src/librustc_metadata/rmeta/encoder.rs

   1 use crate::rmeta::*;
   2 use crate::rmeta::table::FixedSizeEncoding;
   3
   4 use rustc::middle::cstore::{LinkagePreference, NativeLibrary,
   5                             EncodedMetadata, ForeignModule};
   6 use rustc::hir::def::CtorKind;
   7 use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefIndex, DefId, LocalDefId, LOCAL_CRATE};
   8 use rustc::hir::{GenericParamKind, AnonConst};
   9 use rustc::hir::map::definitions::DefPathTable;
  10 use rustc_data_structures::fingerprint::Fingerprint;
  11 use rustc_index::vec::Idx;
  12 use rustc::middle::dependency_format::Linkage;
  13 use rustc::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel,
  14                                       metadata_symbol_name};
  15 use rustc::middle::lang_items;
  16 use rustc::mir::{self, interpret};
  17 use rustc::traits::specialization_graph;
  18 use rustc::ty::{self, Ty, TyCtxt, SymbolName};
  19 use rustc::ty::codec::{self as ty_codec, TyEncoder};
  20 use rustc::ty::layout::VariantIdx;
  21
  22 use rustc::session::config::{self, CrateType};
  23 use rustc::util::nodemap::FxHashMap;
  24
  25 use rustc_data_structures::stable_hasher::StableHasher;
  26 use rustc_data_structures::sync::Lrc;
  27 use rustc_serialize::{Encodable, Encoder, SpecializedEncoder, opaque};
  28
  29 use std::hash::Hash;
  30 use std::num::NonZeroUsize;
  31 use std::path::Path;
  32 use std::u32;
  33 use syntax::ast;
  34 use syntax::attr;
  35 use syntax::expand::is_proc_macro_attr;
  36 use syntax::source_map::Spanned;
  37 use syntax::symbol::{kw, sym, Ident, Symbol};
  38 use syntax_pos::{self, FileName, SourceFile, Span};
  39 use log::{debug, trace};
  40
  41 use rustc::hir::{self, PatKind};
  42 use rustc::hir::itemlikevisit::ItemLikeVisitor;
  43 use rustc::hir::intravisit::{Visitor, NestedVisitorMap};
  44 use rustc::hir::intravisit;
  45
  46 struct EncodeContext<'tcx> {
  47     opaque: opaque::Encoder,
  48     tcx: TyCtxt<'tcx>,
  49
  50     per_def: PerDefTableBuilders<'tcx>,
  51
  52     lazy_state: LazyState,
  53     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
  54     predicate_shorthands: FxHashMap<ty::Predicate<'tcx>, usize>,
  55
  56     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
  57     interpret_allocs_inverse: Vec<interpret::AllocId>,
  58
  59     // This is used to speed up Span encoding.
  60     source_file_cache: Lrc<SourceFile>,
  61 }
  62
  63 macro_rules! encoder_methods {
  64     ($($name:ident($ty:ty);)*) => {
  65         $(fn $name(&mut self, value: $ty) -> Result<(), Self::Error> {
  66             self.opaque.$name(value)
  67         })*
  68     }
  69 }
  70
  71 impl<'tcx> Encoder for EncodeContext<'tcx> {
  72     type Error = <opaque::Encoder as Encoder>::Error;
  73
  74     fn emit_unit(&mut self) -> Result<(), Self::Error> {
  75         Ok(())
  76     }
  77
  78     encoder_methods! {
  79         emit_usize(usize);
  80         emit_u128(u128);
  81         emit_u64(u64);
  82         emit_u32(u32);
  83         emit_u16(u16);
  84         emit_u8(u8);
  85
  86         emit_isize(isize);
  87         emit_i128(i128);
  88         emit_i64(i64);
  89         emit_i32(i32);
  90         emit_i16(i16);
  91         emit_i8(i8);
  92
  93         emit_bool(bool);
  94         emit_f64(f64);
  95         emit_f32(f32);
  96         emit_char(char);
  97         emit_str(&str);
  98     }
  99 }
 100
 101 impl<'tcx, T> SpecializedEncoder<Lazy<T>> for EncodeContext<'tcx> {
 102     fn specialized_encode(&mut self, lazy: &Lazy<T>) -> Result<(), Self::Error> {
 103         self.emit_lazy_distance(*lazy)
 104     }
 105 }
 106
 107 impl<'tcx, T> SpecializedEncoder<Lazy<[T]>> for EncodeContext<'tcx> {
 108     fn specialized_encode(&mut self, lazy: &Lazy<[T]>) -> Result<(), Self::Error> {
 109         self.emit_usize(lazy.meta)?;
 110         if lazy.meta == 0 {
 111             return Ok(());
 112         }
 113         self.emit_lazy_distance(*lazy)
 114     }
 115 }
 116
 117 impl<'tcx, I: Idx, T> SpecializedEncoder<Lazy<Table<I, T>>> for EncodeContext<'tcx>
 118     where Option<T>: FixedSizeEncoding,
 119 {
 120     fn specialized_encode(&mut self, lazy: &Lazy<Table<I, T>>) -> Result<(), Self::Error> {
 121         self.emit_usize(lazy.meta)?;
 122         self.emit_lazy_distance(*lazy)
 123     }
 124 }
 125
 126 impl<'tcx> SpecializedEncoder<CrateNum> for EncodeContext<'tcx> {
 127     #[inline]
 128     fn specialized_encode(&mut self, cnum: &CrateNum) -> Result<(), Self::Error> {
 129         self.emit_u32(cnum.as_u32())
 130     }
 131 }
 132
 133 impl<'tcx> SpecializedEncoder<DefId> for EncodeContext<'tcx> {
 134     #[inline]
 135     fn specialized_encode(&mut self, def_id: &DefId) -> Result<(), Self::Error> {
 136         let DefId {
 137             krate,
 138             index,
 139         } = *def_id;
 140
 141         krate.encode(self)?;
 142         index.encode(self)
 143     }
 144 }
 145
 146 impl<'tcx> SpecializedEncoder<DefIndex> for EncodeContext<'tcx> {
 147     #[inline]
 148     fn specialized_encode(&mut self, def_index: &DefIndex) -> Result<(), Self::Error> {
 149         self.emit_u32(def_index.as_u32())
 150     }
 151 }
 152
 153 impl<'tcx> SpecializedEncoder<Span> for EncodeContext<'tcx> {
 154     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
 155         if span.is_dummy() {
 156             return TAG_INVALID_SPAN.encode(self)
 157         }
 158
 159         let span = span.data();
 160
 161         // The Span infrastructure should make sure that this invariant holds:
 162         debug_assert!(span.lo <= span.hi);
 163
 164         if !self.source_file_cache.contains(span.lo) {
 165             let source_map = self.tcx.sess.source_map();
 166             let source_file_index = source_map.lookup_source_file_idx(span.lo);
 167             self.source_file_cache = source_map.files()[source_file_index].clone();
 168         }
 169
 170         if !self.source_file_cache.contains(span.hi) {
 171             // Unfortunately, macro expansion still sometimes generates Spans
 172             // that malformed in this way.
