!(
562                res,
563                Res::Def(
564                    DefKind::Ctor(_, CtorKind::Const | CtorKind::Fn)
565                        | DefKind::Const
566                        | DefKind::Static { .. }
567                        | DefKind::Fn
568                        | DefKind::AssocFn
569                        | DefKind::AssocConst
570                        | DefKind::ConstParam,
571                    _,
572                ) | Res::Local(..)
573                    | Res::SelfCtor(..)
574            ),
575            PathSource::Pat => {
576                res.expected_in_unit_struct_pat()
577                    || matches!(res, Res::Def(DefKind::Const | DefKind::AssocConst, _))
578            }
579            PathSource::TupleStruct(..) => res.expected_in_tuple_struct_pat(),
580            PathSource::Struct => matches!(
581                res,
582                Res::Def(
583                    DefKind::Struct
584                        | DefKind::Union
585                        | DefKind::Variant
586                        | DefKind::TyAlias
587                        | DefKind::AssocTy,
588                    _,
589                ) | Res::SelfTyParam { .. }
590                    | Res::SelfTyAlias { .. }
591            ),
592            PathSource::TraitItem(ns, _) => match res {
593                Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) if ns == ValueNS => true,
594                Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
595                _ => false,
596            },
597            PathSource::ReturnTypeNotation => match res {
598                Res::Def(DefKind::AssocFn, _) => true,
599                _ => false,
600            },
601            PathSource::Delegation => matches!(res, Res::Def(DefKind::Fn | DefKind::AssocFn, _)),
602            PathSource::PreciseCapturingArg(ValueNS) => {
603                matches!(res, Res::Def(DefKind::ConstParam, _))
604            }
605            // We allow `SelfTyAlias` here so we can give a more descriptive error later.
606            PathSource::PreciseCapturingArg(TypeNS) => matches!(
607                res,
608                Res::Def(DefKind::TyParam, _) | Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }
609            ),
610            PathSource::PreciseCapturingArg(MacroNS) => false,
611        }
612    }
613
614    fn error_code(self, has_unexpected_resolution: bool) -> ErrCode {
615        match (self, has_unexpected_resolution) {
616            (PathSource::Trait(_), true) => E0404,
617            (PathSource::Trait(_), false) => E0405,
618            (PathSource::Type | PathSource::DefineOpaques, true) => E0573,
619            (PathSource::Type | PathSource::DefineOpaques, false) => E0412,
620            (PathSource::Struct, true) => E0574,
621            (PathSource::Struct, false) => E0422,
622            (PathSource::Expr(..), true) | (PathSource::Delegation, true) => E0423,
623            (PathSource::Expr(..), false) | (PathSource::Delegation, false) => E0425,
624            (PathSource::Pat | PathSource::TupleStruct(..), true) => E0532,
625            (PathSource::Pat | PathSource::TupleStruct(..), false) => E0531,
626            (PathSource::TraitItem(..) | PathSource::ReturnTypeNotation, true) => E0575,
627            (PathSource::TraitItem(..) | PathSource::ReturnTypeNotation, false) => E0576,
628            (PathSource::PreciseCapturingArg(..), true) => E0799,
629            (PathSource::PreciseCapturingArg(..), false) => E0800,
630        }
631    }
632}
633
634/// At this point for most items we can answer whether that item is exported or not,
635/// but some items like impls require type information to determine exported-ness, so we make a
636/// conservative estimate for them (e.g. based on nominal visibility).
637#[derive(Clone, Copy)]
638enum MaybeExported<'a> {
639    Ok(NodeId),
640    Impl(Option<DefId>),
641    ImplItem(Result<DefId, &'a Visibility>),
642    NestedUse(&'a Visibility),
643}
644
645impl MaybeExported<'_> {
646    fn eval(self, r: &Resolver<'_, '_>) -> bool {
647        let def_id = match self {
648            MaybeExported::Ok(node_id) => Some(r.local_def_id(node_id)),
649            MaybeExported::Impl(Some(trait_def_id)) | MaybeExported::ImplItem(Ok(trait_def_id)) => {
650                trait_def_id.as_local()
651            }
652            MaybeExported::Impl(None) => return true,
653            MaybeExported::ImplItem(Err(vis)) | MaybeExported::NestedUse(vis) => {
654                return vis.kind.is_pub();
655            }
656        };
657        def_id.is_none_or(|def_id| r.effective_visibilities.is_exported(def_id))
658    }
659}
660
661/// Used for recording UnnecessaryQualification.
662#[derive(Debug)]
663pub(crate) struct UnnecessaryQualification<'ra> {
664    pub binding: LexicalScopeBinding<'ra>,
665    pub node_id: NodeId,
666    pub path_span: Span,
667    pub removal_span: Span,
668}
669
670#[derive(Default, Debug)]
671struct DiagMetadata<'ast> {
672    /// The current trait's associated items' ident, used for diagnostic suggestions.
673    current_trait_assoc_items: Option<&'ast [P<AssocItem>]>,
674
675    /// The current self type if inside an impl (used for better errors).
676    current_self_type: Option<Ty>,
677
678    /// The current self item if inside an ADT (used for better errors).
679    current_self_item: Option<NodeId>,
680
681    /// The current trait (used to suggest).
682    current_item: Option<&'ast Item>,
683
684    /// When processing generic arguments and encountering an unresolved ident not found,
685    /// suggest introducing a type or const param depending on the context.
686    currently_processing_generic_args: bool,
687
688    /// The current enclosing (non-closure) function (used for better errors).
689    current_function: Option<(FnKind<'ast>, Span)>,
690
691    /// A list of labels as of yet unused. Labels will be removed from this map when
692    /// they are used (in a `break` or `continue` statement)
693    unused_labels: FxIndexMap<NodeId, Span>,
694
695    /// Only used for better errors on `let <pat>: <expr, not type>;`.
696    current_let_binding: Option<(Span, Option<Span>, Option<Span>)>,
697
698    current_pat: Option<&'ast Pat>,
699
700    /// Used to detect possible `if let` written without `let` and to provide structured suggestion.
701    in_if_condition: Option<&'ast Expr>,
702
703    /// Used to detect possible new binding written without `let` and to provide structured suggestion.
704    in_assignment: Option<&'ast Expr>,
705    is_assign_rhs: bool,
706
707    /// If we are setting an associated type in trait impl, is it a non-GAT type?
708    in_non_gat_assoc_type: Option<bool>,
709
710    /// Used to detect possible `.` -> `..` typo when calling methods.
711    in_range: Option<(&'ast Expr, &'ast Expr)>,
712
713    /// If we are currently in a trait object definition. Used to point at the bounds when
714    /// encountering a struct or enum.
715    current_trait_object: Option<&'ast [ast::GenericBound]>,
716
717    /// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
718    current_where_predicate: Option<&'ast WherePredicate>,
719
720    current_type_path: Option<&'ast Ty>,
721
722    /// The current impl items (used to suggest).
723    current_impl_items: Option<&'ast [P<AssocItem>]>,
724
725    /// When processing impl trait
726    currently_processing_impl_trait: Option<(TraitRef, Ty)>,
727
728    /// Accumulate the errors due to missed lifetime elision,
729    /// and report them all at once for each function.
730    current_elision_failures: Vec<MissingLifetime>,
731}
732
733struct LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
734    r: &'a mut Resolver<'ra, 'tcx>,
735
736    /// The module that represents the current item scope.
737    parent_scope: ParentScope<'ra>,
738
739    /// The current set of local scopes for types and values.
740    ribs: PerNS<Vec<Rib<'ra>>>,
741
742    /// Previous popped `rib`, only used for diagnostic.
743    last_block_rib: Option<Rib<'ra>>,
744
745    /// The current set of local scopes, for labels.
746    label_ribs: Vec<Rib<'ra, NodeId>>,
747
748    /// The current set of local scopes for lifetimes.
749    lifetime_ribs: Vec<LifetimeRib>,
750
751    /// We are looking for lifetimes in an elision context.
752    /// The set contains all the resolutions that we encountered so far.
753    /// They will be used to determine the correct lifetime for the fn return type.
754    /// The `LifetimeElisionCandidate` is used for diagnostics, to suggest introducing named
755    /// lifetimes.
756    lifetime_elision_candidates: Option<Vec<(LifetimeRes, LifetimeElisionCandidate)>>,
757
758    /// The trait that the current context can refer to.
759    current_trait_ref: Option<(Module<'ra>, TraitRef)>,
760
761    /// Fields used to add information to diagnostic errors.
762    diag_metadata: Box<DiagMetadata<'ast>>,
763
764    /// State used to know whether to ignore resolution errors for function bodies.
765    ///
766    /// In particular, rustdoc uses this to avoid giving errors for `cfg()` items.
767    /// In most cases this will be `None`, in which case errors will always be reported.
768    /// If it is `true`, then it will be updated when entering a nested function or trait body.
769    in_func_body: bool,
770
771    /// Count the number of places a lifetime is used.
772    lifetime_uses: FxHashMap<LocalDefId, LifetimeUseSet>,
773}
774
775/// Walks the whole crate in DFS order, visiting each item, resolving names as it goes.
776impl<'ast, 'ra, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
777    fn visit_attribute(&mut self, _: &'ast Attribute) {
778        // We do not want to resolve expressions that appear in attributes,
779        // as they do not correspond to actual code.
780    }
781    fn visit_item(&mut self, item: &'ast Item) {
782        let prev = replace(&mut self.diag_metadata.current_item, Some(item));
783        // Always report errors in items we just entered.
784        let old_ignore = replace(&mut self.in_func_body, false);
785        self.with_lifetime_rib(LifetimeRibKind::Item, |this| this.resolve_item(item));
786        self.in_func_body = old_ignore;
787        self.diag_metadata.current_item = prev;
788    }
789    fn visit_arm(&mut self, arm: &'ast Arm) {
790        self.resolve_arm(arm);
791    }
792    fn visit_block(&mut self, block: &'ast Block) {
793        let old_macro_rules = self.parent_scope.macro_rules;
794        self.resolve_block(block);
795        self.parent_scope.macro_rules = old_macro_rules;
796    }
797    fn visit_anon_const(&mut self, constant: &'ast AnonConst) {
798        bug!("encountered anon const without a manual call to `resolve_anon_const`: {constant:#?}");
799    }
800    fn visit_expr(&mut self, expr: &'ast Expr) {
801        self.resolve_expr(expr, None);
802    }
803    fn visit_pat(&mut self, p: &'ast Pat) {
804        let prev = self.diag_metadata.current_pat;
805        self.diag_metadata.current_pat = Some(p);
806
807        if let PatKind::Guard(subpat, _) = &p.kind {
808            // We walk the guard expression in `resolve_pattern_inner`. Don't resolve it twice.
809            self.visit_pat(subpat);
810        } else {
811            visit::walk_pat(self, p);
812        }
813
814        self.diag_metadata.current_pat = prev;
815    }
816    fn visit_local(&mut self, local: &'ast Local) {
817        let local_spans = match local.pat.kind {
818            // We check for this to avoid tuple struct fields.
819            PatKind::Wild => None,
820            _ => Some((
821                local.pat.span,
822                local.ty.as_ref().map(|ty| ty.span),
823                local.kind.init().map(|init| init.span),
824            )),
825        };
826        let original = replace(&mut self.diag_metadata.current_let_binding, local_spans);
827        self.resolve_local(local);
828        self.diag_metadata.current_let_binding = original;
829    }
830    fn visit_ty(&mut self, ty: &'ast Ty) {
831        let prev = self.diag_metadata.current_trait_object;
832        let prev_ty = self.diag_metadata.current_type_path;
833        match &ty.kind {
834            TyKind::Ref(None, _) | TyKind::PinnedRef(None, _) => {
835                // Elided lifetime in reference: we resolve as if there was some lifetime `'_` with
836                // NodeId `ty.id`.
837                // This span will be used in case of elision failure.
838                let span = self.r.tcx.sess.source_map().start_point(ty.span);
839                self.resolve_elided_lifetime(ty.id, span);
840                visit::walk_ty(self, ty);
841            }
842            TyKind::Path(qself, path) => {
843                self.diag_metadata.current_type_path = Some(ty);
844
845                // If we have a path that ends with `(..)`, then it must be
846                // return type notation. Resolve that path in the *value*
847                // namespace.
848                let source = if let Some(seg) = path.segments.last()
849                    && let Some(args) = &seg.args
850                    && matches!(**args, GenericArgs::ParenthesizedElided(..))
851                {
852                    PathSource::ReturnTypeNotation
853                } else {
854                    PathSource::Type
855                };
856
857                self.smart_resolve_path(ty.id, qself, path, source);
858
859                // Check whether we should interpret this as a bare trait object.
860                if qself.is_none()
861                    && let Some(partial_res) = self.r.partial_res_map.get(&ty.id)
862                    && let Some(Res::Def(DefKind::Trait | DefKind::TraitAlias, _)) =
863                        partial_res.full_res()
864                {
865                    // This path is actually a bare trait object. In case of a bare `Fn`-trait
866                    // object with anonymous lifetimes, we need this rib to correctly place the
867                    // synthetic lifetimes.
868                    let span = ty.span.shrink_to_lo().to(path.span.shrink_to_lo());
869                    self.with_generic_param_rib(
870                        &[],
871                        RibKind::Normal,
872                        ty.id,
873                        LifetimeBinderKind::PolyTrait,
874                        span,
875                        |this| this.visit_path(path),
876                    );
877                } else {
878                    visit::walk_ty(self, ty)
879                }
880            }
881            TyKind::ImplicitSelf => {
882                let self_ty = Ident::with_dummy_span(kw::SelfUpper);
883                let res = self
884                    .resolve_ident_in_lexical_scope(
885                        self_ty,
886                        TypeNS,
887                        Some(Finalize::new(ty.id, ty.span)),
888                        None,
889                    )
890                    .map_or(Res::Err, |d| d.res());
891                self.r.record_partial_res(ty.id, PartialRes::new(res));
892                visit::walk_ty(self, ty)
893            }
894            TyKind::ImplTrait(..) => {
895                let candidates = self.lifetime_elision_candidates.take();
896                visit::walk_ty(self, ty);
897                self.lifetime_elision_candidates = candidates;
898            }
899            TyKind::TraitObject(bounds, ..) => {
900                self.diag_metadata.current_trait_object = Some(&bounds[..]);
901                visit::walk_ty(self, ty)
902            }
903            TyKind::BareFn(bare_fn) => {
904                let span = ty.span.shrink_to_lo().to(bare_fn.decl_span.shrink_to_lo());
905                self.with_generic_param_rib(
906                    &bare_fn.generic_params,
907                    RibKind::Normal,
908                    ty.id,
909                    LifetimeBinderKind::BareFnType,
910                    span,
911                    |this| {
912                        this.visit_generic_params(&bare_fn.generic_params, false);
913                        this.with_lifetime_rib(
914                            LifetimeRibKind::AnonymousCreateParameter {
915                                binder: ty.id,
916                                report_in_path: false,
917                            },
918                            |this| {
919                                this.resolve_fn_signature(
920                                    ty.id,
921                                    false,
922                                    // We don't need to deal with patterns in parameters, because
923                                    // they are not possible for foreign or bodiless functions.
924                                    bare_fn
925                                        .decl
926                                        .inputs
927                                        .iter()
928                                        .map(|Param { ty, .. }| (None, &**ty)),
929                                    &bare_fn.decl.output,
930                                )
931                            },
932                        );
933                    },
934                )
935            }
936            TyKind::UnsafeBinder(unsafe_binder) => {
937                let span = ty.span.shrink_to_lo().to(unsafe_binder.inner_ty.span.shrink_to_lo());
938                self.with_generic_param_rib(
939                    &unsafe_binder.generic_params,
940                    RibKind::Normal,
941                    ty.id,
942                    LifetimeBinderKind::BareFnType,
943                    span,
944                    |this| {
945                        this.visit_generic_params(&unsafe_binder.generic_params, false);
946                        this.with_lifetime_rib(
947                            // We don't allow anonymous `unsafe &'_ ()` binders,
948                            // although I guess we could.
949                            LifetimeRibKind::AnonymousReportError,
950                            |this| this.visit_ty(&unsafe_binder.inner_ty),
951                        );
952                    },
953                )
954            }
955            TyKind::Array(element_ty, length) => {
956                self.visit_ty(element_ty);
957                self.resolve_anon_const(length, AnonConstKind::ConstArg(IsRepeatExpr::No));
958            }
959            TyKind::Typeof(ct) => {
960                self.resolve_anon_const(ct, AnonConstKind::ConstArg(IsRepeatExpr::No))
961            }
962            _ => visit::walk_ty(self, ty),
963        }
964        self.diag_metadata.current_trait_object = prev;
965        self.diag_metadata.current_type_path = prev_ty;
966    }
967
968    fn visit_ty_pat(&mut self, t: &'ast TyPat) -> Self::Result {
969        match &t.kind {
970            TyPatKind::Range(start, end, _) => {
971                if let Some(start) = start {
972                    self.resolve_anon_const(start, AnonConstKind::ConstArg(IsRepeatExpr::No));
973                }
974                if let Some(end) = end {
975                    self.resolve_anon_const(end, AnonConstKind::ConstArg(IsRepeatExpr::No));
976                }
977            }
978            TyPatKind::Or(patterns) => {
979                for pat in patterns {
980                    self.visit_ty_pat(pat)
981                }
982            }
983            TyPatKind::Err(_) => {}
984        }
985    }
986
987    fn visit_poly_trait_ref(&mut self, tref: &'ast PolyTraitRef) {
988        let span = tref.span.shrink_to_lo().to(tref.trait_ref.path.span.shrink_to_lo());
989        self.with_generic_param_rib(
990            &tref.bound_generic_params,
991            RibKind::Normal,
992            tref.trait_ref.ref_id,
993            LifetimeBinderKind::PolyTrait,
994            span,
995            |this| {
996                this.visit_generic_params(&tref.bound_generic_params, false);
997                this.smart_resolve_path(
998                    tref.trait_ref.ref_id,
999                    &None,
1000                    &tref.trait_ref.path,
1001                    PathSource::Trait(AliasPossibility::Maybe),
1002                );
1003                this.visit_trait_ref(&tref.trait_ref);
1004            },
1005        );
1006    }
1007    fn visit_foreign_item(&mut self, foreign_item: &'ast ForeignItem) {
1008        self.resolve_doc_links(&foreign_item.attrs, MaybeExported::Ok(foreign_item.id));
1009        let def_kind = self.r.local_def_kind(foreign_item.id);
1010        match foreign_item.kind {
1011            ForeignItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
1012                self.with_generic_param_rib(
1013                    &generics.params,
1014                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
1015                    foreign_item.id,
1016                    LifetimeBinderKind::Item,
1017                    generics.span,
1018                    |this| visit::walk_item(this, foreign_item),
1019                );
1020            }
1021            ForeignItemKind::Fn(box Fn { ref generics, .. }) => {
1022                self.with_generic_param_rib(
1023                    &generics.params,
1024                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
1025                    foreign_item.id,
1026                    LifetimeBinderKind::Function,
1027                    generics.span,
1028                    |this| visit::walk_item(this, foreign_item),
1029                );
1030            }
1031            ForeignItemKind::Static(..) => {
1032                self.with_static_rib(def_kind, |this| visit::walk_item(this, foreign_item))
1033            }
1034            ForeignItemKind::MacCall(..) => {
1035                panic!("unexpanded macro in resolve!")
1036            }
1037        }
1038    }
1039    fn visit_fn(&mut self, fn_kind: FnKind<'ast>, sp: Span, fn_id: NodeId) {
1040        let previous_value = self.diag_metadata.current_function;
1041        match fn_kind {
1042            // Bail if the function is foreign, and thus cannot validly have
1043            // a body, or if there's no body for some other reason.
1044            FnKind::Fn(FnCtxt::Foreign, _, Fn { sig, ident, generics, .. })
1045            | FnKind::Fn(_, _, Fn { sig, ident, generics, body: None, .. }) => {
1046                self.visit_fn_header(&sig.header);
1047                self.visit_ident(ident);
1048                self.visit_generics(generics);
1049                self.with_lifetime_rib(
1050                    LifetimeRibKind::AnonymousCreateParameter {
1051                        binder: fn_id,
1052                        report_in_path: false,
1053                    },
1054                    |this| {
1055                        this.resolve_fn_signature(
1056                            fn_id,
1057                            sig.decl.has_self(),
1058                            sig.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
1059                            &sig.decl.output,
1060                        );
1061                    },
1062                );
1063                return;
1064            }
1065            FnKind::Fn(..) => {
1066                self.diag_metadata.current_function = Some((fn_kind, sp));
1067            }
1068            // Do not update `current_function` for closures: it suggests `self` parameters.
1069            FnKind::Closure(..) => {}
1070        };
1071        debug!("(resolving function) entering function");
1072
1073        // Create a value rib for the function.
1074        self.with_rib(ValueNS, RibKind::FnOrCoroutine, |this| {
1075            // Create a label rib for the function.
1076            this.with_label_rib(RibKind::FnOrCoroutine, |this| {
1077                match fn_kind {
1078                    FnKind::Fn(_, _, Fn { sig, generics, contract, body, .. }) => {
1079                        this.visit_generics(generics);
1080
1081                        let declaration = &sig.decl;
1082                        let coro_node_id = sig
1083                            .header
1084                            .coroutine_kind
1085                            .map(|coroutine_kind| coroutine_kind.return_id());
1086
1087                        this.with_lifetime_rib(
1088                            LifetimeRibKind::AnonymousCreateParameter {
1089                                binder: fn_id,
1090                                report_in_path: coro_node_id.is_some(),
1091                            },
1092                            |this| {
1093                                this.resolve_fn_signature(
1094                                    fn_id,
1095                                    declaration.has_self(),
1096                                    declaration
1097                                        .inputs
1098                                        .iter()
1099                                        .map(|Param { pat, ty, .. }| (Some(&**pat), &**ty)),
1100                                    &declaration.output,
1101                                );
1102                            },
1103                        );
1104
1105                        if let Some(contract) = contract {
1106                            this.visit_contract(contract);
1107                        }
1108
1109                        if let Some(body) = body {
1110                            // Ignore errors in function bodies if this is rustdoc
1111                            // Be sure not to set this until the function signature has been resolved.
1112                            let previous_state = replace(&mut this.in_func_body, true);
1113                            // We only care block in the same function
1114                            this.last_block_rib = None;
1115                            // Resolve the function body, potentially inside the body of an async closure
1116                            this.with_lifetime_rib(
1117                                LifetimeRibKind::Elided(LifetimeRes::Infer),
1118                                |this| this.visit_block(body),
1119                            );
1120
1121                            debug!("(resolving function) leaving function");
1122                            this.in_func_body = previous_state;
1123                        }
1124                    }
1125                    FnKind::Closure(binder, _, declaration, body) => {
1126                        this.visit_closure_binder(binder);
1127
1128                        this.with_lifetime_rib(
1129                            match binder {
1130                                // We do not have any explicit generic lifetime parameter.
1131                                ClosureBinder::NotPresent => {
1132                                    LifetimeRibKind::AnonymousCreateParameter {
1133                                        binder: fn_id,
1134                                        report_in_path: false,
1135                                    }
1136                                }
1137                                ClosureBinder::For { .. } => LifetimeRibKind::AnonymousReportError,
1138                            },
1139                            // Add each argument to the rib.
