rustc_metadata/rmeta/
encoder.rs

1use std::borrow::Borrow;
2use std::collections::hash_map::Entry;
3use std::fs::File;
4use std::io::{Read, Seek, Write};
5use std::path::{Path, PathBuf};
6use std::sync::Arc;
7
8use rustc_ast::attr::AttributeExt;
9use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
10use rustc_data_structures::memmap::{Mmap, MmapMut};
11use rustc_data_structures::sync::{join, par_for_each_in};
12use rustc_data_structures::temp_dir::MaybeTempDir;
13use rustc_data_structures::thousands::format_with_underscores;
14use rustc_feature::Features;
15use rustc_hir as hir;
16use rustc_hir::def_id::{CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE, LocalDefId, LocalDefIdSet};
17use rustc_hir::definitions::DefPathData;
18use rustc_hir_pretty::id_to_string;
19use rustc_middle::middle::dependency_format::Linkage;
20use rustc_middle::middle::exported_symbols::metadata_symbol_name;
21use rustc_middle::mir::interpret;
22use rustc_middle::query::Providers;
23use rustc_middle::traits::specialization_graph;
24use rustc_middle::ty::codec::TyEncoder;
25use rustc_middle::ty::fast_reject::{self, TreatParams};
26use rustc_middle::ty::{AssocItemContainer, SymbolName};
27use rustc_middle::{bug, span_bug};
28use rustc_serialize::{Decodable, Decoder, Encodable, Encoder, opaque};
29use rustc_session::config::{CrateType, OptLevel, TargetModifier};
30use rustc_span::hygiene::HygieneEncodeContext;
31use rustc_span::{
32    ExternalSource, FileName, SourceFile, SpanData, SpanEncoder, StableSourceFileId, SyntaxContext,
33    sym,
34};
35use tracing::{debug, instrument, trace};
36
37use crate::errors::{FailCreateFileEncoder, FailWriteFile};
38use crate::rmeta::*;
39
40pub(super) struct EncodeContext<'a, 'tcx> {
41    opaque: opaque::FileEncoder,
42    tcx: TyCtxt<'tcx>,
43    feat: &'tcx rustc_feature::Features,
44    tables: TableBuilders,
45
46    lazy_state: LazyState,
47    span_shorthands: FxHashMap<Span, usize>,
48    type_shorthands: FxHashMap<Ty<'tcx>, usize>,
49    predicate_shorthands: FxHashMap<ty::PredicateKind<'tcx>, usize>,
50
51    interpret_allocs: FxIndexSet<interpret::AllocId>,
52
53    // This is used to speed up Span encoding.
54    // The `usize` is an index into the `MonotonicVec`
55    // that stores the `SourceFile`
56    source_file_cache: (Arc<SourceFile>, usize),
57    // The indices (into the `SourceMap`'s `MonotonicVec`)
58    // of all of the `SourceFiles` that we need to serialize.
59    // When we serialize a `Span`, we insert the index of its
60    // `SourceFile` into the `FxIndexSet`.
61    // The order inside the `FxIndexSet` is used as on-disk
62    // order of `SourceFiles`, and encoded inside `Span`s.
63    required_source_files: Option<FxIndexSet<usize>>,
64    is_proc_macro: bool,
65    hygiene_ctxt: &'a HygieneEncodeContext,
66    symbol_table: FxHashMap<Symbol, usize>,
67}
68
69/// If the current crate is a proc-macro, returns early with `LazyArray::default()`.
70/// This is useful for skipping the encoding of things that aren't needed
71/// for proc-macro crates.
72macro_rules! empty_proc_macro {
73    ($self:ident) => {
74        if $self.is_proc_macro {
75            return LazyArray::default();
76        }
77    };
78}
79
80macro_rules! encoder_methods {
81    ($($name:ident($ty:ty);)*) => {
82        $(fn $name(&mut self, value: $ty) {
83            self.opaque.$name(value)
84        })*
85    }
86}
87
88impl<'a, 'tcx> Encoder for EncodeContext<'a, 'tcx> {
89    encoder_methods! {
90        emit_usize(usize);
91        emit_u128(u128);
92        emit_u64(u64);
93        emit_u32(u32);
94        emit_u16(u16);
95        emit_u8(u8);
96
97        emit_isize(isize);
98        emit_i128(i128);
99        emit_i64(i64);
100        emit_i32(i32);
101        emit_i16(i16);
102
103        emit_raw_bytes(&[u8]);
104    }
105}
106
107impl<'a, 'tcx, T> Encodable<EncodeContext<'a, 'tcx>> for LazyValue<T> {
108    fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
109        e.emit_lazy_distance(self.position);
110    }
111}
112
113impl<'a, 'tcx, T> Encodable<EncodeContext<'a, 'tcx>> for LazyArray<T> {
114    fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
115        e.emit_usize(self.num_elems);
116        if self.num_elems > 0 {
117            e.emit_lazy_distance(self.position)
118        }
119    }
120}
121
122impl<'a, 'tcx, I, T> Encodable<EncodeContext<'a, 'tcx>> for LazyTable<I, T> {
123    fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
124        e.emit_usize(self.width);
125        e.emit_usize(self.len);
126        e.emit_lazy_distance(self.position);
127    }
128}
129
130impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for ExpnIndex {
131    fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
132        s.emit_u32(self.as_u32());
133    }
134}
135
136impl<'a, 'tcx> SpanEncoder for EncodeContext<'a, 'tcx> {
137    fn encode_crate_num(&mut self, crate_num: CrateNum) {
138        if crate_num != LOCAL_CRATE && self.is_proc_macro {
139            panic!("Attempted to encode non-local CrateNum {crate_num:?} for proc-macro crate");
140        }
141        self.emit_u32(crate_num.as_u32());
142    }
143
144    fn encode_def_index(&mut self, def_index: DefIndex) {
145        self.emit_u32(def_index.as_u32());
146    }
147
148    fn encode_def_id(&mut self, def_id: DefId) {
149        def_id.krate.encode(self);
150        def_id.index.encode(self);
151    }
152
153    fn encode_syntax_context(&mut self, syntax_context: SyntaxContext) {
154        rustc_span::hygiene::raw_encode_syntax_context(syntax_context, self.hygiene_ctxt, self);
155    }
156
157    fn encode_expn_id(&mut self, expn_id: ExpnId) {
158        if expn_id.krate == LOCAL_CRATE {
159            // We will only write details for local expansions. Non-local expansions will fetch
160            // data from the corresponding crate's metadata.
161            // FIXME(#43047) FIXME(#74731) We may eventually want to avoid relying on external
162            // metadata from proc-macro crates.
163            self.hygiene_ctxt.schedule_expn_data_for_encoding(expn_id);
164        }
165        expn_id.krate.encode(self);
166        expn_id.local_id.encode(self);
167    }
168
169    fn encode_span(&mut self, span: Span) {
170        match self.span_shorthands.entry(span) {
171            Entry::Occupied(o) => {
172                // If an offset is smaller than the absolute position, we encode with the offset.
173                // This saves space since smaller numbers encode in less bits.
174                let last_location = *o.get();
175                // This cannot underflow. Metadata is written with increasing position(), so any
176                // previously saved offset must be smaller than the current position.
177                let offset = self.opaque.position() - last_location;
178                if offset < last_location {
179                    let needed = bytes_needed(offset);
180                    SpanTag::indirect(true, needed as u8).encode(self);
181                    self.opaque.write_with(|dest| {
182                        *dest = offset.to_le_bytes();
183                        needed
184                    });
185                } else {
186                    let needed = bytes_needed(last_location);
187                    SpanTag::indirect(false, needed as u8).encode(self);
188                    self.opaque.write_with(|dest| {
189                        *dest = last_location.to_le_bytes();
190                        needed
191                    });
192                }
193            }
194            Entry::Vacant(v) => {
195                let position = self.opaque.position();
196                v.insert(position);
197                // Data is encoded with a SpanTag prefix (see below).
198                span.data().encode(self);
199            }
200        }
201    }
202
203    fn encode_symbol(&mut self, symbol: Symbol) {
204        // if symbol preinterned, emit tag and symbol index
205        if symbol.is_preinterned() {
206            self.opaque.emit_u8(SYMBOL_PREINTERNED);
207            self.opaque.emit_u32(symbol.as_u32());
208        } else {
209            // otherwise write it as string or as offset to it
210            match self.symbol_table.entry(symbol) {
211                Entry::Vacant(o) => {
212                    self.opaque.emit_u8(SYMBOL_STR);
213                    let pos = self.opaque.position();
214                    o.insert(pos);
215                    self.emit_str(symbol.as_str());
216                }
217                Entry::Occupied(o) => {
218                    let x = *o.get();
219                    self.emit_u8(SYMBOL_OFFSET);
220                    self.emit_usize(x);
221                }
222            }
223        }
224    }
225}
226
227fn bytes_needed(n: usize) -> usize {
228    (usize::BITS - n.leading_zeros()).div_ceil(u8::BITS) as usize
229}
230
231impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for SpanData {
232    fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
233        // Don't serialize any `SyntaxContext`s from a proc-macro crate,
234        // since we don't load proc-macro dependencies during serialization.
235        // This means that any hygiene information from macros used *within*
236        // a proc-macro crate (e.g. invoking a macro that expands to a proc-macro
237        // definition) will be lost.
238        //
239        // This can show up in two ways:
240        //
241        // 1. Any hygiene information associated with identifier of
242        // a proc macro (e.g. `#[proc_macro] pub fn $name`) will be lost.
243        // Since proc-macros can only be invoked from a different crate,
244        // real code should never need to care about this.
245        //
246        // 2. Using `Span::def_site` or `Span::mixed_site` will not
247        // include any hygiene information associated with the definition
248        // site. This means that a proc-macro cannot emit a `$crate`
249        // identifier which resolves to one of its dependencies,
250        // which also should never come up in practice.
251        //
252        // Additionally, this affects `Span::parent`, and any other
253        // span inspection APIs that would otherwise allow traversing
254        // the `SyntaxContexts` associated with a span.
255        //
256        // None of these user-visible effects should result in any
257        // cross-crate inconsistencies (getting one behavior in the same
258        // crate, and a different behavior in another crate) due to the
259        // limited surface that proc-macros can expose.
260        //
261        // IMPORTANT: If this is ever changed, be sure to update
262        // `rustc_span::hygiene::raw_encode_expn_id` to handle
263        // encoding `ExpnData` for proc-macro crates.
264        let ctxt = if s.is_proc_macro { SyntaxContext::root() } else { self.ctxt };
265
266        if self.is_dummy() {
267            let tag = SpanTag::new(SpanKind::Partial, ctxt, 0);
268            tag.encode(s);
269            if tag.context().is_none() {
270                ctxt.encode(s);
271            }
272            return;
273        }
274
275        // The Span infrastructure should make sure that this invariant holds:
276        debug_assert!(self.lo <= self.hi);
277
278        if !s.source_file_cache.0.contains(self.lo) {
279            let source_map = s.tcx.sess.source_map();
280            let source_file_index = source_map.lookup_source_file_idx(self.lo);
281            s.source_file_cache =
282                (Arc::clone(&source_map.files()[source_file_index]), source_file_index);
283        }
284        let (ref source_file, source_file_index) = s.source_file_cache;
285        debug_assert!(source_file.contains(self.lo));
286
287        if !source_file.contains(self.hi) {
288            // Unfortunately, macro expansion still sometimes generates Spans
289            // that malformed in this way.
290            let tag = SpanTag::new(SpanKind::Partial, ctxt, 0);
291            tag.encode(s);
292            if tag.context().is_none() {
293                ctxt.encode(s);
294            }
295            return;
296        }
297
298        // There are two possible cases here:
299        // 1. This span comes from a 'foreign' crate - e.g. some crate upstream of the
300        // crate we are writing metadata for. When the metadata for *this* crate gets
301        // deserialized, the deserializer will need to know which crate it originally came
302        // from. We use `TAG_VALID_SPAN_FOREIGN` to indicate that a `CrateNum` should
303        // be deserialized after the rest of the span data, which tells the deserializer
304        // which crate contains the source map information.
305        // 2. This span comes from our own crate. No special handling is needed - we just
306        // write `TAG_VALID_SPAN_LOCAL` to let the deserializer know that it should use
307        // our own source map information.
308        //
309        // If we're a proc-macro crate, we always treat this as a local `Span`.
310        // In `encode_source_map`, we serialize foreign `SourceFile`s into our metadata
311        // if we're a proc-macro crate.
312        // This allows us to avoid loading the dependencies of proc-macro crates: all of
313        // the information we need to decode `Span`s is stored in the proc-macro crate.
314        let (kind, metadata_index) = if source_file.is_imported() && !s.is_proc_macro {
315            // To simplify deserialization, we 'rebase' this span onto the crate it originally came
316            // from (the crate that 'owns' the file it references. These rebased 'lo' and 'hi'
317            // values are relative to the source map information for the 'foreign' crate whose
318            // CrateNum we write into the metadata. This allows `imported_source_files` to binary
319            // search through the 'foreign' crate's source map information, using the
320            // deserialized 'lo' and 'hi' values directly.
321            //
322            // All of this logic ensures that the final result of deserialization is a 'normal'
323            // Span that can be used without any additional trouble.