 173             return TAG_INVALID_SPAN.encode(self)
 174         }
 175
 176         // HACK(eddyb) there's no way to indicate which crate a Span is coming
 177         // from right now, so decoding would fail to find the SourceFile if
 178         // it's not local to the crate the Span is found in.
 179         if self.source_file_cache.is_imported() {
 180             return TAG_INVALID_SPAN.encode(self)
 181         }
 182
 183         TAG_VALID_SPAN.encode(self)?;
 184         span.lo.encode(self)?;
 185
 186         // Encode length which is usually less than span.hi and profits more
 187         // from the variable-length integer encoding that we use.
 188         let len = span.hi - span.lo;
 189         len.encode(self)
 190
 191         // Don't encode the expansion context.
 192     }
 193 }
 194
 195 impl SpecializedEncoder<Ident> for EncodeContext<'tcx> {
 196     fn specialized_encode(&mut self, ident: &Ident) -> Result<(), Self::Error> {
 197         // FIXME(jseyfried): intercrate hygiene
 198         ident.name.encode(self)
 199     }
 200 }
 201
 202 impl<'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'tcx> {
 203     #[inline]
 204     fn specialized_encode(&mut self, def_id: &LocalDefId) -> Result<(), Self::Error> {
 205         self.specialized_encode(&def_id.to_def_id())
 206     }
 207 }
 208
 209 impl<'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'tcx> {
 210     fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
 211         ty_codec::encode_with_shorthand(self, ty, |ecx| &mut ecx.type_shorthands)
 212     }
 213 }
 214
 215 impl<'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'tcx> {
 216     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
 217         use std::collections::hash_map::Entry;
 218         let index = match self.interpret_allocs.entry(*alloc_id) {
 219             Entry::Occupied(e) => *e.get(),
 220             Entry::Vacant(e) => {
 221                 let idx = self.interpret_allocs_inverse.len();
 222                 self.interpret_allocs_inverse.push(*alloc_id);
 223                 e.insert(idx);
 224                 idx
 225             },
 226         };
 227
 228         index.encode(self)
 229     }
 230 }
 231
 232 impl<'tcx> SpecializedEncoder<&'tcx [(ty::Predicate<'tcx>, Span)]> for EncodeContext<'tcx> {
 233     fn specialized_encode(&mut self,
 234                           predicates: &&'tcx [(ty::Predicate<'tcx>, Span)])
 235                           -> Result<(), Self::Error> {
 236         ty_codec::encode_spanned_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
 237     }
 238 }
 239
 240 impl<'tcx> SpecializedEncoder<Fingerprint> for EncodeContext<'tcx> {
 241     fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> {
 242         f.encode_opaque(&mut self.opaque)
 243     }
 244 }
 245
 246 impl<'tcx, T: Encodable> SpecializedEncoder<mir::ClearCrossCrate<T>> for EncodeContext<'tcx> {
 247     fn specialized_encode(&mut self,
 248                           _: &mir::ClearCrossCrate<T>)
 249                           -> Result<(), Self::Error> {
 250         Ok(())
 251     }
 252 }
 253
 254 impl<'tcx> TyEncoder for EncodeContext<'tcx> {
 255     fn position(&self) -> usize {
 256         self.opaque.position()
 257     }
 258 }
 259
 260 /// Helper trait to allow overloading `EncodeContext::lazy` for iterators.
 261 trait EncodeContentsForLazy<T: ?Sized + LazyMeta> {
 262     fn encode_contents_for_lazy(self, ecx: &mut EncodeContext<'tcx>) -> T::Meta;
 263 }
 264
 265 impl<T: Encodable> EncodeContentsForLazy<T> for &T {
 266     fn encode_contents_for_lazy(self, ecx: &mut EncodeContext<'tcx>) {
 267         self.encode(ecx).unwrap()
 268     }
 269 }
 270
 271 impl<T: Encodable> EncodeContentsForLazy<T> for T {
 272     fn encode_contents_for_lazy(self, ecx: &mut EncodeContext<'tcx>) {
 273         self.encode(ecx).unwrap()
 274     }
 275 }
 276
 277 impl<I, T: Encodable> EncodeContentsForLazy<[T]> for I
 278     where I: IntoIterator,
 279           I::Item: EncodeContentsForLazy<T>,
 280 {
 281     fn encode_contents_for_lazy(self, ecx: &mut EncodeContext<'tcx>) -> usize {
 282         self.into_iter().map(|value| value.encode_contents_for_lazy(ecx)).count()
 283     }
 284 }
 285
 286 // Shorthand for `$self.$tables.$table.set($def_id.index, $self.lazy($value))`, which would
 287 // normally need extra variables to avoid errors about multiple mutable borrows.
 288 macro_rules! record {
 289     ($self:ident.$tables:ident.$table:ident[$def_id:expr] <- $value:expr) => {{
 290         {
 291             let value = $value;
 292             let lazy = $self.lazy(value);
 293             $self.$tables.$table.set($def_id.index, lazy);
 294         }
 295     }}
 296 }
 297
 298 impl<'tcx> EncodeContext<'tcx> {
 299     fn emit_lazy_distance<T: ?Sized + LazyMeta>(
 300         &mut self,
 301         lazy: Lazy<T>,
 302     ) -> Result<(), <Self as Encoder>::Error> {
 303         let min_end = lazy.position.get() + T::min_size(lazy.meta);
 304         let distance = match self.lazy_state {
 305             LazyState::NoNode => bug!("emit_lazy_distance: outside of a metadata node"),
 306             LazyState::NodeStart(start) => {
 307                 let start = start.get();
 308                 assert!(min_end <= start);
 309                 start - min_end
 310             }
 311             LazyState::Previous(last_min_end) => {
 312                 assert!(
 313                     last_min_end <= lazy.position,
 314                     "make sure that the calls to `lazy*` \
 315                     are in the same order as the metadata fields",
 316                 );
 317                 lazy.position.get() - last_min_end.get()
 318             }
 319         };
 320         self.lazy_state = LazyState::Previous(NonZeroUsize::new(min_end).unwrap());
 321         self.emit_usize(distance)
 322     }
 323
 324     fn lazy<T: ?Sized + LazyMeta>(
 325         &mut self,
 326         value: impl EncodeContentsForLazy<T>,
 327     ) -> Lazy<T> {
 328         let pos = NonZeroUsize::new(self.position()).unwrap();
 329
 330         assert_eq!(self.lazy_state, LazyState::NoNode);
 331         self.lazy_state = LazyState::NodeStart(pos);
 332         let meta = value.encode_contents_for_lazy(self);
 333         self.lazy_state = LazyState::NoNode;
 334
 335         assert!(pos.get() + <T>::min_size(meta) <= self.position());
 336
 337         Lazy::from_position_and_meta(pos, meta)
 338     }
 339
 340     fn encode_info_for_items(&mut self) {
 341         let krate = self.tcx.hir().krate();
 342         let vis = Spanned { span: syntax_pos::DUMMY_SP, node: hir::VisibilityKind::Public };
 343         self.encode_info_for_mod(hir::CRATE_HIR_ID, &krate.module, &krate.attrs, &vis);
 344         krate.visit_all_item_likes(&mut self.as_deep_visitor());
 345         for macro_def in &krate.exported_macros {
 346             self.visit_macro_def(macro_def);
 347         }
 348     }
 349
 350     fn encode_def_path_table(&mut self) -> Lazy<DefPathTable> {
 351         let definitions = self.tcx.hir().definitions();
 352         self.lazy(definitions.def_path_table())
 353     }
 354
 355     fn encode_source_map(&mut self) -> Lazy<[syntax_pos::SourceFile]> {
 356         let source_map = self.tcx.sess.source_map();
 357         let all_source_files = source_map.files();
 358
 359         let (working_dir, _cwd_remapped) = self.tcx.sess.working_dir.clone();
 360
 361         let adapted = all_source_files.iter()
 362             .filter(|source_file| {
 363                 // No need to re-export imported source_files, as any downstream
 364                 // crate will import them from their original source.