1140                            |this| this.resolve_params(&declaration.inputs),
1141                        );
1142                        this.with_lifetime_rib(
1143                            match binder {
1144                                ClosureBinder::NotPresent => {
1145                                    LifetimeRibKind::Elided(LifetimeRes::Infer)
1146                                }
1147                                ClosureBinder::For { .. } => LifetimeRibKind::AnonymousReportError,
1148                            },
1149                            |this| visit::walk_fn_ret_ty(this, &declaration.output),
1150                        );
1151
1152                        // Ignore errors in function bodies if this is rustdoc
1153                        // Be sure not to set this until the function signature has been resolved.
1154                        let previous_state = replace(&mut this.in_func_body, true);
1155                        // Resolve the function body, potentially inside the body of an async closure
1156                        this.with_lifetime_rib(
1157                            LifetimeRibKind::Elided(LifetimeRes::Infer),
1158                            |this| this.visit_expr(body),
1159                        );
1160
1161                        debug!("(resolving function) leaving function");
1162                        this.in_func_body = previous_state;
1163                    }
1164                }
1165            })
1166        });
1167        self.diag_metadata.current_function = previous_value;
1168    }
1169
1170    fn visit_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::LifetimeCtxt) {
1171        self.resolve_lifetime(lifetime, use_ctxt)
1172    }
1173
1174    fn visit_precise_capturing_arg(&mut self, arg: &'ast PreciseCapturingArg) {
1175        match arg {
1176            // Lower the lifetime regularly; we'll resolve the lifetime and check
1177            // it's a parameter later on in HIR lowering.
1178            PreciseCapturingArg::Lifetime(_) => {}
1179
1180            PreciseCapturingArg::Arg(path, id) => {
1181                // we want `impl use<C>` to try to resolve `C` as both a type parameter or
1182                // a const parameter. Since the resolver specifically doesn't allow having
1183                // two generic params with the same name, even if they're a different namespace,
1184                // it doesn't really matter which we try resolving first, but just like
1185                // `Ty::Param` we just fall back to the value namespace only if it's missing
1186                // from the type namespace.
1187                let mut check_ns = |ns| {
1188                    self.maybe_resolve_ident_in_lexical_scope(path.segments[0].ident, ns).is_some()
1189                };
1190                // Like `Ty::Param`, we try resolving this as both a const and a type.
1191                if !check_ns(TypeNS) && check_ns(ValueNS) {
1192                    self.smart_resolve_path(
1193                        *id,
1194                        &None,
1195                        path,
1196                        PathSource::PreciseCapturingArg(ValueNS),
1197                    );
1198                } else {
1199                    self.smart_resolve_path(
1200                        *id,
1201                        &None,
1202                        path,
1203                        PathSource::PreciseCapturingArg(TypeNS),
1204                    );
1205                }
1206            }
1207        }
1208
1209        visit::walk_precise_capturing_arg(self, arg)
1210    }
1211
1212    fn visit_generics(&mut self, generics: &'ast Generics) {
1213        self.visit_generic_params(&generics.params, self.diag_metadata.current_self_item.is_some());
1214        for p in &generics.where_clause.predicates {
1215            self.visit_where_predicate(p);
1216        }
1217    }
1218
1219    fn visit_closure_binder(&mut self, b: &'ast ClosureBinder) {
1220        match b {
1221            ClosureBinder::NotPresent => {}
1222            ClosureBinder::For { generic_params, .. } => {
1223                self.visit_generic_params(
1224                    generic_params,
1225                    self.diag_metadata.current_self_item.is_some(),
1226                );
1227            }
1228        }
1229    }
1230
1231    fn visit_generic_arg(&mut self, arg: &'ast GenericArg) {
1232        debug!("visit_generic_arg({:?})", arg);
1233        let prev = replace(&mut self.diag_metadata.currently_processing_generic_args, true);
1234        match arg {
1235            GenericArg::Type(ty) => {
1236                // We parse const arguments as path types as we cannot distinguish them during
1237                // parsing. We try to resolve that ambiguity by attempting resolution the type
1238                // namespace first, and if that fails we try again in the value namespace. If
1239                // resolution in the value namespace succeeds, we have an generic const argument on
1240                // our hands.
1241                if let TyKind::Path(None, ref path) = ty.kind
1242                    // We cannot disambiguate multi-segment paths right now as that requires type
1243                    // checking.
1244                    && path.is_potential_trivial_const_arg(false)
1245                {
1246                    let mut check_ns = |ns| {
1247                        self.maybe_resolve_ident_in_lexical_scope(path.segments[0].ident, ns)
1248                            .is_some()
1249                    };
1250                    if !check_ns(TypeNS) && check_ns(ValueNS) {
1251                        self.resolve_anon_const_manual(
1252                            true,
1253                            AnonConstKind::ConstArg(IsRepeatExpr::No),
1254                            |this| {
1255                                this.smart_resolve_path(ty.id, &None, path, PathSource::Expr(None));
1256                                this.visit_path(path);
1257                            },
1258                        );
1259
1260                        self.diag_metadata.currently_processing_generic_args = prev;
1261                        return;
1262                    }
1263                }
1264
1265                self.visit_ty(ty);
1266            }
1267            GenericArg::Lifetime(lt) => self.visit_lifetime(lt, visit::LifetimeCtxt::GenericArg),
1268            GenericArg::Const(ct) => {
1269                self.resolve_anon_const(ct, AnonConstKind::ConstArg(IsRepeatExpr::No))
1270            }
1271        }
1272        self.diag_metadata.currently_processing_generic_args = prev;
1273    }
1274
1275    fn visit_assoc_item_constraint(&mut self, constraint: &'ast AssocItemConstraint) {
1276        self.visit_ident(&constraint.ident);
1277        if let Some(ref gen_args) = constraint.gen_args {
1278            // Forbid anonymous lifetimes in GAT parameters until proper semantics are decided.
1279            self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1280                this.visit_generic_args(gen_args)
1281            });
1282        }
1283        match constraint.kind {
1284            AssocItemConstraintKind::Equality { ref term } => match term {
1285                Term::Ty(ty) => self.visit_ty(ty),
1286                Term::Const(c) => {
1287                    self.resolve_anon_const(c, AnonConstKind::ConstArg(IsRepeatExpr::No))
1288                }
1289            },
1290            AssocItemConstraintKind::Bound { ref bounds } => {
1291                walk_list!(self, visit_param_bound, bounds, BoundKind::Bound);
1292            }
1293        }
1294    }
1295
1296    fn visit_path_segment(&mut self, path_segment: &'ast PathSegment) {
1297        let Some(ref args) = path_segment.args else {
1298            return;
1299        };
1300
1301        match &**args {
1302            GenericArgs::AngleBracketed(..) => visit::walk_generic_args(self, args),
1303            GenericArgs::Parenthesized(p_args) => {
1304                // Probe the lifetime ribs to know how to behave.
1305                for rib in self.lifetime_ribs.iter().rev() {
1306                    match rib.kind {
1307                        // We are inside a `PolyTraitRef`. The lifetimes are
1308                        // to be introduced in that (maybe implicit) `for<>` binder.
1309                        LifetimeRibKind::Generics {
1310                            binder,
1311                            kind: LifetimeBinderKind::PolyTrait,
1312                            ..
1313                        } => {
1314                            self.with_lifetime_rib(
1315                                LifetimeRibKind::AnonymousCreateParameter {
1316                                    binder,
1317                                    report_in_path: false,
1318                                },
1319                                |this| {
1320                                    this.resolve_fn_signature(
1321                                        binder,
1322                                        false,
1323                                        p_args.inputs.iter().map(|ty| (None, &**ty)),
1324                                        &p_args.output,
1325                                    )
1326                                },
1327                            );
1328                            break;
1329                        }
1330                        // We have nowhere to introduce generics. Code is malformed,
1331                        // so use regular lifetime resolution to avoid spurious errors.
1332                        LifetimeRibKind::Item | LifetimeRibKind::Generics { .. } => {
1333                            visit::walk_generic_args(self, args);
1334                            break;
1335                        }
1336                        LifetimeRibKind::AnonymousCreateParameter { .. }
1337                        | LifetimeRibKind::AnonymousReportError
1338                        | LifetimeRibKind::StaticIfNoLifetimeInScope { .. }
1339                        | LifetimeRibKind::Elided(_)
1340                        | LifetimeRibKind::ElisionFailure
1341                        | LifetimeRibKind::ConcreteAnonConst(_)
1342                        | LifetimeRibKind::ConstParamTy => {}
1343                    }
1344                }
1345            }
1346            GenericArgs::ParenthesizedElided(_) => {}
1347        }
1348    }
1349
1350    fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
1351        debug!("visit_where_predicate {:?}", p);
1352        let previous_value = replace(&mut self.diag_metadata.current_where_predicate, Some(p));
1353        self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1354            if let WherePredicateKind::BoundPredicate(WhereBoundPredicate {
1355                bounded_ty,
1356                bounds,
1357                bound_generic_params,
1358                ..
1359            }) = &p.kind
1360            {
1361                let span = p.span.shrink_to_lo().to(bounded_ty.span.shrink_to_lo());
1362                this.with_generic_param_rib(
1363                    bound_generic_params,
1364                    RibKind::Normal,
1365                    bounded_ty.id,
1366                    LifetimeBinderKind::WhereBound,
1367                    span,
1368                    |this| {
1369                        this.visit_generic_params(bound_generic_params, false);
1370                        this.visit_ty(bounded_ty);
1371                        for bound in bounds {
1372                            this.visit_param_bound(bound, BoundKind::Bound)
1373                        }
1374                    },
1375                );
1376            } else {
1377                visit::walk_where_predicate(this, p);
1378            }
1379        });
1380        self.diag_metadata.current_where_predicate = previous_value;
1381    }
1382
1383    fn visit_inline_asm(&mut self, asm: &'ast InlineAsm) {
1384        for (op, _) in &asm.operands {
1385            match op {
1386                InlineAsmOperand::In { expr, .. }
1387                | InlineAsmOperand::Out { expr: Some(expr), .. }
1388                | InlineAsmOperand::InOut { expr, .. } => self.visit_expr(expr),
1389                InlineAsmOperand::Out { expr: None, .. } => {}
1390                InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
1391                    self.visit_expr(in_expr);
1392                    if let Some(out_expr) = out_expr {
1393                        self.visit_expr(out_expr);
1394                    }
1395                }
1396                InlineAsmOperand::Const { anon_const, .. } => {
1397                    // Although this is `DefKind::AnonConst`, it is allowed to reference outer
1398                    // generic parameters like an inline const.
1399                    self.resolve_anon_const(anon_const, AnonConstKind::InlineConst);
1400                }
1401                InlineAsmOperand::Sym { sym } => self.visit_inline_asm_sym(sym),
1402                InlineAsmOperand::Label { block } => self.visit_block(block),
1403            }
1404        }
1405    }
1406
1407    fn visit_inline_asm_sym(&mut self, sym: &'ast InlineAsmSym) {
1408        // This is similar to the code for AnonConst.
1409        self.with_rib(ValueNS, RibKind::InlineAsmSym, |this| {
1410            this.with_rib(TypeNS, RibKind::InlineAsmSym, |this| {
1411                this.with_label_rib(RibKind::InlineAsmSym, |this| {
1412                    this.smart_resolve_path(sym.id, &sym.qself, &sym.path, PathSource::Expr(None));
1413                    visit::walk_inline_asm_sym(this, sym);
1414                });
1415            })
1416        });
1417    }
1418
1419    fn visit_variant(&mut self, v: &'ast Variant) {
1420        self.resolve_doc_links(&v.attrs, MaybeExported::Ok(v.id));
1421        self.visit_id(v.id);
1422        walk_list!(self, visit_attribute, &v.attrs);
1423        self.visit_vis(&v.vis);
1424        self.visit_ident(&v.ident);
1425        self.visit_variant_data(&v.data);
1426        if let Some(discr) = &v.disr_expr {
1427            self.resolve_anon_const(discr, AnonConstKind::EnumDiscriminant);
1428        }
1429    }
1430
1431    fn visit_field_def(&mut self, f: &'ast FieldDef) {
1432        self.resolve_doc_links(&f.attrs, MaybeExported::Ok(f.id));
1433        let FieldDef {
1434            attrs,
1435            id: _,
1436            span: _,
1437            vis,
1438            ident,
1439            ty,
1440            is_placeholder: _,
1441            default,
1442            safety: _,
1443        } = f;
1444        walk_list!(self, visit_attribute, attrs);
1445        try_visit!(self.visit_vis(vis));
1446        visit_opt!(self, visit_ident, ident);
1447        try_visit!(self.visit_ty(ty));
1448        if let Some(v) = &default {
1449            self.resolve_anon_const(v, AnonConstKind::FieldDefaultValue);
1450        }
1451    }
1452}
1453
1454impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
1455    fn new(resolver: &'a mut Resolver<'ra, 'tcx>) -> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
1456        // During late resolution we only track the module component of the parent scope,
1457        // although it may be useful to track other components as well for diagnostics.
1458        let graph_root = resolver.graph_root;
1459        let parent_scope = ParentScope::module(graph_root, resolver);
1460        let start_rib_kind = RibKind::Module(graph_root);
1461        LateResolutionVisitor {
1462            r: resolver,
1463            parent_scope,
1464            ribs: PerNS {
1465                value_ns: vec![Rib::new(start_rib_kind)],
1466                type_ns: vec![Rib::new(start_rib_kind)],
1467                macro_ns: vec![Rib::new(start_rib_kind)],
1468            },
1469            last_block_rib: None,
1470            label_ribs: Vec::new(),
1471            lifetime_ribs: Vec::new(),
1472            lifetime_elision_candidates: None,
1473            current_trait_ref: None,
1474            diag_metadata: Default::default(),
1475            // errors at module scope should always be reported
1476            in_func_body: false,
1477            lifetime_uses: Default::default(),
1478        }
1479    }
1480
1481    fn maybe_resolve_ident_in_lexical_scope(
1482        &mut self,
1483        ident: Ident,
1484        ns: Namespace,
1485    ) -> Option<LexicalScopeBinding<'ra>> {
1486        self.r.resolve_ident_in_lexical_scope(
1487            ident,
1488            ns,
1489            &self.parent_scope,
1490            None,
1491            &self.ribs[ns],
1492            None,
1493        )
1494    }
1495
1496    fn resolve_ident_in_lexical_scope(
1497        &mut self,
1498        ident: Ident,
1499        ns: Namespace,
1500        finalize: Option<Finalize>,
1501        ignore_binding: Option<NameBinding<'ra>>,
1502    ) -> Option<LexicalScopeBinding<'ra>> {
1503        self.r.resolve_ident_in_lexical_scope(
1504            ident,
1505            ns,
1506            &self.parent_scope,
1507            finalize,
1508            &self.ribs[ns],
1509            ignore_binding,
1510        )
1511    }
1512
1513    fn resolve_path(
1514        &mut self,
1515        path: &[Segment],
1516        opt_ns: Option<Namespace>, // `None` indicates a module path in import
1517        finalize: Option<Finalize>,
1518    ) -> PathResult<'ra> {
1519        self.r.resolve_path_with_ribs(
1520            path,
1521            opt_ns,
1522            &self.parent_scope,
1523            finalize,
1524            Some(&self.ribs),
1525            None,
1526            None,
1527        )
1528    }
1529
1530    // AST resolution
1531    //
1532    // We maintain a list of value ribs and type ribs.
1533    //
1534    // Simultaneously, we keep track of the current position in the module
1535    // graph in the `parent_scope.module` pointer. When we go to resolve a name in
1536    // the value or type namespaces, we first look through all the ribs and
1537    // then query the module graph. When we resolve a name in the module
1538    // namespace, we can skip all the ribs (since nested modules are not
1539    // allowed within blocks in Rust) and jump straight to the current module
1540    // graph node.
1541    //
1542    // Named implementations are handled separately. When we find a method
1543    // call, we consult the module node to find all of the implementations in
1544    // scope. This information is lazily cached in the module node. We then
1545    // generate a fake "implementation scope" containing all the
1546    // implementations thus found, for compatibility with old resolve pass.
1547
1548    /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
1549    fn with_rib<T>(
1550        &mut self,
1551        ns: Namespace,
1552        kind: RibKind<'ra>,
1553        work: impl FnOnce(&mut Self) -> T,
1554    ) -> T {
1555        self.ribs[ns].push(Rib::new(kind));
1556        let ret = work(self);
1557        self.ribs[ns].pop();
1558        ret
1559    }
1560
1561    fn with_mod_rib<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
1562        let module = self.r.expect_module(self.r.local_def_id(id).to_def_id());
1563        // Move down in the graph.
1564        let orig_module = replace(&mut self.parent_scope.module, module);
1565        self.with_rib(ValueNS, RibKind::Module(module), |this| {
1566            this.with_rib(TypeNS, RibKind::Module(module), |this| {
1567                let ret = f(this);
1568                this.parent_scope.module = orig_module;
1569                ret
1570            })
1571        })
1572    }
1573
1574    fn visit_generic_params(&mut self, params: &'ast [GenericParam], add_self_upper: bool) {
1575        // For type parameter defaults, we have to ban access
1576        // to following type parameters, as the GenericArgs can only
1577        // provide previous type parameters as they're built. We
1578        // put all the parameters on the ban list and then remove
1579        // them one by one as they are processed and become available.
1580        let mut forward_ty_ban_rib =
1581            Rib::new(RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::Default));
1582        let mut forward_const_ban_rib =
1583            Rib::new(RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::Default));
1584        for param in params.iter() {
1585            match param.kind {
1586                GenericParamKind::Type { .. } => {
1587                    forward_ty_ban_rib
1588                        .bindings
1589                        .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1590                }
1591                GenericParamKind::Const { .. } => {
1592                    forward_const_ban_rib
1593                        .bindings
1594                        .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1595                }
1596                GenericParamKind::Lifetime => {}
1597            }
1598        }
1599
1600        // rust-lang/rust#61631: The type `Self` is essentially
1601        // another type parameter. For ADTs, we consider it
1602        // well-defined only after all of the ADT type parameters have
1603        // been provided. Therefore, we do not allow use of `Self`
1604        // anywhere in ADT type parameter defaults.
1605        //
1606        // (We however cannot ban `Self` for defaults on *all* generic
1607        // lists; e.g. trait generics can usefully refer to `Self`,
1608        // such as in the case of `trait Add<Rhs = Self>`.)
1609        if add_self_upper {
1610            // (`Some` if + only if we are in ADT's generics.)
1611            forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
1612        }
1613
1614        // NOTE: We use different ribs here not for a technical reason, but just
1615        // for better diagnostics.
1616        let mut forward_ty_ban_rib_const_param_ty = Rib {
1617            bindings: forward_ty_ban_rib.bindings.clone(),
1618            patterns_with_skipped_bindings: Default::default(),
1619            kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
1620        };
1621        let mut forward_const_ban_rib_const_param_ty = Rib {
1622            bindings: forward_const_ban_rib.bindings.clone(),
1623            patterns_with_skipped_bindings: Default::default(),
1624            kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
1625        };
1626        // We'll ban these with a `ConstParamTy` rib, so just clear these ribs for better
1627        // diagnostics, so we don't mention anything about const param tys having generics at all.
1628        if !self.r.tcx.features().generic_const_parameter_types() {
1629            forward_ty_ban_rib_const_param_ty.bindings.clear();
1630            forward_const_ban_rib_const_param_ty.bindings.clear();
1631        }
1632
1633        self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1634            for param in params {
1635                match param.kind {
1636                    GenericParamKind::Lifetime => {
1637                        for bound in &param.bounds {
1638                            this.visit_param_bound(bound, BoundKind::Bound);
1639                        }
1640                    }
1641                    GenericParamKind::Type { ref default } => {
1642                        for bound in &param.bounds {
1643                            this.visit_param_bound(bound, BoundKind::Bound);
1644                        }
1645
1646                        if let Some(ty) = default {
1647                            this.ribs[TypeNS].push(forward_ty_ban_rib);
1648                            this.ribs[ValueNS].push(forward_const_ban_rib);
1649                            this.visit_ty(ty);
1650                            forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1651                            forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1652                        }
1653
1654                        // Allow all following defaults to refer to this type parameter.
1655                        let i = &Ident::with_dummy_span(param.ident.name);
1656                        forward_ty_ban_rib.bindings.swap_remove(i);
1657                        forward_ty_ban_rib_const_param_ty.bindings.swap_remove(i);
1658                    }
1659                    GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
1660                        // Const parameters can't have param bounds.
1661                        assert!(param.bounds.is_empty());
1662
1663                        this.ribs[TypeNS].push(forward_ty_ban_rib_const_param_ty);
1664                        this.ribs[ValueNS].push(forward_const_ban_rib_const_param_ty);
1665                        if this.r.tcx.features().generic_const_parameter_types() {
1666                            this.visit_ty(ty)
1667                        } else {
1668                            this.ribs[TypeNS].push(Rib::new(RibKind::ConstParamTy));
1669                            this.ribs[ValueNS].push(Rib::new(RibKind::ConstParamTy));
1670                            this.with_lifetime_rib(LifetimeRibKind::ConstParamTy, |this| {
1671                                this.visit_ty(ty)
1672                            });
1673                            this.ribs[TypeNS].pop().unwrap();
1674                            this.ribs[ValueNS].pop().unwrap();
1675                        }
1676                        forward_const_ban_rib_const_param_ty = this.ribs[ValueNS].pop().unwrap();
1677                        forward_ty_ban_rib_const_param_ty = this.ribs[TypeNS].pop().unwrap();
1678
1679                        if let Some(expr) = default {
1680                            this.ribs[TypeNS].push(forward_ty_ban_rib);
1681                            this.ribs[ValueNS].push(forward_const_ban_rib);
1682                            this.resolve_anon_const(
1683                                expr,
1684                                AnonConstKind::ConstArg(IsRepeatExpr::No),
1685                            );
1686                            forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1687                            forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1688                        }
1689
1690                        // Allow all following defaults to refer to this const parameter.
1691                        let i = &Ident::with_dummy_span(param.ident.name);
1692                        forward_const_ban_rib.bindings.swap_remove(i);
1693                        forward_const_ban_rib_const_param_ty.bindings.swap_remove(i);
1694                    }
1695                }
1696            }
1697        })
1698    }
1699
1700    #[instrument(level = "debug", skip(self, work))]
1701    fn with_lifetime_rib<T>(
1702        &mut self,
1703        kind: LifetimeRibKind,
1704        work: impl FnOnce(&mut Self) -> T,
1705    ) -> T {
1706        self.lifetime_ribs.push(LifetimeRib::new(kind));
1707        let outer_elision_candidates = self.lifetime_elision_candidates.take();
1708        let ret = work(self);
1709        self.lifetime_elision_candidates = outer_elision_candidates;
1710        self.lifetime_ribs.pop();
1711        ret
1712    }
1713
1714    #[instrument(level = "debug", skip(self))]
1715    fn resolve_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::LifetimeCtxt) {
1716        let ident = lifetime.ident;
1717
1718        if ident.name == kw::StaticLifetime {
1719            self.record_lifetime_res(
1720                lifetime.id,
1721                LifetimeRes::Static,
1722                LifetimeElisionCandidate::Named,
1723            );
1724            return;
1725        }
1726
1727        if ident.name == kw::UnderscoreLifetime {
1728            return self.resolve_anonymous_lifetime(lifetime, lifetime.id, false);
1729        }
1730
1731        let mut lifetime_rib_iter = self.lifetime_ribs.iter().rev();
1732        while let Some(rib) = lifetime_rib_iter.next() {
1733            let normalized_ident = ident.normalize_to_macros_2_0();
1734            if let Some(&(_, res)) = rib.bindings.get(&normalized_ident) {
1735                self.record_lifetime_res(lifetime.id, res, LifetimeElisionCandidate::Named);
1736
1737                if let LifetimeRes::Param { param, binder } = res {
1738                    match self.lifetime_uses.entry(param) {
1739                        Entry::Vacant(v) => {
1740                            debug!("First use of {:?} at {:?}", res, ident.span);
1741                            let use_set = self
1742                                .lifetime_ribs
1743                                .iter()
1744                                .rev()
1745                                .find_map(|rib| match rib.kind {
1746                                    // Do not suggest eliding a lifetime where an anonymous
1747                                    // lifetime would be illegal.