324            let metadata_index = {
325                // Introduce a new scope so that we drop the 'read()' temporary
326                match &*source_file.external_src.read() {
327                    ExternalSource::Foreign { metadata_index, .. } => *metadata_index,
328                    src => panic!("Unexpected external source {src:?}"),
329                }
330            };
331
332            (SpanKind::Foreign, metadata_index)
333        } else {
334            // Record the fact that we need to encode the data for this `SourceFile`
335            let source_files =
336                s.required_source_files.as_mut().expect("Already encoded SourceMap!");
337            let (metadata_index, _) = source_files.insert_full(source_file_index);
338            let metadata_index: u32 =
339                metadata_index.try_into().expect("cannot export more than U32_MAX files");
340
341            (SpanKind::Local, metadata_index)
342        };
343
344        // Encode the start position relative to the file start, so we profit more from the
345        // variable-length integer encoding.
346        let lo = self.lo - source_file.start_pos;
347
348        // Encode length which is usually less than span.hi and profits more
349        // from the variable-length integer encoding that we use.
350        let len = self.hi - self.lo;
351
352        let tag = SpanTag::new(kind, ctxt, len.0 as usize);
353        tag.encode(s);
354        if tag.context().is_none() {
355            ctxt.encode(s);
356        }
357        lo.encode(s);
358        if tag.length().is_none() {
359            len.encode(s);
360        }
361
362        // Encode the index of the `SourceFile` for the span, in order to make decoding faster.
363        metadata_index.encode(s);
364
365        if kind == SpanKind::Foreign {
366            // This needs to be two lines to avoid holding the `s.source_file_cache`
367            // while calling `cnum.encode(s)`
368            let cnum = s.source_file_cache.0.cnum;
369            cnum.encode(s);
370        }
371    }
372}
373
374impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for [u8] {
375    fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
376        Encoder::emit_usize(e, self.len());
377        e.emit_raw_bytes(self);
378    }
379}
380
381impl<'a, 'tcx> TyEncoder<'tcx> for EncodeContext<'a, 'tcx> {
382    const CLEAR_CROSS_CRATE: bool = true;
383
384    fn position(&self) -> usize {
385        self.opaque.position()
386    }
387
388    fn type_shorthands(&mut self) -> &mut FxHashMap<Ty<'tcx>, usize> {
389        &mut self.type_shorthands
390    }
391
392    fn predicate_shorthands(&mut self) -> &mut FxHashMap<ty::PredicateKind<'tcx>, usize> {
393        &mut self.predicate_shorthands
394    }
395
396    fn encode_alloc_id(&mut self, alloc_id: &rustc_middle::mir::interpret::AllocId) {
397        let (index, _) = self.interpret_allocs.insert_full(*alloc_id);
398
399        index.encode(self);
400    }
401}
402
403// Shorthand for `$self.$tables.$table.set_some($def_id.index, $self.lazy($value))`, which would
404// normally need extra variables to avoid errors about multiple mutable borrows.
405macro_rules! record {
406    ($self:ident.$tables:ident.$table:ident[$def_id:expr] <- $value:expr) => {{
407        {
408            let value = $value;
409            let lazy = $self.lazy(value);
410            $self.$tables.$table.set_some($def_id.index, lazy);
411        }
412    }};
413}
414
415// Shorthand for `$self.$tables.$table.set_some($def_id.index, $self.lazy_array($value))`, which would
416// normally need extra variables to avoid errors about multiple mutable borrows.
417macro_rules! record_array {
418    ($self:ident.$tables:ident.$table:ident[$def_id:expr] <- $value:expr) => {{
419        {
420            let value = $value;
421            let lazy = $self.lazy_array(value);
422            $self.$tables.$table.set_some($def_id.index, lazy);
423        }
424    }};
425}
426
427macro_rules! record_defaulted_array {
428    ($self:ident.$tables:ident.$table:ident[$def_id:expr] <- $value:expr) => {{
429        {
430            let value = $value;
431            let lazy = $self.lazy_array(value);
432            $self.$tables.$table.set($def_id.index, lazy);
433        }
434    }};
435}
436
437impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
438    fn emit_lazy_distance(&mut self, position: NonZero<usize>) {
439        let pos = position.get();
440        let distance = match self.lazy_state {
441            LazyState::NoNode => bug!("emit_lazy_distance: outside of a metadata node"),
442            LazyState::NodeStart(start) => {
443                let start = start.get();
444                assert!(pos <= start);
445                start - pos
446            }
447            LazyState::Previous(last_pos) => {
448                assert!(
449                    last_pos <= position,
450                    "make sure that the calls to `lazy*` \
451                     are in the same order as the metadata fields",
452                );
453                position.get() - last_pos.get()
454            }
455        };
456        self.lazy_state = LazyState::Previous(NonZero::new(pos).unwrap());
457        self.emit_usize(distance);
458    }
459
460    fn lazy<T: ParameterizedOverTcx, B: Borrow<T::Value<'tcx>>>(&mut self, value: B) -> LazyValue<T>
461    where
462        T::Value<'tcx>: Encodable<EncodeContext<'a, 'tcx>>,
463    {
464        let pos = NonZero::new(self.position()).unwrap();
465
466        assert_eq!(self.lazy_state, LazyState::NoNode);
467        self.lazy_state = LazyState::NodeStart(pos);
468        value.borrow().encode(self);
469        self.lazy_state = LazyState::NoNode;
470
471        assert!(pos.get() <= self.position());
472
473        LazyValue::from_position(pos)
474    }
475
476    fn lazy_array<T: ParameterizedOverTcx, I: IntoIterator<Item = B>, B: Borrow<T::Value<'tcx>>>(
477        &mut self,
478        values: I,
479    ) -> LazyArray<T>
480    where
481        T::Value<'tcx>: Encodable<EncodeContext<'a, 'tcx>>,
482    {
483        let pos = NonZero::new(self.position()).unwrap();
484
485        assert_eq!(self.lazy_state, LazyState::NoNode);
486        self.lazy_state = LazyState::NodeStart(pos);
487        let len = values.into_iter().map(|value| value.borrow().encode(self)).count();
488        self.lazy_state = LazyState::NoNode;
489
490        assert!(pos.get() <= self.position());
491
492        LazyArray::from_position_and_num_elems(pos, len)
493    }
494
495    fn encode_def_path_table(&mut self) {
496        let table = self.tcx.def_path_table();
497        if self.is_proc_macro {
498            for def_index in std::iter::once(CRATE_DEF_INDEX)
499                .chain(self.tcx.resolutions(()).proc_macros.iter().map(|p| p.local_def_index))
500            {
501                let def_key = self.lazy(table.def_key(def_index));
502                let def_path_hash = table.def_path_hash(def_index);
503                self.tables.def_keys.set_some(def_index, def_key);
504                self.tables.def_path_hashes.set(def_index, def_path_hash.local_hash().as_u64());
505            }
506        } else {
507            for (def_index, def_key, def_path_hash) in table.enumerated_keys_and_path_hashes() {
508                let def_key = self.lazy(def_key);
509                self.tables.def_keys.set_some(def_index, def_key);
510                self.tables.def_path_hashes.set(def_index, def_path_hash.local_hash().as_u64());
511            }
512        }
513    }
514
515    fn encode_def_path_hash_map(&mut self) -> LazyValue<DefPathHashMapRef<'static>> {
516        self.lazy(DefPathHashMapRef::BorrowedFromTcx(self.tcx.def_path_hash_to_def_index_map()))
517    }
518
519    fn encode_source_map(&mut self) -> LazyTable<u32, Option<LazyValue<rustc_span::SourceFile>>> {
520        let source_map = self.tcx.sess.source_map();
521        let all_source_files = source_map.files();
522
523        // By replacing the `Option` with `None`, we ensure that we can't
524        // accidentally serialize any more `Span`s after the source map encoding
525        // is done.
526        let required_source_files = self.required_source_files.take().unwrap();
527
528        let working_directory = &self.tcx.sess.opts.working_dir;
529
530        let mut adapted = TableBuilder::default();
531
532        let local_crate_stable_id = self.tcx.stable_crate_id(LOCAL_CRATE);
533
534        // Only serialize `SourceFile`s that were used during the encoding of a `Span`.
535        //
536        // The order in which we encode source files is important here: the on-disk format for
537        // `Span` contains the index of the corresponding `SourceFile`.
538        for (on_disk_index, &source_file_index) in required_source_files.iter().enumerate() {
539            let source_file = &all_source_files[source_file_index];
540            // Don't serialize imported `SourceFile`s, unless we're in a proc-macro crate.
541            assert!(!source_file.is_imported() || self.is_proc_macro);
542
543            // At export time we expand all source file paths to absolute paths because
544            // downstream compilation sessions can have a different compiler working
545            // directory, so relative paths from this or any other upstream crate
546            // won't be valid anymore.
547            //
548            // At this point we also erase the actual on-disk path and only keep
549            // the remapped version -- as is necessary for reproducible builds.
550            let mut adapted_source_file = (**source_file).clone();
551
552            match source_file.name {
553                FileName::Real(ref original_file_name) => {
554                    // FIXME: This should probably to conditionally remapped under
555                    // a RemapPathScopeComponents but which one?
556                    let adapted_file_name = source_map
557                        .path_mapping()
558                        .to_embeddable_absolute_path(original_file_name.clone(), working_directory);
559
560                    adapted_source_file.name = FileName::Real(adapted_file_name);
561                }
562                _ => {
563                    // expanded code, not from a file
564                }
565            };
566
567            // We're serializing this `SourceFile` into our crate metadata,
568            // so mark it as coming from this crate.
569            // This also ensures that we don't try to deserialize the
570            // `CrateNum` for a proc-macro dependency - since proc macro
571            // dependencies aren't loaded when we deserialize a proc-macro,
572            // trying to remap the `CrateNum` would fail.
573            if self.is_proc_macro {
574                adapted_source_file.cnum = LOCAL_CRATE;
575            }
576
577            // Update the `StableSourceFileId` to make sure it incorporates the
578            // id of the current crate. This way it will be unique within the
579            // crate graph during downstream compilation sessions.
580            adapted_source_file.stable_id = StableSourceFileId::from_filename_for_export(
581                &adapted_source_file.name,
582                local_crate_stable_id,
583            );
584
585            let on_disk_index: u32 =
586                on_disk_index.try_into().expect("cannot export more than U32_MAX files");
587            adapted.set_some(on_disk_index, self.lazy(adapted_source_file));
588        }
589
590        adapted.encode(&mut self.opaque)
591    }
592
593    fn encode_crate_root(&mut self) -> LazyValue<CrateRoot> {
594        let tcx = self.tcx;
595        let mut stats: Vec<(&'static str, usize)> = Vec::with_capacity(32);
596
597        macro_rules! stat {
598            ($label:literal, $f:expr) => {{
599                let orig_pos = self.position();
600                let res = $f();
601                stats.push(($label, self.position() - orig_pos));
602                res
603            }};
604        }
605
606        // We have already encoded some things. Get their combined size from the current position.
607        stats.push(("preamble", self.position()));
608
609        let (crate_deps, dylib_dependency_formats) =
610            stat!("dep", || (self.encode_crate_deps(), self.encode_dylib_dependency_formats()));
611
612        let lib_features = stat!("lib-features", || self.encode_lib_features());
613
614        let stability_implications =
615            stat!("stability-implications", || self.encode_stability_implications());
616
617        let (lang_items, lang_items_missing) = stat!("lang-items", || {
618            (self.encode_lang_items(), self.encode_lang_items_missing())
619        });
620
621        let stripped_cfg_items = stat!("stripped-cfg-items", || self.encode_stripped_cfg_items());
622
623        let diagnostic_items = stat!("diagnostic-items", || self.encode_diagnostic_items());
624
625        let native_libraries = stat!("native-libs", || self.encode_native_libraries());
626
627        let foreign_modules = stat!("foreign-modules", || self.encode_foreign_modules());
628
629        _ = stat!("def-path-table", || self.encode_def_path_table());
630
631        // Encode the def IDs of traits, for rustdoc and diagnostics.
632        let traits = stat!("traits", || self.encode_traits());
633
634        // Encode the def IDs of impls, for coherence checking.
635        let impls = stat!("impls", || self.encode_impls());
636
637        let incoherent_impls = stat!("incoherent-impls", || self.encode_incoherent_impls());
638
639        _ = stat!("mir", || self.encode_mir());
640
641        _ = stat!("def-ids", || self.encode_def_ids());
642
643        let interpret_alloc_index = stat!("interpret-alloc-index", || {
644            let mut interpret_alloc_index = Vec::new();
645            let mut n = 0;
646            trace!("beginning to encode alloc ids");
647            loop {
648                let new_n = self.interpret_allocs.len();
649                // if we have found new ids, serialize those, too
650                if n == new_n {
651                    // otherwise, abort
652                    break;
653                }
654                trace!("encoding {} further alloc ids", new_n - n);
655                for idx in n..new_n {
656                    let id = self.interpret_allocs[idx];
657                    let pos = self.position() as u64;
658                    interpret_alloc_index.push(pos);
659                    interpret::specialized_encode_alloc_id(self, tcx, id);
660                }
661                n = new_n;
662            }
663            self.lazy_array(interpret_alloc_index)
664        });
665
666        // Encode the proc macro data. This affects `tables`, so we need to do this before we
667        // encode the tables. This overwrites def_keys, so it must happen after
668        // encode_def_path_table.