 365                 // FIXME(eddyb) the `Span` encoding should take that into account.
 366                 !source_file.is_imported()
 367             })
 368             .map(|source_file| {
 369                 match source_file.name {
 370                     // This path of this SourceFile has been modified by
 371                     // path-remapping, so we use it verbatim (and avoid
 372                     // cloning the whole map in the process).
 373                     _  if source_file.name_was_remapped => source_file.clone(),
 374
 375                     // Otherwise expand all paths to absolute paths because
 376                     // any relative paths are potentially relative to a
 377                     // wrong directory.
 378                     FileName::Real(ref name) => {
 379                         let mut adapted = (**source_file).clone();
 380                         adapted.name = Path::new(&working_dir).join(name).into();
 381                         adapted.name_hash = {
 382                             let mut hasher: StableHasher = StableHasher::new();
 383                             adapted.name.hash(&mut hasher);
 384                             hasher.finish::<u128>()
 385                         };
 386                         Lrc::new(adapted)
 387                     },
 388
 389                     // expanded code, not from a file
 390                     _ => source_file.clone(),
 391                 }
 392             })
 393             .collect::<Vec<_>>();
 394
 395         self.lazy(adapted.iter().map(|rc| &**rc))
 396     }
 397
 398     fn encode_crate_root(&mut self) -> Lazy<CrateRoot<'tcx>> {
 399         let is_proc_macro = self.tcx.sess.crate_types.borrow().contains(&CrateType::ProcMacro);
 400
 401         let mut i = self.position();
 402
 403         let crate_deps = self.encode_crate_deps();
 404         let dylib_dependency_formats = self.encode_dylib_dependency_formats();
 405         let dep_bytes = self.position() - i;
 406
 407         // Encode the lib features.
 408         i = self.position();
 409         let lib_features = self.encode_lib_features();
 410         let lib_feature_bytes = self.position() - i;
 411
 412         // Encode the language items.
 413         i = self.position();
 414         let lang_items = self.encode_lang_items();
 415         let lang_items_missing = self.encode_lang_items_missing();
 416         let lang_item_bytes = self.position() - i;
 417
 418         // Encode the diagnostic items.
 419         i = self.position();
 420         let diagnostic_items = self.encode_diagnostic_items();
 421         let diagnostic_item_bytes = self.position() - i;
 422
 423         // Encode the native libraries used
 424         i = self.position();
 425         let native_libraries = self.encode_native_libraries();
 426         let native_lib_bytes = self.position() - i;
 427
 428         let foreign_modules = self.encode_foreign_modules();
 429
 430         // Encode source_map
 431         i = self.position();
 432         let source_map = self.encode_source_map();
 433         let source_map_bytes = self.position() - i;
 434
 435         // Encode DefPathTable
 436         i = self.position();
 437         let def_path_table = self.encode_def_path_table();
 438         let def_path_table_bytes = self.position() - i;
 439
 440         // Encode the def IDs of impls, for coherence checking.
 441         i = self.position();
 442         let impls = self.encode_impls();
 443         let impl_bytes = self.position() - i;
 444
 445         // Encode exported symbols info.
 446         i = self.position();
 447         let exported_symbols = self.tcx.exported_symbols(LOCAL_CRATE);
 448         let exported_symbols = self.encode_exported_symbols(&exported_symbols);
 449         let exported_symbols_bytes = self.position() - i;
 450
 451         let tcx = self.tcx;
 452
 453         // Encode the items.
 454         i = self.position();
 455         self.encode_info_for_items();
 456         let item_bytes = self.position() - i;
 457
 458         // Encode the allocation index
 459         let interpret_alloc_index = {
 460             let mut interpret_alloc_index = Vec::new();
 461             let mut n = 0;
 462             trace!("beginning to encode alloc ids");
 463             loop {
 464                 let new_n = self.interpret_allocs_inverse.len();
 465                 // if we have found new ids, serialize those, too
 466                 if n == new_n {
 467                     // otherwise, abort
 468                     break;
 469                 }
 470                 trace!("encoding {} further alloc ids", new_n - n);
 471                 for idx in n..new_n {
 472                     let id = self.interpret_allocs_inverse[idx];
 473                     let pos = self.position() as u32;
 474                     interpret_alloc_index.push(pos);
 475                     interpret::specialized_encode_alloc_id(
 476                         self,
 477                         tcx,
 478                         id,
 479                     ).unwrap();
 480                 }
 481                 n = new_n;
 482             }
 483             self.lazy(interpret_alloc_index)
 484         };
 485
 486
 487         i = self.position();
 488         let per_def = self.per_def.encode(&mut self.opaque);
 489         let per_def_bytes = self.position() - i;
 490
 491         // Encode the proc macro data
 492         i = self.position();
 493         let proc_macro_data = self.encode_proc_macros();
 494         let proc_macro_data_bytes = self.position() - i;
 495
 496
 497         let attrs = tcx.hir().krate_attrs();
 498         let has_default_lib_allocator = attr::contains_name(&attrs, sym::default_lib_allocator);
 499
 500         let root = self.lazy(CrateRoot {
 501             name: tcx.crate_name(LOCAL_CRATE),
 502             extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
 503             triple: tcx.sess.opts.target_triple.clone(),
 504             hash: tcx.crate_hash(LOCAL_CRATE),
 505             disambiguator: tcx.sess.local_crate_disambiguator(),
 506             panic_strategy: tcx.sess.panic_strategy(),
 507             edition: tcx.sess.edition(),
 508             has_global_allocator: tcx.has_global_allocator(LOCAL_CRATE),
 509             has_panic_handler: tcx.has_panic_handler(LOCAL_CRATE),
 510             has_default_lib_allocator: has_default_lib_allocator,
 511             plugin_registrar_fn: tcx.plugin_registrar_fn(LOCAL_CRATE).map(|id| id.index),
