rustc_hir_typeck/
lib.rs

1// tidy-alphabetical-start
2#![allow(rustc::diagnostic_outside_of_impl)]
3#![allow(rustc::untranslatable_diagnostic)]
4#![feature(assert_matches)]
5#![feature(box_patterns)]
6#![feature(if_let_guard)]
7#![feature(iter_intersperse)]
8#![feature(never_type)]
9// tidy-alphabetical-end
10
11mod _match;
12mod autoderef;
13mod callee;
14// Used by clippy;
15pub mod cast;
16mod check;
17mod closure;
18mod coercion;
19mod demand;
20mod diverges;
21mod errors;
22mod expectation;
23mod expr;
24mod inline_asm;
25// Used by clippy;
26pub mod expr_use_visitor;
27mod fallback;
28mod fn_ctxt;
29mod gather_locals;
30mod intrinsicck;
31mod loops;
32mod method;
33mod naked_functions;
34mod op;
35mod opaque_types;
36mod pat;
37mod place_op;
38mod rvalue_scopes;
39mod typeck_root_ctxt;
40mod upvar;
41mod writeback;
42
43pub use coercion::can_coerce;
44use fn_ctxt::FnCtxt;
45use rustc_attr_data_structures::{AttributeKind, find_attr};
46use rustc_data_structures::unord::UnordSet;
47use rustc_errors::codes::*;
48use rustc_errors::{Applicability, ErrorGuaranteed, pluralize, struct_span_code_err};
49use rustc_hir as hir;
50use rustc_hir::def::{DefKind, Res};
51use rustc_hir::{HirId, HirIdMap, Node};
52use rustc_hir_analysis::check::{check_abi, check_custom_abi};
53use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
54use rustc_infer::traits::{ObligationCauseCode, ObligationInspector, WellFormedLoc};
55use rustc_middle::query::Providers;
56use rustc_middle::ty::{self, Ty, TyCtxt};
57use rustc_middle::{bug, span_bug};
58use rustc_session::config;
59use rustc_span::Span;
60use rustc_span::def_id::LocalDefId;
61use tracing::{debug, instrument};
62use typeck_root_ctxt::TypeckRootCtxt;
63
64use crate::check::check_fn;
65use crate::coercion::DynamicCoerceMany;
66use crate::diverges::Diverges;
67use crate::expectation::Expectation;
68use crate::fn_ctxt::LoweredTy;
69use crate::gather_locals::GatherLocalsVisitor;
70
71rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
72
73#[macro_export]
74macro_rules! type_error_struct {
75    ($dcx:expr, $span:expr, $typ:expr, $code:expr, $($message:tt)*) => ({
76        let mut err = rustc_errors::struct_span_code_err!($dcx, $span, $code, $($message)*);
77
78        if $typ.references_error() {
79            err.downgrade_to_delayed_bug();
80        }
81
82        err
83    })
84}
85
86fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &UnordSet<LocalDefId> {
87    &tcx.typeck(def_id).used_trait_imports
88}
89
90fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
91    typeck_with_inspect(tcx, def_id, None)
92}
93
94/// Same as `typeck` but `inspect` is invoked on evaluation of each root obligation.
95/// Inspecting obligations only works with the new trait solver.
96/// This function is *only to be used* by external tools, it should not be
97/// called from within rustc. Note, this is not a query, and thus is not cached.
98pub fn inspect_typeck<'tcx>(
99    tcx: TyCtxt<'tcx>,
100    def_id: LocalDefId,
101    inspect: ObligationInspector<'tcx>,
102) -> &'tcx ty::TypeckResults<'tcx> {
103    typeck_with_inspect(tcx, def_id, Some(inspect))
104}
105
106#[instrument(level = "debug", skip(tcx, inspector), ret)]
107fn typeck_with_inspect<'tcx>(
108    tcx: TyCtxt<'tcx>,
109    def_id: LocalDefId,
110    inspector: Option<ObligationInspector<'tcx>>,
111) -> &'tcx ty::TypeckResults<'tcx> {
112    // Closures' typeck results come from their outermost function,
113    // as they are part of the same "inference environment".