669        let proc_macro_data = stat!("proc-macro-data", || self.encode_proc_macros());
670
671        let tables = stat!("tables", || self.tables.encode(&mut self.opaque));
672
673        let debugger_visualizers =
674            stat!("debugger-visualizers", || self.encode_debugger_visualizers());
675
676        // Encode exported symbols info. This is prefetched in `encode_metadata`.
677        let exported_symbols = stat!("exported-symbols", || {
678            self.encode_exported_symbols(tcx.exported_symbols(LOCAL_CRATE))
679        });
680
681        // Encode the hygiene data.
682        // IMPORTANT: this *must* be the last thing that we encode (other than `SourceMap`). The
683        // process of encoding other items (e.g. `optimized_mir`) may cause us to load data from
684        // the incremental cache. If this causes us to deserialize a `Span`, then we may load
685        // additional `SyntaxContext`s into the global `HygieneData`. Therefore, we need to encode
686        // the hygiene data last to ensure that we encode any `SyntaxContext`s that might be used.
687        let (syntax_contexts, expn_data, expn_hashes) = stat!("hygiene", || self.encode_hygiene());
688
689        let def_path_hash_map = stat!("def-path-hash-map", || self.encode_def_path_hash_map());
690
691        // Encode source_map. This needs to be done last, because encoding `Span`s tells us which
692        // `SourceFiles` we actually need to encode.
693        let source_map = stat!("source-map", || self.encode_source_map());
694        let target_modifiers = stat!("target-modifiers", || self.encode_target_modifiers());
695
696        let root = stat!("final", || {
697            let attrs = tcx.hir_krate_attrs();
698            self.lazy(CrateRoot {
699                header: CrateHeader {
700                    name: tcx.crate_name(LOCAL_CRATE),
701                    triple: tcx.sess.opts.target_triple.clone(),
702                    hash: tcx.crate_hash(LOCAL_CRATE),
703                    is_proc_macro_crate: proc_macro_data.is_some(),
704                },
705                extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
706                stable_crate_id: tcx.def_path_hash(LOCAL_CRATE.as_def_id()).stable_crate_id(),
707                required_panic_strategy: tcx.required_panic_strategy(LOCAL_CRATE),
708                panic_in_drop_strategy: tcx.sess.opts.unstable_opts.panic_in_drop,
709                edition: tcx.sess.edition(),
710                has_global_allocator: tcx.has_global_allocator(LOCAL_CRATE),
711                has_alloc_error_handler: tcx.has_alloc_error_handler(LOCAL_CRATE),
712                has_panic_handler: tcx.has_panic_handler(LOCAL_CRATE),
713                has_default_lib_allocator: ast::attr::contains_name(
714                    attrs,
715                    sym::default_lib_allocator,
716                ),
717                proc_macro_data,
718                debugger_visualizers,
719                compiler_builtins: ast::attr::contains_name(attrs, sym::compiler_builtins),
720                needs_allocator: ast::attr::contains_name(attrs, sym::needs_allocator),
721                needs_panic_runtime: ast::attr::contains_name(attrs, sym::needs_panic_runtime),
722                no_builtins: ast::attr::contains_name(attrs, sym::no_builtins),
723                panic_runtime: ast::attr::contains_name(attrs, sym::panic_runtime),
724                profiler_runtime: ast::attr::contains_name(attrs, sym::profiler_runtime),
725                symbol_mangling_version: tcx.sess.opts.get_symbol_mangling_version(),
726
727                crate_deps,
728                dylib_dependency_formats,
729                lib_features,
730                stability_implications,
731                lang_items,
732                diagnostic_items,
733                lang_items_missing,
734                stripped_cfg_items,
735                native_libraries,
736                foreign_modules,
737                source_map,
738                target_modifiers,
739                traits,
740                impls,
741                incoherent_impls,
742                exported_symbols,
743                interpret_alloc_index,
744                tables,
745                syntax_contexts,
746                expn_data,
747                expn_hashes,
748                def_path_hash_map,
749                specialization_enabled_in: tcx.specialization_enabled_in(LOCAL_CRATE),
750            })
751        });
752
753        let total_bytes = self.position();
754
755        let computed_total_bytes: usize = stats.iter().map(|(_, size)| size).sum();
756        assert_eq!(total_bytes, computed_total_bytes);
757
758        if tcx.sess.opts.unstable_opts.meta_stats {
759            self.opaque.flush();
760
761            // Rewind and re-read all the metadata to count the zero bytes we wrote.
762            let pos_before_rewind = self.opaque.file().stream_position().unwrap();
763            let mut zero_bytes = 0;
764            self.opaque.file().rewind().unwrap();
765            let file = std::io::BufReader::new(self.opaque.file());
766            for e in file.bytes() {
767                if e.unwrap() == 0 {
768                    zero_bytes += 1;
769                }
770            }
771            assert_eq!(self.opaque.file().stream_position().unwrap(), pos_before_rewind);
772
773            stats.sort_by_key(|&(_, usize)| usize);
774
775            let prefix = "meta-stats";
776            let perc = |bytes| (bytes * 100) as f64 / total_bytes as f64;
777
778            eprintln!("{prefix} METADATA STATS");
779            eprintln!("{} {:<23}{:>10}", prefix, "Section", "Size");
780            eprintln!("{prefix} ----------------------------------------------------------------");
781            for (label, size) in stats {
782                eprintln!(
783                    "{} {:<23}{:>10} ({:4.1}%)",
784                    prefix,
785                    label,
786                    format_with_underscores(size),
787                    perc(size)
788                );
789            }
790            eprintln!("{prefix} ----------------------------------------------------------------");
791            eprintln!(
792                "{} {:<23}{:>10} (of which {:.1}% are zero bytes)",
793                prefix,
794                "Total",
795                format_with_underscores(total_bytes),
796                perc(zero_bytes)
797            );
798            eprintln!("{prefix}");
799        }
800
801        root
802    }
803}
804
805struct AnalyzeAttrState<'a> {
806    is_exported: bool,
807    is_doc_hidden: bool,
808    features: &'a Features,
809}
810
811/// Returns whether an attribute needs to be recorded in metadata, that is, if it's usable and
812/// useful in downstream crates. Local-only attributes are an obvious example, but some
813/// rustdoc-specific attributes can equally be of use while documenting the current crate only.
814///
815/// Removing these superfluous attributes speeds up compilation by making the metadata smaller.
816///
817/// Note: the `is_exported` parameter is used to cache whether the given `DefId` has a public
818/// visibility: this is a piece of data that can be computed once per defid, and not once per
819/// attribute. Some attributes would only be usable downstream if they are public.
820#[inline]
821fn analyze_attr(attr: &impl AttributeExt, state: &mut AnalyzeAttrState<'_>) -> bool {
822    let mut should_encode = false;
823    if !rustc_feature::encode_cross_crate(attr.name_or_empty()) {
824        // Attributes not marked encode-cross-crate don't need to be encoded for downstream crates.
825    } else if attr.doc_str().is_some() {
826        // We keep all doc comments reachable to rustdoc because they might be "imported" into
827        // downstream crates if they use `#[doc(inline)]` to copy an item's documentation into
828        // their own.
829        if state.is_exported {
830            should_encode = true;
831        }
832    } else if attr.has_name(sym::doc) {
833        // If this is a `doc` attribute that doesn't have anything except maybe `inline` (as in
834        // `#[doc(inline)]`), then we can remove it. It won't be inlinable in downstream crates.
835        if let Some(item_list) = attr.meta_item_list() {
836            for item in item_list {
837                if !item.has_name(sym::inline) {
838                    should_encode = true;
839                    if item.has_name(sym::hidden) {
840                        state.is_doc_hidden = true;
841                        break;
842                    }
843                }
844            }
845        }
846    } else if let &[sym::diagnostic, seg] = &*attr.path() {
847        should_encode = rustc_feature::is_stable_diagnostic_attribute(seg, state.features);
848    } else {
849        should_encode = true;
850    }
851    should_encode
852}
853
854fn should_encode_span(def_kind: DefKind) -> bool {
855    match def_kind {
856        DefKind::Mod
857        | DefKind::Struct
858        | DefKind::Union
859        | DefKind::Enum
860        | DefKind::Variant
861        | DefKind::Trait
862        | DefKind::TyAlias
863        | DefKind::ForeignTy
864        | DefKind::TraitAlias
865        | DefKind::AssocTy
866        | DefKind::TyParam
867        | DefKind::ConstParam
868        | DefKind::LifetimeParam
869        | DefKind::Fn
870        | DefKind::Const
871        | DefKind::Static { .. }
872        | DefKind::Ctor(..)
873        | DefKind::AssocFn
874        | DefKind::AssocConst
875        | DefKind::Macro(_)
876        | DefKind::ExternCrate
877        | DefKind::Use
878        | DefKind::AnonConst
879        | DefKind::InlineConst
880        | DefKind::OpaqueTy
881        | DefKind::Field
882        | DefKind::Impl { .. }
883        | DefKind::Closure
884        | DefKind::SyntheticCoroutineBody => true,
885        DefKind::ForeignMod | DefKind::GlobalAsm => false,
886    }
887}
888
889fn should_encode_attrs(def_kind: DefKind) -> bool {
890    match def_kind {
891        DefKind::Mod
892        | DefKind::Struct
893        | DefKind::Union
894        | DefKind::Enum
895        | DefKind::Variant
896        | DefKind::Trait
897        | DefKind::TyAlias
898        | DefKind::ForeignTy
899        | DefKind::TraitAlias
900        | DefKind::AssocTy
901        | DefKind::Fn
902        | DefKind::Const
903        | DefKind::Static { nested: false, .. }
904        | DefKind::AssocFn
905        | DefKind::AssocConst
906        | DefKind::Macro(_)
907        | DefKind::Field
908        | DefKind::Impl { .. } => true,
909        // Tools may want to be able to detect their tool lints on
910        // closures from upstream crates, too. This is used by
911        // https://github.com/model-checking/kani and is not a performance
912        // or maintenance issue for us.
913        DefKind::Closure => true,
914        DefKind::SyntheticCoroutineBody => false,
915        DefKind::TyParam
916        | DefKind::ConstParam
917        | DefKind::Ctor(..)
918        | DefKind::ExternCrate
919        | DefKind::Use
920        | DefKind::ForeignMod
921        | DefKind::AnonConst
922        | DefKind::InlineConst
923        | DefKind::OpaqueTy
924        | DefKind::LifetimeParam
925        | DefKind::Static { nested: true, .. }
926        | DefKind::GlobalAsm => false,
927    }
928}
929
930fn should_encode_expn_that_defined(def_kind: DefKind) -> bool {
931    match def_kind {
932        DefKind::Mod
933        | DefKind::Struct
934        | DefKind::Union
935        | DefKind::Enum
936        | DefKind::Variant
937        | DefKind::Trait
938        | DefKind::Impl { .. } => true,
939        DefKind::TyAlias
940        | DefKind::ForeignTy
941        | DefKind::TraitAlias
942        | DefKind::AssocTy
943        | DefKind::TyParam
944        | DefKind::Fn
945        | DefKind::Const
946        | DefKind::ConstParam
947        | DefKind::Static { .. }
948        | DefKind::Ctor(..)
949        | DefKind::AssocFn
950        | DefKind::AssocConst
951        | DefKind::Macro(_)
952        | DefKind::ExternCrate
953        | DefKind::Use
954        | DefKind::ForeignMod
955        | DefKind::AnonConst
956        | DefKind::InlineConst
957        | DefKind::OpaqueTy
958        | DefKind::Field
959        | DefKind::LifetimeParam
960        | DefKind::GlobalAsm
961        | DefKind::Closure
962        | DefKind::SyntheticCoroutineBody => false,
963    }
964}
965
966fn should_encode_visibility(def_kind: DefKind) -> bool {
967    match def_kind {
968        DefKind::Mod
969        | DefKind::Struct
970        | DefKind::Union
971        | DefKind::Enum
972        | DefKind::Variant
973        | DefKind::Trait
974        | DefKind::TyAlias
975        | DefKind::ForeignTy
976        | DefKind::TraitAlias
977        | DefKind::AssocTy
978        | DefKind::Fn
979        | DefKind::Const
980        | DefKind::Static { nested: false, .. }
981        | DefKind::Ctor(..)
982        | DefKind::AssocFn
983        | DefKind::AssocConst
984        | DefKind::Macro(..)
985        | DefKind::Field => true,
986        DefKind::Use
987        | DefKind::ForeignMod
988        | DefKind::TyParam
989        | DefKind::ConstParam
990        | DefKind::LifetimeParam
991        | DefKind::AnonConst
992        | DefKind::InlineConst
993        | DefKind::Static { nested: true, .. }
994        | DefKind::OpaqueTy
995        | DefKind::GlobalAsm
996        | DefKind::Impl { .. }
997        | DefKind::Closure
998        | DefKind::ExternCrate
999        | DefKind::SyntheticCoroutineBody => false,
1000    }
1001}
1002
1003fn should_encode_stability(def_kind: DefKind) -> bool {
1004    match def_kind {
1005        DefKind::Mod
1006        | DefKind::Ctor(..)