 512             proc_macro_decls_static: if is_proc_macro {
 513                 let id = tcx.proc_macro_decls_static(LOCAL_CRATE).unwrap();
 514                 Some(id.index)
 515             } else {
 516                 None
 517             },
 518             proc_macro_data,
 519             proc_macro_stability: if is_proc_macro {
 520                 tcx.lookup_stability(DefId::local(CRATE_DEF_INDEX)).map(|stab| stab.clone())
 521             } else {
 522                 None
 523             },
 524             compiler_builtins: attr::contains_name(&attrs, sym::compiler_builtins),
 525             needs_allocator: attr::contains_name(&attrs, sym::needs_allocator),
 526             needs_panic_runtime: attr::contains_name(&attrs, sym::needs_panic_runtime),
 527             no_builtins: attr::contains_name(&attrs, sym::no_builtins),
 528             panic_runtime: attr::contains_name(&attrs, sym::panic_runtime),
 529             profiler_runtime: attr::contains_name(&attrs, sym::profiler_runtime),
 530             sanitizer_runtime: attr::contains_name(&attrs, sym::sanitizer_runtime),
 531             symbol_mangling_version: tcx.sess.opts.debugging_opts.symbol_mangling_version,
 532
 533             crate_deps,
 534             dylib_dependency_formats,
 535             lib_features,
 536             lang_items,
 537             diagnostic_items,
 538             lang_items_missing,
 539             native_libraries,
 540             foreign_modules,
 541             source_map,
 542             def_path_table,
 543             impls,
 544             exported_symbols,
 545             interpret_alloc_index,
 546             per_def,
 547         });
 548
 549         let total_bytes = self.position();
 550
 551         if self.tcx.sess.meta_stats() {
 552             let mut zero_bytes = 0;
 553             for e in self.opaque.data.iter() {
 554                 if *e == 0 {
 555                     zero_bytes += 1;
 556                 }
 557             }
 558
 559             println!("metadata stats:");
 560             println!("             dep bytes: {}", dep_bytes);
 561             println!("     lib feature bytes: {}", lib_feature_bytes);
 562             println!("       lang item bytes: {}", lang_item_bytes);
 563             println!(" diagnostic item bytes: {}", diagnostic_item_bytes);
 564             println!("          native bytes: {}", native_lib_bytes);
 565             println!("         source_map bytes: {}", source_map_bytes);
 566             println!("            impl bytes: {}", impl_bytes);
 567             println!("    exp. symbols bytes: {}", exported_symbols_bytes);
 568             println!("  def-path table bytes: {}", def_path_table_bytes);
 569             println!(" proc-macro-data-bytes: {}", proc_macro_data_bytes);
 570             println!("            item bytes: {}", item_bytes);
 571             println!("   per-def table bytes: {}", per_def_bytes);
 572             println!("            zero bytes: {}", zero_bytes);
 573             println!("           total bytes: {}", total_bytes);
 574         }
 575
 576         root
 577     }
 578 }
 579
 580 impl EncodeContext<'tcx> {
 581     fn encode_variances_of(&mut self, def_id: DefId) {
 582         debug!("EncodeContext::encode_variances_of({:?})", def_id);
 583         record!(self.per_def.variances[def_id] <- &self.tcx.variances_of(def_id)[..]);
 584     }
 585
 586     fn encode_item_type(&mut self, def_id: DefId) {
 587         debug!("EncodeContext::encode_item_type({:?})", def_id);
 588         record!(self.per_def.ty[def_id] <- self.tcx.type_of(def_id));
 589     }
 590
 591     fn encode_enum_variant_info(
 592         &mut self,
 593         enum_did: DefId,
 594         index: VariantIdx,
 595     ) {
 596         let tcx = self.tcx;
 597         let def = tcx.adt_def(enum_did);
 598         let variant = &def.variants[index];
 599         let def_id = variant.def_id;
 600         debug!("EncodeContext::encode_enum_variant_info({:?})", def_id);
 601
 602         let data = VariantData {
 603             ctor_kind: variant.ctor_kind,
 604             discr: variant.discr,
 605             ctor: variant.ctor_def_id.map(|did| did.index),
 606         };
 607
 608         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
 609         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 610
 611         record!(self.per_def.kind[def_id] <- EntryKind::Variant(self.lazy(data)));
 612         record!(self.per_def.visibility[def_id] <-
 613             ty::Visibility::from_hir(enum_vis, enum_id, self.tcx));
 614         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
 615         record!(self.per_def.attributes[def_id] <- &self.tcx.get_attrs(def_id)[..]);
 616         record!(self.per_def.children[def_id] <- variant.fields.iter().map(|f| {
 617             assert!(f.did.is_local());
 618             f.did.index
 619         }));
 620         self.encode_stability(def_id);
 621         self.encode_deprecation(def_id);
 622         self.encode_item_type(def_id);
 623         if variant.ctor_kind == CtorKind::Fn {
 624             // FIXME(eddyb) encode signature only in `encode_enum_variant_ctor`.
 625             if let Some(ctor_def_id) = variant.ctor_def_id {
 626                 record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(ctor_def_id));
 627             }
 628             // FIXME(eddyb) is this ever used?
 629             self.encode_variances_of(def_id);
 630         }
 631         self.encode_generics(def_id);
 632         self.encode_explicit_predicates(def_id);
 633         self.encode_inferred_outlives(def_id);
 634         self.encode_optimized_mir(def_id);
 635         self.encode_promoted_mir(def_id);
 636     }
 637
 638     fn encode_enum_variant_ctor(
 639         &mut self,
 640         enum_did: DefId,
 641         index: VariantIdx,
 642     ) {
 643         let tcx = self.tcx;
 644         let def = tcx.adt_def(enum_did);
 645         let variant = &def.variants[index];
 646         let def_id = variant.ctor_def_id.unwrap();
 647         debug!("EncodeContext::encode_enum_variant_ctor({:?})", def_id);
 648
 649         // FIXME(eddyb) encode only the `CtorKind` for constructors.
 650         let data = VariantData {
 651             ctor_kind: variant.ctor_kind,
 652             discr: variant.discr,
 653             ctor: Some(def_id.index),
 654         };
 655
 656         // Variant constructors have the same visibility as the parent enums, unless marked as
 657         // non-exhaustive, in which case they are lowered to `pub(crate)`.