114    let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
115    if typeck_root_def_id != def_id {
116        return tcx.typeck(typeck_root_def_id);
117    }
118
119    let id = tcx.local_def_id_to_hir_id(def_id);
120    let node = tcx.hir_node(id);
121    let span = tcx.def_span(def_id);
122
123    // Figure out what primary body this item has.
124    let body_id = node.body_id().unwrap_or_else(|| {
125        span_bug!(span, "can't type-check body of {:?}", def_id);
126    });
127    let body = tcx.hir_body(body_id);
128
129    let param_env = tcx.param_env(def_id);
130
131    let root_ctxt = TypeckRootCtxt::new(tcx, def_id);
132    if let Some(inspector) = inspector {
133        root_ctxt.infcx.attach_obligation_inspector(inspector);
134    }
135    let mut fcx = FnCtxt::new(&root_ctxt, param_env, def_id);
136
137    if let hir::Node::Item(hir::Item { kind: hir::ItemKind::GlobalAsm { .. }, .. }) = node {
138        // Check the fake body of a global ASM. There's not much to do here except
139        // for visit the asm expr of the body.
140        let ty = fcx.check_expr(body.value);
141        fcx.write_ty(id, ty);
142    } else if let Some(hir::FnSig { header, decl, span: fn_sig_span }) = node.fn_sig() {
143        let fn_sig = if decl.output.is_suggestable_infer_ty().is_some() {
144            // In the case that we're recovering `fn() -> W<_>` or some other return
145            // type that has an infer in it, lower the type directly so that it'll
146            // be correctly filled with infer. We'll use this inference to provide
147            // a suggestion later on.
148            fcx.lowerer().lower_fn_ty(id, header.safety(), header.abi, decl, None, None)
149        } else {
150            tcx.fn_sig(def_id).instantiate_identity()
151        };
152
153        check_abi(tcx, id, span, fn_sig.abi());
154        check_custom_abi(tcx, def_id, fn_sig.skip_binder(), *fn_sig_span);
155
156        loops::check(tcx, def_id, body);
157
158        // Compute the function signature from point of view of inside the fn.
159        let mut fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
160
161        // Normalize the input and output types one at a time, using a different
162        // `WellFormedLoc` for each. We cannot call `normalize_associated_types`
163        // on the entire `FnSig`, since this would use the same `WellFormedLoc`
164        // for each type, preventing the HIR wf check from generating
165        // a nice error message.
166        let arg_span =
167            |idx| decl.inputs.get(idx).map_or(decl.output.span(), |arg: &hir::Ty<'_>| arg.span);
168
169        fn_sig.inputs_and_output = tcx.mk_type_list_from_iter(
170            fn_sig
171                .inputs_and_output
172                .iter()
173                .enumerate()
174                .map(|(idx, ty)| fcx.normalize(arg_span(idx), ty)),
175        );
176
177        if find_attr!(tcx.get_all_attrs(def_id), AttributeKind::Naked(..)) {
178            naked_functions::typeck_naked_fn(tcx, def_id, body);
179        }
180
181        check_fn(&mut fcx, fn_sig, None, decl, def_id, body, tcx.features().unsized_fn_params());
182    } else {
183        let expected_type = if let Some(infer_ty) = infer_type_if_missing(&fcx, node) {
184            infer_ty
185        } else if let Some(ty) = node.ty()
186            && ty.is_suggestable_infer_ty()
187        {
188            // In the case that we're recovering `const X: [T; _]` or some other
189            // type that has an infer in it, lower the type directly so that it'll
190            // be correctly filled with infer. We'll use this inference to provide
191            // a suggestion later on.
192            fcx.lowerer().lower_ty(ty)
193        } else {
194            tcx.type_of(def_id).instantiate_identity()
195        };
196
197        loops::check(tcx, def_id, body);
198
199        let expected_type = fcx.normalize(body.value.span, expected_type);
200
201        let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
202        fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
203
204        fcx.check_expr_coercible_to_type(body.value, expected_type, None);
205
206        fcx.write_ty(id, expected_type);
207    };
208
209    // Whether to check repeat exprs before/after inference fallback is somewhat
210    // arbitrary of a decision as neither option is strictly more permissive than
211    // the other. However, we opt to check repeat exprs first as errors from not
212    // having inferred array lengths yet seem less confusing than errors from inference
213    // fallback arbitrarily inferring something incompatible with `Copy` inference
214    // side effects.