1007        | DefKind::Variant
1008        | DefKind::Field
1009        | DefKind::Struct
1010        | DefKind::AssocTy
1011        | DefKind::AssocFn
1012        | DefKind::AssocConst
1013        | DefKind::TyParam
1014        | DefKind::ConstParam
1015        | DefKind::Static { .. }
1016        | DefKind::Const
1017        | DefKind::Fn
1018        | DefKind::ForeignMod
1019        | DefKind::TyAlias
1020        | DefKind::OpaqueTy
1021        | DefKind::Enum
1022        | DefKind::Union
1023        | DefKind::Impl { .. }
1024        | DefKind::Trait
1025        | DefKind::TraitAlias
1026        | DefKind::Macro(..)
1027        | DefKind::ForeignTy => true,
1028        DefKind::Use
1029        | DefKind::LifetimeParam
1030        | DefKind::AnonConst
1031        | DefKind::InlineConst
1032        | DefKind::GlobalAsm
1033        | DefKind::Closure
1034        | DefKind::ExternCrate
1035        | DefKind::SyntheticCoroutineBody => false,
1036    }
1037}
1038
1039/// Whether we should encode MIR. Return a pair, resp. for CTFE and for LLVM.
1040///
1041/// Computing, optimizing and encoding the MIR is a relatively expensive operation.
1042/// We want to avoid this work when not required. Therefore:
1043/// - we only compute `mir_for_ctfe` on items with const-eval semantics;
1044/// - we skip `optimized_mir` for check runs.
1045/// - we only encode `optimized_mir` that could be generated in other crates, that is, a code that
1046///   is either generic or has inline hint, and is reachable from the other crates (contained
1047///   in reachable set).
1048///
1049/// Note: Reachable set describes definitions that might be generated or referenced from other
1050/// crates and it can be used to limit optimized MIR that needs to be encoded. On the other hand,
1051/// the reachable set doesn't have much to say about which definitions might be evaluated at compile
1052/// time in other crates, so it cannot be used to omit CTFE MIR. For example, `f` below is
1053/// unreachable and yet it can be evaluated in other crates:
1054///
1055/// ```
1056/// const fn f() -> usize { 0 }
1057/// pub struct S { pub a: [usize; f()] }
1058/// ```
1059fn should_encode_mir(
1060    tcx: TyCtxt<'_>,
1061    reachable_set: &LocalDefIdSet,
1062    def_id: LocalDefId,
1063) -> (bool, bool) {
1064    match tcx.def_kind(def_id) {
1065        // Constructors
1066        DefKind::Ctor(_, _) => {
1067            let mir_opt_base = tcx.sess.opts.output_types.should_codegen()
1068                || tcx.sess.opts.unstable_opts.always_encode_mir;
1069            (true, mir_opt_base)
1070        }
1071        // Constants
1072        DefKind::AnonConst | DefKind::InlineConst | DefKind::AssocConst | DefKind::Const => {
1073            (true, false)
1074        }
1075        // Coroutines require optimized MIR to compute layout.
1076        DefKind::Closure if tcx.is_coroutine(def_id.to_def_id()) => (false, true),
1077        DefKind::SyntheticCoroutineBody => (false, true),
1078        // Full-fledged functions + closures
1079        DefKind::AssocFn | DefKind::Fn | DefKind::Closure => {
1080            let generics = tcx.generics_of(def_id);
1081            let opt = tcx.sess.opts.unstable_opts.always_encode_mir
1082                || (tcx.sess.opts.output_types.should_codegen()
1083                    && reachable_set.contains(&def_id)
1084                    && (generics.requires_monomorphization(tcx)
1085                        || tcx.cross_crate_inlinable(def_id)));
1086            // The function has a `const` modifier or is in a `#[const_trait]`.
1087            let is_const_fn = tcx.is_const_fn(def_id.to_def_id())
1088                || tcx.is_const_default_method(def_id.to_def_id());
1089            (is_const_fn, opt)
1090        }
1091        // The others don't have MIR.
1092        _ => (false, false),
1093    }
1094}
1095
1096fn should_encode_variances<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, def_kind: DefKind) -> bool {
1097    match def_kind {
1098        DefKind::Struct
1099        | DefKind::Union
1100        | DefKind::Enum
1101        | DefKind::Variant
1102        | DefKind::OpaqueTy
1103        | DefKind::Fn
1104        | DefKind::Ctor(..)
1105        | DefKind::AssocFn => true,
1106        DefKind::AssocTy => {
1107            // Only encode variances for RPITITs (for traits)
1108            matches!(tcx.opt_rpitit_info(def_id), Some(ty::ImplTraitInTraitData::Trait { .. }))
1109        }
1110        DefKind::Mod
1111        | DefKind::Field
1112        | DefKind::AssocConst
1113        | DefKind::TyParam
1114        | DefKind::ConstParam
1115        | DefKind::Static { .. }
1116        | DefKind::Const
1117        | DefKind::ForeignMod
1118        | DefKind::Impl { .. }
1119        | DefKind::Trait
1120        | DefKind::TraitAlias
1121        | DefKind::Macro(..)
1122        | DefKind::ForeignTy
1123        | DefKind::Use
1124        | DefKind::LifetimeParam
1125        | DefKind::AnonConst
1126        | DefKind::InlineConst
1127        | DefKind::GlobalAsm
1128        | DefKind::Closure
1129        | DefKind::ExternCrate
1130        | DefKind::SyntheticCoroutineBody => false,
1131        DefKind::TyAlias => tcx.type_alias_is_lazy(def_id),
1132    }
1133}
1134
1135fn should_encode_generics(def_kind: DefKind) -> bool {
1136    match def_kind {
1137        DefKind::Struct
1138        | DefKind::Union
1139        | DefKind::Enum
1140        | DefKind::Variant
1141        | DefKind::Trait
1142        | DefKind::TyAlias
1143        | DefKind::ForeignTy
1144        | DefKind::TraitAlias
1145        | DefKind::AssocTy
1146        | DefKind::Fn
1147        | DefKind::Const
1148        | DefKind::Static { .. }
1149        | DefKind::Ctor(..)
1150        | DefKind::AssocFn
1151        | DefKind::AssocConst
1152        | DefKind::AnonConst
1153        | DefKind::InlineConst
1154        | DefKind::OpaqueTy
1155        | DefKind::Impl { .. }
1156        | DefKind::Field
1157        | DefKind::TyParam
1158        | DefKind::Closure
1159        | DefKind::SyntheticCoroutineBody => true,
1160        DefKind::Mod
1161        | DefKind::ForeignMod
1162        | DefKind::ConstParam
1163        | DefKind::Macro(..)
1164        | DefKind::Use
1165        | DefKind::LifetimeParam
1166        | DefKind::GlobalAsm
1167        | DefKind::ExternCrate => false,
1168    }
1169}
1170
1171fn should_encode_type(tcx: TyCtxt<'_>, def_id: LocalDefId, def_kind: DefKind) -> bool {
1172    match def_kind {
1173        DefKind::Struct
1174        | DefKind::Union
1175        | DefKind::Enum
1176        | DefKind::Variant
1177        | DefKind::Ctor(..)
1178        | DefKind::Field
1179        | DefKind::Fn
1180        | DefKind::Const
1181        | DefKind::Static { nested: false, .. }
1182        | DefKind::TyAlias
1183        | DefKind::ForeignTy
1184        | DefKind::Impl { .. }
1185        | DefKind::AssocFn
1186        | DefKind::AssocConst
1187        | DefKind::Closure
1188        | DefKind::ConstParam
1189        | DefKind::AnonConst
1190        | DefKind::InlineConst
1191        | DefKind::SyntheticCoroutineBody => true,
1192
1193        DefKind::OpaqueTy => {
1194            let origin = tcx.local_opaque_ty_origin(def_id);
1195            if let hir::OpaqueTyOrigin::FnReturn { parent, .. }
1196            | hir::OpaqueTyOrigin::AsyncFn { parent, .. } = origin
1197                && let hir::Node::TraitItem(trait_item) = tcx.hir_node_by_def_id(parent)
1198                && let (_, hir::TraitFn::Required(..)) = trait_item.expect_fn()
1199            {
1200                false
1201            } else {
1202                true
1203            }
1204        }
1205
1206        DefKind::AssocTy => {
1207            let assoc_item = tcx.associated_item(def_id);
1208            match assoc_item.container {
1209                ty::AssocItemContainer::Impl => true,
1210                ty::AssocItemContainer::Trait => assoc_item.defaultness(tcx).has_value(),
1211            }
1212        }
1213        DefKind::TyParam => {
1214            let hir::Node::GenericParam(param) = tcx.hir_node_by_def_id(def_id) else { bug!() };
1215            let hir::GenericParamKind::Type { default, .. } = param.kind else { bug!() };
1216            default.is_some()
1217        }
1218
1219        DefKind::Trait
1220        | DefKind::TraitAlias
1221        | DefKind::Mod
1222        | DefKind::ForeignMod
1223        | DefKind::Macro(..)
1224        | DefKind::Static { nested: true, .. }
1225        | DefKind::Use
1226        | DefKind::LifetimeParam
1227        | DefKind::GlobalAsm
1228        | DefKind::ExternCrate => false,
1229    }
1230}
1231
1232fn should_encode_fn_sig(def_kind: DefKind) -> bool {
1233    match def_kind {
1234        DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fn) => true,
1235
1236        DefKind::Struct
1237        | DefKind::Union
1238        | DefKind::Enum
1239        | DefKind::Variant
1240        | DefKind::Field
1241        | DefKind::Const
1242        | DefKind::Static { .. }
1243        | DefKind::Ctor(..)
1244        | DefKind::TyAlias
1245        | DefKind::OpaqueTy
1246        | DefKind::ForeignTy
1247        | DefKind::Impl { .. }
1248        | DefKind::AssocConst
1249        | DefKind::Closure
1250        | DefKind::ConstParam
1251        | DefKind::AnonConst
1252        | DefKind::InlineConst
1253        | DefKind::AssocTy
1254        | DefKind::TyParam
1255        | DefKind::Trait
1256        | DefKind::TraitAlias
1257        | DefKind::Mod
1258        | DefKind::ForeignMod
1259        | DefKind::Macro(..)
1260        | DefKind::Use
1261        | DefKind::LifetimeParam
1262        | DefKind::GlobalAsm
1263        | DefKind::ExternCrate
1264        | DefKind::SyntheticCoroutineBody => false,
1265    }
1266}
1267
1268fn should_encode_constness(def_kind: DefKind) -> bool {
1269    match def_kind {
1270        DefKind::Fn | DefKind::AssocFn | DefKind::Closure | DefKind::Ctor(_, CtorKind::Fn) => true,
1271
1272        DefKind::Struct
1273        | DefKind::Union
1274        | DefKind::Enum
1275        | DefKind::Field
1276        | DefKind::Const
1277        | DefKind::AssocConst
1278        | DefKind::AnonConst
1279        | DefKind::Static { .. }
1280        | DefKind::TyAlias
1281        | DefKind::OpaqueTy
1282        | DefKind::Impl { .. }
1283        | DefKind::ForeignTy
1284        | DefKind::ConstParam
1285        | DefKind::InlineConst
1286        | DefKind::AssocTy
1287        | DefKind::TyParam
1288        | DefKind::Trait
1289        | DefKind::TraitAlias
1290        | DefKind::Mod
1291        | DefKind::ForeignMod
1292        | DefKind::Macro(..)
1293        | DefKind::Use
1294        | DefKind::LifetimeParam
1295        | DefKind::GlobalAsm
1296        | DefKind::ExternCrate
1297        | DefKind::Ctor(_, CtorKind::Const)
1298        | DefKind::Variant
1299        | DefKind::SyntheticCoroutineBody => false,
1300    }
1301}
1302
1303fn should_encode_const(def_kind: DefKind) -> bool {
1304    match def_kind {
1305        DefKind::Const | DefKind::AssocConst | DefKind::AnonConst | DefKind::InlineConst => true,
1306
1307        DefKind::Struct
1308        | DefKind::Union
1309        | DefKind::Enum
1310        | DefKind::Variant
1311        | DefKind::Ctor(..)
1312        | DefKind::Field
1313        | DefKind::Fn
1314        | DefKind::Static { .. }
1315        | DefKind::TyAlias
1316        | DefKind::OpaqueTy
1317        | DefKind::ForeignTy
1318        | DefKind::Impl { .. }
1319        | DefKind::AssocFn
1320        | DefKind::Closure
1321        | DefKind::ConstParam
1322        | DefKind::AssocTy
1323        | DefKind::TyParam
1324        | DefKind::Trait
1325        | DefKind::TraitAlias
1326        | DefKind::Mod
1327        | DefKind::ForeignMod
1328        | DefKind::Macro(..)