 658         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
 659         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 660         let mut ctor_vis = ty::Visibility::from_hir(enum_vis, enum_id, tcx);
 661         if variant.is_field_list_non_exhaustive() && ctor_vis == ty::Visibility::Public {
 662             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 663         }
 664
 665         record!(self.per_def.kind[def_id] <- EntryKind::Variant(self.lazy(data)));
 666         record!(self.per_def.visibility[def_id] <- ctor_vis);
 667         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
 668         self.encode_stability(def_id);
 669         self.encode_deprecation(def_id);
 670         self.encode_item_type(def_id);
 671         if variant.ctor_kind == CtorKind::Fn {
 672             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
 673             self.encode_variances_of(def_id);
 674         }
 675         self.encode_generics(def_id);
 676         self.encode_explicit_predicates(def_id);
 677         self.encode_inferred_outlives(def_id);
 678         self.encode_optimized_mir(def_id);
 679         self.encode_promoted_mir(def_id);
 680     }
 681
 682     fn encode_info_for_mod(
 683         &mut self,
 684         id: hir::HirId,
 685         md: &hir::Mod,
 686         attrs: &[ast::Attribute],
 687         vis: &hir::Visibility,
 688     ) {
 689         let tcx = self.tcx;
 690         let def_id = tcx.hir().local_def_id(id);
 691         debug!("EncodeContext::encode_info_for_mod({:?})", def_id);
 692
 693         let data = ModData {
 694             reexports: match tcx.module_exports(def_id) {
 695                 Some(exports) => self.lazy(exports),
 696                 _ => Lazy::empty(),
 697             },
 698         };
 699
 700         record!(self.per_def.kind[def_id] <- EntryKind::Mod(self.lazy(data)));
 701         record!(self.per_def.visibility[def_id] <- ty::Visibility::from_hir(vis, id, self.tcx));
 702         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
 703         record!(self.per_def.attributes[def_id] <- attrs);
 704         record!(self.per_def.children[def_id] <- md.item_ids.iter().map(|item_id| {
 705             tcx.hir().local_def_id(item_id.id).index
 706         }));
 707         self.encode_stability(def_id);
 708         self.encode_deprecation(def_id);
 709     }
 710
 711     fn encode_field(
 712         &mut self,
 713         adt_def_id: DefId,
 714         variant_index: VariantIdx,
 715         field_index: usize,
 716     ) {
 717         let tcx = self.tcx;
 718         let variant = &tcx.adt_def(adt_def_id).variants[variant_index];
 719         let field = &variant.fields[field_index];
 720
 721         let def_id = field.did;
 722         debug!("EncodeContext::encode_field({:?})", def_id);
 723
 724         let variant_id = tcx.hir().as_local_hir_id(variant.def_id).unwrap();
 725         let variant_data = tcx.hir().expect_variant_data(variant_id);
 726
 727         record!(self.per_def.kind[def_id] <- EntryKind::Field);
 728         record!(self.per_def.visibility[def_id] <- field.vis);
 729         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
 730         record!(self.per_def.attributes[def_id] <- &variant_data.fields()[field_index].attrs);
 731         self.encode_stability(def_id);
 732         self.encode_deprecation(def_id);
 733         self.encode_item_type(def_id);
 734         self.encode_generics(def_id);
 735         self.encode_explicit_predicates(def_id);
 736         self.encode_inferred_outlives(def_id);
 737     }
 738
 739     fn encode_struct_ctor(&mut self, adt_def_id: DefId, def_id: DefId) {
 740         debug!("EncodeContext::encode_struct_ctor({:?})", def_id);
 741         let tcx = self.tcx;
 742         let adt_def = tcx.adt_def(adt_def_id);
 743         let variant = adt_def.non_enum_variant();
 744
 745         let data = VariantData {
 746             ctor_kind: variant.ctor_kind,
 747             discr: variant.discr,
 748             ctor: Some(def_id.index),
 749         };
 750
 751         let struct_id = tcx.hir().as_local_hir_id(adt_def_id).unwrap();
 752         let struct_vis = &tcx.hir().expect_item(struct_id).vis;
 753         let mut ctor_vis = ty::Visibility::from_hir(struct_vis, struct_id, tcx);
 754         for field in &variant.fields {
 755             if ctor_vis.is_at_least(field.vis, tcx) {
 756                 ctor_vis = field.vis;
 757             }
 758         }
 759
 760         // If the structure is marked as non_exhaustive then lower the visibility
 761         // to within the crate.
 762         if adt_def.non_enum_variant().is_field_list_non_exhaustive() &&
 763             ctor_vis == ty::Visibility::Public
 764         {
 765             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 766         }
 767
 768         record!(self.per_def.kind[def_id] <- EntryKind::Struct(self.lazy(data), adt_def.repr));
 769         record!(self.per_def.visibility[def_id] <- ctor_vis);
 770         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
 771         self.encode_stability(def_id);
 772         self.encode_deprecation(def_id);
 773         self.encode_item_type(def_id);
 774         if variant.ctor_kind == CtorKind::Fn {
 775             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
 776             self.encode_variances_of(def_id);
 777         }
 778         self.encode_generics(def_id);
 779         self.encode_explicit_predicates(def_id);
 780         self.encode_inferred_outlives(def_id);
 781         self.encode_optimized_mir(def_id);
 782         self.encode_promoted_mir(def_id);
 783     }
 784
 785     fn encode_generics(&mut self, def_id: DefId) {
 786         debug!("EncodeContext::encode_generics({:?})", def_id);
 787         record!(self.per_def.generics[def_id] <- self.tcx.generics_of(def_id));
 788     }
 789
 790     fn encode_explicit_predicates(&mut self, def_id: DefId) {
 791         debug!("EncodeContext::encode_explicit_predicates({:?})", def_id);
 792         record!(self.per_def.explicit_predicates[def_id] <-
 793             self.tcx.explicit_predicates_of(def_id));
 794     }
 795
 796     fn encode_inferred_outlives(&mut self, def_id: DefId) {
 797         debug!("EncodeContext::encode_inferred_outlives({:?})", def_id);
 798         let inferred_outlives = self.tcx.inferred_outlives_of(def_id);
 799         if !inferred_outlives.is_empty() {
 800             record!(self.per_def.inferred_outlives[def_id] <- inferred_outlives);
 801         }
 802     }
 803
 804     fn encode_super_predicates(&mut self, def_id: DefId) {
 805         debug!("EncodeContext::encode_super_predicates({:?})", def_id);
 806         record!(self.per_def.super_predicates[def_id] <- self.tcx.super_predicates_of(def_id));
 807     }
 808
 809     fn encode_info_for_trait_item(&mut self, def_id: DefId) {
 810         debug!("EncodeContext::encode_info_for_trait_item({:?})", def_id);
 811         let tcx = self.tcx;
 812
 813         let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 814         let ast_item = tcx.hir().expect_trait_item(hir_id);
 815         let trait_item = tcx.associated_item(def_id);
 816
 817         let container = match trait_item.defaultness {
 818             hir::Defaultness::Default { has_value: true } =>
 819                 AssocContainer::TraitWithDefault,
 820             hir::Defaultness::Default { has_value: false } =>
 821                 AssocContainer::TraitRequired,
 822             hir::Defaultness::Final =>
 823                 span_bug!(ast_item.span, "traits cannot have final items"),
 824         };
 825
 826         record!(self.per_def.kind[def_id] <- match trait_item.kind {
 827             ty::AssocKind::Const => {
 828                 let rendered =
 829                     hir::print::to_string(self.tcx.hir(), |s| s.print_trait_item(ast_item));
 830                 let rendered_const = self.lazy(RenderedConst(rendered));
 831
 832                 EntryKind::AssocConst(
 833                     container,
 834                     Default::default(),
 835                     rendered_const,
 836                 )
 837             }
 838             ty::AssocKind::Method => {
 839                 let fn_data = if let hir::TraitItemKind::Method(m_sig, m) = &ast_item.kind {
 840                     let param_names = match *m {
 841                         hir::TraitMethod::Required(ref names) => {
 842                             self.encode_fn_param_names(names)
 843                         }
 844                         hir::TraitMethod::Provided(body) => {
 845                             self.encode_fn_param_names_for_body(body)
 846                         }
 847                     };
 848                     FnData {
 849                         asyncness: m_sig.header.asyncness,
 850                         constness: hir::Constness::NotConst,
 851                         param_names,
 852                     }
 853                 } else {
 854                     bug!()
 855                 };
 856                 EntryKind::Method(self.lazy(MethodData {
 857                     fn_data,
 858                     container,
 859                     has_self: trait_item.method_has_self_argument,
 860                 }))
 861             }
 862             ty::AssocKind::Type => EntryKind::AssocType(container),
 863             ty::AssocKind::OpaqueTy => span_bug!(ast_item.span, "opaque type in trait"),
 864         });
 865         record!(self.per_def.visibility[def_id] <- trait_item.vis);
 866         record!(self.per_def.span[def_id] <- ast_item.span);
 867         record!(self.per_def.attributes[def_id] <- &ast_item.attrs);
 868         self.encode_stability(def_id);
 869         self.encode_const_stability(def_id);
 870         self.encode_deprecation(def_id);
 871         match trait_item.kind {
 872             ty::AssocKind::Const |
 873             ty::AssocKind::Method => {
 874                 self.encode_item_type(def_id);
 875             }
 876             ty::AssocKind::Type => {
 877                 if trait_item.defaultness.has_value() {
 878                     self.encode_item_type(def_id);
 879                 }
 880             }
 881             ty::AssocKind::OpaqueTy => unreachable!(),
 882         }
 883         if trait_item.kind == ty::AssocKind::Method {
 884             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
 885             self.encode_variances_of(def_id);
 886         }
 887         self.encode_generics(def_id);
 888         self.encode_explicit_predicates(def_id);
 889         self.encode_inferred_outlives(def_id);
 890         self.encode_optimized_mir(def_id);
 891         self.encode_promoted_mir(def_id);
 892     }
 893
 894     fn metadata_output_only(&self) -> bool {
 895         // MIR optimisation can be skipped when we're just interested in the metadata.