215    //
216    // FIXME(#140855): This should also be forwards compatible with moving
217    // repeat expr checks to a custom goal kind or using marker traits in
218    // the future.
219    fcx.check_repeat_exprs();
220
221    fcx.type_inference_fallback();
222
223    // Even though coercion casts provide type hints, we check casts after fallback for
224    // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
225    fcx.check_casts();
226    fcx.select_obligations_where_possible(|_| {});
227
228    // Closure and coroutine analysis may run after fallback
229    // because they don't constrain other type variables.
230    fcx.closure_analyze(body);
231    assert!(fcx.deferred_call_resolutions.borrow().is_empty());
232    // Before the coroutine analysis, temporary scopes shall be marked to provide more
233    // precise information on types to be captured.
234    fcx.resolve_rvalue_scopes(def_id.to_def_id());
235
236    for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
237        let ty = fcx.normalize(span, ty);
238        fcx.require_type_is_sized(ty, span, code);
239    }
240
241    fcx.select_obligations_where_possible(|_| {});
242
243    debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
244
245    // This must be the last thing before `report_ambiguity_errors`.
246    fcx.resolve_coroutine_interiors();
247
248    debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
249
250    if let None = fcx.infcx.tainted_by_errors() {
251        fcx.report_ambiguity_errors();
252    }
253
254    if let None = fcx.infcx.tainted_by_errors() {
255        fcx.check_transmutes();
256    }
257
258    fcx.check_asms();
259
260    let typeck_results = fcx.resolve_type_vars_in_body(body);
261
262    fcx.detect_opaque_types_added_during_writeback();
263
264    // Consistency check our TypeckResults instance can hold all ItemLocalIds
265    // it will need to hold.
266    assert_eq!(typeck_results.hir_owner, id.owner);
267
268    typeck_results
269}
270
271fn infer_type_if_missing<'tcx>(fcx: &FnCtxt<'_, 'tcx>, node: Node<'tcx>) -> Option<Ty<'tcx>> {
272    let tcx = fcx.tcx;
273    let def_id = fcx.body_id;
274    let expected_type = if let Some(&hir::Ty { kind: hir::TyKind::Infer(()), span, .. }) = node.ty()
275    {
276        if let Some(item) = tcx.opt_associated_item(def_id.into())
277            && let ty::AssocKind::Const { .. } = item.kind
278            && let ty::AssocItemContainer::Impl = item.container
279            && let Some(trait_item_def_id) = item.trait_item_def_id
280        {
281            let impl_def_id = item.container_id(tcx);
282            let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity();
283            let args = ty::GenericArgs::identity_for_item(tcx, def_id).rebase_onto(
284                tcx,
285                impl_def_id,
286                impl_trait_ref.args,
287            );
288            tcx.check_args_compatible(trait_item_def_id, args)
289                .then(|| tcx.type_of(trait_item_def_id).instantiate(tcx, args))
290        } else {
291            Some(fcx.next_ty_var(span))
292        }
293    } else if let Node::AnonConst(_) = node {
294        let id = tcx.local_def_id_to_hir_id(def_id);
295        match tcx.parent_hir_node(id) {
296            Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref anon_const), span, .. })
297                if anon_const.hir_id == id =>
298            {
299                Some(fcx.next_ty_var(span))
300            }
301            Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), span, .. })
302            | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm { asm, .. }, span, .. }) => {
303                asm.operands.iter().find_map(|(op, _op_sp)| match op {
304                    hir::InlineAsmOperand::Const { anon_const } if anon_const.hir_id == id => {
305                        Some(fcx.next_ty_var(span))
306                    }
307                    _ => None,
308                })
309            }
310            _ => None,
311        }
312    } else {
313        None
314    };
315    expected_type
316}
317
318/// When `check_fn` is invoked on a coroutine (i.e., a body that
319/// includes yield), it returns back some information about the yield
320/// points.
321#[derive(Debug, PartialEq, Copy, Clone)]
322struct CoroutineTypes<'tcx> {
323    /// Type of coroutine argument / values returned by `yield`.