1748                                    LifetimeRibKind::Item
1749                                    | LifetimeRibKind::AnonymousReportError
1750                                    | LifetimeRibKind::StaticIfNoLifetimeInScope { .. }
1751                                    | LifetimeRibKind::ElisionFailure => Some(LifetimeUseSet::Many),
1752                                    // An anonymous lifetime is legal here, and bound to the right
1753                                    // place, go ahead.
1754                                    LifetimeRibKind::AnonymousCreateParameter {
1755                                        binder: anon_binder,
1756                                        ..
1757                                    } => Some(if binder == anon_binder {
1758                                        LifetimeUseSet::One { use_span: ident.span, use_ctxt }
1759                                    } else {
1760                                        LifetimeUseSet::Many
1761                                    }),
1762                                    // Only report if eliding the lifetime would have the same
1763                                    // semantics.
1764                                    LifetimeRibKind::Elided(r) => Some(if res == r {
1765                                        LifetimeUseSet::One { use_span: ident.span, use_ctxt }
1766                                    } else {
1767                                        LifetimeUseSet::Many
1768                                    }),
1769                                    LifetimeRibKind::Generics { .. }
1770                                    | LifetimeRibKind::ConstParamTy => None,
1771                                    LifetimeRibKind::ConcreteAnonConst(_) => {
1772                                        span_bug!(ident.span, "unexpected rib kind: {:?}", rib.kind)
1773                                    }
1774                                })
1775                                .unwrap_or(LifetimeUseSet::Many);
1776                            debug!(?use_ctxt, ?use_set);
1777                            v.insert(use_set);
1778                        }
1779                        Entry::Occupied(mut o) => {
1780                            debug!("Many uses of {:?} at {:?}", res, ident.span);
1781                            *o.get_mut() = LifetimeUseSet::Many;
1782                        }
1783                    }
1784                }
1785                return;
1786            }
1787
1788            match rib.kind {
1789                LifetimeRibKind::Item => break,
1790                LifetimeRibKind::ConstParamTy => {
1791                    self.emit_non_static_lt_in_const_param_ty_error(lifetime);
1792                    self.record_lifetime_res(
1793                        lifetime.id,
1794                        LifetimeRes::Error,
1795                        LifetimeElisionCandidate::Ignore,
1796                    );
1797                    return;
1798                }
1799                LifetimeRibKind::ConcreteAnonConst(cause) => {
1800                    self.emit_forbidden_non_static_lifetime_error(cause, lifetime);
1801                    self.record_lifetime_res(
1802                        lifetime.id,
1803                        LifetimeRes::Error,
1804                        LifetimeElisionCandidate::Ignore,
1805                    );
1806                    return;
1807                }
1808                LifetimeRibKind::AnonymousCreateParameter { .. }
1809                | LifetimeRibKind::Elided(_)
1810                | LifetimeRibKind::Generics { .. }
1811                | LifetimeRibKind::ElisionFailure
1812                | LifetimeRibKind::AnonymousReportError
1813                | LifetimeRibKind::StaticIfNoLifetimeInScope { .. } => {}
1814            }
1815        }
1816
1817        let normalized_ident = ident.normalize_to_macros_2_0();
1818        let outer_res = lifetime_rib_iter
1819            .find_map(|rib| rib.bindings.get_key_value(&normalized_ident).map(|(&outer, _)| outer));
1820
1821        self.emit_undeclared_lifetime_error(lifetime, outer_res);
1822        self.record_lifetime_res(lifetime.id, LifetimeRes::Error, LifetimeElisionCandidate::Named);
1823    }
1824
1825    #[instrument(level = "debug", skip(self))]
1826    fn resolve_anonymous_lifetime(
1827        &mut self,
1828        lifetime: &Lifetime,
1829        id_for_lint: NodeId,
1830        elided: bool,
1831    ) {
1832        debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);
1833
1834        let kind =
1835            if elided { MissingLifetimeKind::Ampersand } else { MissingLifetimeKind::Underscore };
1836        let missing_lifetime = MissingLifetime {
1837            id: lifetime.id,
1838            span: lifetime.ident.span,
1839            kind,
1840            count: 1,
1841            id_for_lint,
1842        };
1843        let elision_candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
1844        for (i, rib) in self.lifetime_ribs.iter().enumerate().rev() {
1845            debug!(?rib.kind);
1846            match rib.kind {
1847                LifetimeRibKind::AnonymousCreateParameter { binder, .. } => {
1848                    let res = self.create_fresh_lifetime(lifetime.ident, binder, kind);
1849                    self.record_lifetime_res(lifetime.id, res, elision_candidate);
1850                    return;
1851                }
1852                LifetimeRibKind::StaticIfNoLifetimeInScope { lint_id: node_id, emit_lint } => {
1853                    let mut lifetimes_in_scope = vec![];
1854                    for rib in self.lifetime_ribs[..i].iter().rev() {
1855                        lifetimes_in_scope.extend(rib.bindings.iter().map(|(ident, _)| ident.span));
1856                        // Consider any anonymous lifetimes, too
1857                        if let LifetimeRibKind::AnonymousCreateParameter { binder, .. } = rib.kind
1858                            && let Some(extra) = self.r.extra_lifetime_params_map.get(&binder)
1859                        {
1860                            lifetimes_in_scope.extend(extra.iter().map(|(ident, _, _)| ident.span));
1861                        }
1862                        if let LifetimeRibKind::Item = rib.kind {
1863                            break;
1864                        }
1865                    }
1866                    if lifetimes_in_scope.is_empty() {
1867                        self.record_lifetime_res(
1868                            lifetime.id,
1869                            LifetimeRes::Static,
1870                            elision_candidate,
1871                        );
1872                        return;
1873                    } else if emit_lint {
1874                        self.r.lint_buffer.buffer_lint(
1875                            lint::builtin::ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
1876                            node_id,
1877                            lifetime.ident.span,
1878                            lint::BuiltinLintDiag::AssociatedConstElidedLifetime {
1879                                elided,
1880                                span: lifetime.ident.span,
1881                                lifetimes_in_scope: lifetimes_in_scope.into(),
1882                            },
1883                        );
1884                    }
1885                }
1886                LifetimeRibKind::AnonymousReportError => {
1887                    if elided {
1888                        let suggestion = self.lifetime_ribs[i..].iter().rev().find_map(|rib| {
1889                            if let LifetimeRibKind::Generics {
1890                                span,
1891                                kind: LifetimeBinderKind::PolyTrait | LifetimeBinderKind::WhereBound,
1892                                ..
1893                            } = rib.kind
1894                            {
1895                                Some(errors::ElidedAnonymousLivetimeReportErrorSuggestion {
1896                                    lo: span.shrink_to_lo(),
1897                                    hi: lifetime.ident.span.shrink_to_hi(),
1898                                })
1899                            } else {
1900                                None
1901                            }
1902                        });
1903                        // are we trying to use an anonymous lifetime
1904                        // on a non GAT associated trait type?
1905                        if !self.in_func_body
1906                            && let Some((module, _)) = &self.current_trait_ref
1907                            && let Some(ty) = &self.diag_metadata.current_self_type
1908                            && Some(true) == self.diag_metadata.in_non_gat_assoc_type
1909                            && let crate::ModuleKind::Def(DefKind::Trait, trait_id, _) = module.kind
1910                        {
1911                            if def_id_matches_path(
1912                                self.r.tcx,
1913                                trait_id,
1914                                &["core", "iter", "traits", "iterator", "Iterator"],
1915                            ) {
1916                                self.r.dcx().emit_err(errors::LendingIteratorReportError {
1917                                    lifetime: lifetime.ident.span,
1918                                    ty: ty.span,
1919                                });
1920                            } else {
1921                                self.r.dcx().emit_err(errors::AnonymousLivetimeNonGatReportError {
1922                                    lifetime: lifetime.ident.span,
1923                                });
1924                            }
1925                        } else {
1926                            self.r.dcx().emit_err(errors::ElidedAnonymousLivetimeReportError {
1927                                span: lifetime.ident.span,
1928                                suggestion,
1929                            });
1930                        }
1931                    } else {
1932                        self.r.dcx().emit_err(errors::ExplicitAnonymousLivetimeReportError {
1933                            span: lifetime.ident.span,
1934                        });
1935                    };
1936                    self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1937                    return;
1938                }
1939                LifetimeRibKind::Elided(res) => {
1940                    self.record_lifetime_res(lifetime.id, res, elision_candidate);
1941                    return;
1942                }
1943                LifetimeRibKind::ElisionFailure => {
1944                    self.diag_metadata.current_elision_failures.push(missing_lifetime);
1945                    self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1946                    return;
1947                }
1948                LifetimeRibKind::Item => break,
1949                LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstParamTy => {}
1950                LifetimeRibKind::ConcreteAnonConst(_) => {
1951                    // There is always an `Elided(LifetimeRes::Infer)` inside an `AnonConst`.
1952                    span_bug!(lifetime.ident.span, "unexpected rib kind: {:?}", rib.kind)
1953                }
1954            }
1955        }
1956        self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1957        self.report_missing_lifetime_specifiers(vec![missing_lifetime], None);
1958    }
1959
1960    #[instrument(level = "debug", skip(self))]
1961    fn resolve_elided_lifetime(&mut self, anchor_id: NodeId, span: Span) {
1962        let id = self.r.next_node_id();
1963        let lt = Lifetime { id, ident: Ident::new(kw::UnderscoreLifetime, span) };
1964
1965        self.record_lifetime_res(
1966            anchor_id,
1967            LifetimeRes::ElidedAnchor { start: id, end: id + 1 },
1968            LifetimeElisionCandidate::Ignore,
1969        );
1970        self.resolve_anonymous_lifetime(&lt, anchor_id, true);
1971    }
1972
1973    #[instrument(level = "debug", skip(self))]
1974    fn create_fresh_lifetime(
1975        &mut self,
1976        ident: Ident,
1977        binder: NodeId,
1978        kind: MissingLifetimeKind,
1979    ) -> LifetimeRes {
1980        debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
1981        debug!(?ident.span);
1982
1983        // Leave the responsibility to create the `LocalDefId` to lowering.
1984        let param = self.r.next_node_id();
1985        let res = LifetimeRes::Fresh { param, binder, kind };
1986        self.record_lifetime_param(param, res);
1987
1988        // Record the created lifetime parameter so lowering can pick it up and add it to HIR.
1989        self.r
1990            .extra_lifetime_params_map
1991            .entry(binder)
1992            .or_insert_with(Vec::new)
1993            .push((ident, param, res));
1994        res
1995    }
1996
1997    #[instrument(level = "debug", skip(self))]
1998    fn resolve_elided_lifetimes_in_path(
1999        &mut self,
2000        partial_res: PartialRes,
2001        path: &[Segment],
2002        source: PathSource<'_, '_, '_>,
2003        path_span: Span,
2004    ) {
2005        let proj_start = path.len() - partial_res.unresolved_segments();
2006        for (i, segment) in path.iter().enumerate() {
2007            if segment.has_lifetime_args {
2008                continue;
2009            }
2010            let Some(segment_id) = segment.id else {
2011                continue;
2012            };
2013
2014            // Figure out if this is a type/trait segment,
2015            // which may need lifetime elision performed.
2016            let type_def_id = match partial_res.base_res() {
2017                Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
2018                    self.r.tcx.parent(def_id)
2019                }
2020                Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
2021                    self.r.tcx.parent(def_id)
2022                }
2023                Res::Def(DefKind::Struct, def_id)
2024                | Res::Def(DefKind::Union, def_id)
2025                | Res::Def(DefKind::Enum, def_id)
2026                | Res::Def(DefKind::TyAlias, def_id)
2027                | Res::Def(DefKind::Trait, def_id)
2028                    if i + 1 == proj_start =>
2029                {
2030                    def_id
2031                }
2032                _ => continue,
2033            };
2034
2035            let expected_lifetimes = self.r.item_generics_num_lifetimes(type_def_id);
2036            if expected_lifetimes == 0 {
2037                continue;
2038            }
2039
2040            let node_ids = self.r.next_node_ids(expected_lifetimes);
2041            self.record_lifetime_res(
2042                segment_id,
2043                LifetimeRes::ElidedAnchor { start: node_ids.start, end: node_ids.end },
2044                LifetimeElisionCandidate::Ignore,
2045            );
2046
2047            let inferred = match source {
2048                PathSource::Trait(..)
2049                | PathSource::TraitItem(..)
2050                | PathSource::Type
2051                | PathSource::PreciseCapturingArg(..)
2052                | PathSource::ReturnTypeNotation => false,
2053                PathSource::Expr(..)
2054                | PathSource::Pat
2055                | PathSource::Struct
2056                | PathSource::TupleStruct(..)
2057                | PathSource::DefineOpaques
2058                | PathSource::Delegation => true,
2059            };
2060            if inferred {
2061                // Do not create a parameter for patterns and expressions: type checking can infer
2062                // the appropriate lifetime for us.
2063                for id in node_ids {
2064                    self.record_lifetime_res(
2065                        id,
2066                        LifetimeRes::Infer,
2067                        LifetimeElisionCandidate::Named,
2068                    );
2069                }
2070                continue;
2071            }
2072
2073            let elided_lifetime_span = if segment.has_generic_args {
2074                // If there are brackets, but not generic arguments, then use the opening bracket
2075                segment.args_span.with_hi(segment.args_span.lo() + BytePos(1))
2076            } else {
2077                // If there are no brackets, use the identifier span.
2078                // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
2079                // originating from macros, since the segment's span might be from a macro arg.
2080                segment.ident.span.find_ancestor_inside(path_span).unwrap_or(path_span)
2081            };
2082            let ident = Ident::new(kw::UnderscoreLifetime, elided_lifetime_span);
2083
2084            let kind = if segment.has_generic_args {
2085                MissingLifetimeKind::Comma
2086            } else {
2087                MissingLifetimeKind::Brackets
2088            };
2089            let missing_lifetime = MissingLifetime {
2090                id: node_ids.start,
2091                id_for_lint: segment_id,
2092                span: elided_lifetime_span,
2093                kind,
2094                count: expected_lifetimes,
2095            };
2096            let mut should_lint = true;
2097            for rib in self.lifetime_ribs.iter().rev() {
2098                match rib.kind {
2099                    // In create-parameter mode we error here because we don't want to support
2100                    // deprecated impl elision in new features like impl elision and `async fn`,
2101                    // both of which work using the `CreateParameter` mode:
2102                    //
2103                    //     impl Foo for std::cell::Ref<u32> // note lack of '_
2104                    //     async fn foo(_: std::cell::Ref<u32>) { ... }
2105                    LifetimeRibKind::AnonymousCreateParameter { report_in_path: true, .. }
2106                    | LifetimeRibKind::StaticIfNoLifetimeInScope { .. } => {
2107                        let sess = self.r.tcx.sess;
2108                        let subdiag = rustc_errors::elided_lifetime_in_path_suggestion(
2109                            sess.source_map(),
2110                            expected_lifetimes,
2111                            path_span,
2112                            !segment.has_generic_args,
2113                            elided_lifetime_span,
2114                        );
2115                        self.r.dcx().emit_err(errors::ImplicitElidedLifetimeNotAllowedHere {
2116                            span: path_span,
2117                            subdiag,
2118                        });
2119                        should_lint = false;
2120
2121                        for id in node_ids {
2122                            self.record_lifetime_res(
2123                                id,
2124                                LifetimeRes::Error,
2125                                LifetimeElisionCandidate::Named,
2126                            );
2127                        }
2128                        break;
2129                    }
2130                    // Do not create a parameter for patterns and expressions.
2131                    LifetimeRibKind::AnonymousCreateParameter { binder, .. } => {
2132                        // Group all suggestions into the first record.
2133                        let mut candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
2134                        for id in node_ids {
2135                            let res = self.create_fresh_lifetime(ident, binder, kind);
2136                            self.record_lifetime_res(
2137                                id,
2138                                res,
2139                                replace(&mut candidate, LifetimeElisionCandidate::Named),
2140                            );
2141                        }
2142                        break;
2143                    }
2144                    LifetimeRibKind::Elided(res) => {
2145                        let mut candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
2146                        for id in node_ids {
2147                            self.record_lifetime_res(
2148                                id,
2149                                res,
2150                                replace(&mut candidate, LifetimeElisionCandidate::Ignore),
2151                            );
2152                        }
2153                        break;
2154                    }
2155                    LifetimeRibKind::ElisionFailure => {
2156                        self.diag_metadata.current_elision_failures.push(missing_lifetime);
2157                        for id in node_ids {
2158                            self.record_lifetime_res(
2159                                id,
2160                                LifetimeRes::Error,
2161                                LifetimeElisionCandidate::Ignore,
2162                            );
2163                        }
2164                        break;
2165                    }
2166                    // `LifetimeRes::Error`, which would usually be used in the case of
2167                    // `ReportError`, is unsuitable here, as we don't emit an error yet. Instead,
2168                    // we simply resolve to an implicit lifetime, which will be checked later, at
2169                    // which point a suitable error will be emitted.
2170                    LifetimeRibKind::AnonymousReportError | LifetimeRibKind::Item => {
2171                        for id in node_ids {
2172                            self.record_lifetime_res(
2173                                id,
2174                                LifetimeRes::Error,
2175                                LifetimeElisionCandidate::Ignore,
2176                            );
2177                        }
2178                        self.report_missing_lifetime_specifiers(vec![missing_lifetime], None);
2179                        break;
2180                    }
2181                    LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstParamTy => {}
2182                    LifetimeRibKind::ConcreteAnonConst(_) => {
2183                        // There is always an `Elided(LifetimeRes::Infer)` inside an `AnonConst`.
2184                        span_bug!(elided_lifetime_span, "unexpected rib kind: {:?}", rib.kind)
2185                    }
2186                }
2187            }
2188
2189            if should_lint {
2190                self.r.lint_buffer.buffer_lint(
2191                    lint::builtin::ELIDED_LIFETIMES_IN_PATHS,
2192                    segment_id,
2193                    elided_lifetime_span,
2194                    lint::BuiltinLintDiag::ElidedLifetimesInPaths(
2195                        expected_lifetimes,
2196                        path_span,
2197                        !segment.has_generic_args,
2198                        elided_lifetime_span,
2199                    ),
2200                );
2201            }
2202        }
2203    }
2204
2205    #[instrument(level = "debug", skip(self))]
2206    fn record_lifetime_res(
2207        &mut self,
2208        id: NodeId,
2209        res: LifetimeRes,
2210        candidate: LifetimeElisionCandidate,
2211    ) {
2212        if let Some(prev_res) = self.r.lifetimes_res_map.insert(id, res) {
2213            panic!("lifetime {id:?} resolved multiple times ({prev_res:?} before, {res:?} now)")
2214        }
2215
2216        match res {
2217            LifetimeRes::Param { .. } | LifetimeRes::Fresh { .. } | LifetimeRes::Static { .. } => {
2218                if let Some(ref mut candidates) = self.lifetime_elision_candidates {
2219                    candidates.push((res, candidate));
2220                }
2221            }
2222            LifetimeRes::Infer | LifetimeRes::Error | LifetimeRes::ElidedAnchor { .. } => {}
2223        }
2224    }
2225
2226    #[instrument(level = "debug", skip(self))]
2227    fn record_lifetime_param(&mut self, id: NodeId, res: LifetimeRes) {
2228        if let Some(prev_res) = self.r.lifetimes_res_map.insert(id, res) {
2229            panic!(
2230                "lifetime parameter {id:?} resolved multiple times ({prev_res:?} before, {res:?} now)"
2231            )
2232        }
2233    }
2234
2235    /// Perform resolution of a function signature, accounting for lifetime elision.
2236    #[instrument(level = "debug", skip(self, inputs))]
2237    fn resolve_fn_signature(
2238        &mut self,
2239        fn_id: NodeId,
2240        has_self: bool,
2241        inputs: impl Iterator<Item = (Option<&'ast Pat>, &'ast Ty)> + Clone,
2242        output_ty: &'ast FnRetTy,
2243    ) {
2244        // Add each argument to the rib.
2245        let elision_lifetime = self.resolve_fn_params(has_self, inputs);
2246        debug!(?elision_lifetime);
2247
2248        let outer_failures = take(&mut self.diag_metadata.current_elision_failures);
2249        let output_rib = if let Ok(res) = elision_lifetime.as_ref() {
2250            self.r.lifetime_elision_allowed.insert(fn_id);
2251            LifetimeRibKind::Elided(*res)
2252        } else {
2253            LifetimeRibKind::ElisionFailure
2254        };
2255        self.with_lifetime_rib(output_rib, |this| visit::walk_fn_ret_ty(this, output_ty));
2256        let elision_failures =
2257            replace(&mut self.diag_metadata.current_elision_failures, outer_failures);
2258        if !elision_failures.is_empty() {
2259            let Err(failure_info) = elision_lifetime else { bug!() };
2260            self.report_missing_lifetime_specifiers(elision_failures, Some(failure_info));
2261        }
2262    }
2263
2264    /// Resolve inside function parameters and parameter types.
2265    /// Returns the lifetime for elision in fn return type,
2266    /// or diagnostic information in case of elision failure.
2267    fn resolve_fn_params(
2268        &mut self,
2269        has_self: bool,
2270        inputs: impl Iterator<Item = (Option<&'ast Pat>, &'ast Ty)> + Clone,
2271    ) -> Result<LifetimeRes, (Vec<MissingLifetime>, Vec<ElisionFnParameter>)> {
2272        enum Elision {
2273            /// We have not found any candidate.
2274            None,
2275            /// We have a candidate bound to `self`.
2276            Self_(LifetimeRes),
2277            /// We have a candidate bound to a parameter.
2278            Param(LifetimeRes),
2279            /// We failed elision.
2280            Err,
2281        }
2282
2283        // Save elision state to reinstate it later.
2284        let outer_candidates = self.lifetime_elision_candidates.take();
2285
2286        // Result of elision.
2287        let mut elision_lifetime = Elision::None;
2288        // Information for diagnostics.
2289        let mut parameter_info = Vec::new();
2290        let mut all_candidates = Vec::new();
2291
2292        // Resolve and apply bindings first so diagnostics can see if they're used in types.
2293        let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
2294        for (pat, _) in inputs.clone() {
2295            debug!("resolving bindings in pat = {pat:?}");
2296            self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
2297                if let Some(pat) = pat {
2298                    this.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
2299                }
2300            });
2301        }
2302        self.apply_pattern_bindings(bindings);
2303
2304        for (index, (pat, ty)) in inputs.enumerate() {
2305            debug!("resolving type for pat = {pat:?}, ty = {ty:?}");
2306            // Record elision candidates only for this parameter.