 896         !self.tcx.sess.opts.output_types.should_codegen()
 897     }
 898
 899     fn encode_info_for_impl_item(&mut self, def_id: DefId) {
 900         debug!("EncodeContext::encode_info_for_impl_item({:?})", def_id);
 901         let tcx = self.tcx;
 902
 903         let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
 904         let ast_item = self.tcx.hir().expect_impl_item(hir_id);
 905         let impl_item = self.tcx.associated_item(def_id);
 906
 907         let container = match impl_item.defaultness {
 908             hir::Defaultness::Default { has_value: true } => AssocContainer::ImplDefault,
 909             hir::Defaultness::Final => AssocContainer::ImplFinal,
 910             hir::Defaultness::Default { has_value: false } =>
 911                 span_bug!(ast_item.span, "impl items always have values (currently)"),
 912         };
 913
 914         record!(self.per_def.kind[def_id] <- match impl_item.kind {
 915             ty::AssocKind::Const => {
 916                 if let hir::ImplItemKind::Const(_, body_id) = ast_item.kind {
 917                     let qualifs = self.tcx.at(ast_item.span).mir_const_qualif(def_id);
 918
 919                     EntryKind::AssocConst(
 920                         container,
 921                         qualifs,
 922                         self.encode_rendered_const_for_body(body_id))
 923                 } else {
 924                     bug!()
 925                 }
 926             }
 927             ty::AssocKind::Method => {
 928                 let fn_data = if let hir::ImplItemKind::Method(ref sig, body) = ast_item.kind {
 929                     FnData {
 930                         asyncness: sig.header.asyncness,
 931                         constness: sig.header.constness,
 932                         param_names: self.encode_fn_param_names_for_body(body),
 933                     }
 934                 } else {
 935                     bug!()
 936                 };
 937                 EntryKind::Method(self.lazy(MethodData {
 938                     fn_data,
 939                     container,
 940                     has_self: impl_item.method_has_self_argument,
 941                 }))
 942             }
 943             ty::AssocKind::OpaqueTy => EntryKind::AssocOpaqueTy(container),
 944             ty::AssocKind::Type => EntryKind::AssocType(container)
 945         });
 946         record!(self.per_def.visibility[def_id] <- impl_item.vis);
 947         record!(self.per_def.span[def_id] <- ast_item.span);
 948         record!(self.per_def.attributes[def_id] <- &ast_item.attrs);
 949         self.encode_stability(def_id);
 950         self.encode_const_stability(def_id);
 951         self.encode_deprecation(def_id);
 952         self.encode_item_type(def_id);
 953         if impl_item.kind == ty::AssocKind::Method {
 954             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
 955             self.encode_variances_of(def_id);
 956         }
 957         self.encode_generics(def_id);
 958         self.encode_explicit_predicates(def_id);
 959         self.encode_inferred_outlives(def_id);
 960         let mir = match ast_item.kind {
 961             hir::ImplItemKind::Const(..) => true,
 962             hir::ImplItemKind::Method(ref sig, _) => {
 963                 let generics = self.tcx.generics_of(def_id);
 964                 let needs_inline = (generics.requires_monomorphization(self.tcx) ||
 965                                     tcx.codegen_fn_attrs(def_id).requests_inline()) &&
 966                                     !self.metadata_output_only();
 967                 let is_const_fn = sig.header.constness == hir::Constness::Const;
 968                 let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
 969                 needs_inline || is_const_fn || always_encode_mir
 970             },
 971             hir::ImplItemKind::OpaqueTy(..) |
 972             hir::ImplItemKind::TyAlias(..) => false,
 973         };
 974         if mir {
 975             self.encode_optimized_mir(def_id);
 976             self.encode_promoted_mir(def_id);
 977         }
 978     }
 979
 980     fn encode_fn_param_names_for_body(&mut self, body_id: hir::BodyId)
 981                                     -> Lazy<[ast::Name]> {
 982         self.tcx.dep_graph.with_ignore(|| {
 983             let body = self.tcx.hir().body(body_id);
 984             self.lazy(body.params.iter().map(|arg| {
 985                 match arg.pat.kind {
 986                     PatKind::Binding(_, _, ident, _) => ident.name,
 987                     _ => kw::Invalid,
 988                 }
 989             }))
 990         })
 991     }
 992
 993     fn encode_fn_param_names(&mut self, param_names: &[ast::Ident]) -> Lazy<[ast::Name]> {
 994         self.lazy(param_names.iter().map(|ident| ident.name))
 995     }
 996
 997     fn encode_optimized_mir(&mut self, def_id: DefId) {
 998         debug!("EntryBuilder::encode_mir({:?})", def_id);
 999         if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id) {
1000             record!(self.per_def.mir[def_id] <- self.tcx.optimized_mir(def_id));
1001         }
1002     }
1003
1004     fn encode_promoted_mir(&mut self, def_id: DefId) {
1005         debug!("EncodeContext::encode_promoted_mir({:?})", def_id);
1006         if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id) {
1007             record!(self.per_def.promoted_mir[def_id] <- self.tcx.promoted_mir(def_id));
1008         }
1009     }
1010
1011     // Encodes the inherent implementations of a structure, enumeration, or trait.