1329        | DefKind::Use
1330        | DefKind::LifetimeParam
1331        | DefKind::GlobalAsm
1332        | DefKind::ExternCrate
1333        | DefKind::SyntheticCoroutineBody => false,
1334    }
1335}
1336
1337fn should_encode_fn_impl_trait_in_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
1338    if let Some(assoc_item) = tcx.opt_associated_item(def_id)
1339        && assoc_item.container == ty::AssocItemContainer::Trait
1340        && assoc_item.kind == ty::AssocKind::Fn
1341    {
1342        true
1343    } else {
1344        false
1345    }
1346}
1347
1348impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
1349    fn encode_attrs(&mut self, def_id: LocalDefId) {
1350        let tcx = self.tcx;
1351        let mut state = AnalyzeAttrState {
1352            is_exported: tcx.effective_visibilities(()).is_exported(def_id),
1353            is_doc_hidden: false,
1354            features: &tcx.features(),
1355        };
1356        let attr_iter = tcx
1357            .hir_attrs(tcx.local_def_id_to_hir_id(def_id))
1358            .iter()
1359            .filter(|attr| analyze_attr(*attr, &mut state));
1360
1361        record_array!(self.tables.attributes[def_id.to_def_id()] <- attr_iter);
1362
1363        let mut attr_flags = AttrFlags::empty();
1364        if state.is_doc_hidden {
1365            attr_flags |= AttrFlags::IS_DOC_HIDDEN;
1366        }
1367        self.tables.attr_flags.set(def_id.local_def_index, attr_flags);
1368    }
1369
1370    fn encode_def_ids(&mut self) {
1371        self.encode_info_for_mod(CRATE_DEF_ID);
1372
1373        // Proc-macro crates only export proc-macro items, which are looked
1374        // up using `proc_macro_data`
1375        if self.is_proc_macro {
1376            return;
1377        }
1378
1379        let tcx = self.tcx;
1380
1381        for local_id in tcx.iter_local_def_id() {
1382            let def_id = local_id.to_def_id();
1383            let def_kind = tcx.def_kind(local_id);
1384            self.tables.def_kind.set_some(def_id.index, def_kind);
1385
1386            // The `DefCollector` will sometimes create unnecessary `DefId`s
1387            // for trivial const arguments which are directly lowered to
1388            // `ConstArgKind::Path`. We never actually access this `DefId`
1389            // anywhere so we don't need to encode it for other crates.
1390            if def_kind == DefKind::AnonConst
1391                && match tcx.hir_node_by_def_id(local_id) {
1392                    hir::Node::ConstArg(hir::ConstArg { kind, .. }) => match kind {
1393                        // Skip encoding defs for these as they should not have had a `DefId` created
1394                        hir::ConstArgKind::Path(..) | hir::ConstArgKind::Infer(..) => true,
1395                        hir::ConstArgKind::Anon(..) => false,
1396                    },
1397                    _ => false,
1398                }
1399            {
1400                continue;
1401            }
1402
1403            if def_kind == DefKind::Field
1404                && let hir::Node::Field(field) = tcx.hir_node_by_def_id(local_id)
1405                && let Some(anon) = field.default
1406            {
1407                record!(self.tables.default_fields[def_id] <- anon.def_id.to_def_id());
1408            }
1409
1410            if should_encode_span(def_kind) {
1411                let def_span = tcx.def_span(local_id);
1412                record!(self.tables.def_span[def_id] <- def_span);
1413            }
1414            if should_encode_attrs(def_kind) {
1415                self.encode_attrs(local_id);
1416            }
1417            if should_encode_expn_that_defined(def_kind) {
1418                record!(self.tables.expn_that_defined[def_id] <- self.tcx.expn_that_defined(def_id));
1419            }
1420            if should_encode_span(def_kind)
1421                && let Some(ident_span) = tcx.def_ident_span(def_id)
1422            {
1423                record!(self.tables.def_ident_span[def_id] <- ident_span);
1424            }
1425            if def_kind.has_codegen_attrs() {
1426                record!(self.tables.codegen_fn_attrs[def_id] <- self.tcx.codegen_fn_attrs(def_id));
1427            }
1428            if should_encode_visibility(def_kind) {
1429                let vis =
1430                    self.tcx.local_visibility(local_id).map_id(|def_id| def_id.local_def_index);
1431                record!(self.tables.visibility[def_id] <- vis);
1432            }
1433            if should_encode_stability(def_kind) {
1434                self.encode_stability(def_id);
1435                self.encode_const_stability(def_id);
1436                self.encode_default_body_stability(def_id);
1437                self.encode_deprecation(def_id);
1438            }
1439            if should_encode_variances(tcx, def_id, def_kind) {
1440                let v = self.tcx.variances_of(def_id);
1441                record_array!(self.tables.variances_of[def_id] <- v);
1442            }
1443            if should_encode_fn_sig(def_kind) {
1444                record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
1445            }
1446            if should_encode_generics(def_kind) {
1447                let g = tcx.generics_of(def_id);
1448                record!(self.tables.generics_of[def_id] <- g);
1449                record!(self.tables.explicit_predicates_of[def_id] <- self.tcx.explicit_predicates_of(def_id));
1450                let inferred_outlives = self.tcx.inferred_outlives_of(def_id);
1451                record_defaulted_array!(self.tables.inferred_outlives_of[def_id] <- inferred_outlives);
1452
1453                for param in &g.own_params {
1454                    if let ty::GenericParamDefKind::Const { has_default: true, .. } = param.kind {
1455                        let default = self.tcx.const_param_default(param.def_id);
1456                        record!(self.tables.const_param_default[param.def_id] <- default);
1457                    }
1458                }
1459            }
1460            if tcx.is_conditionally_const(def_id) {
1461                record!(self.tables.const_conditions[def_id] <- self.tcx.const_conditions(def_id));
1462            }
1463            if should_encode_type(tcx, local_id, def_kind) {
1464                record!(self.tables.type_of[def_id] <- self.tcx.type_of(def_id));
1465            }
1466            if should_encode_constness(def_kind) {
1467                self.tables.constness.set_some(def_id.index, self.tcx.constness(def_id));
1468            }
1469            if let DefKind::Fn | DefKind::AssocFn = def_kind {
1470                self.tables.asyncness.set_some(def_id.index, tcx.asyncness(def_id));
1471                record_array!(self.tables.fn_arg_names[def_id] <- tcx.fn_arg_names(def_id));
1472            }
1473            if let Some(name) = tcx.intrinsic(def_id) {
1474                record!(self.tables.intrinsic[def_id] <- name);
1475            }
1476            if let DefKind::TyParam = def_kind {
1477                let default = self.tcx.object_lifetime_default(def_id);
1478                record!(self.tables.object_lifetime_default[def_id] <- default);
1479            }
1480            if let DefKind::Trait = def_kind {
1481                record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
1482                record_defaulted_array!(self.tables.explicit_super_predicates_of[def_id] <-
1483                    self.tcx.explicit_super_predicates_of(def_id).skip_binder());
1484                record_defaulted_array!(self.tables.explicit_implied_predicates_of[def_id] <-
1485                    self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
1486                let module_children = self.tcx.module_children_local(local_id);
1487                record_array!(self.tables.module_children_non_reexports[def_id] <-
1488                    module_children.iter().map(|child| child.res.def_id().index));
1489                if self.tcx.is_const_trait(def_id) {
1490                    record_defaulted_array!(self.tables.explicit_implied_const_bounds[def_id]
1491                        <- self.tcx.explicit_implied_const_bounds(def_id).skip_binder());
1492                }
1493            }
1494            if let DefKind::TraitAlias = def_kind {
1495                record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
1496                record_defaulted_array!(self.tables.explicit_super_predicates_of[def_id] <-
1497                    self.tcx.explicit_super_predicates_of(def_id).skip_binder());
1498                record_defaulted_array!(self.tables.explicit_implied_predicates_of[def_id] <-
1499                    self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
1500            }
1501            if let DefKind::Trait | DefKind::Impl { .. } = def_kind {
1502                let associated_item_def_ids = self.tcx.associated_item_def_ids(def_id);
1503                record_array!(self.tables.associated_item_or_field_def_ids[def_id] <-
1504                    associated_item_def_ids.iter().map(|&def_id| {
1505                        assert!(def_id.is_local());
1506                        def_id.index
1507                    })
1508                );
1509                for &def_id in associated_item_def_ids {
1510                    self.encode_info_for_assoc_item(def_id);
1511                }
1512            }
1513            if let DefKind::Closure | DefKind::SyntheticCoroutineBody = def_kind
1514                && let Some(coroutine_kind) = self.tcx.coroutine_kind(def_id)
1515            {
1516                self.tables.coroutine_kind.set(def_id.index, Some(coroutine_kind))
1517            }
1518            if def_kind == DefKind::Closure
1519                && tcx.type_of(def_id).skip_binder().is_coroutine_closure()
1520            {
1521                let coroutine_for_closure = self.tcx.coroutine_for_closure(def_id);
1522                self.tables
1523                    .coroutine_for_closure
1524                    .set_some(def_id.index, coroutine_for_closure.into());
1525
1526                // If this async closure has a by-move body, record it too.
1527                if tcx.needs_coroutine_by_move_body_def_id(coroutine_for_closure) {
1528                    self.tables.coroutine_by_move_body_def_id.set_some(
1529                        coroutine_for_closure.index,
1530                        self.tcx.coroutine_by_move_body_def_id(coroutine_for_closure).into(),
1531                    );
1532                }
1533            }
1534            if let DefKind::Static { .. } = def_kind {
1535                if !self.tcx.is_foreign_item(def_id) {
1536                    let data = self.tcx.eval_static_initializer(def_id).unwrap();
1537                    record!(self.tables.eval_static_initializer[def_id] <- data);
1538                }
1539            }
1540            if let DefKind::Enum | DefKind::Struct | DefKind::Union = def_kind {
1541                self.encode_info_for_adt(local_id);
1542            }
1543            if let DefKind::Mod = def_kind {
1544                self.encode_info_for_mod(local_id);
1545            }
1546            if let DefKind::Macro(_) = def_kind {
1547                self.encode_info_for_macro(local_id);
1548            }
1549            if let DefKind::TyAlias = def_kind {
1550                self.tables
1551                    .type_alias_is_lazy
1552                    .set(def_id.index, self.tcx.type_alias_is_lazy(def_id));
1553            }
1554            if let DefKind::OpaqueTy = def_kind {
1555                self.encode_explicit_item_bounds(def_id);
1556                self.encode_explicit_item_self_bounds(def_id);
1557                record!(self.tables.opaque_ty_origin[def_id] <- self.tcx.opaque_ty_origin(def_id));
1558                self.encode_precise_capturing_args(def_id);
1559                if tcx.is_conditionally_const(def_id) {
1560                    record_defaulted_array!(self.tables.explicit_implied_const_bounds[def_id]
1561                        <- tcx.explicit_implied_const_bounds(def_id).skip_binder());
1562                }
1563            }
1564            if tcx.impl_method_has_trait_impl_trait_tys(def_id)
1565                && let Ok(table) = self.tcx.collect_return_position_impl_trait_in_trait_tys(def_id)
1566            {
1567                record!(self.tables.trait_impl_trait_tys[def_id] <- table);
1568            }
1569            if should_encode_fn_impl_trait_in_trait(tcx, def_id) {
1570                let table = tcx.associated_types_for_impl_traits_in_associated_fn(def_id);
1571                record_defaulted_array!(self.tables.associated_types_for_impl_traits_in_associated_fn[def_id] <- table);
1572            }
1573        }
1574
1575        for (def_id, impls) in &tcx.crate_inherent_impls(()).0.inherent_impls {
1576            record_defaulted_array!(self.tables.inherent_impls[def_id.to_def_id()] <- impls.iter().map(|def_id| {
1577                assert!(def_id.is_local());
1578                def_id.index
1579            }));
1580        }
1581
1582        for (def_id, res_map) in &tcx.resolutions(()).doc_link_resolutions {
1583            record!(self.tables.doc_link_resolutions[def_id.to_def_id()] <- res_map);
1584        }
1585
1586        for (def_id, traits) in &tcx.resolutions(()).doc_link_traits_in_scope {
1587            record_array!(self.tables.doc_link_traits_in_scope[def_id.to_def_id()] <- traits);
1588        }
1589    }
1590
1591    #[instrument(level = "trace", skip(self))]
1592    fn encode_info_for_adt(&mut self, local_def_id: LocalDefId) {
1593        let def_id = local_def_id.to_def_id();
1594        let tcx = self.tcx;
1595        let adt_def = tcx.adt_def(def_id);
1596        record!(self.tables.repr_options[def_id] <- adt_def.repr());
1597
1598        let params_in_repr = self.tcx.params_in_repr(def_id);
1599        record!(self.tables.params_in_repr[def_id] <- params_in_repr);
1600
1601        if adt_def.is_enum() {
1602            let module_children = tcx.module_children_local(local_def_id);
1603            record_array!(self.tables.module_children_non_reexports[def_id] <-
1604                module_children.iter().map(|child| child.res.def_id().index));
1605        } else {
1606            // For non-enum, there is only one variant, and its def_id is the adt's.
1607            debug_assert_eq!(adt_def.variants().len(), 1);
1608            debug_assert_eq!(adt_def.non_enum_variant().def_id, def_id);
1609            // Therefore, the loop over variants will encode its fields as the adt's children.