2307            debug_assert_matches!(self.lifetime_elision_candidates, None);
2308            self.lifetime_elision_candidates = Some(Default::default());
2309            self.visit_ty(ty);
2310            let local_candidates = self.lifetime_elision_candidates.take();
2311
2312            if let Some(candidates) = local_candidates {
2313                let distinct: UnordSet<_> = candidates.iter().map(|(res, _)| *res).collect();
2314                let lifetime_count = distinct.len();
2315                if lifetime_count != 0 {
2316                    parameter_info.push(ElisionFnParameter {
2317                        index,
2318                        ident: if let Some(pat) = pat
2319                            && let PatKind::Ident(_, ident, _) = pat.kind
2320                        {
2321                            Some(ident)
2322                        } else {
2323                            None
2324                        },
2325                        lifetime_count,
2326                        span: ty.span,
2327                    });
2328                    all_candidates.extend(candidates.into_iter().filter_map(|(_, candidate)| {
2329                        match candidate {
2330                            LifetimeElisionCandidate::Ignore | LifetimeElisionCandidate::Named => {
2331                                None
2332                            }
2333                            LifetimeElisionCandidate::Missing(missing) => Some(missing),
2334                        }
2335                    }));
2336                }
2337                if !distinct.is_empty() {
2338                    match elision_lifetime {
2339                        // We are the first parameter to bind lifetimes.
2340                        Elision::None => {
2341                            if let Some(res) = distinct.get_only() {
2342                                // We have a single lifetime => success.
2343                                elision_lifetime = Elision::Param(*res)
2344                            } else {
2345                                // We have multiple lifetimes => error.
2346                                elision_lifetime = Elision::Err;
2347                            }
2348                        }
2349                        // We have 2 parameters that bind lifetimes => error.
2350                        Elision::Param(_) => elision_lifetime = Elision::Err,
2351                        // `self` elision takes precedence over everything else.
2352                        Elision::Self_(_) | Elision::Err => {}
2353                    }
2354                }
2355            }
2356
2357            // Handle `self` specially.
2358            if index == 0 && has_self {
2359                let self_lifetime = self.find_lifetime_for_self(ty);
2360                elision_lifetime = match self_lifetime {
2361                    // We found `self` elision.
2362                    Set1::One(lifetime) => Elision::Self_(lifetime),
2363                    // `self` itself had ambiguous lifetimes, e.g.
2364                    // &Box<&Self>. In this case we won't consider
2365                    // taking an alternative parameter lifetime; just avoid elision
2366                    // entirely.
2367                    Set1::Many => Elision::Err,
2368                    // We do not have `self` elision: disregard the `Elision::Param` that we may
2369                    // have found.
2370                    Set1::Empty => Elision::None,
2371                }
2372            }
2373            debug!("(resolving function / closure) recorded parameter");
2374        }
2375
2376        // Reinstate elision state.
2377        debug_assert_matches!(self.lifetime_elision_candidates, None);
2378        self.lifetime_elision_candidates = outer_candidates;
2379
2380        if let Elision::Param(res) | Elision::Self_(res) = elision_lifetime {
2381            return Ok(res);
2382        }
2383
2384        // We do not have a candidate.
2385        Err((all_candidates, parameter_info))
2386    }
2387
2388    /// List all the lifetimes that appear in the provided type.
2389    fn find_lifetime_for_self(&self, ty: &'ast Ty) -> Set1<LifetimeRes> {
2390        /// Visits a type to find all the &references, and determines the
2391        /// set of lifetimes for all of those references where the referent
2392        /// contains Self.
2393        struct FindReferenceVisitor<'a, 'ra, 'tcx> {
2394            r: &'a Resolver<'ra, 'tcx>,
2395            impl_self: Option<Res>,
2396            lifetime: Set1<LifetimeRes>,
2397        }
2398
2399        impl<'ra> Visitor<'ra> for FindReferenceVisitor<'_, '_, '_> {
2400            fn visit_ty(&mut self, ty: &'ra Ty) {
2401                trace!("FindReferenceVisitor considering ty={:?}", ty);
2402                if let TyKind::Ref(lt, _) | TyKind::PinnedRef(lt, _) = ty.kind {
2403                    // See if anything inside the &thing contains Self
2404                    let mut visitor =
2405                        SelfVisitor { r: self.r, impl_self: self.impl_self, self_found: false };
2406                    visitor.visit_ty(ty);
2407                    trace!("FindReferenceVisitor: SelfVisitor self_found={:?}", visitor.self_found);
2408                    if visitor.self_found {
2409                        let lt_id = if let Some(lt) = lt {
2410                            lt.id
2411                        } else {
2412                            let res = self.r.lifetimes_res_map[&ty.id];
2413                            let LifetimeRes::ElidedAnchor { start, .. } = res else { bug!() };
2414                            start
2415                        };
2416                        let lt_res = self.r.lifetimes_res_map[&lt_id];
2417                        trace!("FindReferenceVisitor inserting res={:?}", lt_res);
2418                        self.lifetime.insert(lt_res);
2419                    }
2420                }
2421                visit::walk_ty(self, ty)
2422            }
2423
2424            // A type may have an expression as a const generic argument.
2425            // We do not want to recurse into those.
2426            fn visit_expr(&mut self, _: &'ra Expr) {}
2427        }
2428
2429        /// Visitor which checks the referent of a &Thing to see if the
2430        /// Thing contains Self
2431        struct SelfVisitor<'a, 'ra, 'tcx> {
2432            r: &'a Resolver<'ra, 'tcx>,
2433            impl_self: Option<Res>,
2434            self_found: bool,
2435        }
2436
2437        impl SelfVisitor<'_, '_, '_> {
2438            // Look for `self: &'a Self` - also desugared from `&'a self`
2439            fn is_self_ty(&self, ty: &Ty) -> bool {
2440                match ty.kind {
2441                    TyKind::ImplicitSelf => true,
2442                    TyKind::Path(None, _) => {
2443                        let path_res = self.r.partial_res_map[&ty.id].full_res();
2444                        if let Some(Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }) = path_res {
2445                            return true;
2446                        }
2447                        self.impl_self.is_some() && path_res == self.impl_self
2448                    }
2449                    _ => false,
2450                }
2451            }
2452        }
2453
2454        impl<'ra> Visitor<'ra> for SelfVisitor<'_, '_, '_> {
2455            fn visit_ty(&mut self, ty: &'ra Ty) {
2456                trace!("SelfVisitor considering ty={:?}", ty);
2457                if self.is_self_ty(ty) {
2458                    trace!("SelfVisitor found Self");
2459                    self.self_found = true;
2460                }
2461                visit::walk_ty(self, ty)
2462            }
2463
2464            // A type may have an expression as a const generic argument.
2465            // We do not want to recurse into those.
2466            fn visit_expr(&mut self, _: &'ra Expr) {}
2467        }
2468
2469        let impl_self = self
2470            .diag_metadata
2471            .current_self_type
2472            .as_ref()
2473            .and_then(|ty| {
2474                if let TyKind::Path(None, _) = ty.kind {
2475                    self.r.partial_res_map.get(&ty.id)
2476                } else {
2477                    None
2478                }
2479            })
2480            .and_then(|res| res.full_res())
2481            .filter(|res| {
2482                // Permit the types that unambiguously always
2483                // result in the same type constructor being used
2484                // (it can't differ between `Self` and `self`).
2485                matches!(
2486                    res,
2487                    Res::Def(DefKind::Struct | DefKind::Union | DefKind::Enum, _,) | Res::PrimTy(_)
2488                )
2489            });
2490        let mut visitor = FindReferenceVisitor { r: self.r, impl_self, lifetime: Set1::Empty };
2491        visitor.visit_ty(ty);
2492        trace!("FindReferenceVisitor found={:?}", visitor.lifetime);
2493        visitor.lifetime
2494    }
2495
2496    /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved
2497    /// label and reports an error if the label is not found or is unreachable.
2498    fn resolve_label(&mut self, mut label: Ident) -> Result<(NodeId, Span), ResolutionError<'ra>> {
2499        let mut suggestion = None;
2500
2501        for i in (0..self.label_ribs.len()).rev() {
2502            let rib = &self.label_ribs[i];
2503
2504            if let RibKind::MacroDefinition(def) = rib.kind
2505                // If an invocation of this macro created `ident`, give up on `ident`
2506                // and switch to `ident`'s source from the macro definition.
2507                && def == self.r.macro_def(label.span.ctxt())
2508            {
2509                label.span.remove_mark();
2510            }
2511
2512            let ident = label.normalize_to_macro_rules();
2513            if let Some((ident, id)) = rib.bindings.get_key_value(&ident) {
2514                let definition_span = ident.span;
2515                return if self.is_label_valid_from_rib(i) {
2516                    Ok((*id, definition_span))
2517                } else {
2518                    Err(ResolutionError::UnreachableLabel {
2519                        name: label.name,
2520                        definition_span,
2521                        suggestion,
2522                    })
2523                };
2524            }
2525
2526            // Diagnostics: Check if this rib contains a label with a similar name, keep track of
2527            // the first such label that is encountered.
2528            suggestion = suggestion.or_else(|| self.suggestion_for_label_in_rib(i, label));
2529        }
2530
2531        Err(ResolutionError::UndeclaredLabel { name: label.name, suggestion })
2532    }
2533
2534    /// Determine whether or not a label from the `rib_index`th label rib is reachable.
2535    fn is_label_valid_from_rib(&self, rib_index: usize) -> bool {
2536        let ribs = &self.label_ribs[rib_index + 1..];
2537        ribs.iter().all(|rib| !rib.kind.is_label_barrier())
2538    }
2539
2540    fn resolve_adt(&mut self, item: &'ast Item, generics: &'ast Generics) {
2541        debug!("resolve_adt");
2542        let kind = self.r.local_def_kind(item.id);
2543        self.with_current_self_item(item, |this| {
2544            this.with_generic_param_rib(
2545                &generics.params,
2546                RibKind::Item(HasGenericParams::Yes(generics.span), kind),
2547                item.id,
2548                LifetimeBinderKind::Item,
2549                generics.span,
2550                |this| {
2551                    let item_def_id = this.r.local_def_id(item.id).to_def_id();
2552                    this.with_self_rib(
2553                        Res::SelfTyAlias {
2554                            alias_to: item_def_id,
2555                            forbid_generic: false,
2556                            is_trait_impl: false,
2557                        },
2558                        |this| {
2559                            visit::walk_item(this, item);
2560                        },
2561                    );
2562                },
2563            );
2564        });
2565    }
2566
2567    fn future_proof_import(&mut self, use_tree: &UseTree) {
2568        if let [segment, rest @ ..] = use_tree.prefix.segments.as_slice() {
2569            let ident = segment.ident;
2570            if ident.is_path_segment_keyword() || ident.span.is_rust_2015() {
2571                return;
2572            }
2573
2574            let nss = match use_tree.kind {
2575                UseTreeKind::Simple(..) if rest.is_empty() => &[TypeNS, ValueNS][..],
2576                _ => &[TypeNS],
2577            };
2578            let report_error = |this: &Self, ns| {
2579                if this.should_report_errs() {
2580                    let what = if ns == TypeNS { "type parameters" } else { "local variables" };
2581                    this.r.dcx().emit_err(errors::ImportsCannotReferTo { span: ident.span, what });
2582                }
2583            };
2584
2585            for &ns in nss {
2586                match self.maybe_resolve_ident_in_lexical_scope(ident, ns) {
2587                    Some(LexicalScopeBinding::Res(..)) => {
2588                        report_error(self, ns);
2589                    }
2590                    Some(LexicalScopeBinding::Item(binding)) => {
2591                        if let Some(LexicalScopeBinding::Res(..)) =
2592                            self.resolve_ident_in_lexical_scope(ident, ns, None, Some(binding))
2593                        {
2594                            report_error(self, ns);
2595                        }
2596                    }
2597                    None => {}
2598                }
2599            }
2600        } else if let UseTreeKind::Nested { items, .. } = &use_tree.kind {
2601            for (use_tree, _) in items {
2602                self.future_proof_import(use_tree);
2603            }
2604        }
2605    }
2606
2607    fn resolve_item(&mut self, item: &'ast Item) {
2608        let mod_inner_docs =
2609            matches!(item.kind, ItemKind::Mod(..)) && rustdoc::inner_docs(&item.attrs);
2610        if !mod_inner_docs && !matches!(item.kind, ItemKind::Impl(..) | ItemKind::Use(..)) {
2611            self.resolve_doc_links(&item.attrs, MaybeExported::Ok(item.id));
2612        }
2613
2614        debug!("(resolving item) resolving {:?} ({:?})", item.kind.ident(), item.kind);
2615
2616        let def_kind = self.r.local_def_kind(item.id);
2617        match item.kind {
2618            ItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
2619                self.with_generic_param_rib(
2620                    &generics.params,
2621                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
2622                    item.id,
2623                    LifetimeBinderKind::Item,
2624                    generics.span,
2625                    |this| visit::walk_item(this, item),
2626                );
2627            }
2628
2629            ItemKind::Fn(box Fn { ref generics, ref define_opaque, .. }) => {
2630                self.with_generic_param_rib(
2631                    &generics.params,
2632                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
2633                    item.id,
2634                    LifetimeBinderKind::Function,
2635                    generics.span,
2636                    |this| visit::walk_item(this, item),
2637                );
2638                self.resolve_define_opaques(define_opaque);
2639            }
2640
2641            ItemKind::Enum(_, ref generics, _)
2642            | ItemKind::Struct(_, ref generics, _)
2643            | ItemKind::Union(_, ref generics, _) => {
2644                self.resolve_adt(item, generics);
2645            }
2646
2647            ItemKind::Impl(box Impl {
2648                ref generics,
2649                ref of_trait,
2650                ref self_ty,
2651                items: ref impl_items,
2652                ..
2653            }) => {
2654                self.diag_metadata.current_impl_items = Some(impl_items);
2655                self.resolve_implementation(
2656                    &item.attrs,
2657                    generics,
2658                    of_trait,
2659                    self_ty,
2660                    item.id,
2661                    impl_items,
2662                );
2663                self.diag_metadata.current_impl_items = None;
2664            }
2665
2666            ItemKind::Trait(box Trait { ref generics, ref bounds, ref items, .. }) => {
2667                // Create a new rib for the trait-wide type parameters.
2668                self.with_generic_param_rib(
2669                    &generics.params,
2670                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
2671                    item.id,
2672                    LifetimeBinderKind::Item,
2673                    generics.span,
2674                    |this| {
2675                        let local_def_id = this.r.local_def_id(item.id).to_def_id();
2676                        this.with_self_rib(Res::SelfTyParam { trait_: local_def_id }, |this| {
2677                            this.visit_generics(generics);
2678                            walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits);
2679                            this.resolve_trait_items(items);
2680                        });
2681                    },
2682                );
2683            }
2684
2685            ItemKind::TraitAlias(_, ref generics, ref bounds) => {
2686                // Create a new rib for the trait-wide type parameters.
2687                self.with_generic_param_rib(
2688                    &generics.params,
2689                    RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
2690                    item.id,
2691                    LifetimeBinderKind::Item,
2692                    generics.span,
2693                    |this| {
2694                        let local_def_id = this.r.local_def_id(item.id).to_def_id();
2695                        this.with_self_rib(Res::SelfTyParam { trait_: local_def_id }, |this| {
2696                            this.visit_generics(generics);
2697                            walk_list!(this, visit_param_bound, bounds, BoundKind::Bound);
2698                        });
2699                    },
2700                );
2701            }
2702
2703            ItemKind::Mod(..) => {
2704                self.with_mod_rib(item.id, |this| {
2705                    if mod_inner_docs {
2706                        this.resolve_doc_links(&item.attrs, MaybeExported::Ok(item.id));
2707                    }
2708                    let old_macro_rules = this.parent_scope.macro_rules;
2709                    visit::walk_item(this, item);
2710                    // Maintain macro_rules scopes in the same way as during early resolution
2711                    // for diagnostics and doc links.
2712                    if item.attrs.iter().all(|attr| {
2713                        !attr.has_name(sym::macro_use) && !attr.has_name(sym::macro_escape)
2714                    }) {
2715                        this.parent_scope.macro_rules = old_macro_rules;
2716                    }
2717                });
2718            }
2719
2720            ItemKind::Static(box ast::StaticItem {
2721                ident,
2722                ref ty,
2723                ref expr,
2724                ref define_opaque,
2725                ..
2726            }) => {
2727                self.with_static_rib(def_kind, |this| {
2728                    this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Static), |this| {
2729                        this.visit_ty(ty);
2730                    });
2731                    if let Some(expr) = expr {
2732                        // We already forbid generic params because of the above item rib,
2733                        // so it doesn't matter whether this is a trivial constant.
2734                        this.resolve_const_body(expr, Some((ident, ConstantItemKind::Static)));
2735                    }
2736                });
2737                self.resolve_define_opaques(define_opaque);
2738            }
2739
2740            ItemKind::Const(box ast::ConstItem {
2741                ident,
2742                ref generics,
2743                ref ty,
2744                ref expr,
2745                ref define_opaque,
2746                ..
2747            }) => {
2748                self.with_generic_param_rib(
2749                    &generics.params,
2750                    RibKind::Item(
2751                        if self.r.tcx.features().generic_const_items() {
2752                            HasGenericParams::Yes(generics.span)
2753                        } else {
2754                            HasGenericParams::No
2755                        },
2756                        def_kind,
2757                    ),
2758                    item.id,
2759                    LifetimeBinderKind::ConstItem,
2760                    generics.span,
2761                    |this| {
2762                        this.visit_generics(generics);
2763
2764                        this.with_lifetime_rib(
2765                            LifetimeRibKind::Elided(LifetimeRes::Static),
2766                            |this| this.visit_ty(ty),
2767                        );
2768
2769                        if let Some(expr) = expr {
2770                            this.resolve_const_body(expr, Some((ident, ConstantItemKind::Const)));
2771                        }
2772                    },
2773                );
2774                self.resolve_define_opaques(define_opaque);
2775            }
2776
2777            ItemKind::Use(ref use_tree) => {
2778                let maybe_exported = match use_tree.kind {
2779                    UseTreeKind::Simple(_) | UseTreeKind::Glob => MaybeExported::Ok(item.id),
2780                    UseTreeKind::Nested { .. } => MaybeExported::NestedUse(&item.vis),
2781                };
2782                self.resolve_doc_links(&item.attrs, maybe_exported);
2783
2784                self.future_proof_import(use_tree);
2785            }
2786
2787            ItemKind::MacroDef(_, ref macro_def) => {
2788                // Maintain macro_rules scopes in the same way as during early resolution
2789                // for diagnostics and doc links.
2790                if macro_def.macro_rules {
2791                    let def_id = self.r.local_def_id(item.id);
2792                    self.parent_scope.macro_rules = self.r.macro_rules_scopes[&def_id];
2793                }
2794            }
2795
2796            ItemKind::ForeignMod(_) | ItemKind::GlobalAsm(_) => {
2797                visit::walk_item(self, item);
2798            }
2799
2800            ItemKind::Delegation(ref delegation) => {
2801                let span = delegation.path.segments.last().unwrap().ident.span;
2802                self.with_generic_param_rib(
2803                    &[],
2804                    RibKind::Item(HasGenericParams::Yes(span), def_kind),
2805                    item.id,
2806                    LifetimeBinderKind::Function,
2807                    span,
2808                    |this| this.resolve_delegation(delegation),
2809                );
2810            }
2811
2812            ItemKind::ExternCrate(..) => {}
2813
2814            ItemKind::MacCall(_) | ItemKind::DelegationMac(..) => {
2815                panic!("unexpanded macro in resolve!")
2816            }
2817        }
2818    }
2819
2820    fn with_generic_param_rib<'c, F>(
2821        &'c mut self,
2822        params: &'c [GenericParam],
2823        kind: RibKind<'ra>,
2824        binder: NodeId,
2825        generics_kind: LifetimeBinderKind,
2826        generics_span: Span,
2827        f: F,
2828    ) where
2829        F: FnOnce(&mut Self),
2830    {
2831        debug!("with_generic_param_rib");
2832        let lifetime_kind =
2833            LifetimeRibKind::Generics { binder, span: generics_span, kind: generics_kind };
2834
2835        let mut function_type_rib = Rib::new(kind);
2836        let mut function_value_rib = Rib::new(kind);
2837        let mut function_lifetime_rib = LifetimeRib::new(lifetime_kind);
2838
2839        // Only check for shadowed bindings if we're declaring new params.
2840        if !params.is_empty() {
2841            let mut seen_bindings = FxHashMap::default();
2842            // Store all seen lifetimes names from outer scopes.
2843            let mut seen_lifetimes = FxHashSet::default();
2844
2845            // We also can't shadow bindings from associated parent items.
2846            for ns in [ValueNS, TypeNS] {
2847                for parent_rib in self.ribs[ns].iter().rev() {
2848                    // Break at mod level, to account for nested items which are
2849                    // allowed to shadow generic param names.
2850                    if matches!(parent_rib.kind, RibKind::Module(..)) {
2851                        break;
2852                    }
2853
2854                    seen_bindings
2855                        .extend(parent_rib.bindings.keys().map(|ident| (*ident, ident.span)));
2856                }
2857            }
2858
2859            // Forbid shadowing lifetime bindings
2860            for rib in self.lifetime_ribs.iter().rev() {
2861                seen_lifetimes.extend(rib.bindings.iter().map(|(ident, _)| *ident));
2862                if let LifetimeRibKind::Item = rib.kind {
2863                    break;
2864                }
2865            }
2866
2867            for param in params {
2868                let ident = param.ident.normalize_to_macros_2_0();
2869                debug!("with_generic_param_rib: {}", param.id);
2870
2871                if let GenericParamKind::Lifetime = param.kind
2872                    && let Some(&original) = seen_lifetimes.get(&ident)
2873                {
2874                    diagnostics::signal_lifetime_shadowing(self.r.tcx.sess, original, param.ident);
2875                    // Record lifetime res, so lowering knows there is something fishy.
2876                    self.record_lifetime_param(param.id, LifetimeRes::Error);
2877                    continue;
2878                }
2879
2880                match seen_bindings.entry(ident) {
2881                    Entry::Occupied(entry) => {
2882                        let span = *entry.get();
2883                        let err = ResolutionError::NameAlreadyUsedInParameterList(ident, span);
2884                        self.report_error(param.ident.span, err);
2885                        let rib = match param.kind {
2886                            GenericParamKind::Lifetime => {
2887                                // Record lifetime res, so lowering knows there is something fishy.
2888                                self.record_lifetime_param(param.id, LifetimeRes::Error);
2889                                continue;
2890                            }
2891                            GenericParamKind::Type { .. } => &mut function_type_rib,
2892                            GenericParamKind::Const { .. } => &mut function_value_rib,
2893                        };
2894
2895                        // Taint the resolution in case of errors to prevent follow up errors in typeck
2896                        self.r.record_partial_res(param.id, PartialRes::new(Res::Err));
2897                        rib.bindings.insert(ident, Res::Err);
2898                        continue;
2899                    }
2900                    Entry::Vacant(entry) => {
2901                        entry.insert(param.ident.span);
2902                    }
2903                }
2904
2905                if param.ident.name == kw::UnderscoreLifetime {
2906                    self.r
2907                        .dcx()
2908                        .emit_err(errors::UnderscoreLifetimeIsReserved { span: param.ident.span });
2909                    // Record lifetime res, so lowering knows there is something fishy.