1012     fn encode_inherent_implementations(&mut self, def_id: DefId) {
1013         debug!("EncodeContext::encode_inherent_implementations({:?})", def_id);
1014         let implementations = self.tcx.inherent_impls(def_id);
1015         if !implementations.is_empty() {
1016             record!(self.per_def.inherent_impls[def_id] <- implementations.iter().map(|&def_id| {
1017                 assert!(def_id.is_local());
1018                 def_id.index
1019             }));
1020         }
1021     }
1022
1023     fn encode_stability(&mut self, def_id: DefId) {
1024         debug!("EncodeContext::encode_stability({:?})", def_id);
1025         if let Some(stab) = self.tcx.lookup_stability(def_id) {
1026             record!(self.per_def.stability[def_id] <- stab)
1027         }
1028     }
1029
1030     fn encode_const_stability(&mut self, def_id: DefId) {
1031         debug!("EncodeContext::encode_const_stability({:?})", def_id);
1032         if let Some(stab) = self.tcx.lookup_const_stability(def_id) {
1033             record!(self.per_def.const_stability[def_id] <- stab)
1034         }
1035     }
1036
1037     fn encode_deprecation(&mut self, def_id: DefId) {
1038         debug!("EncodeContext::encode_deprecation({:?})", def_id);
1039         if let Some(depr) = self.tcx.lookup_deprecation(def_id) {
1040             record!(self.per_def.deprecation[def_id] <- depr);
1041         }
1042     }
1043
1044     fn encode_rendered_const_for_body(&mut self, body_id: hir::BodyId) -> Lazy<RenderedConst> {
1045         let body = self.tcx.hir().body(body_id);
1046         let rendered = hir::print::to_string(self.tcx.hir(), |s| s.print_expr(&body.value));
1047         let rendered_const = &RenderedConst(rendered);
1048         self.lazy(rendered_const)
1049     }
1050
1051     fn encode_info_for_item(&mut self, def_id: DefId, item: &'tcx hir::Item) {
1052         let tcx = self.tcx;
1053
1054         debug!("EncodeContext::encode_info_for_item({:?})", def_id);
1055
1056         record!(self.per_def.kind[def_id] <- match item.kind {
1057             hir::ItemKind::Static(_, hir::Mutability::Mutable, _) => EntryKind::MutStatic,
1058             hir::ItemKind::Static(_, hir::Mutability::Immutable, _) => EntryKind::ImmStatic,
1059             hir::ItemKind::Const(_, body_id) => {
1060                 let qualifs = self.tcx.at(item.span).mir_const_qualif(def_id);
1061                 EntryKind::Const(
1062                     qualifs,
1063                     self.encode_rendered_const_for_body(body_id)
1064                 )
1065             }
1066             hir::ItemKind::Fn(ref sig, .., body) => {
1067                 let data = FnData {
1068                     asyncness: sig.header.asyncness,
1069                     constness: sig.header.constness,
1070                     param_names: self.encode_fn_param_names_for_body(body),
1071                 };
1072
1073                 EntryKind::Fn(self.lazy(data))
1074             }
1075             hir::ItemKind::Mod(ref m) => {
1076                 return self.encode_info_for_mod(item.hir_id, m, &item.attrs, &item.vis);
1077             }
1078             hir::ItemKind::ForeignMod(_) => EntryKind::ForeignMod,
1079             hir::ItemKind::GlobalAsm(..) => EntryKind::GlobalAsm,
1080             hir::ItemKind::TyAlias(..) => EntryKind::Type,
1081             hir::ItemKind::OpaqueTy(..) => EntryKind::OpaqueTy,
1082             hir::ItemKind::Enum(..) => EntryKind::Enum(self.tcx.adt_def(def_id).repr),
1083             hir::ItemKind::Struct(ref struct_def, _) => {
1084                 let adt_def = self.tcx.adt_def(def_id);
1085                 let variant = adt_def.non_enum_variant();
1086
1087                 // Encode def_ids for each field and method
1088                 // for methods, write all the stuff get_trait_method
1089                 // needs to know
1090                 let ctor = struct_def.ctor_hir_id().map(|ctor_hir_id| {
1091                     self.tcx.hir().local_def_id(ctor_hir_id).index
1092                 });
1093
1094                 EntryKind::Struct(self.lazy(VariantData {
1095                     ctor_kind: variant.ctor_kind,
1096                     discr: variant.discr,
1097                     ctor,
1098                 }), adt_def.repr)
1099             }
1100             hir::ItemKind::Union(..) => {
1101                 let adt_def = self.tcx.adt_def(def_id);
1102                 let variant = adt_def.non_enum_variant();
1103
1104                 EntryKind::Union(self.lazy(VariantData {
1105                     ctor_kind: variant.ctor_kind,
1106                     discr: variant.discr,
1107                     ctor: None,
1108                 }), adt_def.repr)
1109             }
1110             hir::ItemKind::Impl(_, _, defaultness, ..) => {
1111                 let trait_ref = self.tcx.impl_trait_ref(def_id);
1112                 let polarity = self.tcx.impl_polarity(def_id);
1113                 let parent = if let Some(trait_ref) = trait_ref {
1114                     let trait_def = self.tcx.trait_def(trait_ref.def_id);
1115                     trait_def.ancestors(self.tcx, def_id).nth(1).and_then(|node| {
1116                         match node {
1117                             specialization_graph::Node::Impl(parent) => Some(parent),
1118                             _ => None,
1119                         }
1120                     })
1121                 } else {
1122                     None
1123                 };
1124
1125                 // if this is an impl of `CoerceUnsized`, create its
1126                 // "unsized info", else just store None
1127                 let coerce_unsized_info =
1128                     trait_ref.and_then(|t| {
1129                         if Some(t.def_id) == self.tcx.lang_items().coerce_unsized_trait() {
1130                             Some(self.tcx.at(item.span).coerce_unsized_info(def_id))
1131                         } else {
1132                             None
1133                         }
1134                     });
1135
1136                 let data = ImplData {
1137                     polarity,
1138                     defaultness,
1139                     parent_impl: parent,
1140                     coerce_unsized_info,
1141                 };
1142
1143                 EntryKind::Impl(self.lazy(data))
1144             }
1145             hir::ItemKind::Trait(..) => {
1146                 let trait_def = self.tcx.trait_def(def_id);
1147                 let data = TraitData {
1148                     unsafety: trait_def.unsafety,
1149                     paren_sugar: trait_def.paren_sugar,
1150                     has_auto_impl: self.tcx.trait_is_auto(def_id),
1151                     is_marker: trait_def.is_marker,
1152                 };
1153
1154                 EntryKind::Trait(self.lazy(data))
1155             }
1156             hir::ItemKind::TraitAlias(..) => EntryKind::TraitAlias,
1157             hir::ItemKind::ExternCrate(_) |
1158             hir::ItemKind::Use(..) => bug!("cannot encode info for item {:?}", item),
1159         });
1160         record!(self.per_def.visibility[def_id] <-
1161             ty::Visibility::from_hir(&item.vis, item.hir_id, tcx));
1162         record!(self.per_def.span[def_id] <- item.span);
1163         record!(self.per_def.attributes[def_id] <- &item.attrs);
1164         // FIXME(eddyb) there should be a nicer way to do this.