324    resume_ty: Ty<'tcx>,
325
326    /// Type of value that is yielded.
327    yield_ty: Ty<'tcx>,
328}
329
330#[derive(Copy, Clone, Debug, PartialEq, Eq)]
331pub enum Needs {
332    MutPlace,
333    None,
334}
335
336impl Needs {
337    fn maybe_mut_place(m: hir::Mutability) -> Self {
338        match m {
339            hir::Mutability::Mut => Needs::MutPlace,
340            hir::Mutability::Not => Needs::None,
341        }
342    }
343}
344
345#[derive(Debug, Copy, Clone)]
346pub enum PlaceOp {
347    Deref,
348    Index,
349}
350
351pub struct BreakableCtxt<'tcx> {
352    may_break: bool,
353
354    // this is `null` for loops where break with a value is illegal,
355    // such as `while`, `for`, and `while let`
356    coerce: Option<DynamicCoerceMany<'tcx>>,
357}
358
359pub struct EnclosingBreakables<'tcx> {
360    stack: Vec<BreakableCtxt<'tcx>>,
361    by_id: HirIdMap<usize>,
362}
363
364impl<'tcx> EnclosingBreakables<'tcx> {
365    fn find_breakable(&mut self, target_id: HirId) -> &mut BreakableCtxt<'tcx> {
366        self.opt_find_breakable(target_id).unwrap_or_else(|| {
367            bug!("could not find enclosing breakable with id {}", target_id);
368        })
369    }
370
371    fn opt_find_breakable(&mut self, target_id: HirId) -> Option<&mut BreakableCtxt<'tcx>> {
372        match self.by_id.get(&target_id) {
373            Some(ix) => Some(&mut self.stack[*ix]),
374            None => None,
375        }
376    }
377}
378
379fn report_unexpected_variant_res(
380    tcx: TyCtxt<'_>,
381    res: Res,
382    expr: Option<&hir::Expr<'_>>,
383    qpath: &hir::QPath<'_>,
384    span: Span,
385    err_code: ErrCode,
386    expected: &str,
387) -> ErrorGuaranteed {
388    let res_descr = match res {
389        Res::Def(DefKind::Variant, _) => "struct variant",
390        _ => res.descr(),
391    };
392    let path_str = rustc_hir_pretty::qpath_to_string(&tcx, qpath);
393    let mut err = tcx
394        .dcx()
395        .struct_span_err(span, format!("expected {expected}, found {res_descr} `{path_str}`"))
396        .with_code(err_code);
397    match res {
398        Res::Def(DefKind::Fn | DefKind::AssocFn, _) if err_code == E0164 => {
399            let patterns_url = "https://doc.rust-lang.org/book/ch19-00-patterns.html";
400            err.with_span_label(span, "`fn` calls are not allowed in patterns")
401                .with_help(format!("for more information, visit {patterns_url}"))
402        }
403        Res::Def(DefKind::Variant, _) if let Some(expr) = expr => {
404            err.span_label(span, format!("not a {expected}"));
405            let variant = tcx.expect_variant_res(res);
406            let sugg = if variant.fields.is_empty() {
407                " {}".to_string()
408            } else {
409                format!(
410                    " {{ {} }}",
411                    variant
412                        .fields
413                        .iter()
414                        .map(|f| format!("{}: /* value */", f.name))
415                        .collect::<Vec<_>>()
416                        .join(", ")
417                )
418            };
419            let descr = "you might have meant to create a new value of the struct";
420            let mut suggestion = vec![];
421            match tcx.parent_hir_node(expr.hir_id) {
422                hir::Node::Expr(hir::Expr {
423                    kind: hir::ExprKind::Call(..),
424                    span: call_span,
425                    ..