2910                    self.record_lifetime_param(param.id, LifetimeRes::Error);
2911                    continue;
2912                }
2913
2914                if param.ident.name == kw::StaticLifetime {
2915                    self.r.dcx().emit_err(errors::StaticLifetimeIsReserved {
2916                        span: param.ident.span,
2917                        lifetime: param.ident,
2918                    });
2919                    // Record lifetime res, so lowering knows there is something fishy.
2920                    self.record_lifetime_param(param.id, LifetimeRes::Error);
2921                    continue;
2922                }
2923
2924                let def_id = self.r.local_def_id(param.id);
2925
2926                // Plain insert (no renaming).
2927                let (rib, def_kind) = match param.kind {
2928                    GenericParamKind::Type { .. } => (&mut function_type_rib, DefKind::TyParam),
2929                    GenericParamKind::Const { .. } => {
2930                        (&mut function_value_rib, DefKind::ConstParam)
2931                    }
2932                    GenericParamKind::Lifetime => {
2933                        let res = LifetimeRes::Param { param: def_id, binder };
2934                        self.record_lifetime_param(param.id, res);
2935                        function_lifetime_rib.bindings.insert(ident, (param.id, res));
2936                        continue;
2937                    }
2938                };
2939
2940                let res = match kind {
2941                    RibKind::Item(..) | RibKind::AssocItem => {
2942                        Res::Def(def_kind, def_id.to_def_id())
2943                    }
2944                    RibKind::Normal => {
2945                        // FIXME(non_lifetime_binders): Stop special-casing
2946                        // const params to error out here.
2947                        if self.r.tcx.features().non_lifetime_binders()
2948                            && matches!(param.kind, GenericParamKind::Type { .. })
2949                        {
2950                            Res::Def(def_kind, def_id.to_def_id())
2951                        } else {
2952                            Res::Err
2953                        }
2954                    }
2955                    _ => span_bug!(param.ident.span, "Unexpected rib kind {:?}", kind),
2956                };
2957                self.r.record_partial_res(param.id, PartialRes::new(res));
2958                rib.bindings.insert(ident, res);
2959            }
2960        }
2961
2962        self.lifetime_ribs.push(function_lifetime_rib);
2963        self.ribs[ValueNS].push(function_value_rib);
2964        self.ribs[TypeNS].push(function_type_rib);
2965
2966        f(self);
2967
2968        self.ribs[TypeNS].pop();
2969        self.ribs[ValueNS].pop();
2970        let function_lifetime_rib = self.lifetime_ribs.pop().unwrap();
2971
2972        // Do not account for the parameters we just bound for function lifetime elision.
2973        if let Some(ref mut candidates) = self.lifetime_elision_candidates {
2974            for (_, res) in function_lifetime_rib.bindings.values() {
2975                candidates.retain(|(r, _)| r != res);
2976            }
2977        }
2978
2979        if let LifetimeBinderKind::BareFnType
2980        | LifetimeBinderKind::WhereBound
2981        | LifetimeBinderKind::Function
2982        | LifetimeBinderKind::ImplBlock = generics_kind
2983        {
2984            self.maybe_report_lifetime_uses(generics_span, params)
2985        }
2986    }
2987
2988    fn with_label_rib(&mut self, kind: RibKind<'ra>, f: impl FnOnce(&mut Self)) {
2989        self.label_ribs.push(Rib::new(kind));
2990        f(self);
2991        self.label_ribs.pop();
2992    }
2993
2994    fn with_static_rib(&mut self, def_kind: DefKind, f: impl FnOnce(&mut Self)) {
2995        let kind = RibKind::Item(HasGenericParams::No, def_kind);
2996        self.with_rib(ValueNS, kind, |this| this.with_rib(TypeNS, kind, f))
2997    }
2998
2999    // HACK(min_const_generics, generic_const_exprs): We
3000    // want to keep allowing `[0; size_of::<*mut T>()]`
3001    // with a future compat lint for now. We do this by adding an
3002    // additional special case for repeat expressions.
3003    //
3004    // Note that we intentionally still forbid `[0; N + 1]` during
3005    // name resolution so that we don't extend the future
3006    // compat lint to new cases.
3007    #[instrument(level = "debug", skip(self, f))]
3008    fn with_constant_rib(
3009        &mut self,
3010        is_repeat: IsRepeatExpr,
3011        may_use_generics: ConstantHasGenerics,
3012        item: Option<(Ident, ConstantItemKind)>,
3013        f: impl FnOnce(&mut Self),
3014    ) {
3015        let f = |this: &mut Self| {
3016            this.with_rib(ValueNS, RibKind::ConstantItem(may_use_generics, item), |this| {
3017                this.with_rib(
3018                    TypeNS,
3019                    RibKind::ConstantItem(
3020                        may_use_generics.force_yes_if(is_repeat == IsRepeatExpr::Yes),
3021                        item,
3022                    ),
3023                    |this| {
3024                        this.with_label_rib(RibKind::ConstantItem(may_use_generics, item), f);
3025                    },
3026                )
3027            })
3028        };
3029
3030        if let ConstantHasGenerics::No(cause) = may_use_generics {
3031            self.with_lifetime_rib(LifetimeRibKind::ConcreteAnonConst(cause), f)
3032        } else {
3033            f(self)
3034        }
3035    }
3036
3037    fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
3038        // Handle nested impls (inside fn bodies)
3039        let previous_value =
3040            replace(&mut self.diag_metadata.current_self_type, Some(self_type.clone()));
3041        let result = f(self);
3042        self.diag_metadata.current_self_type = previous_value;
3043        result
3044    }
3045
3046    fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
3047        let previous_value = replace(&mut self.diag_metadata.current_self_item, Some(self_item.id));
3048        let result = f(self);
3049        self.diag_metadata.current_self_item = previous_value;
3050        result
3051    }
3052
3053    /// When evaluating a `trait` use its associated types' idents for suggestions in E0412.
3054    fn resolve_trait_items(&mut self, trait_items: &'ast [P<AssocItem>]) {
3055        let trait_assoc_items =
3056            replace(&mut self.diag_metadata.current_trait_assoc_items, Some(trait_items));
3057
3058        let walk_assoc_item =
3059            |this: &mut Self, generics: &Generics, kind, item: &'ast AssocItem| {
3060                this.with_generic_param_rib(
3061                    &generics.params,
3062                    RibKind::AssocItem,
3063                    item.id,
3064                    kind,
3065                    generics.span,
3066                    |this| visit::walk_assoc_item(this, item, AssocCtxt::Trait),
3067                );
3068            };
3069
3070        for item in trait_items {
3071            self.resolve_doc_links(&item.attrs, MaybeExported::Ok(item.id));
3072            match &item.kind {
3073                AssocItemKind::Const(box ast::ConstItem {
3074                    generics,
3075                    ty,
3076                    expr,
3077                    define_opaque,
3078                    ..
3079                }) => {
3080                    self.with_generic_param_rib(
3081                        &generics.params,
3082                        RibKind::AssocItem,
3083                        item.id,
3084                        LifetimeBinderKind::ConstItem,
3085                        generics.span,
3086                        |this| {
3087                            this.with_lifetime_rib(
3088                                LifetimeRibKind::StaticIfNoLifetimeInScope {
3089                                    lint_id: item.id,
3090                                    emit_lint: false,
3091                                },
3092                                |this| {
3093                                    this.visit_generics(generics);
3094                                    this.visit_ty(ty);
3095
3096                                    // Only impose the restrictions of `ConstRibKind` for an
3097                                    // actual constant expression in a provided default.
3098                                    if let Some(expr) = expr {
3099                                        // We allow arbitrary const expressions inside of associated consts,
3100                                        // even if they are potentially not const evaluatable.
3101                                        //
3102                                        // Type parameters can already be used and as associated consts are
3103                                        // not used as part of the type system, this is far less surprising.
3104                                        this.resolve_const_body(expr, None);
3105                                    }
3106                                },
3107                            )
3108                        },
3109                    );
3110
3111                    self.resolve_define_opaques(define_opaque);
3112                }
3113                AssocItemKind::Fn(box Fn { generics, define_opaque, .. }) => {
3114                    walk_assoc_item(self, generics, LifetimeBinderKind::Function, item);
3115
3116                    self.resolve_define_opaques(define_opaque);
3117                }
3118                AssocItemKind::Delegation(delegation) => {
3119                    self.with_generic_param_rib(
3120                        &[],
3121                        RibKind::AssocItem,
3122                        item.id,
3123                        LifetimeBinderKind::Function,
3124                        delegation.path.segments.last().unwrap().ident.span,
3125                        |this| this.resolve_delegation(delegation),
3126                    );
3127                }
3128                AssocItemKind::Type(box TyAlias { generics, .. }) => self
3129                    .with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
3130                        walk_assoc_item(this, generics, LifetimeBinderKind::Item, item)
3131                    }),
3132                AssocItemKind::MacCall(_) | AssocItemKind::DelegationMac(..) => {
3133                    panic!("unexpanded macro in resolve!")
3134                }
3135            };
3136        }
3137
3138        self.diag_metadata.current_trait_assoc_items = trait_assoc_items;
3139    }
3140
3141    /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
3142    fn with_optional_trait_ref<T>(
3143        &mut self,
3144        opt_trait_ref: Option<&TraitRef>,
3145        self_type: &'ast Ty,
3146        f: impl FnOnce(&mut Self, Option<DefId>) -> T,
3147    ) -> T {
3148        let mut new_val = None;
3149        let mut new_id = None;
3150        if let Some(trait_ref) = opt_trait_ref {
3151            let path: Vec<_> = Segment::from_path(&trait_ref.path);
3152            self.diag_metadata.currently_processing_impl_trait =
3153                Some((trait_ref.clone(), self_type.clone()));
3154            let res = self.smart_resolve_path_fragment(
3155                &None,
3156                &path,
3157                PathSource::Trait(AliasPossibility::No),
3158                Finalize::new(trait_ref.ref_id, trait_ref.path.span),
3159                RecordPartialRes::Yes,
3160                None,
3161            );
3162            self.diag_metadata.currently_processing_impl_trait = None;
3163            if let Some(def_id) = res.expect_full_res().opt_def_id() {
3164                new_id = Some(def_id);
3165                new_val = Some((self.r.expect_module(def_id), trait_ref.clone()));
3166            }
3167        }
3168        let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
3169        let result = f(self, new_id);
3170        self.current_trait_ref = original_trait_ref;
3171        result
3172    }
3173
3174    fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
3175        let mut self_type_rib = Rib::new(RibKind::Normal);
3176
3177        // Plain insert (no renaming, since types are not currently hygienic)
3178        self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
3179        self.ribs[ns].push(self_type_rib);
3180        f(self);
3181        self.ribs[ns].pop();
3182    }
3183
3184    fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
3185        self.with_self_rib_ns(TypeNS, self_res, f)
3186    }
3187
3188    fn resolve_implementation(
3189        &mut self,
3190        attrs: &[ast::Attribute],
3191        generics: &'ast Generics,
3192        opt_trait_reference: &'ast Option<TraitRef>,
3193        self_type: &'ast Ty,
3194        item_id: NodeId,
3195        impl_items: &'ast [P<AssocItem>],
3196    ) {
3197        debug!("resolve_implementation");
3198        // If applicable, create a rib for the type parameters.
3199        self.with_generic_param_rib(
3200            &generics.params,
3201            RibKind::Item(HasGenericParams::Yes(generics.span), self.r.local_def_kind(item_id)),
3202            item_id,
3203            LifetimeBinderKind::ImplBlock,
3204            generics.span,
3205            |this| {
3206                // Dummy self type for better errors if `Self` is used in the trait path.
3207                this.with_self_rib(Res::SelfTyParam { trait_: LOCAL_CRATE.as_def_id() }, |this| {
3208                    this.with_lifetime_rib(
3209                        LifetimeRibKind::AnonymousCreateParameter {
3210                            binder: item_id,
3211                            report_in_path: true
3212                        },
3213                        |this| {
3214                            // Resolve the trait reference, if necessary.
3215                            this.with_optional_trait_ref(
3216                                opt_trait_reference.as_ref(),
3217                                self_type,
3218                                |this, trait_id| {
3219                                    this.resolve_doc_links(attrs, MaybeExported::Impl(trait_id));
3220
3221                                    let item_def_id = this.r.local_def_id(item_id);
3222
3223                                    // Register the trait definitions from here.
3224                                    if let Some(trait_id) = trait_id {
3225                                        this.r
3226                                            .trait_impls
3227                                            .entry(trait_id)
3228                                            .or_default()
3229                                            .push(item_def_id);
3230                                    }
3231
3232                                    let item_def_id = item_def_id.to_def_id();
3233                                    let res = Res::SelfTyAlias {
3234                                        alias_to: item_def_id,
3235                                        forbid_generic: false,
3236                                        is_trait_impl: trait_id.is_some()
3237                                    };
3238                                    this.with_self_rib(res, |this| {
3239                                        if let Some(trait_ref) = opt_trait_reference.as_ref() {
3240                                            // Resolve type arguments in the trait path.
3241                                            visit::walk_trait_ref(this, trait_ref);
3242                                        }
3243                                        // Resolve the self type.
3244                                        this.visit_ty(self_type);
3245                                        // Resolve the generic parameters.
3246                                        this.visit_generics(generics);
3247
3248                                        // Resolve the items within the impl.
3249                                        this.with_current_self_type(self_type, |this| {
3250                                            this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
3251                                                debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
3252                                                let mut seen_trait_items = Default::default();
3253                                                for item in impl_items {
3254                                                    this.resolve_impl_item(&**item, &mut seen_trait_items, trait_id);
3255                                                }
3256                                            });
3257                                        });
3258                                    });
3259                                },
3260                            )
3261                        },
3262                    );
3263                });
3264            },
3265        );
3266    }
3267
3268    fn resolve_impl_item(
3269        &mut self,
3270        item: &'ast AssocItem,
3271        seen_trait_items: &mut FxHashMap<DefId, Span>,
3272        trait_id: Option<DefId>,
3273    ) {
3274        use crate::ResolutionError::*;
3275        self.resolve_doc_links(&item.attrs, MaybeExported::ImplItem(trait_id.ok_or(&item.vis)));
3276        match &item.kind {
3277            AssocItemKind::Const(box ast::ConstItem {
3278                ident,
3279                generics,
3280                ty,
3281                expr,
3282                define_opaque,
3283                ..
3284            }) => {
3285                debug!("resolve_implementation AssocItemKind::Const");
3286                self.with_generic_param_rib(
3287                    &generics.params,
3288                    RibKind::AssocItem,
3289                    item.id,
3290                    LifetimeBinderKind::ConstItem,
3291                    generics.span,
3292                    |this| {
3293                        this.with_lifetime_rib(
3294                            // Until these are a hard error, we need to create them within the
3295                            // correct binder, Otherwise the lifetimes of this assoc const think
3296                            // they are lifetimes of the trait.
3297                            LifetimeRibKind::AnonymousCreateParameter {
3298                                binder: item.id,
3299                                report_in_path: true,
3300                            },
3301                            |this| {
3302                                this.with_lifetime_rib(
3303                                    LifetimeRibKind::StaticIfNoLifetimeInScope {
3304                                        lint_id: item.id,
3305                                        // In impls, it's not a hard error yet due to backcompat.
3306                                        emit_lint: true,
3307                                    },
3308                                    |this| {
3309                                        // If this is a trait impl, ensure the const
3310                                        // exists in trait
3311                                        this.check_trait_item(
3312                                            item.id,
3313                                            *ident,
3314                                            &item.kind,
3315                                            ValueNS,
3316                                            item.span,
3317                                            seen_trait_items,
3318                                            |i, s, c| ConstNotMemberOfTrait(i, s, c),
3319                                        );
3320
3321                                        this.visit_generics(generics);
3322                                        this.visit_ty(ty);
3323                                        if let Some(expr) = expr {
3324                                            // We allow arbitrary const expressions inside of associated consts,
3325                                            // even if they are potentially not const evaluatable.
3326                                            //
3327                                            // Type parameters can already be used and as associated consts are
3328                                            // not used as part of the type system, this is far less surprising.
3329                                            this.resolve_const_body(expr, None);
3330                                        }
3331                                    },
3332                                )
3333                            },
3334                        );
3335                    },
3336                );
3337                self.resolve_define_opaques(define_opaque);
3338            }
3339            AssocItemKind::Fn(box Fn { ident, generics, define_opaque, .. }) => {
3340                debug!("resolve_implementation AssocItemKind::Fn");
3341                // We also need a new scope for the impl item type parameters.
3342                self.with_generic_param_rib(
3343                    &generics.params,
3344                    RibKind::AssocItem,
3345                    item.id,
3346                    LifetimeBinderKind::Function,
3347                    generics.span,
3348                    |this| {
3349                        // If this is a trait impl, ensure the method
3350                        // exists in trait
3351                        this.check_trait_item(
3352                            item.id,
3353                            *ident,
3354                            &item.kind,
3355                            ValueNS,
3356                            item.span,
3357                            seen_trait_items,
3358                            |i, s, c| MethodNotMemberOfTrait(i, s, c),
3359                        );
3360
3361                        visit::walk_assoc_item(this, item, AssocCtxt::Impl { of_trait: true })
3362                    },
3363                );
3364
3365                self.resolve_define_opaques(define_opaque);
3366            }
3367            AssocItemKind::Type(box TyAlias { ident, generics, .. }) => {
3368                self.diag_metadata.in_non_gat_assoc_type = Some(generics.params.is_empty());
3369                debug!("resolve_implementation AssocItemKind::Type");
3370                // We also need a new scope for the impl item type parameters.
3371                self.with_generic_param_rib(
3372                    &generics.params,
3373                    RibKind::AssocItem,
3374                    item.id,
3375                    LifetimeBinderKind::Item,
3376                    generics.span,
3377                    |this| {
3378                        this.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
3379                            // If this is a trait impl, ensure the type
3380                            // exists in trait
3381                            this.check_trait_item(
3382                                item.id,
3383                                *ident,
3384                                &item.kind,
3385                                TypeNS,
3386                                item.span,
3387                                seen_trait_items,
3388                                |i, s, c| TypeNotMemberOfTrait(i, s, c),
3389                            );
3390
3391                            visit::walk_assoc_item(this, item, AssocCtxt::Impl { of_trait: true })
3392                        });
3393                    },
3394                );
3395                self.diag_metadata.in_non_gat_assoc_type = None;
3396            }
3397            AssocItemKind::Delegation(box delegation) => {
3398                debug!("resolve_implementation AssocItemKind::Delegation");
3399                self.with_generic_param_rib(
3400                    &[],
3401                    RibKind::AssocItem,
3402                    item.id,
3403                    LifetimeBinderKind::Function,
3404                    delegation.path.segments.last().unwrap().ident.span,
3405                    |this| {
3406                        this.check_trait_item(
3407                            item.id,
3408                            delegation.ident,
3409                            &item.kind,
3410                            ValueNS,
3411                            item.span,
3412                            seen_trait_items,
3413                            |i, s, c| MethodNotMemberOfTrait(i, s, c),
3414                        );
3415
3416                        this.resolve_delegation(delegation)
3417                    },
3418                );
3419            }
3420            AssocItemKind::MacCall(_) | AssocItemKind::DelegationMac(..) => {
3421                panic!("unexpanded macro in resolve!")
3422            }
3423        }
3424    }
3425
3426    fn check_trait_item<F>(
3427        &mut self,
3428        id: NodeId,
3429        mut ident: Ident,
3430        kind: &AssocItemKind,
3431        ns: Namespace,
3432        span: Span,
3433        seen_trait_items: &mut FxHashMap<DefId, Span>,
3434        err: F,
3435    ) where
3436        F: FnOnce(Ident, String, Option<Symbol>) -> ResolutionError<'ra>,
3437    {
3438        // If there is a TraitRef in scope for an impl, then the method must be in the trait.
3439        let Some((module, _)) = self.current_trait_ref else {
3440            return;
3441        };
3442        ident.span.normalize_to_macros_2_0_and_adjust(module.expansion);
3443        let key = BindingKey::new(ident, ns);
3444        let mut binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
3445        debug!(?binding);
3446        if binding.is_none() {
3447            // We could not find the trait item in the correct namespace.
3448            // Check the other namespace to report an error.
3449            let ns = match ns {
3450                ValueNS => TypeNS,
3451                TypeNS => ValueNS,
3452                _ => ns,
3453            };
3454            let key = BindingKey::new(ident, ns);
3455            binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
3456            debug!(?binding);
3457        }
3458
3459        let feed_visibility = |this: &mut Self, def_id| {
3460            let vis = this.r.tcx.visibility(def_id);
3461            let vis = if vis.is_visible_locally() {
3462                vis.expect_local()
3463            } else {
3464                this.r.dcx().span_delayed_bug(
3465                    span,
3466                    "error should be emitted when an unexpected trait item is used",
3467                );
3468                rustc_middle::ty::Visibility::Public
3469            };
3470            this.r.feed_visibility(this.r.feed(id), vis);
3471        };
3472
3473        let Some(binding) = binding else {
3474            // We could not find the method: report an error.
3475            let candidate = self.find_similarly_named_assoc_item(ident.name, kind);
3476            let path = &self.current_trait_ref.as_ref().unwrap().1.path;
3477            let path_names = path_names_to_string(path);
3478            self.report_error(span, err(ident, path_names, candidate));
3479            feed_visibility(self, module.def_id());
3480            return;
3481        };
3482
3483        let res = binding.res();
3484        let Res::Def(def_kind, id_in_trait) = res else { bug!() };
3485        feed_visibility(self, id_in_trait);
3486
3487        match seen_trait_items.entry(id_in_trait) {
3488            Entry::Occupied(entry) => {
3489                self.report_error(
3490                    span,
3491                    ResolutionError::TraitImplDuplicate {
3492                        name: ident,
3493                        old_span: *entry.get(),
3494                        trait_item_span: binding.span,
3495                    },
3496                );
3497                return;
3498            }
3499            Entry::Vacant(entry) => {
3500                entry.insert(span);
3501            }
3502        };
3503
3504        match (def_kind, kind) {
3505            (DefKind::AssocTy, AssocItemKind::Type(..))
3506            | (DefKind::AssocFn, AssocItemKind::Fn(..))
3507            | (DefKind::AssocConst, AssocItemKind::Const(..))
3508            | (DefKind::AssocFn, AssocItemKind::Delegation(..)) => {
3509                self.r.record_partial_res(id, PartialRes::new(res));
3510                return;
3511            }
3512            _ => {}
3513        }
3514
3515        // The method kind does not correspond to what appeared in the trait, report.