1610        }
1611
1612        for (idx, variant) in adt_def.variants().iter_enumerated() {
1613            let data = VariantData {
1614                discr: variant.discr,
1615                idx,
1616                ctor: variant.ctor.map(|(kind, def_id)| (kind, def_id.index)),
1617                is_non_exhaustive: variant.is_field_list_non_exhaustive(),
1618            };
1619            record!(self.tables.variant_data[variant.def_id] <- data);
1620
1621            record_array!(self.tables.associated_item_or_field_def_ids[variant.def_id] <- variant.fields.iter().map(|f| {
1622                assert!(f.did.is_local());
1623                f.did.index
1624            }));
1625
1626            for field in &variant.fields {
1627                self.tables.safety.set_some(field.did.index, field.safety);
1628            }
1629
1630            if let Some((CtorKind::Fn, ctor_def_id)) = variant.ctor {
1631                let fn_sig = tcx.fn_sig(ctor_def_id);
1632                // FIXME only encode signature for ctor_def_id
1633                record!(self.tables.fn_sig[variant.def_id] <- fn_sig);
1634            }
1635        }
1636    }
1637
1638    #[instrument(level = "debug", skip(self))]
1639    fn encode_info_for_mod(&mut self, local_def_id: LocalDefId) {
1640        let tcx = self.tcx;
1641        let def_id = local_def_id.to_def_id();
1642
1643        // If we are encoding a proc-macro crates, `encode_info_for_mod` will
1644        // only ever get called for the crate root. We still want to encode
1645        // the crate root for consistency with other crates (some of the resolver
1646        // code uses it). However, we skip encoding anything relating to child
1647        // items - we encode information about proc-macros later on.
1648        if self.is_proc_macro {
1649            // Encode this here because we don't do it in encode_def_ids.
1650            record!(self.tables.expn_that_defined[def_id] <- tcx.expn_that_defined(local_def_id));
1651        } else {
1652            let module_children = tcx.module_children_local(local_def_id);
1653
1654            record_array!(self.tables.module_children_non_reexports[def_id] <-
1655                module_children.iter().filter(|child| child.reexport_chain.is_empty())
1656                    .map(|child| child.res.def_id().index));
1657
1658            record_defaulted_array!(self.tables.module_children_reexports[def_id] <-
1659                module_children.iter().filter(|child| !child.reexport_chain.is_empty()));
1660        }
1661    }
1662
1663    fn encode_explicit_item_bounds(&mut self, def_id: DefId) {
1664        debug!("EncodeContext::encode_explicit_item_bounds({:?})", def_id);
1665        let bounds = self.tcx.explicit_item_bounds(def_id).skip_binder();
1666        record_defaulted_array!(self.tables.explicit_item_bounds[def_id] <- bounds);
1667    }
1668
1669    fn encode_explicit_item_self_bounds(&mut self, def_id: DefId) {
1670        debug!("EncodeContext::encode_explicit_item_self_bounds({:?})", def_id);
1671        let bounds = self.tcx.explicit_item_self_bounds(def_id).skip_binder();
1672        record_defaulted_array!(self.tables.explicit_item_self_bounds[def_id] <- bounds);
1673    }
1674
1675    #[instrument(level = "debug", skip(self))]
1676    fn encode_info_for_assoc_item(&mut self, def_id: DefId) {
1677        let tcx = self.tcx;
1678        let item = tcx.associated_item(def_id);
1679
1680        self.tables.defaultness.set_some(def_id.index, item.defaultness(tcx));
1681        self.tables.assoc_container.set_some(def_id.index, item.container);
1682
1683        match item.container {
1684            AssocItemContainer::Trait => {
1685                if let ty::AssocKind::Type = item.kind {
1686                    self.encode_explicit_item_bounds(def_id);
1687                    self.encode_explicit_item_self_bounds(def_id);
1688                    if tcx.is_conditionally_const(def_id) {
1689                        record_defaulted_array!(self.tables.explicit_implied_const_bounds[def_id]
1690                            <- self.tcx.explicit_implied_const_bounds(def_id).skip_binder());
1691                    }
1692                }
1693            }
1694            AssocItemContainer::Impl => {
1695                if let Some(trait_item_def_id) = item.trait_item_def_id {
1696                    self.tables.trait_item_def_id.set_some(def_id.index, trait_item_def_id.into());
1697                }
1698            }
1699        }
1700        if let Some(rpitit_info) = item.opt_rpitit_info {
1701            record!(self.tables.opt_rpitit_info[def_id] <- rpitit_info);
1702            if matches!(rpitit_info, ty::ImplTraitInTraitData::Trait { .. }) {
1703                record_array!(
1704                    self.tables.assumed_wf_types_for_rpitit[def_id]
1705                        <- self.tcx.assumed_wf_types_for_rpitit(def_id)
1706                );
1707                self.encode_precise_capturing_args(def_id);
1708            }
1709        }
1710    }
1711
1712    fn encode_precise_capturing_args(&mut self, def_id: DefId) {
1713        let Some(precise_capturing_args) = self.tcx.rendered_precise_capturing_args(def_id) else {
1714            return;
1715        };
1716
1717        record_array!(self.tables.rendered_precise_capturing_args[def_id] <- precise_capturing_args);
1718    }
1719
1720    fn encode_mir(&mut self) {
1721        if self.is_proc_macro {
1722            return;
1723        }
1724
1725        let tcx = self.tcx;
1726        let reachable_set = tcx.reachable_set(());
1727
1728        let keys_and_jobs = tcx.mir_keys(()).iter().filter_map(|&def_id| {
1729            let (encode_const, encode_opt) = should_encode_mir(tcx, reachable_set, def_id);
1730            if encode_const || encode_opt { Some((def_id, encode_const, encode_opt)) } else { None }
1731        });
1732        for (def_id, encode_const, encode_opt) in keys_and_jobs {
1733            debug_assert!(encode_const || encode_opt);
1734
1735            debug!("EntryBuilder::encode_mir({:?})", def_id);
1736            if encode_opt {
1737                record!(self.tables.optimized_mir[def_id.to_def_id()] <- tcx.optimized_mir(def_id));
1738                self.tables
1739                    .cross_crate_inlinable
1740                    .set(def_id.to_def_id().index, self.tcx.cross_crate_inlinable(def_id));
1741                record!(self.tables.closure_saved_names_of_captured_variables[def_id.to_def_id()]
1742                    <- tcx.closure_saved_names_of_captured_variables(def_id));
1743
1744                if self.tcx.is_coroutine(def_id.to_def_id())
1745                    && let Some(witnesses) = tcx.mir_coroutine_witnesses(def_id)
1746                {
1747                    record!(self.tables.mir_coroutine_witnesses[def_id.to_def_id()] <- witnesses);
1748                }
1749            }
1750            if encode_const {
1751                record!(self.tables.mir_for_ctfe[def_id.to_def_id()] <- tcx.mir_for_ctfe(def_id));
1752
1753                // FIXME(generic_const_exprs): this feels wrong to have in `encode_mir`
1754                let abstract_const = tcx.thir_abstract_const(def_id);
1755                if let Ok(Some(abstract_const)) = abstract_const {
1756                    record!(self.tables.thir_abstract_const[def_id.to_def_id()] <- abstract_const);
1757                }
1758
1759                if should_encode_const(tcx.def_kind(def_id)) {
1760                    let qualifs = tcx.mir_const_qualif(def_id);
1761                    record!(self.tables.mir_const_qualif[def_id.to_def_id()] <- qualifs);
1762                    let body = tcx.hir_maybe_body_owned_by(def_id);
1763                    if let Some(body) = body {
1764                        let const_data = rendered_const(self.tcx, &body, def_id);
1765                        record!(self.tables.rendered_const[def_id.to_def_id()] <- const_data);
1766                    }
1767                }
1768            }
1769            record!(self.tables.promoted_mir[def_id.to_def_id()] <- tcx.promoted_mir(def_id));
1770
1771            if self.tcx.is_coroutine(def_id.to_def_id())
1772                && let Some(witnesses) = tcx.mir_coroutine_witnesses(def_id)
1773            {
1774                record!(self.tables.mir_coroutine_witnesses[def_id.to_def_id()] <- witnesses);
1775            }
1776        }
1777
1778        // Encode all the deduced parameter attributes for everything that has MIR, even for items
1779        // that can't be inlined. But don't if we aren't optimizing in non-incremental mode, to
1780        // save the query traffic.
1781        if tcx.sess.opts.output_types.should_codegen()
1782            && tcx.sess.opts.optimize != OptLevel::No
1783            && tcx.sess.opts.incremental.is_none()
1784        {
1785            for &local_def_id in tcx.mir_keys(()) {
1786                if let DefKind::AssocFn | DefKind::Fn = tcx.def_kind(local_def_id) {
1787                    record_array!(self.tables.deduced_param_attrs[local_def_id.to_def_id()] <-
1788                        self.tcx.deduced_param_attrs(local_def_id.to_def_id()));
1789                }
1790            }
1791        }
1792    }
1793
1794    #[instrument(level = "debug", skip(self))]
1795    fn encode_stability(&mut self, def_id: DefId) {
1796        // The query lookup can take a measurable amount of time in crates with many items. Check if
1797        // the stability attributes are even enabled before using their queries.
1798        if self.feat.staged_api() || self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked {
1799            if let Some(stab) = self.tcx.lookup_stability(def_id) {
1800                record!(self.tables.lookup_stability[def_id] <- stab)
1801            }
1802        }
1803    }
1804
1805    #[instrument(level = "debug", skip(self))]
1806    fn encode_const_stability(&mut self, def_id: DefId) {
1807        // The query lookup can take a measurable amount of time in crates with many items. Check if
1808        // the stability attributes are even enabled before using their queries.
1809        if self.feat.staged_api() || self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked {
1810            if let Some(stab) = self.tcx.lookup_const_stability(def_id) {
1811                record!(self.tables.lookup_const_stability[def_id] <- stab)
1812            }
1813        }
1814    }
1815
1816    #[instrument(level = "debug", skip(self))]
1817    fn encode_default_body_stability(&mut self, def_id: DefId) {
1818        // The query lookup can take a measurable amount of time in crates with many items. Check if
1819        // the stability attributes are even enabled before using their queries.
1820        if self.feat.staged_api() || self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked {
1821            if let Some(stab) = self.tcx.lookup_default_body_stability(def_id) {
1822                record!(self.tables.lookup_default_body_stability[def_id] <- stab)
1823            }
1824        }
1825    }
1826
1827    #[instrument(level = "debug", skip(self))]
1828    fn encode_deprecation(&mut self, def_id: DefId) {
1829        if let Some(depr) = self.tcx.lookup_deprecation(def_id) {
1830            record!(self.tables.lookup_deprecation_entry[def_id] <- depr);
1831        }
1832    }
1833
1834    #[instrument(level = "debug", skip(self))]
1835    fn encode_info_for_macro(&mut self, def_id: LocalDefId) {
1836        let tcx = self.tcx;
1837
1838        let (_, macro_def, _) = tcx.hir_expect_item(def_id).expect_macro();
1839        self.tables.is_macro_rules.set(def_id.local_def_index, macro_def.macro_rules);
1840        record!(self.tables.macro_definition[def_id.to_def_id()] <- &*macro_def.body);
1841    }
1842
1843    fn encode_native_libraries(&mut self) -> LazyArray<NativeLib> {
1844        empty_proc_macro!(self);
1845        let used_libraries = self.tcx.native_libraries(LOCAL_CRATE);
1846        self.lazy_array(used_libraries.iter())
1847    }
1848
1849    fn encode_foreign_modules(&mut self) -> LazyArray<ForeignModule> {
1850        empty_proc_macro!(self);
1851        let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
1852        self.lazy_array(foreign_modules.iter().map(|(_, m)| m).cloned())
1853    }
1854
1855    fn encode_hygiene(&mut self) -> (SyntaxContextTable, ExpnDataTable, ExpnHashTable) {
1856        let mut syntax_contexts: TableBuilder<_, _> = Default::default();
1857        let mut expn_data_table: TableBuilder<_, _> = Default::default();
1858        let mut expn_hash_table: TableBuilder<_, _> = Default::default();
1859
1860        self.hygiene_ctxt.encode(
1861            &mut (&mut *self, &mut syntax_contexts, &mut expn_data_table, &mut expn_hash_table),
1862            |(this, syntax_contexts, _, _), index, ctxt_data| {
1863                syntax_contexts.set_some(index, this.lazy(ctxt_data));
1864            },
1865            |(this, _, expn_data_table, expn_hash_table), index, expn_data, hash| {
1866                if let Some(index) = index.as_local() {
1867                    expn_data_table.set_some(index.as_raw(), this.lazy(expn_data));
1868                    expn_hash_table.set_some(index.as_raw(), this.lazy(hash));
1869                }
1870            },
1871        );
1872
1873        (
1874            syntax_contexts.encode(&mut self.opaque),
1875            expn_data_table.encode(&mut self.opaque),
1876            expn_hash_table.encode(&mut self.opaque),
1877        )
1878    }
1879
1880    fn encode_proc_macros(&mut self) -> Option<ProcMacroData> {
1881        let is_proc_macro = self.tcx.crate_types().contains(&CrateType::ProcMacro);
1882        if is_proc_macro {
1883            let tcx = self.tcx;
1884            let hir = tcx.hir();
1885
1886            let proc_macro_decls_static = tcx.proc_macro_decls_static(()).unwrap().local_def_index;
1887            let stability = tcx.lookup_stability(CRATE_DEF_ID);
1888            let macros =
1889                self.lazy_array(tcx.resolutions(()).proc_macros.iter().map(|p| p.local_def_index));
1890            for (i, span) in self.tcx.sess.psess.proc_macro_quoted_spans() {
1891                let span = self.lazy(span);
1892                self.tables.proc_macro_quoted_spans.set_some(i, span);
1893            }
1894
1895            self.tables.def_kind.set_some(LOCAL_CRATE.as_def_id().index, DefKind::Mod);
1896            record!(self.tables.def_span[LOCAL_CRATE.as_def_id()] <- tcx.def_span(LOCAL_CRATE.as_def_id()));
1897            self.encode_attrs(LOCAL_CRATE.as_def_id().expect_local());
1898            let vis = tcx.local_visibility(CRATE_DEF_ID).map_id(|def_id| def_id.local_def_index);
1899            record!(self.tables.visibility[LOCAL_CRATE.as_def_id()] <- vis);
1900            if let Some(stability) = stability {
1901                record!(self.tables.lookup_stability[LOCAL_CRATE.as_def_id()] <- stability);
1902            }
1903            self.encode_deprecation(LOCAL_CRATE.as_def_id());
1904            if let Some(res_map) = tcx.resolutions(()).doc_link_resolutions.get(&CRATE_DEF_ID) {
1905                record!(self.tables.doc_link_resolutions[LOCAL_CRATE.as_def_id()] <- res_map);
1906            }
1907            if let Some(traits) = tcx.resolutions(()).doc_link_traits_in_scope.get(&CRATE_DEF_ID) {
1908                record_array!(self.tables.doc_link_traits_in_scope[LOCAL_CRATE.as_def_id()] <- traits);
1909            }
1910
1911            // Normally, this information is encoded when we walk the items
1912            // defined in this crate. However, we skip doing that for proc-macro crates,
1913            // so we manually encode just the information that we need
1914            for &proc_macro in &tcx.resolutions(()).proc_macros {
1915                let id = proc_macro;
1916                let proc_macro = tcx.local_def_id_to_hir_id(proc_macro);
1917                let mut name = tcx.hir_name(proc_macro);
1918                let span = hir.span(proc_macro);
1919                // Proc-macros may have attributes like `#[allow_internal_unstable]`,
1920                // so downstream crates need access to them.