426                }) => {
427                    suggestion.push((span.shrink_to_hi().with_hi(call_span.hi()), sugg));
428                }
429                hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Binary(..), hir_id, .. }) => {
430                    suggestion.push((expr.span.shrink_to_lo(), "(".to_string()));
431                    if let hir::Node::Expr(drop_temps) = tcx.parent_hir_node(*hir_id)
432                        && let hir::ExprKind::DropTemps(_) = drop_temps.kind
433                        && let hir::Node::Expr(parent) = tcx.parent_hir_node(drop_temps.hir_id)
434                        && let hir::ExprKind::If(condition, block, None) = parent.kind
435                        && condition.hir_id == drop_temps.hir_id
436                        && let hir::ExprKind::Block(block, _) = block.kind
437                        && block.stmts.is_empty()
438                        && let Some(expr) = block.expr
439                        && let hir::ExprKind::Path(..) = expr.kind
440                    {
441                        // Special case: you can incorrectly write an equality condition:
442                        // if foo == Struct { field } { /* if body */ }
443                        // which should have been written
444                        // if foo == (Struct { field }) { /* if body */ }
445                        suggestion.push((block.span.shrink_to_hi(), ")".to_string()));
446                    } else {
447                        suggestion.push((span.shrink_to_hi().with_hi(expr.span.hi()), sugg));
448                    }
449                }
450                _ => {
451                    suggestion.push((span.shrink_to_hi(), sugg));
452                }
453            }
454
455            err.multipart_suggestion_verbose(descr, suggestion, Applicability::HasPlaceholders);
456            err
457        }
458        Res::Def(DefKind::Variant, _) if expr.is_none() => {
459            err.span_label(span, format!("not a {expected}"));
460
461            let fields = &tcx.expect_variant_res(res).fields.raw;
462            let span = qpath.span().shrink_to_hi().to(span.shrink_to_hi());
463            let (msg, sugg) = if fields.is_empty() {
464                ("use the struct variant pattern syntax".to_string(), " {}".to_string())
465            } else {
466                let msg = format!(
467                    "the struct variant's field{s} {are} being ignored",
468                    s = pluralize!(fields.len()),
469                    are = pluralize!("is", fields.len())
470                );
471                let fields = fields
472                    .iter()
473                    .map(|field| format!("{}: _", field.ident(tcx)))
474                    .collect::<Vec<_>>()
475                    .join(", ");
476                let sugg = format!(" {{ {} }}", fields);
477                (msg, sugg)
478            };
479
480            err.span_suggestion_verbose(
481                qpath.span().shrink_to_hi().to(span.shrink_to_hi()),
482                msg,
483                sugg,
484                Applicability::HasPlaceholders,
485            );
486            err
487        }
488        _ => err.with_span_label(span, format!("not a {expected}")),
489    }
490    .emit()
491}
492
493/// Controls whether the arguments are tupled. This is used for the call
494/// operator.
495///
496/// Tupling means that all call-side arguments are packed into a tuple and
497/// passed as a single parameter. For example, if tupling is enabled, this
498/// function:
499/// ```
500/// fn f(x: (isize, isize)) {}
501/// ```
502/// Can be called as:
503/// ```ignore UNSOLVED (can this be done in user code?)
504/// # fn f(x: (isize, isize)) {}
505/// f(1, 2);
506/// ```
507/// Instead of:
508/// ```
509/// # fn f(x: (isize, isize)) {}
510/// f((1, 2));
511/// ```
512#[derive(Copy, Clone, Eq, PartialEq)]
513enum TupleArgumentsFlag {
514    DontTupleArguments,
515    TupleArguments,
516}
517
518fn fatally_break_rust(tcx: TyCtxt<'_>, span: Span) -> ! {
519    let dcx = tcx.dcx();
520    let mut diag = dcx.struct_span_bug(
521        span,
522        "It looks like you're trying to break rust; would you like some ICE?",
523    );
524    diag.note("the compiler expectedly panicked. this is a feature.");
525    diag.note(
526        "we would appreciate a joke overview: \
527         https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
528    );
529    diag.note(format!("rustc {} running on {}", tcx.sess.cfg_version, config::host_tuple(),));
530    if let Some((flags, excluded_cargo_defaults)) = rustc_session::utils::extra_compiler_flags() {
531        diag.note(format!("compiler flags: {}", flags.join(" ")));
532        if excluded_cargo_defaults {
533            diag.note("some of the compiler flags provided by cargo are hidden");
534        }
535    }
536    diag.emit()
537}
538
539pub fn provide(providers: &mut Providers) {
540    method::provide(providers);
541    *providers = Providers { typeck, used_trait_imports, ..*providers };
542}