3516        let path = &self.current_trait_ref.as_ref().unwrap().1.path;
3517        let (code, kind) = match kind {
3518            AssocItemKind::Const(..) => (E0323, "const"),
3519            AssocItemKind::Fn(..) => (E0324, "method"),
3520            AssocItemKind::Type(..) => (E0325, "type"),
3521            AssocItemKind::Delegation(..) => (E0324, "method"),
3522            AssocItemKind::MacCall(..) | AssocItemKind::DelegationMac(..) => {
3523                span_bug!(span, "unexpanded macro")
3524            }
3525        };
3526        let trait_path = path_names_to_string(path);
3527        self.report_error(
3528            span,
3529            ResolutionError::TraitImplMismatch {
3530                name: ident,
3531                kind,
3532                code,
3533                trait_path,
3534                trait_item_span: binding.span,
3535            },
3536        );
3537    }
3538
3539    fn resolve_const_body(&mut self, expr: &'ast Expr, item: Option<(Ident, ConstantItemKind)>) {
3540        self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
3541            this.with_constant_rib(IsRepeatExpr::No, ConstantHasGenerics::Yes, item, |this| {
3542                this.visit_expr(expr)
3543            });
3544        })
3545    }
3546
3547    fn resolve_delegation(&mut self, delegation: &'ast Delegation) {
3548        self.smart_resolve_path(
3549            delegation.id,
3550            &delegation.qself,
3551            &delegation.path,
3552            PathSource::Delegation,
3553        );
3554        if let Some(qself) = &delegation.qself {
3555            self.visit_ty(&qself.ty);
3556        }
3557        self.visit_path(&delegation.path);
3558        let Some(body) = &delegation.body else { return };
3559        self.with_rib(ValueNS, RibKind::FnOrCoroutine, |this| {
3560            let span = delegation.path.segments.last().unwrap().ident.span;
3561            let ident = Ident::new(kw::SelfLower, span.normalize_to_macro_rules());
3562            let res = Res::Local(delegation.id);
3563            this.innermost_rib_bindings(ValueNS).insert(ident, res);
3564            this.visit_block(body);
3565        });
3566    }
3567
3568    fn resolve_params(&mut self, params: &'ast [Param]) {
3569        let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
3570        self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
3571            for Param { pat, .. } in params {
3572                this.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
3573            }
3574            this.apply_pattern_bindings(bindings);
3575        });
3576        for Param { ty, .. } in params {
3577            self.visit_ty(ty);
3578        }
3579    }
3580
3581    fn resolve_local(&mut self, local: &'ast Local) {
3582        debug!("resolving local ({:?})", local);
3583        // Resolve the type.
3584        visit_opt!(self, visit_ty, &local.ty);
3585
3586        // Resolve the initializer.
3587        if let Some((init, els)) = local.kind.init_else_opt() {
3588            self.visit_expr(init);
3589
3590            // Resolve the `else` block
3591            if let Some(els) = els {
3592                self.visit_block(els);
3593            }
3594        }
3595
3596        // Resolve the pattern.
3597        self.resolve_pattern_top(&local.pat, PatternSource::Let);
3598    }
3599
3600    /// Build a map from pattern identifiers to binding-info's, and check the bindings are
3601    /// consistent when encountering or-patterns and never patterns.
3602    /// This is done hygienically: this could arise for a macro that expands into an or-pattern
3603    /// where one 'x' was from the user and one 'x' came from the macro.
3604    ///
3605    /// A never pattern by definition indicates an unreachable case. For example, matching on
3606    /// `Result<T, &!>` could look like:
3607    /// ```rust
3608    /// # #![feature(never_type)]
3609    /// # #![feature(never_patterns)]
3610    /// # fn bar(_x: u32) {}
3611    /// let foo: Result<u32, &!> = Ok(0);
3612    /// match foo {
3613    ///     Ok(x) => bar(x),
3614    ///     Err(&!),
3615    /// }
3616    /// ```
3617    /// This extends to product types: `(x, !)` is likewise unreachable. So it doesn't make sense to
3618    /// have a binding here, and we tell the user to use `_` instead.
3619    fn compute_and_check_binding_map(
3620        &mut self,
3621        pat: &Pat,
3622    ) -> Result<FxIndexMap<Ident, BindingInfo>, IsNeverPattern> {
3623        let mut binding_map = FxIndexMap::default();
3624        let mut is_never_pat = false;
3625
3626        pat.walk(&mut |pat| {
3627            match pat.kind {
3628                PatKind::Ident(annotation, ident, ref sub_pat)
3629                    if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
3630                {
3631                    binding_map.insert(ident, BindingInfo { span: ident.span, annotation });
3632                }
3633                PatKind::Or(ref ps) => {
3634                    // Check the consistency of this or-pattern and
3635                    // then add all bindings to the larger map.
3636                    match self.compute_and_check_or_pat_binding_map(ps) {
3637                        Ok(bm) => binding_map.extend(bm),
3638                        Err(IsNeverPattern) => is_never_pat = true,
3639                    }
3640                    return false;
3641                }
3642                PatKind::Never => is_never_pat = true,
3643                _ => {}
3644            }
3645
3646            true
3647        });
3648
3649        if is_never_pat {
3650            for (_, binding) in binding_map {
3651                self.report_error(binding.span, ResolutionError::BindingInNeverPattern);
3652            }
3653            Err(IsNeverPattern)
3654        } else {
3655            Ok(binding_map)
3656        }
3657    }
3658
3659    fn is_base_res_local(&self, nid: NodeId) -> bool {
3660        matches!(
3661            self.r.partial_res_map.get(&nid).map(|res| res.expect_full_res()),
3662            Some(Res::Local(..))
3663        )
3664    }
3665
3666    /// Compute the binding map for an or-pattern. Checks that all of the arms in the or-pattern
3667    /// have exactly the same set of bindings, with the same binding modes for each.
3668    /// Returns the computed binding map and a boolean indicating whether the pattern is a never
3669    /// pattern.
3670    ///
3671    /// A never pattern by definition indicates an unreachable case. For example, destructuring a
3672    /// `Result<T, &!>` could look like:
3673    /// ```rust
3674    /// # #![feature(never_type)]
3675    /// # #![feature(never_patterns)]
3676    /// # fn foo() -> Result<bool, &'static !> { Ok(true) }
3677    /// let (Ok(x) | Err(&!)) = foo();
3678    /// # let _ = x;
3679    /// ```
3680    /// Because the `Err(&!)` branch is never reached, it does not need to have the same bindings as
3681    /// the other branches of the or-pattern. So we must ignore never pattern when checking the
3682    /// bindings of an or-pattern.
3683    /// Moreover, if all the subpatterns are never patterns (e.g. `Ok(!) | Err(!)`), then the
3684    /// pattern as a whole counts as a never pattern (since it's definitionallly unreachable).
3685    fn compute_and_check_or_pat_binding_map(
3686        &mut self,
3687        pats: &[P<Pat>],
3688    ) -> Result<FxIndexMap<Ident, BindingInfo>, IsNeverPattern> {
3689        let mut missing_vars = FxIndexMap::default();
3690        let mut inconsistent_vars = FxIndexMap::default();
3691
3692        // 1) Compute the binding maps of all arms; we must ignore never patterns here.
3693        let not_never_pats = pats
3694            .iter()
3695            .filter_map(|pat| {
3696                let binding_map = self.compute_and_check_binding_map(pat).ok()?;
3697                Some((binding_map, pat))
3698            })
3699            .collect::<Vec<_>>();
3700
3701        // 2) Record any missing bindings or binding mode inconsistencies.
3702        for (map_outer, pat_outer) in not_never_pats.iter() {
3703            // Check against all arms except for the same pattern which is always self-consistent.
3704            let inners = not_never_pats
3705                .iter()
3706                .filter(|(_, pat)| pat.id != pat_outer.id)
3707                .flat_map(|(map, _)| map);
3708
3709            for (&name, binding_inner) in inners {
3710                match map_outer.get(&name) {
3711                    None => {
3712                        // The inner binding is missing in the outer.
3713                        let binding_error =
3714                            missing_vars.entry(name).or_insert_with(|| BindingError {
3715                                name,
3716                                origin: BTreeSet::new(),
3717                                target: BTreeSet::new(),
3718                                could_be_path: name.as_str().starts_with(char::is_uppercase),
3719                            });
3720                        binding_error.origin.insert(binding_inner.span);
3721                        binding_error.target.insert(pat_outer.span);
3722                    }
3723                    Some(binding_outer) => {
3724                        if binding_outer.annotation != binding_inner.annotation {
3725                            // The binding modes in the outer and inner bindings differ.
3726                            inconsistent_vars
3727                                .entry(name)
3728                                .or_insert((binding_inner.span, binding_outer.span));
3729                        }
3730                    }
3731                }
3732            }
3733        }
3734
3735        // 3) Report all missing variables we found.
3736        for (name, mut v) in missing_vars {
3737            if inconsistent_vars.contains_key(&name) {
3738                v.could_be_path = false;
3739            }
3740            self.report_error(
3741                *v.origin.iter().next().unwrap(),
3742                ResolutionError::VariableNotBoundInPattern(v, self.parent_scope),
3743            );
3744        }
3745
3746        // 4) Report all inconsistencies in binding modes we found.
3747        for (name, v) in inconsistent_vars {
3748            self.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(name, v.1));
3749        }
3750
3751        // 5) Bubble up the final binding map.
3752        if not_never_pats.is_empty() {
3753            // All the patterns are never patterns, so the whole or-pattern is one too.
3754            Err(IsNeverPattern)
3755        } else {
3756            let mut binding_map = FxIndexMap::default();
3757            for (bm, _) in not_never_pats {
3758                binding_map.extend(bm);
3759            }
3760            Ok(binding_map)
3761        }
3762    }
3763
3764    /// Check the consistency of bindings wrt or-patterns and never patterns.
3765    fn check_consistent_bindings(&mut self, pat: &'ast Pat) {
3766        let mut is_or_or_never = false;
3767        pat.walk(&mut |pat| match pat.kind {
3768            PatKind::Or(..) | PatKind::Never => {
3769                is_or_or_never = true;
3770                false
3771            }
3772            _ => true,
3773        });
3774        if is_or_or_never {
3775            let _ = self.compute_and_check_binding_map(pat);
3776        }
3777    }
3778
3779    fn resolve_arm(&mut self, arm: &'ast Arm) {
3780        self.with_rib(ValueNS, RibKind::Normal, |this| {
3781            this.resolve_pattern_top(&arm.pat, PatternSource::Match);
3782            visit_opt!(this, visit_expr, &arm.guard);
3783            visit_opt!(this, visit_expr, &arm.body);
3784        });
3785    }
3786
3787    /// Arising from `source`, resolve a top level pattern.
3788    fn resolve_pattern_top(&mut self, pat: &'ast Pat, pat_src: PatternSource) {
3789        let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
3790        self.resolve_pattern(pat, pat_src, &mut bindings);
3791        self.apply_pattern_bindings(bindings);
3792    }
3793
3794    /// Apply the bindings from a pattern to the innermost rib of the current scope.
3795    fn apply_pattern_bindings(&mut self, mut pat_bindings: PatternBindings) {
3796        let rib_bindings = self.innermost_rib_bindings(ValueNS);
3797        let Some((_, pat_bindings)) = pat_bindings.pop() else {
3798            bug!("tried applying nonexistent bindings from pattern");
3799        };
3800
3801        if rib_bindings.is_empty() {
3802            // Often, such as for match arms, the bindings are introduced into a new rib.
3803            // In this case, we can move the bindings over directly.
3804            *rib_bindings = pat_bindings;
3805        } else {
3806            rib_bindings.extend(pat_bindings);
3807        }
3808    }
3809
3810    /// Resolve bindings in a pattern. `apply_pattern_bindings` must be called after to introduce
3811    /// the bindings into scope.
3812    fn resolve_pattern(
3813        &mut self,
3814        pat: &'ast Pat,
3815        pat_src: PatternSource,
3816        bindings: &mut PatternBindings,
3817    ) {
3818        // We walk the pattern before declaring the pattern's inner bindings,
3819        // so that we avoid resolving a literal expression to a binding defined
3820        // by the pattern.
3821        // NB: `Self::visit_pat` must be used rather than `visit::walk_pat` to avoid resolving guard
3822        // patterns' guard expressions multiple times (#141265).
3823        self.visit_pat(pat);
3824        self.resolve_pattern_inner(pat, pat_src, bindings);
3825        // This has to happen *after* we determine which pat_idents are variants:
3826        self.check_consistent_bindings(pat);
3827    }
3828
3829    /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
3830    ///
3831    /// ### `bindings`
3832    ///
3833    /// A stack of sets of bindings accumulated.
3834    ///
3835    /// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
3836    /// be interpreted as re-binding an already bound binding. This results in an error.
3837    /// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
3838    /// in reusing this binding rather than creating a fresh one.
3839    ///
3840    /// When called at the top level, the stack must have a single element
3841    /// with `PatBound::Product`. Otherwise, pushing to the stack happens as
3842    /// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
3843    /// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
3844    /// When each `p_i` has been dealt with, the top set is merged with its parent.
3845    /// When a whole or-pattern has been dealt with, the thing happens.
3846    ///
3847    /// See the implementation and `fresh_binding` for more details.
3848    #[tracing::instrument(skip(self, bindings), level = "debug")]
3849    fn resolve_pattern_inner(
3850        &mut self,
3851        pat: &'ast Pat,
3852        pat_src: PatternSource,
3853        bindings: &mut PatternBindings,
3854    ) {
3855        // Visit all direct subpatterns of this pattern.
3856        pat.walk(&mut |pat| {
3857            match pat.kind {
3858                PatKind::Ident(bmode, ident, ref sub) => {
3859                    // First try to resolve the identifier as some existing entity,
3860                    // then fall back to a fresh binding.
3861                    let has_sub = sub.is_some();
3862                    let res = self
3863                        .try_resolve_as_non_binding(pat_src, bmode, ident, has_sub)
3864                        .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
3865                    self.r.record_partial_res(pat.id, PartialRes::new(res));
3866                    self.r.record_pat_span(pat.id, pat.span);
3867                }
3868                PatKind::TupleStruct(ref qself, ref path, ref sub_patterns) => {
3869                    self.smart_resolve_path(
3870                        pat.id,
3871                        qself,
3872                        path,
3873                        PathSource::TupleStruct(
3874                            pat.span,
3875                            self.r.arenas.alloc_pattern_spans(sub_patterns.iter().map(|p| p.span)),
3876                        ),
3877                    );
3878                }
3879                PatKind::Path(ref qself, ref path) => {
3880                    self.smart_resolve_path(pat.id, qself, path, PathSource::Pat);
3881                }
3882                PatKind::Struct(ref qself, ref path, ref _fields, ref rest) => {
3883                    self.smart_resolve_path(pat.id, qself, path, PathSource::Struct);
3884                    self.record_patterns_with_skipped_bindings(pat, rest);
3885                }
3886                PatKind::Or(ref ps) => {
3887                    // Add a new set of bindings to the stack. `Or` here records that when a
3888                    // binding already exists in this set, it should not result in an error because
3889                    // `V1(a) | V2(a)` must be allowed and are checked for consistency later.
3890                    bindings.push((PatBoundCtx::Or, Default::default()));
3891                    for p in ps {
3892                        // Now we need to switch back to a product context so that each
3893                        // part of the or-pattern internally rejects already bound names.
3894                        // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
3895                        bindings.push((PatBoundCtx::Product, Default::default()));
3896                        self.resolve_pattern_inner(p, pat_src, bindings);
3897                        // Move up the non-overlapping bindings to the or-pattern.
3898                        // Existing bindings just get "merged".
3899                        let collected = bindings.pop().unwrap().1;
3900                        bindings.last_mut().unwrap().1.extend(collected);
3901                    }
3902                    // This or-pattern itself can itself be part of a product,
3903                    // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
3904                    // Both cases bind `a` again in a product pattern and must be rejected.
3905                    let collected = bindings.pop().unwrap().1;
3906                    bindings.last_mut().unwrap().1.extend(collected);
3907
3908                    // Prevent visiting `ps` as we've already done so above.
3909                    return false;
3910                }
3911                PatKind::Guard(ref subpat, ref guard) => {
3912                    // Add a new set of bindings to the stack to collect bindings in `subpat`.
3913                    bindings.push((PatBoundCtx::Product, Default::default()));
3914                    // Resolving `subpat` adds bindings onto the newly-pushed context. After, the
3915                    // total number of contexts on the stack should be the same as before.
3916                    let binding_ctx_stack_len = bindings.len();
3917                    self.resolve_pattern_inner(subpat, pat_src, bindings);
3918                    assert_eq!(bindings.len(), binding_ctx_stack_len);
3919                    // These bindings, but none from the surrounding pattern, are visible in the
3920                    // guard; put them in scope and resolve `guard`.
3921                    let subpat_bindings = bindings.pop().unwrap().1;
3922                    self.with_rib(ValueNS, RibKind::Normal, |this| {
3923                        *this.innermost_rib_bindings(ValueNS) = subpat_bindings.clone();
3924                        this.resolve_expr(guard, None);
3925                    });
3926                    // Propagate the subpattern's bindings upwards.
3927                    // FIXME(guard_patterns): For `if let` guards, we'll also need to get the
3928                    // bindings introduced by the guard from its rib and propagate them upwards.
3929                    // This will require checking the identifiers for overlaps with `bindings`, like
3930                    // what `fresh_binding` does (ideally sharing its logic). To keep them separate
3931                    // from `subpat_bindings`, we can introduce a fresh rib for the guard.
3932                    bindings.last_mut().unwrap().1.extend(subpat_bindings);
3933                    // Prevent visiting `subpat` as we've already done so above.
3934                    return false;
3935                }
3936                _ => {}
3937            }
3938            true
3939        });
3940    }
3941
3942    fn record_patterns_with_skipped_bindings(&mut self, pat: &Pat, rest: &ast::PatFieldsRest) {
3943        match rest {
3944            ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) => {
3945                // Record that the pattern doesn't introduce all the bindings it could.
3946                if let Some(partial_res) = self.r.partial_res_map.get(&pat.id)
3947                    && let Some(res) = partial_res.full_res()
3948                    && let Some(def_id) = res.opt_def_id()
3949                {
3950                    self.ribs[ValueNS]
3951                        .last_mut()
3952                        .unwrap()
3953                        .patterns_with_skipped_bindings
3954                        .entry(def_id)
3955                        .or_default()
3956                        .push((
3957                            pat.span,
3958                            match rest {
3959                                ast::PatFieldsRest::Recovered(guar) => Err(*guar),
3960                                _ => Ok(()),
3961                            },
3962                        ));
3963                }
3964            }
3965            ast::PatFieldsRest::None => {}
3966        }
3967    }
3968
3969    fn fresh_binding(
3970        &mut self,
3971        ident: Ident,
3972        pat_id: NodeId,
3973        pat_src: PatternSource,
3974        bindings: &mut PatternBindings,
3975    ) -> Res {
3976        // Add the binding to the bindings map, if it doesn't already exist.
3977        // (We must not add it if it's in the bindings map because that breaks the assumptions
3978        // later passes make about or-patterns.)
3979        let ident = ident.normalize_to_macro_rules();
3980
3981        // Already bound in a product pattern? e.g. `(a, a)` which is not allowed.
3982        let already_bound_and = bindings
3983            .iter()
3984            .any(|(ctx, map)| *ctx == PatBoundCtx::Product && map.contains_key(&ident));
3985        if already_bound_and {
3986            // Overlap in a product pattern somewhere; report an error.
3987            use ResolutionError::*;
3988            let error = match pat_src {
3989                // `fn f(a: u8, a: u8)`:
3990                PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
3991                // `Variant(a, a)`:
3992                _ => IdentifierBoundMoreThanOnceInSamePattern,
3993            };
3994            self.report_error(ident.span, error(ident));
3995        }
3996
3997        // Already bound in an or-pattern? e.g. `V1(a) | V2(a)`.
3998        // This is *required* for consistency which is checked later.
3999        let already_bound_or = bindings
4000            .iter()
4001            .find_map(|(ctx, map)| if *ctx == PatBoundCtx::Or { map.get(&ident) } else { None });
4002        let res = if let Some(&res) = already_bound_or {
4003            // `Variant1(a) | Variant2(a)`, ok
4004            // Reuse definition from the first `a`.
4005            res
4006        } else {
4007            // A completely fresh binding is added to the map.
4008            Res::Local(pat_id)
4009        };
4010
4011        // Record as bound.
4012        bindings.last_mut().unwrap().1.insert(ident, res);
4013        res
4014    }
4015
4016    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut FxIndexMap<Ident, Res> {
4017        &mut self.ribs[ns].last_mut().unwrap().bindings
4018    }
4019
4020    fn try_resolve_as_non_binding(
4021        &mut self,
4022        pat_src: PatternSource,
4023        ann: BindingMode,
4024        ident: Ident,
4025        has_sub: bool,
4026    ) -> Option<Res> {
4027        // An immutable (no `mut`) by-value (no `ref`) binding pattern without
4028        // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
4029        // also be interpreted as a path to e.g. a constant, variant, etc.
4030        let is_syntactic_ambiguity = !has_sub && ann == BindingMode::NONE;
4031
4032        let ls_binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS)?;
4033        let (res, binding) = match ls_binding {
4034            LexicalScopeBinding::Item(binding)
4035                if is_syntactic_ambiguity && binding.is_ambiguity_recursive() =>
4036            {
4037                // For ambiguous bindings we don't know all their definitions and cannot check
4038                // whether they can be shadowed by fresh bindings or not, so force an error.
4039                // issues/33118#issuecomment-233962221 (see below) still applies here,
4040                // but we have to ignore it for backward compatibility.
4041                self.r.record_use(ident, binding, Used::Other);
4042                return None;
4043            }
4044            LexicalScopeBinding::Item(binding) => (binding.res(), Some(binding)),
4045            LexicalScopeBinding::Res(res) => (res, None),
4046        };
4047
4048        match res {
4049            Res::SelfCtor(_) // See #70549.
4050            | Res::Def(
4051                DefKind::Ctor(_, CtorKind::Const) | DefKind::Const | DefKind::AssocConst | DefKind::ConstParam,
4052                _,
4053            ) if is_syntactic_ambiguity => {
4054                // Disambiguate in favor of a unit struct/variant or constant pattern.
4055                if let Some(binding) = binding {
4056                    self.r.record_use(ident, binding, Used::Other);
4057                }
4058                Some(res)
4059            }
4060            Res::Def(DefKind::Ctor(..) | DefKind::Const | DefKind::AssocConst | DefKind::Static { .. }, _) => {
4061                // This is unambiguously a fresh binding, either syntactically
4062                // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
4063                // to something unusable as a pattern (e.g., constructor function),
4064                // but we still conservatively report an error, see
4065                // issues/33118#issuecomment-233962221 for one reason why.
4066                let binding = binding.expect("no binding for a ctor or static");
4067                self.report_error(
4068                    ident.span,
4069                    ResolutionError::BindingShadowsSomethingUnacceptable {
4070                        shadowing_binding: pat_src,
4071                        name: ident.name,
4072                        participle: if binding.is_import() { "imported" } else { "defined" },
4073                        article: binding.res().article(),
4074                        shadowed_binding: binding.res(),
4075                        shadowed_binding_span: binding.span,
4076                    },
4077                );
4078                None
4079            }
4080            Res::Def(DefKind::ConstParam, def_id) => {
4081                // Same as for DefKind::Const above, but here, `binding` is `None`, so we
4082                // have to construct the error differently
4083                self.report_error(
4084                    ident.span,
4085                    ResolutionError::BindingShadowsSomethingUnacceptable {
4086                        shadowing_binding: pat_src,
4087                        name: ident.name,
4088                        participle: "defined",
4089                        article: res.article(),
4090                        shadowed_binding: res,
4091                        shadowed_binding_span: self.r.def_span(def_id),
4092                    }
4093                );
4094                None
4095            }
4096            Res::Def(DefKind::Fn | DefKind::AssocFn, _) | Res::Local(..) | Res::Err => {
4097                // These entities are explicitly allowed to be shadowed by fresh bindings.