1921                let attrs = tcx.hir_attrs(proc_macro);
1922                let macro_kind = if ast::attr::contains_name(attrs, sym::proc_macro) {
1923                    MacroKind::Bang
1924                } else if ast::attr::contains_name(attrs, sym::proc_macro_attribute) {
1925                    MacroKind::Attr
1926                } else if let Some(attr) = ast::attr::find_by_name(attrs, sym::proc_macro_derive) {
1927                    // This unwrap chain should have been checked by the proc-macro harness.
1928                    name = attr.meta_item_list().unwrap()[0]
1929                        .meta_item()
1930                        .unwrap()
1931                        .ident()
1932                        .unwrap()
1933                        .name;
1934                    MacroKind::Derive
1935                } else {
1936                    bug!("Unknown proc-macro type for item {:?}", id);
1937                };
1938
1939                let mut def_key = self.tcx.hir_def_key(id);
1940                def_key.disambiguated_data.data = DefPathData::MacroNs(name);
1941
1942                let def_id = id.to_def_id();
1943                self.tables.def_kind.set_some(def_id.index, DefKind::Macro(macro_kind));
1944                self.tables.proc_macro.set_some(def_id.index, macro_kind);
1945                self.encode_attrs(id);
1946                record!(self.tables.def_keys[def_id] <- def_key);
1947                record!(self.tables.def_ident_span[def_id] <- span);
1948                record!(self.tables.def_span[def_id] <- span);
1949                record!(self.tables.visibility[def_id] <- ty::Visibility::Public);
1950                if let Some(stability) = stability {
1951                    record!(self.tables.lookup_stability[def_id] <- stability);
1952                }
1953            }
1954
1955            Some(ProcMacroData { proc_macro_decls_static, stability, macros })
1956        } else {
1957            None
1958        }
1959    }
1960
1961    fn encode_debugger_visualizers(&mut self) -> LazyArray<DebuggerVisualizerFile> {
1962        empty_proc_macro!(self);
1963        self.lazy_array(
1964            self.tcx
1965                .debugger_visualizers(LOCAL_CRATE)
1966                .iter()
1967                // Erase the path since it may contain privacy sensitive data
1968                // that we don't want to end up in crate metadata.
1969                // The path is only needed for the local crate because of
1970                // `--emit dep-info`.
1971                .map(DebuggerVisualizerFile::path_erased),
1972        )
1973    }
1974
1975    fn encode_crate_deps(&mut self) -> LazyArray<CrateDep> {
1976        empty_proc_macro!(self);
1977
1978        let deps = self
1979            .tcx
1980            .crates(())
1981            .iter()
1982            .map(|&cnum| {
1983                let dep = CrateDep {
1984                    name: self.tcx.crate_name(cnum),
1985                    hash: self.tcx.crate_hash(cnum),
1986                    host_hash: self.tcx.crate_host_hash(cnum),
1987                    kind: self.tcx.dep_kind(cnum),
1988                    extra_filename: self.tcx.extra_filename(cnum).clone(),
1989                    is_private: self.tcx.is_private_dep(cnum),
1990                };
1991                (cnum, dep)
1992            })
1993            .collect::<Vec<_>>();
1994
1995        {
1996            // Sanity-check the crate numbers
1997            let mut expected_cnum = 1;
1998            for &(n, _) in &deps {
1999                assert_eq!(n, CrateNum::new(expected_cnum));
2000                expected_cnum += 1;
2001            }
2002        }
2003
2004        // We're just going to write a list of crate 'name-hash-version's, with
2005        // the assumption that they are numbered 1 to n.
2006        // FIXME (#2166): This is not nearly enough to support correct versioning
2007        // but is enough to get transitive crate dependencies working.
2008        self.lazy_array(deps.iter().map(|(_, dep)| dep))
2009    }
2010
2011    fn encode_target_modifiers(&mut self) -> LazyArray<TargetModifier> {
2012        empty_proc_macro!(self);
2013        let tcx = self.tcx;
2014        self.lazy_array(tcx.sess.opts.gather_target_modifiers())
2015    }
2016
2017    fn encode_lib_features(&mut self) -> LazyArray<(Symbol, FeatureStability)> {
2018        empty_proc_macro!(self);
2019        let tcx = self.tcx;
2020        let lib_features = tcx.lib_features(LOCAL_CRATE);
2021        self.lazy_array(lib_features.to_sorted_vec())
2022    }
2023
2024    fn encode_stability_implications(&mut self) -> LazyArray<(Symbol, Symbol)> {
2025        empty_proc_macro!(self);
2026        let tcx = self.tcx;
2027        let implications = tcx.stability_implications(LOCAL_CRATE);
2028        let sorted = implications.to_sorted_stable_ord();
2029        self.lazy_array(sorted.into_iter().map(|(k, v)| (*k, *v)))
2030    }
2031
2032    fn encode_diagnostic_items(&mut self) -> LazyArray<(Symbol, DefIndex)> {
2033        empty_proc_macro!(self);
2034        let tcx = self.tcx;
2035        let diagnostic_items = &tcx.diagnostic_items(LOCAL_CRATE).name_to_id;
2036        self.lazy_array(diagnostic_items.iter().map(|(&name, def_id)| (name, def_id.index)))
2037    }
2038
2039    fn encode_lang_items(&mut self) -> LazyArray<(DefIndex, LangItem)> {
2040        empty_proc_macro!(self);
2041        let lang_items = self.tcx.lang_items().iter();
2042        self.lazy_array(lang_items.filter_map(|(lang_item, def_id)| {
2043            def_id.as_local().map(|id| (id.local_def_index, lang_item))
2044        }))
2045    }
2046
2047    fn encode_lang_items_missing(&mut self) -> LazyArray<LangItem> {
2048        empty_proc_macro!(self);
2049        let tcx = self.tcx;
2050        self.lazy_array(&tcx.lang_items().missing)
2051    }
2052
2053    fn encode_stripped_cfg_items(&mut self) -> LazyArray<StrippedCfgItem<DefIndex>> {
2054        self.lazy_array(
2055            self.tcx
2056                .stripped_cfg_items(LOCAL_CRATE)
2057                .into_iter()
2058                .map(|item| item.clone().map_mod_id(|def_id| def_id.index)),
2059        )
2060    }
2061
2062    fn encode_traits(&mut self) -> LazyArray<DefIndex> {
2063        empty_proc_macro!(self);
2064        self.lazy_array(self.tcx.traits(LOCAL_CRATE).iter().map(|def_id| def_id.index))
2065    }
2066
2067    /// Encodes an index, mapping each trait to its (local) implementations.
2068    #[instrument(level = "debug", skip(self))]
2069    fn encode_impls(&mut self) -> LazyArray<TraitImpls> {
2070        empty_proc_macro!(self);
2071        let tcx = self.tcx;
2072        let mut trait_impls: FxIndexMap<DefId, Vec<(DefIndex, Option<SimplifiedType>)>> =
2073            FxIndexMap::default();
2074
2075        for id in tcx.hir_free_items() {
2076            let DefKind::Impl { of_trait } = tcx.def_kind(id.owner_id) else {
2077                continue;
2078            };
2079            let def_id = id.owner_id.to_def_id();
2080
2081            self.tables.defaultness.set_some(def_id.index, tcx.defaultness(def_id));
2082
2083            if of_trait && let Some(header) = tcx.impl_trait_header(def_id) {
2084                record!(self.tables.impl_trait_header[def_id] <- header);
2085
2086                let trait_ref = header.trait_ref.instantiate_identity();
2087                let simplified_self_ty = fast_reject::simplify_type(
2088                    self.tcx,
2089                    trait_ref.self_ty(),
2090                    TreatParams::InstantiateWithInfer,
2091                );
2092                trait_impls
2093                    .entry(trait_ref.def_id)
2094                    .or_default()
2095                    .push((id.owner_id.def_id.local_def_index, simplified_self_ty));
2096
2097                let trait_def = tcx.trait_def(trait_ref.def_id);
2098                if let Ok(mut an) = trait_def.ancestors(tcx, def_id) {
2099                    if let Some(specialization_graph::Node::Impl(parent)) = an.nth(1) {
2100                        self.tables.impl_parent.set_some(def_id.index, parent.into());
2101                    }
2102                }
2103
2104                // if this is an impl of `CoerceUnsized`, create its
2105                // "unsized info", else just store None
2106                if tcx.is_lang_item(trait_ref.def_id, LangItem::CoerceUnsized) {
2107                    let coerce_unsized_info = tcx.coerce_unsized_info(def_id).unwrap();
2108                    record!(self.tables.coerce_unsized_info[def_id] <- coerce_unsized_info);
2109                }
2110            }
2111        }
2112
2113        let trait_impls: Vec<_> = trait_impls
2114            .into_iter()
2115            .map(|(trait_def_id, impls)| TraitImpls {
2116                trait_id: (trait_def_id.krate.as_u32(), trait_def_id.index),
2117                impls: self.lazy_array(&impls),
2118            })
2119            .collect();
2120
2121        self.lazy_array(&trait_impls)
2122    }
2123
2124    #[instrument(level = "debug", skip(self))]
2125    fn encode_incoherent_impls(&mut self) -> LazyArray<IncoherentImpls> {
2126        empty_proc_macro!(self);
2127        let tcx = self.tcx;
2128
2129        let all_impls: Vec<_> = tcx
2130            .crate_inherent_impls(())
2131            .0
2132            .incoherent_impls
2133            .iter()
2134            .map(|(&simp, impls)| IncoherentImpls {
2135                self_ty: simp,
2136                impls: self.lazy_array(impls.iter().map(|def_id| def_id.local_def_index)),
2137            })
2138            .collect();
2139
2140        self.lazy_array(&all_impls)
2141    }
2142
2143    // Encodes all symbols exported from this crate into the metadata.
2144    //
2145    // This pass is seeded off the reachability list calculated in the
2146    // middle::reachable module but filters out items that either don't have a
2147    // symbol associated with them (they weren't translated) or if they're an FFI
2148    // definition (as that's not defined in this crate).
2149    fn encode_exported_symbols(
2150        &mut self,
2151        exported_symbols: &[(ExportedSymbol<'tcx>, SymbolExportInfo)],
2152    ) -> LazyArray<(ExportedSymbol<'static>, SymbolExportInfo)> {
2153        empty_proc_macro!(self);
2154        // The metadata symbol name is special. It should not show up in
2155        // downstream crates.
2156        let metadata_symbol_name = SymbolName::new(self.tcx, &metadata_symbol_name(self.tcx));
2157
2158        self.lazy_array(
2159            exported_symbols
2160                .iter()
2161                .filter(|&(exported_symbol, _)| match *exported_symbol {
2162                    ExportedSymbol::NoDefId(symbol_name) => symbol_name != metadata_symbol_name,
2163                    _ => true,
2164                })
2165                .cloned(),
2166        )
2167    }
2168
2169    fn encode_dylib_dependency_formats(&mut self) -> LazyArray<Option<LinkagePreference>> {
2170        empty_proc_macro!(self);
2171        let formats = self.tcx.dependency_formats(());
2172        if let Some(arr) = formats.get(&CrateType::Dylib) {
2173            return self.lazy_array(arr.iter().skip(1 /* skip LOCAL_CRATE */).map(
2174                |slot| match *slot {
2175                    Linkage::NotLinked | Linkage::IncludedFromDylib => None,
2176
2177                    Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
2178                    Linkage::Static => Some(LinkagePreference::RequireStatic),
2179                },
2180            ));
2181        }
2182        LazyArray::default()
2183    }
2184}
2185
2186/// Used to prefetch queries which will be needed later by metadata encoding.