4098                None
4099            }
4100            Res::SelfCtor(_) => {
4101                // We resolve `Self` in pattern position as an ident sometimes during recovery,
4102                // so delay a bug instead of ICEing.
4103                self.r.dcx().span_delayed_bug(
4104                    ident.span,
4105                    "unexpected `SelfCtor` in pattern, expected identifier"
4106                );
4107                None
4108            }
4109            _ => span_bug!(
4110                ident.span,
4111                "unexpected resolution for an identifier in pattern: {:?}",
4112                res,
4113            ),
4114        }
4115    }
4116
4117    // High-level and context dependent path resolution routine.
4118    // Resolves the path and records the resolution into definition map.
4119    // If resolution fails tries several techniques to find likely
4120    // resolution candidates, suggest imports or other help, and report
4121    // errors in user friendly way.
4122    fn smart_resolve_path(
4123        &mut self,
4124        id: NodeId,
4125        qself: &Option<P<QSelf>>,
4126        path: &Path,
4127        source: PathSource<'_, 'ast, '_>,
4128    ) {
4129        self.smart_resolve_path_fragment(
4130            qself,
4131            &Segment::from_path(path),
4132            source,
4133            Finalize::new(id, path.span),
4134            RecordPartialRes::Yes,
4135            None,
4136        );
4137    }
4138
4139    #[instrument(level = "debug", skip(self))]
4140    fn smart_resolve_path_fragment(
4141        &mut self,
4142        qself: &Option<P<QSelf>>,
4143        path: &[Segment],
4144        source: PathSource<'_, 'ast, '_>,
4145        finalize: Finalize,
4146        record_partial_res: RecordPartialRes,
4147        parent_qself: Option<&QSelf>,
4148    ) -> PartialRes {
4149        let ns = source.namespace();
4150
4151        let Finalize { node_id, path_span, .. } = finalize;
4152        let report_errors = |this: &mut Self, res: Option<Res>| {
4153            if this.should_report_errs() {
4154                let (err, candidates) = this.smart_resolve_report_errors(
4155                    path,
4156                    None,
4157                    path_span,
4158                    source,
4159                    res,
4160                    parent_qself,
4161                );
4162
4163                let def_id = this.parent_scope.module.nearest_parent_mod();
4164                let instead = res.is_some();
4165                let suggestion = if let Some((start, end)) = this.diag_metadata.in_range
4166                    && path[0].ident.span.lo() == end.span.lo()
4167                    && !matches!(start.kind, ExprKind::Lit(_))
4168                {
4169                    let mut sugg = ".";
4170                    let mut span = start.span.between(end.span);
4171                    if span.lo() + BytePos(2) == span.hi() {
4172                        // There's no space between the start, the range op and the end, suggest
4173                        // removal which will look better.
4174                        span = span.with_lo(span.lo() + BytePos(1));
4175                        sugg = "";
4176                    }
4177                    Some((
4178                        span,
4179                        "you might have meant to write `.` instead of `..`",
4180                        sugg.to_string(),
4181                        Applicability::MaybeIncorrect,
4182                    ))
4183                } else if res.is_none()
4184                    && let PathSource::Type
4185                    | PathSource::Expr(_)
4186                    | PathSource::PreciseCapturingArg(..) = source
4187                {
4188                    this.suggest_adding_generic_parameter(path, source)
4189                } else {
4190                    None
4191                };
4192
4193                let ue = UseError {
4194                    err,
4195                    candidates,
4196                    def_id,
4197                    instead,
4198                    suggestion,
4199                    path: path.into(),
4200                    is_call: source.is_call(),
4201                };
4202
4203                this.r.use_injections.push(ue);
4204            }
4205
4206            PartialRes::new(Res::Err)
4207        };
4208
4209        // For paths originating from calls (like in `HashMap::new()`), tries
4210        // to enrich the plain `failed to resolve: ...` message with hints
4211        // about possible missing imports.
4212        //
4213        // Similar thing, for types, happens in `report_errors` above.
4214        let report_errors_for_call =
4215            |this: &mut Self, parent_err: Spanned<ResolutionError<'ra>>| {
4216                // Before we start looking for candidates, we have to get our hands
4217                // on the type user is trying to perform invocation on; basically:
4218                // we're transforming `HashMap::new` into just `HashMap`.
4219                let (following_seg, prefix_path) = match path.split_last() {
4220                    Some((last, path)) if !path.is_empty() => (Some(last), path),
4221                    _ => return Some(parent_err),
4222                };
4223
4224                let (mut err, candidates) = this.smart_resolve_report_errors(
4225                    prefix_path,
4226                    following_seg,
4227                    path_span,
4228                    PathSource::Type,
4229                    None,
4230                    parent_qself,
4231                );
4232
4233                // There are two different error messages user might receive at
4234                // this point:
4235                // - E0412 cannot find type `{}` in this scope
4236                // - E0433 failed to resolve: use of undeclared type or module `{}`
4237                //
4238                // The first one is emitted for paths in type-position, and the
4239                // latter one - for paths in expression-position.
4240                //
4241                // Thus (since we're in expression-position at this point), not to
4242                // confuse the user, we want to keep the *message* from E0433 (so
4243                // `parent_err`), but we want *hints* from E0412 (so `err`).
4244                //
4245                // And that's what happens below - we're just mixing both messages
4246                // into a single one.
4247                let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
4248
4249                // overwrite all properties with the parent's error message
4250                err.messages = take(&mut parent_err.messages);
4251                err.code = take(&mut parent_err.code);
4252                swap(&mut err.span, &mut parent_err.span);
4253                err.children = take(&mut parent_err.children);
4254                err.sort_span = parent_err.sort_span;
4255                err.is_lint = parent_err.is_lint.clone();
4256
4257                // merge the parent_err's suggestions with the typo (err's) suggestions
4258                match &mut err.suggestions {
4259                    Suggestions::Enabled(typo_suggestions) => match &mut parent_err.suggestions {
4260                        Suggestions::Enabled(parent_suggestions) => {
4261                            // If both suggestions are enabled, append parent_err's suggestions to err's suggestions.
4262                            typo_suggestions.append(parent_suggestions)
4263                        }
4264                        Suggestions::Sealed(_) | Suggestions::Disabled => {
4265                            // If the parent's suggestions are either sealed or disabled, it signifies that
4266                            // new suggestions cannot be added or removed from the diagnostic. Therefore,
4267                            // we assign both types of suggestions to err's suggestions and discard the
4268                            // existing suggestions in err.
4269                            err.suggestions = std::mem::take(&mut parent_err.suggestions);
4270                        }
4271                    },
4272                    Suggestions::Sealed(_) | Suggestions::Disabled => (),
4273                }
4274
4275                parent_err.cancel();
4276
4277                let def_id = this.parent_scope.module.nearest_parent_mod();
4278
4279                if this.should_report_errs() {
4280                    if candidates.is_empty() {
4281                        if path.len() == 2
4282                            && let [segment] = prefix_path
4283                        {
4284                            // Delay to check whether methond name is an associated function or not
4285                            // ```
4286                            // let foo = Foo {};
4287                            // foo::bar(); // possibly suggest to foo.bar();
4288                            //```
4289                            err.stash(segment.ident.span, rustc_errors::StashKey::CallAssocMethod);
4290                        } else {
4291                            // When there is no suggested imports, we can just emit the error
4292                            // and suggestions immediately. Note that we bypass the usually error
4293                            // reporting routine (ie via `self.r.report_error`) because we need
4294                            // to post-process the `ResolutionError` above.
4295                            err.emit();
4296                        }
4297                    } else {
4298                        // If there are suggested imports, the error reporting is delayed
4299                        this.r.use_injections.push(UseError {
4300                            err,
4301                            candidates,
4302                            def_id,
4303                            instead: false,
4304                            suggestion: None,
4305                            path: prefix_path.into(),
4306                            is_call: source.is_call(),
4307                        });
4308                    }
4309                } else {
4310                    err.cancel();
4311                }
4312
4313                // We don't return `Some(parent_err)` here, because the error will
4314                // be already printed either immediately or as part of the `use` injections
4315                None
4316            };
4317
4318        let partial_res = match self.resolve_qpath_anywhere(
4319            qself,
4320            path,
4321            ns,
4322            path_span,
4323            source.defer_to_typeck(),
4324            finalize,
4325            source,
4326        ) {
4327            Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
4328                // if we also have an associated type that matches the ident, stash a suggestion
4329                if let Some(items) = self.diag_metadata.current_trait_assoc_items
4330                    && let [Segment { ident, .. }] = path
4331                    && items.iter().any(|item| {
4332                        if let AssocItemKind::Type(alias) = &item.kind
4333                            && alias.ident == *ident
4334                        {
4335                            true
4336                        } else {
4337                            false
4338                        }
4339                    })
4340                {
4341                    let mut diag = self.r.tcx.dcx().struct_allow("");
4342                    diag.span_suggestion_verbose(
4343                        path_span.shrink_to_lo(),
4344                        "there is an associated type with the same name",
4345                        "Self::",
4346                        Applicability::MaybeIncorrect,
4347                    );
4348                    diag.stash(path_span, StashKey::AssociatedTypeSuggestion);
4349                }
4350
4351                if source.is_expected(res) || res == Res::Err {
4352                    partial_res
4353                } else {
4354                    report_errors(self, Some(res))
4355                }
4356            }
4357
4358            Ok(Some(partial_res)) if source.defer_to_typeck() => {
4359                // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
4360                // or `<T>::A::B`. If `B` should be resolved in value namespace then
4361                // it needs to be added to the trait map.
4362                if ns == ValueNS {
4363                    let item_name = path.last().unwrap().ident;
4364                    let traits = self.traits_in_scope(item_name, ns);
4365                    self.r.trait_map.insert(node_id, traits);
4366                }
4367
4368                if PrimTy::from_name(path[0].ident.name).is_some() {
4369                    let mut std_path = Vec::with_capacity(1 + path.len());
4370
4371                    std_path.push(Segment::from_ident(Ident::with_dummy_span(sym::std)));
4372                    std_path.extend(path);
4373                    if let PathResult::Module(_) | PathResult::NonModule(_) =
4374                        self.resolve_path(&std_path, Some(ns), None)
4375                    {
4376                        // Check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
4377                        let item_span =
4378                            path.iter().last().map_or(path_span, |segment| segment.ident.span);
4379
4380                        self.r.confused_type_with_std_module.insert(item_span, path_span);
4381                        self.r.confused_type_with_std_module.insert(path_span, path_span);
4382                    }
4383                }
4384
4385                partial_res
4386            }
4387
4388            Err(err) => {
4389                if let Some(err) = report_errors_for_call(self, err) {
4390                    self.report_error(err.span, err.node);
4391                }
4392
4393                PartialRes::new(Res::Err)
4394            }
4395
4396            _ => report_errors(self, None),
4397        };
4398
4399        if record_partial_res == RecordPartialRes::Yes {
4400            // Avoid recording definition of `A::B` in `<T as A>::B::C`.
4401            self.r.record_partial_res(node_id, partial_res);
4402            self.resolve_elided_lifetimes_in_path(partial_res, path, source, path_span);
4403            self.lint_unused_qualifications(path, ns, finalize);
4404        }
4405
4406        partial_res
4407    }
4408
4409    fn self_type_is_available(&mut self) -> bool {
4410        let binding = self
4411            .maybe_resolve_ident_in_lexical_scope(Ident::with_dummy_span(kw::SelfUpper), TypeNS);
4412        if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
4413    }
4414
4415    fn self_value_is_available(&mut self, self_span: Span) -> bool {
4416        let ident = Ident::new(kw::SelfLower, self_span);
4417        let binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS);
4418        if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
4419    }
4420
4421    /// A wrapper around [`Resolver::report_error`].
4422    ///
4423    /// This doesn't emit errors for function bodies if this is rustdoc.
4424    fn report_error(&mut self, span: Span, resolution_error: ResolutionError<'ra>) {
4425        if self.should_report_errs() {
4426            self.r.report_error(span, resolution_error);
4427        }
4428    }
4429
4430    #[inline]
4431    /// If we're actually rustdoc then avoid giving a name resolution error for `cfg()` items or
4432    // an invalid `use foo::*;` was found, which can cause unbounded amounts of "item not found"
4433    // errors. We silence them all.
4434    fn should_report_errs(&self) -> bool {
4435        !(self.r.tcx.sess.opts.actually_rustdoc && self.in_func_body)
4436            && !self.r.glob_error.is_some()
4437    }
4438
4439    // Resolve in alternative namespaces if resolution in the primary namespace fails.
4440    fn resolve_qpath_anywhere(
4441        &mut self,
4442        qself: &Option<P<QSelf>>,
4443        path: &[Segment],
4444        primary_ns: Namespace,
4445        span: Span,
4446        defer_to_typeck: bool,
4447        finalize: Finalize,
4448        source: PathSource<'_, 'ast, '_>,
4449    ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'ra>>> {
4450        let mut fin_res = None;
4451
4452        for (i, &ns) in [primary_ns, TypeNS, ValueNS].iter().enumerate() {
4453            if i == 0 || ns != primary_ns {
4454                match self.resolve_qpath(qself, path, ns, finalize, source)? {
4455                    Some(partial_res)
4456                        if partial_res.unresolved_segments() == 0 || defer_to_typeck =>
4457                    {
4458                        return Ok(Some(partial_res));
4459                    }
4460                    partial_res => {
4461                        if fin_res.is_none() {
4462                            fin_res = partial_res;
4463                        }
4464                    }
4465                }
4466            }
4467        }
4468
4469        assert!(primary_ns != MacroNS);
4470
4471        if qself.is_none() {
4472            let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
4473            let path = Path { segments: path.iter().map(path_seg).collect(), span, tokens: None };
4474            if let Ok((_, res)) =
4475                self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false, None, None)
4476            {
4477                return Ok(Some(PartialRes::new(res)));
4478            }
4479        }
4480
4481        Ok(fin_res)
4482    }
4483
4484    /// Handles paths that may refer to associated items.
4485    fn resolve_qpath(
4486        &mut self,
4487        qself: &Option<P<QSelf>>,
4488        path: &[Segment],
4489        ns: Namespace,
4490        finalize: Finalize,
4491        source: PathSource<'_, 'ast, '_>,
4492    ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'ra>>> {
4493        debug!(
4494            "resolve_qpath(qself={:?}, path={:?}, ns={:?}, finalize={:?})",
4495            qself, path, ns, finalize,
4496        );
4497
4498        if let Some(qself) = qself {
4499            if qself.position == 0 {
4500                // This is a case like `<T>::B`, where there is no
4501                // trait to resolve. In that case, we leave the `B`
4502                // segment to be resolved by type-check.
4503                return Ok(Some(PartialRes::with_unresolved_segments(
4504                    Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id()),
4505                    path.len(),
4506                )));
4507            }
4508
4509            let num_privacy_errors = self.r.privacy_errors.len();
4510            // Make sure that `A` in `<T as A>::B::C` is a trait.
4511            let trait_res = self.smart_resolve_path_fragment(
4512                &None,
4513                &path[..qself.position],
4514                PathSource::Trait(AliasPossibility::No),
4515                Finalize::new(finalize.node_id, qself.path_span),
4516                RecordPartialRes::No,
4517                Some(&qself),
4518            );
4519
4520            if trait_res.expect_full_res() == Res::Err {
4521                return Ok(Some(trait_res));
4522            }
4523
4524            // Truncate additional privacy errors reported above,
4525            // because they'll be recomputed below.
4526            self.r.privacy_errors.truncate(num_privacy_errors);
4527
4528            // Make sure `A::B` in `<T as A>::B::C` is a trait item.
4529            //
4530            // Currently, `path` names the full item (`A::B::C`, in
4531            // our example). so we extract the prefix of that that is
4532            // the trait (the slice upto and including
4533            // `qself.position`). And then we recursively resolve that,
4534            // but with `qself` set to `None`.
4535            let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
4536            let partial_res = self.smart_resolve_path_fragment(
4537                &None,
4538                &path[..=qself.position],
4539                PathSource::TraitItem(ns, &source),
4540                Finalize::with_root_span(finalize.node_id, finalize.path_span, qself.path_span),
4541                RecordPartialRes::No,
4542                Some(&qself),
4543            );
4544
4545            // The remaining segments (the `C` in our example) will
4546            // have to be resolved by type-check, since that requires doing
4547            // trait resolution.
4548            return Ok(Some(PartialRes::with_unresolved_segments(
4549                partial_res.base_res(),
4550                partial_res.unresolved_segments() + path.len() - qself.position - 1,
4551            )));
4552        }
4553
4554        let result = match self.resolve_path(path, Some(ns), Some(finalize)) {
4555            PathResult::NonModule(path_res) => path_res,
4556            PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => {
4557                PartialRes::new(module.res().unwrap())
4558            }
4559            // A part of this path references a `mod` that had a parse error. To avoid resolution
4560            // errors for each reference to that module, we don't emit an error for them until the
4561            // `mod` is fixed. this can have a significant cascade effect.
4562            PathResult::Failed { error_implied_by_parse_error: true, .. } => {
4563                PartialRes::new(Res::Err)
4564            }
4565            // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
4566            // don't report an error right away, but try to fallback to a primitive type.
4567            // So, we are still able to successfully resolve something like
4568            //
4569            // use std::u8; // bring module u8 in scope
4570            // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
4571            //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
4572            //                     // not to nonexistent std::u8::max_value
4573            // }
4574            //
4575            // Such behavior is required for backward compatibility.
4576            // The same fallback is used when `a` resolves to nothing.
4577            PathResult::Module(ModuleOrUniformRoot::Module(_)) | PathResult::Failed { .. }
4578                if (ns == TypeNS || path.len() > 1)
4579                    && PrimTy::from_name(path[0].ident.name).is_some() =>
4580            {
4581                let prim = PrimTy::from_name(path[0].ident.name).unwrap();
4582                let tcx = self.r.tcx();
4583
4584                let gate_err_sym_msg = match prim {
4585                    PrimTy::Float(FloatTy::F16) if !tcx.features().f16() => {
4586                        Some((sym::f16, "the type `f16` is unstable"))
4587                    }
4588                    PrimTy::Float(FloatTy::F128) if !tcx.features().f128() => {
4589                        Some((sym::f128, "the type `f128` is unstable"))
4590                    }
4591                    _ => None,
4592                };
4593
4594                if let Some((sym, msg)) = gate_err_sym_msg {
4595                    let span = path[0].ident.span;
4596                    if !span.allows_unstable(sym) {
4597                        feature_err(tcx.sess, sym, span, msg).emit();
4598                    }
4599                };
4600
4601                // Fix up partial res of segment from `resolve_path` call.
4602                if let Some(id) = path[0].id {
4603                    self.r.partial_res_map.insert(id, PartialRes::new(Res::PrimTy(prim)));
4604                }
4605
4606                PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
4607            }
4608            PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
4609                PartialRes::new(module.res().unwrap())
4610            }
4611            PathResult::Failed {
4612                is_error_from_last_segment: false,
4613                span,
4614                label,
4615                suggestion,
4616                module,
4617                segment_name,
4618                error_implied_by_parse_error: _,
4619            } => {
4620                return Err(respan(
4621                    span,
4622                    ResolutionError::FailedToResolve {
4623                        segment: Some(segment_name),
4624                        label,
4625                        suggestion,
4626                        module,
4627                    },
4628                ));
4629            }
4630            PathResult::Module(..) | PathResult::Failed { .. } => return Ok(None),
4631            PathResult::Indeterminate => bug!("indeterminate path result in resolve_qpath"),
4632        };
4633
4634        Ok(Some(result))
4635    }
4636
4637    fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
4638        if let Some(label) = label {
4639            if label.ident.as_str().as_bytes()[1] != b'_' {
4640                self.diag_metadata.unused_labels.insert(id, label.ident.span);
4641            }
4642
4643            if let Ok((_, orig_span)) = self.resolve_label(label.ident) {
4644                diagnostics::signal_label_shadowing(self.r.tcx.sess, orig_span, label.ident)
4645            }
4646
4647            self.with_label_rib(RibKind::Normal, |this| {
4648                let ident = label.ident.normalize_to_macro_rules();
4649                this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
4650                f(this);
4651            });
4652        } else {
4653            f(self);
4654        }
4655    }
4656
4657    fn resolve_labeled_block(&mut self, label: Option<Label>, id: NodeId, block: &'ast Block) {
4658        self.with_resolved_label(label, id, |this| this.visit_block(block));
4659    }
4660
4661    fn resolve_block(&mut self, block: &'ast Block) {
4662        debug!("(resolving block) entering block");
4663        // Move down in the graph, if there's an anonymous module rooted here.
4664        let orig_module = self.parent_scope.module;
4665        let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
4666
4667        let mut num_macro_definition_ribs = 0;
4668        if let Some(anonymous_module) = anonymous_module {
4669            debug!("(resolving block) found anonymous module, moving down");
4670            self.ribs[ValueNS].push(Rib::new(RibKind::Module(anonymous_module)));
4671            self.ribs[TypeNS].push(Rib::new(RibKind::Module(anonymous_module)));
4672            self.parent_scope.module = anonymous_module;
4673        } else {
4674            self.ribs[ValueNS].push(Rib::new(RibKind::Normal));
4675        }
4676
4677        // Descend into the block.
4678        for stmt in &block.stmts {
4679            if let StmtKind::Item(ref item) = stmt.kind
4680                && let ItemKind::MacroDef(..) = item.kind
4681            {
4682                num_macro_definition_ribs += 1;
4683                let res = self.r.local_def_id(item.id).to_def_id();
4684                self.ribs[ValueNS].push(Rib::new(RibKind::MacroDefinition(res)));
4685                self.label_ribs.push(Rib::new(RibKind::MacroDefinition(res)));
4686            }
4687
4688            self.visit_stmt(stmt);
4689        }
4690
4691        // Move back up.
4692        self.parent_scope.module = orig_module;
4693        for _ in 0..num_macro_definition_ribs {
4694            self.ribs[ValueNS].pop();
4695            self.label_ribs.pop();
4696        }
4697        self.last_block_rib = self.ribs[ValueNS].pop();
4698        if anonymous_module.is_some() {
4699            self.ribs[TypeNS].pop();
4700        }
4701        debug!("(resolving block) leaving block");
4702    }
4703
4704    fn resolve_anon_const(&mut self, constant: &'ast AnonConst, anon_const_kind: AnonConstKind) {
4705        debug!(
4706            "resolve_anon_const(constant: {:?}, anon_const_kind: {:?})",
4707            constant, anon_const_kind
4708        );
4709
4710        let is_trivial_const_arg = constant
4711            .value
4712            .is_potential_trivial_const_arg(self.r.tcx.features().min_generic_const_args());
4713        self.resolve_anon_const_manual(is_trivial_const_arg, anon_const_kind, |this| {
4714            this.resolve_expr(&constant.value, None)
4715        })
4716    }
4717
4718    /// There are a few places that we need to resolve an anon const but we did not parse an
4719    /// anon const so cannot provide an `&'ast AnonConst`. Right now this is just unbraced
4720    /// const arguments that were parsed as type arguments, and `legacy_const_generics` which
4721    /// parse as normal function argument expressions. To avoid duplicating the code for resolving
4722    /// an anon const we have this function which lets the caller manually call `resolve_expr` or
4723    /// `smart_resolve_path`.