2187/// Only a subset of the queries are actually prefetched to keep this code smaller.
2188fn prefetch_mir(tcx: TyCtxt<'_>) {
2189    if !tcx.sess.opts.output_types.should_codegen() {
2190        // We won't emit MIR, so don't prefetch it.
2191        return;
2192    }
2193
2194    let reachable_set = tcx.reachable_set(());
2195    par_for_each_in(tcx.mir_keys(()), |&def_id| {
2196        let (encode_const, encode_opt) = should_encode_mir(tcx, reachable_set, def_id);
2197
2198        if encode_const {
2199            tcx.ensure_done().mir_for_ctfe(def_id);
2200        }
2201        if encode_opt {
2202            tcx.ensure_done().optimized_mir(def_id);
2203        }
2204        if encode_opt || encode_const {
2205            tcx.ensure_done().promoted_mir(def_id);
2206        }
2207    })
2208}
2209
2210// NOTE(eddyb) The following comment was preserved for posterity, even
2211// though it's no longer relevant as EBML (which uses nested & tagged
2212// "documents") was replaced with a scheme that can't go out of bounds.
2213//
2214// And here we run into yet another obscure archive bug: in which metadata
2215// loaded from archives may have trailing garbage bytes. Awhile back one of
2216// our tests was failing sporadically on the macOS 64-bit builders (both nopt
2217// and opt) by having ebml generate an out-of-bounds panic when looking at
2218// metadata.
2219//
2220// Upon investigation it turned out that the metadata file inside of an rlib
2221// (and ar archive) was being corrupted. Some compilations would generate a
2222// metadata file which would end in a few extra bytes, while other
2223// compilations would not have these extra bytes appended to the end. These
2224// extra bytes were interpreted by ebml as an extra tag, so they ended up
2225// being interpreted causing the out-of-bounds.
2226//
2227// The root cause of why these extra bytes were appearing was never
2228// discovered, and in the meantime the solution we're employing is to insert
2229// the length of the metadata to the start of the metadata. Later on this
2230// will allow us to slice the metadata to the precise length that we just
2231// generated regardless of trailing bytes that end up in it.
2232
2233pub struct EncodedMetadata {
2234    // The declaration order matters because `mmap` should be dropped before `_temp_dir`.
2235    mmap: Option<Mmap>,
2236    // We need to carry MaybeTempDir to avoid deleting the temporary
2237    // directory while accessing the Mmap.
2238    _temp_dir: Option<MaybeTempDir>,
2239}
2240
2241impl EncodedMetadata {
2242    #[inline]
2243    pub fn from_path(path: PathBuf, temp_dir: Option<MaybeTempDir>) -> std::io::Result<Self> {
2244        let file = std::fs::File::open(&path)?;
2245        let file_metadata = file.metadata()?;
2246        if file_metadata.len() == 0 {
2247            return Ok(Self { mmap: None, _temp_dir: None });
2248        }
2249        let mmap = unsafe { Some(Mmap::map(file)?) };
2250        Ok(Self { mmap, _temp_dir: temp_dir })
2251    }
2252
2253    #[inline]
2254    pub fn raw_data(&self) -> &[u8] {
2255        self.mmap.as_deref().unwrap_or_default()
2256    }
2257}
2258
2259impl<S: Encoder> Encodable<S> for EncodedMetadata {
2260    fn encode(&self, s: &mut S) {
2261        let slice = self.raw_data();
2262        slice.encode(s)
2263    }
2264}
2265
2266impl<D: Decoder> Decodable<D> for EncodedMetadata {
2267    fn decode(d: &mut D) -> Self {
2268        let len = d.read_usize();
2269        let mmap = if len > 0 {
2270            let mut mmap = MmapMut::map_anon(len).unwrap();
2271            mmap.copy_from_slice(d.read_raw_bytes(len));
2272            Some(mmap.make_read_only().unwrap())
2273        } else {
2274            None
2275        };
2276
2277        Self { mmap, _temp_dir: None }
2278    }
2279}
2280
2281pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path) {
2282    let _prof_timer = tcx.prof.verbose_generic_activity("generate_crate_metadata");
2283
2284    // Since encoding metadata is not in a query, and nothing is cached,
2285    // there's no need to do dep-graph tracking for any of it.
2286    tcx.dep_graph.assert_ignored();
2287
2288    if tcx.sess.threads() != 1 {
2289        // Prefetch some queries used by metadata encoding.
2290        // This is not necessary for correctness, but is only done for performance reasons.
2291        // It can be removed if it turns out to cause trouble or be detrimental to performance.
2292        join(|| prefetch_mir(tcx), || tcx.exported_symbols(LOCAL_CRATE));
2293    }
2294
2295    let mut encoder = opaque::FileEncoder::new(path)
2296        .unwrap_or_else(|err| tcx.dcx().emit_fatal(FailCreateFileEncoder { err }));
2297    encoder.emit_raw_bytes(METADATA_HEADER);
2298
2299    // Will be filled with the root position after encoding everything.
2300    encoder.emit_raw_bytes(&0u64.to_le_bytes());
2301
2302    let source_map_files = tcx.sess.source_map().files();
2303    let source_file_cache = (Arc::clone(&source_map_files[0]), 0);
2304    let required_source_files = Some(FxIndexSet::default());
2305    drop(source_map_files);
2306
2307    let hygiene_ctxt = HygieneEncodeContext::default();
2308
2309    let mut ecx = EncodeContext {
2310        opaque: encoder,
2311        tcx,
2312        feat: tcx.features(),
2313        tables: Default::default(),
2314        lazy_state: LazyState::NoNode,
2315        span_shorthands: Default::default(),
2316        type_shorthands: Default::default(),
2317        predicate_shorthands: Default::default(),
2318        source_file_cache,
2319        interpret_allocs: Default::default(),
2320        required_source_files,
2321        is_proc_macro: tcx.crate_types().contains(&CrateType::ProcMacro),
2322        hygiene_ctxt: &hygiene_ctxt,
2323        symbol_table: Default::default(),
2324    };
2325
2326    // Encode the rustc version string in a predictable location.
2327    rustc_version(tcx.sess.cfg_version).encode(&mut ecx);
2328
2329    // Encode all the entries and extra information in the crate,
2330    // culminating in the `CrateRoot` which points to all of it.
2331    let root = ecx.encode_crate_root();
2332
2333    // Make sure we report any errors from writing to the file.
2334    // If we forget this, compilation can succeed with an incomplete rmeta file,
2335    // causing an ICE when the rmeta file is read by another compilation.
2336    if let Err((path, err)) = ecx.opaque.finish() {
2337        tcx.dcx().emit_fatal(FailWriteFile { path: &path, err });
2338    }
2339
2340    let file = ecx.opaque.file();
2341    if let Err(err) = encode_root_position(file, root.position.get()) {
2342        tcx.dcx().emit_fatal(FailWriteFile { path: ecx.opaque.path(), err });
2343    }
2344
2345    // Record metadata size for self-profiling
2346    tcx.prof.artifact_size("crate_metadata", "crate_metadata", file.metadata().unwrap().len());
2347}
2348
2349fn encode_root_position(mut file: &File, pos: usize) -> Result<(), std::io::Error> {
2350    // We will return to this position after writing the root position.
2351    let pos_before_seek = file.stream_position().unwrap();
2352
2353    // Encode the root position.
2354    let header = METADATA_HEADER.len();
2355    file.seek(std::io::SeekFrom::Start(header as u64))?;
2356    file.write_all(&pos.to_le_bytes())?;
2357
2358    // Return to the position where we are before writing the root position.
2359    file.seek(std::io::SeekFrom::Start(pos_before_seek))?;
2360    Ok(())
2361}
2362
2363pub(crate) fn provide(providers: &mut Providers) {
2364    *providers = Providers {
2365        doc_link_resolutions: |tcx, def_id| {
2366            tcx.resolutions(())
2367                .doc_link_resolutions
2368                .get(&def_id)
2369                .unwrap_or_else(|| span_bug!(tcx.def_span(def_id), "no resolutions for a doc link"))
2370        },
2371        doc_link_traits_in_scope: |tcx, def_id| {
2372            tcx.resolutions(()).doc_link_traits_in_scope.get(&def_id).unwrap_or_else(|| {
2373                span_bug!(tcx.def_span(def_id), "no traits in scope for a doc link")
2374            })
2375        },
2376
2377        ..*providers
2378    }
2379}
2380
2381/// Build a textual representation of an unevaluated constant expression.
2382///
2383/// If the const expression is too complex, an underscore `_` is returned.
2384/// For const arguments, it's `{ _ }` to be precise.
2385/// This means that the output is not necessarily valid Rust code.
2386///
2387/// Currently, only
2388///
2389/// * literals (optionally with a leading `-`)
2390/// * unit `()`
2391/// * blocks (`{ … }`) around simple expressions and
2392/// * paths without arguments
2393///
2394/// are considered simple enough. Simple blocks are included since they are
2395/// necessary to disambiguate unit from the unit type.
2396/// This list might get extended in the future.
2397///
2398/// Without this censoring, in a lot of cases the output would get too large
2399/// and verbose. Consider `match` expressions, blocks and deeply nested ADTs.
2400/// Further, private and `doc(hidden)` fields of structs would get leaked
2401/// since HIR datatypes like the `body` parameter do not contain enough
2402/// semantic information for this function to be able to hide them –
2403/// at least not without significant performance overhead.
2404///
2405/// Whenever possible, prefer to evaluate the constant first and try to
2406/// use a different method for pretty-printing. Ideally this function
2407/// should only ever be used as a fallback.
2408pub fn rendered_const<'tcx>(tcx: TyCtxt<'tcx>, body: &hir::Body<'_>, def_id: LocalDefId) -> String {
2409    let value = body.value;
2410
2411    #[derive(PartialEq, Eq)]
2412    enum Classification {
2413        Literal,
2414        Simple,
2415        Complex,
2416    }
2417
2418    use Classification::*;
2419
2420    fn classify(expr: &hir::Expr<'_>) -> Classification {
2421        match &expr.kind {
2422            hir::ExprKind::Unary(hir::UnOp::Neg, expr) => {
2423                if matches!(expr.kind, hir::ExprKind::Lit(_)) { Literal } else { Complex }
2424            }
2425            hir::ExprKind::Lit(_) => Literal,
2426            hir::ExprKind::Tup([]) => Simple,
2427            hir::ExprKind::Block(hir::Block { stmts: [], expr: Some(expr), .. }, _) => {
2428                if classify(expr) == Complex { Complex } else { Simple }
2429            }
2430            // Paths with a self-type or arguments are too “complex” following our measure since
2431            // they may leak private fields of structs (with feature `adt_const_params`).
2432            // Consider: `<Self as Trait<{ Struct { private: () } }>>::CONSTANT`.
2433            // Paths without arguments are definitely harmless though.
2434            hir::ExprKind::Path(hir::QPath::Resolved(_, hir::Path { segments, .. })) => {
2435                if segments.iter().all(|segment| segment.args.is_none()) { Simple } else { Complex }
2436            }
2437            // FIXME: Claiming that those kinds of QPaths are simple is probably not true if the Ty
2438            //        contains const arguments. Is there a *concise* way to check for this?
2439            hir::ExprKind::Path(hir::QPath::TypeRelative(..)) => Simple,
2440            // FIXME: Can they contain const arguments and thus leak private struct fields?
2441            hir::ExprKind::Path(hir::QPath::LangItem(..)) => Simple,
2442            _ => Complex,
2443        }
2444    }
2445
2446    match classify(value) {
2447        // For non-macro literals, we avoid invoking the pretty-printer and use the source snippet
2448        // instead to preserve certain stylistic choices the user likely made for the sake of
2449        // legibility, like:
2450        //
2451        // * hexadecimal notation
2452        // * underscores
2453        // * character escapes
2454        //
2455        // FIXME: This passes through `-/*spacer*/0` verbatim.
2456        Literal
2457            if !value.span.from_expansion()
2458                && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(value.span) =>
2459        {
2460            snippet
2461        }
2462
2463        // Otherwise we prefer pretty-printing to get rid of extraneous whitespace, comments and
2464        // other formatting artifacts.
2465        Literal | Simple => id_to_string(&tcx, body.id().hir_id),
2466
2467        // FIXME: Omit the curly braces if the enclosing expression is an array literal
2468        //        with a repeated element (an `ExprKind::Repeat`) as in such case it
2469        //        would not actually need any disambiguation.
2470        Complex => {
2471            if tcx.def_kind(def_id) == DefKind::AnonConst {
2472                "{ _ }".to_owned()
2473            } else {
2474                "_".to_owned()
2475            }
2476        }
2477    }
2478}