4724    fn resolve_anon_const_manual(
4725        &mut self,
4726        is_trivial_const_arg: bool,
4727        anon_const_kind: AnonConstKind,
4728        resolve_expr: impl FnOnce(&mut Self),
4729    ) {
4730        let is_repeat_expr = match anon_const_kind {
4731            AnonConstKind::ConstArg(is_repeat_expr) => is_repeat_expr,
4732            _ => IsRepeatExpr::No,
4733        };
4734
4735        let may_use_generics = match anon_const_kind {
4736            AnonConstKind::EnumDiscriminant => {
4737                ConstantHasGenerics::No(NoConstantGenericsReason::IsEnumDiscriminant)
4738            }
4739            AnonConstKind::FieldDefaultValue => ConstantHasGenerics::Yes,
4740            AnonConstKind::InlineConst => ConstantHasGenerics::Yes,
4741            AnonConstKind::ConstArg(_) => {
4742                if self.r.tcx.features().generic_const_exprs() || is_trivial_const_arg {
4743                    ConstantHasGenerics::Yes
4744                } else {
4745                    ConstantHasGenerics::No(NoConstantGenericsReason::NonTrivialConstArg)
4746                }
4747            }
4748        };
4749
4750        self.with_constant_rib(is_repeat_expr, may_use_generics, None, |this| {
4751            this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
4752                resolve_expr(this);
4753            });
4754        });
4755    }
4756
4757    fn resolve_expr_field(&mut self, f: &'ast ExprField, e: &'ast Expr) {
4758        self.resolve_expr(&f.expr, Some(e));
4759        self.visit_ident(&f.ident);
4760        walk_list!(self, visit_attribute, f.attrs.iter());
4761    }
4762
4763    fn resolve_expr(&mut self, expr: &'ast Expr, parent: Option<&'ast Expr>) {
4764        // First, record candidate traits for this expression if it could
4765        // result in the invocation of a method call.
4766
4767        self.record_candidate_traits_for_expr_if_necessary(expr);
4768
4769        // Next, resolve the node.
4770        match expr.kind {
4771            ExprKind::Path(ref qself, ref path) => {
4772                self.smart_resolve_path(expr.id, qself, path, PathSource::Expr(parent));
4773                visit::walk_expr(self, expr);
4774            }
4775
4776            ExprKind::Struct(ref se) => {
4777                self.smart_resolve_path(expr.id, &se.qself, &se.path, PathSource::Struct);
4778                // This is the same as `visit::walk_expr(self, expr);`, but we want to pass the
4779                // parent in for accurate suggestions when encountering `Foo { bar }` that should
4780                // have been `Foo { bar: self.bar }`.
4781                if let Some(qself) = &se.qself {
4782                    self.visit_ty(&qself.ty);
4783                }
4784                self.visit_path(&se.path);
4785                walk_list!(self, resolve_expr_field, &se.fields, expr);
4786                match &se.rest {
4787                    StructRest::Base(expr) => self.visit_expr(expr),
4788                    StructRest::Rest(_span) => {}
4789                    StructRest::None => {}
4790                }
4791            }
4792
4793            ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
4794                match self.resolve_label(label.ident) {
4795                    Ok((node_id, _)) => {
4796                        // Since this res is a label, it is never read.
4797                        self.r.label_res_map.insert(expr.id, node_id);
4798                        self.diag_metadata.unused_labels.swap_remove(&node_id);
4799                    }
4800                    Err(error) => {
4801                        self.report_error(label.ident.span, error);
4802                    }
4803                }
4804
4805                // visit `break` argument if any
4806                visit::walk_expr(self, expr);
4807            }
4808
4809            ExprKind::Break(None, Some(ref e)) => {
4810                // We use this instead of `visit::walk_expr` to keep the parent expr around for
4811                // better diagnostics.
4812                self.resolve_expr(e, Some(expr));
4813            }
4814
4815            ExprKind::Let(ref pat, ref scrutinee, _, Recovered::No) => {
4816                self.visit_expr(scrutinee);
4817                self.resolve_pattern_top(pat, PatternSource::Let);
4818            }
4819
4820            ExprKind::Let(ref pat, ref scrutinee, _, Recovered::Yes(_)) => {
4821                self.visit_expr(scrutinee);
4822                // This is basically a tweaked, inlined `resolve_pattern_top`.
4823                let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
4824                self.resolve_pattern(pat, PatternSource::Let, &mut bindings);
4825                // We still collect the bindings in this `let` expression which is in
4826                // an invalid position (and therefore shouldn't declare variables into
4827                // its parent scope). To avoid unnecessary errors though, we do just
4828                // reassign the resolutions to `Res::Err`.
4829                for (_, bindings) in &mut bindings {
4830                    for (_, binding) in bindings {
4831                        *binding = Res::Err;
4832                    }
4833                }
4834                self.apply_pattern_bindings(bindings);
4835            }
4836
4837            ExprKind::If(ref cond, ref then, ref opt_else) => {
4838                self.with_rib(ValueNS, RibKind::Normal, |this| {
4839                    let old = this.diag_metadata.in_if_condition.replace(cond);
4840                    this.visit_expr(cond);
4841                    this.diag_metadata.in_if_condition = old;
4842                    this.visit_block(then);
4843                });
4844                if let Some(expr) = opt_else {
4845                    self.visit_expr(expr);
4846                }
4847            }
4848
4849            ExprKind::Loop(ref block, label, _) => {
4850                self.resolve_labeled_block(label, expr.id, block)
4851            }
4852
4853            ExprKind::While(ref cond, ref block, label) => {
4854                self.with_resolved_label(label, expr.id, |this| {
4855                    this.with_rib(ValueNS, RibKind::Normal, |this| {
4856                        let old = this.diag_metadata.in_if_condition.replace(cond);
4857                        this.visit_expr(cond);
4858                        this.diag_metadata.in_if_condition = old;
4859                        this.visit_block(block);
4860                    })
4861                });
4862            }
4863
4864            ExprKind::ForLoop { ref pat, ref iter, ref body, label, kind: _ } => {
4865                self.visit_expr(iter);
4866                self.with_rib(ValueNS, RibKind::Normal, |this| {
4867                    this.resolve_pattern_top(pat, PatternSource::For);
4868                    this.resolve_labeled_block(label, expr.id, body);
4869                });
4870            }
4871
4872            ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
4873
4874            // Equivalent to `visit::walk_expr` + passing some context to children.
4875            ExprKind::Field(ref subexpression, _) => {
4876                self.resolve_expr(subexpression, Some(expr));
4877            }
4878            ExprKind::MethodCall(box MethodCall { ref seg, ref receiver, ref args, .. }) => {
4879                self.resolve_expr(receiver, Some(expr));
4880                for arg in args {
4881                    self.resolve_expr(arg, None);
4882                }
4883                self.visit_path_segment(seg);
4884            }
4885
4886            ExprKind::Call(ref callee, ref arguments) => {
4887                self.resolve_expr(callee, Some(expr));
4888                let const_args = self.r.legacy_const_generic_args(callee).unwrap_or_default();
4889                for (idx, argument) in arguments.iter().enumerate() {
4890                    // Constant arguments need to be treated as AnonConst since
4891                    // that is how they will be later lowered to HIR.
4892                    if const_args.contains(&idx) {
4893                        let is_trivial_const_arg = argument.is_potential_trivial_const_arg(
4894                            self.r.tcx.features().min_generic_const_args(),
4895                        );
4896                        self.resolve_anon_const_manual(
4897                            is_trivial_const_arg,
4898                            AnonConstKind::ConstArg(IsRepeatExpr::No),
4899                            |this| this.resolve_expr(argument, None),
4900                        );
4901                    } else {
4902                        self.resolve_expr(argument, None);
4903                    }
4904                }
4905            }
4906            ExprKind::Type(ref _type_expr, ref _ty) => {
4907                visit::walk_expr(self, expr);
4908            }
4909            // For closures, RibKind::FnOrCoroutine is added in visit_fn
4910            ExprKind::Closure(box ast::Closure {
4911                binder: ClosureBinder::For { ref generic_params, span },
4912                ..
4913            }) => {
4914                self.with_generic_param_rib(
4915                    generic_params,
4916                    RibKind::Normal,
4917                    expr.id,
4918                    LifetimeBinderKind::Closure,
4919                    span,
4920                    |this| visit::walk_expr(this, expr),
4921                );
4922            }
4923            ExprKind::Closure(..) => visit::walk_expr(self, expr),
4924            ExprKind::Gen(..) => {
4925                self.with_label_rib(RibKind::FnOrCoroutine, |this| visit::walk_expr(this, expr));
4926            }
4927            ExprKind::Repeat(ref elem, ref ct) => {
4928                self.visit_expr(elem);
4929                self.resolve_anon_const(ct, AnonConstKind::ConstArg(IsRepeatExpr::Yes));
4930            }
4931            ExprKind::ConstBlock(ref ct) => {
4932                self.resolve_anon_const(ct, AnonConstKind::InlineConst);
4933            }
4934            ExprKind::Index(ref elem, ref idx, _) => {
4935                self.resolve_expr(elem, Some(expr));
4936                self.visit_expr(idx);
4937            }
4938            ExprKind::Assign(ref lhs, ref rhs, _) => {
4939                if !self.diag_metadata.is_assign_rhs {
4940                    self.diag_metadata.in_assignment = Some(expr);
4941                }
4942                self.visit_expr(lhs);
4943                self.diag_metadata.is_assign_rhs = true;
4944                self.diag_metadata.in_assignment = None;
4945                self.visit_expr(rhs);
4946                self.diag_metadata.is_assign_rhs = false;
4947            }
4948            ExprKind::Range(Some(ref start), Some(ref end), RangeLimits::HalfOpen) => {
4949                self.diag_metadata.in_range = Some((start, end));
4950                self.resolve_expr(start, Some(expr));
4951                self.resolve_expr(end, Some(expr));
4952                self.diag_metadata.in_range = None;
4953            }
4954            _ => {
4955                visit::walk_expr(self, expr);
4956            }
4957        }
4958    }
4959
4960    fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &'ast Expr) {
4961        match expr.kind {
4962            ExprKind::Field(_, ident) => {
4963                // #6890: Even though you can't treat a method like a field,
4964                // we need to add any trait methods we find that match the
4965                // field name so that we can do some nice error reporting
4966                // later on in typeck.
4967                let traits = self.traits_in_scope(ident, ValueNS);
4968                self.r.trait_map.insert(expr.id, traits);
4969            }
4970            ExprKind::MethodCall(ref call) => {
4971                debug!("(recording candidate traits for expr) recording traits for {}", expr.id);
4972                let traits = self.traits_in_scope(call.seg.ident, ValueNS);
4973                self.r.trait_map.insert(expr.id, traits);
4974            }
4975            _ => {
4976                // Nothing to do.
4977            }
4978        }
4979    }
4980
4981    fn traits_in_scope(&mut self, ident: Ident, ns: Namespace) -> Vec<TraitCandidate> {
4982        self.r.traits_in_scope(
4983            self.current_trait_ref.as_ref().map(|(module, _)| *module),
4984            &self.parent_scope,
4985            ident.span.ctxt(),
4986            Some((ident.name, ns)),
4987        )
4988    }
4989
4990    fn resolve_and_cache_rustdoc_path(&mut self, path_str: &str, ns: Namespace) -> Option<Res> {
4991        // FIXME: This caching may be incorrect in case of multiple `macro_rules`
4992        // items with the same name in the same module.
4993        // Also hygiene is not considered.
4994        let mut doc_link_resolutions = std::mem::take(&mut self.r.doc_link_resolutions);
4995        let res = *doc_link_resolutions
4996            .entry(self.parent_scope.module.nearest_parent_mod().expect_local())
4997            .or_default()
4998            .entry((Symbol::intern(path_str), ns))
4999            .or_insert_with_key(|(path, ns)| {
5000                let res = self.r.resolve_rustdoc_path(path.as_str(), *ns, self.parent_scope);
5001                if let Some(res) = res
5002                    && let Some(def_id) = res.opt_def_id()
5003                    && self.is_invalid_proc_macro_item_for_doc(def_id)
5004                {
5005                    // Encoding def ids in proc macro crate metadata will ICE,
5006                    // because it will only store proc macros for it.
5007                    return None;
5008                }
5009                res
5010            });
5011        self.r.doc_link_resolutions = doc_link_resolutions;
5012        res
5013    }
5014
5015    fn is_invalid_proc_macro_item_for_doc(&self, did: DefId) -> bool {
5016        if !matches!(self.r.tcx.sess.opts.resolve_doc_links, ResolveDocLinks::ExportedMetadata)
5017            || !self.r.tcx.crate_types().contains(&CrateType::ProcMacro)
5018        {
5019            return false;
5020        }
5021        let Some(local_did) = did.as_local() else { return true };
5022        !self.r.proc_macros.contains(&local_did)
5023    }
5024
5025    fn resolve_doc_links(&mut self, attrs: &[Attribute], maybe_exported: MaybeExported<'_>) {
5026        match self.r.tcx.sess.opts.resolve_doc_links {
5027            ResolveDocLinks::None => return,
5028            ResolveDocLinks::ExportedMetadata
5029                if !self.r.tcx.crate_types().iter().copied().any(CrateType::has_metadata)
5030                    || !maybe_exported.eval(self.r) =>
5031            {
5032                return;
5033            }
5034            ResolveDocLinks::Exported
5035                if !maybe_exported.eval(self.r)
5036                    && !rustdoc::has_primitive_or_keyword_docs(attrs) =>
5037            {
5038                return;
5039            }
5040            ResolveDocLinks::ExportedMetadata
5041            | ResolveDocLinks::Exported
5042            | ResolveDocLinks::All => {}
5043        }
5044
5045        if !attrs.iter().any(|attr| attr.may_have_doc_links()) {
5046            return;
5047        }
5048
5049        let mut need_traits_in_scope = false;
5050        for path_str in rustdoc::attrs_to_preprocessed_links(attrs) {
5051            // Resolve all namespaces due to no disambiguator or for diagnostics.
5052            let mut any_resolved = false;
5053            let mut need_assoc = false;
5054            for ns in [TypeNS, ValueNS, MacroNS] {
5055                if let Some(res) = self.resolve_and_cache_rustdoc_path(&path_str, ns) {
5056                    // Rustdoc ignores tool attribute resolutions and attempts
5057                    // to resolve their prefixes for diagnostics.
5058                    any_resolved = !matches!(res, Res::NonMacroAttr(NonMacroAttrKind::Tool));
5059                } else if ns != MacroNS {
5060                    need_assoc = true;
5061                }
5062            }
5063
5064            // Resolve all prefixes for type-relative resolution or for diagnostics.
5065            if need_assoc || !any_resolved {
5066                let mut path = &path_str[..];
5067                while let Some(idx) = path.rfind("::") {
5068                    path = &path[..idx];
5069                    need_traits_in_scope = true;
5070                    for ns in [TypeNS, ValueNS, MacroNS] {
5071                        self.resolve_and_cache_rustdoc_path(path, ns);
5072                    }
5073                }
5074            }
5075        }
5076
5077        if need_traits_in_scope {
5078            // FIXME: hygiene is not considered.
5079            let mut doc_link_traits_in_scope = std::mem::take(&mut self.r.doc_link_traits_in_scope);
5080            doc_link_traits_in_scope
5081                .entry(self.parent_scope.module.nearest_parent_mod().expect_local())
5082                .or_insert_with(|| {
5083                    self.r
5084                        .traits_in_scope(None, &self.parent_scope, SyntaxContext::root(), None)
5085                        .into_iter()
5086                        .filter_map(|tr| {
5087                            if self.is_invalid_proc_macro_item_for_doc(tr.def_id) {
5088                                // Encoding def ids in proc macro crate metadata will ICE.
5089                                // because it will only store proc macros for it.
5090                                return None;
5091                            }
5092                            Some(tr.def_id)
5093                        })
5094                        .collect()
5095                });
5096            self.r.doc_link_traits_in_scope = doc_link_traits_in_scope;
5097        }
5098    }
5099
5100    fn lint_unused_qualifications(&mut self, path: &[Segment], ns: Namespace, finalize: Finalize) {
5101        // Don't lint on global paths because the user explicitly wrote out the full path.
5102        if let Some(seg) = path.first()
5103            && seg.ident.name == kw::PathRoot
5104        {
5105            return;
5106        }
5107
5108        if finalize.path_span.from_expansion()
5109            || path.iter().any(|seg| seg.ident.span.from_expansion())
5110        {
5111            return;
5112        }
5113
5114        let end_pos =
5115            path.iter().position(|seg| seg.has_generic_args).map_or(path.len(), |pos| pos + 1);
5116        let unqualified = path[..end_pos].iter().enumerate().skip(1).rev().find_map(|(i, seg)| {
5117            // Preserve the current namespace for the final path segment, but use the type
5118            // namespace for all preceding segments
5119            //
5120            // e.g. for `std::env::args` check the `ValueNS` for `args` but the `TypeNS` for
5121            // `std` and `env`
5122            //
5123            // If the final path segment is beyond `end_pos` all the segments to check will
5124            // use the type namespace
5125            let ns = if i + 1 == path.len() { ns } else { TypeNS };
5126            let res = self.r.partial_res_map.get(&seg.id?)?.full_res()?;
5127            let binding = self.resolve_ident_in_lexical_scope(seg.ident, ns, None, None)?;
5128            (res == binding.res()).then_some((seg, binding))
5129        });
5130
5131        if let Some((seg, binding)) = unqualified {
5132            self.r.potentially_unnecessary_qualifications.push(UnnecessaryQualification {
5133                binding,
5134                node_id: finalize.node_id,
5135                path_span: finalize.path_span,
5136                removal_span: path[0].ident.span.until(seg.ident.span),
5137            });
5138        }
5139    }
5140
5141    fn resolve_define_opaques(&mut self, define_opaque: &Option<ThinVec<(NodeId, Path)>>) {
5142        if let Some(define_opaque) = define_opaque {
5143            for (id, path) in define_opaque {
5144                self.smart_resolve_path(*id, &None, path, PathSource::DefineOpaques);
5145            }
5146        }
5147    }
5148}
5149
5150/// Walks the whole crate in DFS order, visiting each item, counting the declared number of
5151/// lifetime generic parameters and function parameters.
5152struct ItemInfoCollector<'a, 'ra, 'tcx> {
5153    r: &'a mut Resolver<'ra, 'tcx>,
5154}
5155
5156impl ItemInfoCollector<'_, '_, '_> {
5157    fn collect_fn_info(
5158        &mut self,
5159        header: FnHeader,
5160        decl: &FnDecl,
5161        id: NodeId,
5162        attrs: &[Attribute],
5163    ) {
5164        let sig = DelegationFnSig {
5165            header,
5166            param_count: decl.inputs.len(),
5167            has_self: decl.has_self(),
5168            c_variadic: decl.c_variadic(),
5169            target_feature: attrs.iter().any(|attr| attr.has_name(sym::target_feature)),
5170        };
5171        self.r.delegation_fn_sigs.insert(self.r.local_def_id(id), sig);
5172    }
5173}
5174
5175impl<'ast> Visitor<'ast> for ItemInfoCollector<'_, '_, '_> {
5176    fn visit_item(&mut self, item: &'ast Item) {
5177        match &item.kind {
5178            ItemKind::TyAlias(box TyAlias { generics, .. })
5179            | ItemKind::Const(box ConstItem { generics, .. })
5180            | ItemKind::Fn(box Fn { generics, .. })
5181            | ItemKind::Enum(_, generics, _)
5182            | ItemKind::Struct(_, generics, _)
5183            | ItemKind::Union(_, generics, _)
5184            | ItemKind::Impl(box Impl { generics, .. })
5185            | ItemKind::Trait(box Trait { generics, .. })
5186            | ItemKind::TraitAlias(_, generics, _) => {
5187                if let ItemKind::Fn(box Fn { sig, .. }) = &item.kind {
5188                    self.collect_fn_info(sig.header, &sig.decl, item.id, &item.attrs);
5189                }
5190
5191                let def_id = self.r.local_def_id(item.id);
5192                let count = generics
5193                    .params
5194                    .iter()
5195                    .filter(|param| matches!(param.kind, ast::GenericParamKind::Lifetime { .. }))
5196                    .count();
5197                self.r.item_generics_num_lifetimes.insert(def_id, count);
5198            }
5199
5200            ItemKind::ForeignMod(ForeignMod { extern_span, safety: _, abi, items }) => {
5201                for foreign_item in items {
5202                    if let ForeignItemKind::Fn(box Fn { sig, .. }) = &foreign_item.kind {
5203                        let new_header =
5204                            FnHeader { ext: Extern::from_abi(*abi, *extern_span), ..sig.header };
5205                        self.collect_fn_info(new_header, &sig.decl, foreign_item.id, &item.attrs);
5206                    }
5207                }
5208            }
5209
5210            ItemKind::Mod(..)
5211            | ItemKind::Static(..)
5212            | ItemKind::Use(..)
5213            | ItemKind::ExternCrate(..)
5214            | ItemKind::MacroDef(..)
5215            | ItemKind::GlobalAsm(..)
5216            | ItemKind::MacCall(..)
5217            | ItemKind::DelegationMac(..) => {}
5218            ItemKind::Delegation(..) => {
5219                // Delegated functions have lifetimes, their count is not necessarily zero.
5220                // But skipping the delegation items here doesn't mean that the count will be considered zero,
5221                // it means there will be a panic when retrieving the count,
5222                // but for delegation items we are never actually retrieving that count in practice.
5223            }
5224        }
5225        visit::walk_item(self, item)
5226    }
5227
5228    fn visit_assoc_item(&mut self, item: &'ast AssocItem, ctxt: AssocCtxt) {
5229        if let AssocItemKind::Fn(box Fn { sig, .. }) = &item.kind {
5230            self.collect_fn_info(sig.header, &sig.decl, item.id, &item.attrs);
5231        }
5232        visit::walk_assoc_item(self, item, ctxt);
5233    }
5234}
5235
5236impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
5237    pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
5238        visit::walk_crate(&mut ItemInfoCollector { r: self }, krate);
5239        let mut late_resolution_visitor = LateResolutionVisitor::new(self);
5240        late_resolution_visitor.resolve_doc_links(&krate.attrs, MaybeExported::Ok(CRATE_NODE_ID));
5241        visit::walk_crate(&mut late_resolution_visitor, krate);
5242        for (id, span) in late_resolution_visitor.diag_metadata.unused_labels.iter() {
5243            self.lint_buffer.buffer_lint(
5244                lint::builtin::UNUSED_LABELS,
5245                *id,
5246                *span,
5247                BuiltinLintDiag::UnusedLabel,
5248            );
5249        }
5250    }
5251}
5252
5253/// Check if definition matches a path
5254fn def_id_matches_path(tcx: TyCtxt<'_>, mut def_id: DefId, expected_path: &[&str]) -> bool {
5255    let mut path = expected_path.iter().rev();
5256    while let (Some(parent), Some(next_step)) = (tcx.opt_parent(def_id), path.next()) {
5257        if !tcx.opt_item_name(def_id).is_some_and(|n| n.as_str() == *next_step) {
5258            return false;
5259        }
5260        def_id = parent;
5261    }
5262    true
5263}