1165         match item.kind {
1166             hir::ItemKind::ForeignMod(ref fm) => record!(self.per_def.children[def_id] <-
1167                 fm.items
1168                     .iter()
1169                     .map(|foreign_item| tcx.hir().local_def_id(
1170                         foreign_item.hir_id).index)
1171             ),
1172             hir::ItemKind::Enum(..) => record!(self.per_def.children[def_id] <-
1173                 self.tcx.adt_def(def_id).variants.iter().map(|v| {
1174                     assert!(v.def_id.is_local());
1175                     v.def_id.index
1176                 })
1177             ),
1178             hir::ItemKind::Struct(..) |
1179             hir::ItemKind::Union(..) => record!(self.per_def.children[def_id] <-
1180                 self.tcx.adt_def(def_id).non_enum_variant().fields.iter().map(|f| {
1181                     assert!(f.did.is_local());
1182                     f.did.index
1183                 })
1184             ),
1185             hir::ItemKind::Impl(..) |
1186             hir::ItemKind::Trait(..) => {
1187                 let associated_item_def_ids = self.tcx.associated_item_def_ids(def_id);
1188                 record!(self.per_def.children[def_id] <-
1189                     associated_item_def_ids.iter().map(|&def_id| {
1190                         assert!(def_id.is_local());
1191                         def_id.index
1192                     })
1193                 );
1194             }
1195             _ => {}
1196         }
1197         self.encode_stability(def_id);
1198         self.encode_const_stability(def_id);
1199         self.encode_deprecation(def_id);
1200         match item.kind {
1201             hir::ItemKind::Static(..) |
1202             hir::ItemKind::Const(..) |
1203             hir::ItemKind::Fn(..) |
1204             hir::ItemKind::TyAlias(..) |
1205             hir::ItemKind::OpaqueTy(..) |
1206             hir::ItemKind::Enum(..) |
1207             hir::ItemKind::Struct(..) |
1208             hir::ItemKind::Union(..) |
1209             hir::ItemKind::Impl(..) => self.encode_item_type(def_id),
1210             _ => {}
1211         }
1212         if let hir::ItemKind::Fn(..) = item.kind {
1213             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
1214         }
1215         if let hir::ItemKind::Impl(..) = item.kind {
1216             if let Some(trait_ref) = self.tcx.impl_trait_ref(def_id) {
1217                 record!(self.per_def.impl_trait_ref[def_id] <- trait_ref);
1218             }
1219         }
1220         self.encode_inherent_implementations(def_id);
1221         match item.kind {
1222             hir::ItemKind::Enum(..) |
1223             hir::ItemKind::Struct(..) |
1224             hir::ItemKind::Union(..) |
1225             hir::ItemKind::Fn(..) => self.encode_variances_of(def_id),
1226             _ => {}
1227         }
1228         match item.kind {
1229             hir::ItemKind::Static(..) |
1230             hir::ItemKind::Const(..) |
1231             hir::ItemKind::Fn(..) |
1232             hir::ItemKind::TyAlias(..) |
1233             hir::ItemKind::Enum(..) |
1234             hir::ItemKind::Struct(..) |
1235             hir::ItemKind::Union(..) |
1236             hir::ItemKind::Impl(..) |
1237             hir::ItemKind::OpaqueTy(..) |
1238             hir::ItemKind::Trait(..) |
1239             hir::ItemKind::TraitAlias(..) => {
1240                 self.encode_generics(def_id);
1241                 self.encode_explicit_predicates(def_id);
1242                 self.encode_inferred_outlives(def_id);
1243             }
1244             _ => {}
1245         }
1246         match item.kind {
1247             hir::ItemKind::Trait(..) |
1248             hir::ItemKind::TraitAlias(..) => {
1249                 self.encode_super_predicates(def_id);
1250             }
1251             _ => {}
1252         }
1253
1254         let mir = match item.kind {
1255             hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => true,
1256             hir::ItemKind::Fn(ref sig, ..) => {
1257                 let generics = tcx.generics_of(def_id);
1258                 let needs_inline =
1259                     (generics.requires_monomorphization(tcx) ||
1260                         tcx.codegen_fn_attrs(def_id).requests_inline()) &&
1261                         !self.metadata_output_only();
1262                 let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
1263                 needs_inline || sig.header.constness == hir::Constness::Const || always_encode_mir
1264             }
1265             _ => false,
1266         };
1267         if mir {
1268             self.encode_optimized_mir(def_id);
1269             self.encode_promoted_mir(def_id);
1270         }
1271     }
1272
1273     /// Serialize the text of exported macros
1274     fn encode_info_for_macro_def(&mut self, macro_def: &hir::MacroDef) {
1275         use syntax::print::pprust;
1276         let def_id = self.tcx.hir().local_def_id(macro_def.hir_id);
1277         record!(self.per_def.kind[def_id] <- EntryKind::MacroDef(self.lazy(MacroDef {
1278             body: pprust::tts_to_string(macro_def.body.clone()),
1279             legacy: macro_def.legacy,
1280         })));
1281         record!(self.per_def.visibility[def_id] <- ty::Visibility::Public);
1282         record!(self.per_def.span[def_id] <- macro_def.span);
1283         record!(self.per_def.attributes[def_id] <- &macro_def.attrs);
1284         self.encode_stability(def_id);
1285         self.encode_deprecation(def_id);
1286     }
1287
1288     fn encode_info_for_generic_param(
1289         &mut self,
1290         def_id: DefId,
1291         kind: EntryKind<'tcx>,
1292         encode_type: bool,
1293     ) {
1294         record!(self.per_def.kind[def_id] <- kind);
1295         record!(self.per_def.visibility[def_id] <- ty::Visibility::Public);
1296         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
1297         if encode_type {
1298             self.encode_item_type(def_id);
1299         }
1300     }
1301
1302     fn encode_info_for_closure(&mut self, def_id: DefId) {
1303         debug!("EncodeContext::encode_info_for_closure({:?})", def_id);
1304
1305         // NOTE(eddyb) `tcx.type_of(def_id)` isn't used because it's fully generic,
1306         // including on the signature, which is inferred in `typeck_tables_of.
1307         let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
1308         let ty = self.tcx.typeck_tables_of(def_id).node_type(hir_id);
1309
1310         record!(self.per_def.kind[def_id] <- match ty.kind {
1311             ty::Generator(def_id, ..) => {
1312                 let layout = self.tcx.generator_layout(def_id);
1313                 let data = GeneratorData {
1314                     layout: layout.clone(),
1315                 };
1316                 EntryKind::Generator(self.lazy(data))
1317             }
1318
1319             ty::Closure(..) => EntryKind::Closure,
1320
1321             _ => bug!("closure that is neither generator nor closure"),
1322         });
1323         record!(self.per_def.visibility[def_id] <- ty::Visibility::Public);
1324         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
1325         record!(self.per_def.attributes[def_id] <- &self.tcx.get_attrs(def_id)[..]);
1326         self.encode_item_type(def_id);
1327         if let ty::Closure(def_id, substs) = ty.kind {
1328             record!(self.per_def.fn_sig[def_id] <- substs.as_closure().sig(def_id, self.tcx));
1329         }
1330         self.encode_generics(def_id);
1331         self.encode_optimized_mir(def_id);
1332         self.encode_promoted_mir(def_id);
1333     }
1334
1335     fn encode_info_for_anon_const(&mut self, def_id: DefId) {
1336         debug!("EncodeContext::encode_info_for_anon_const({:?})", def_id);
1337         let id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
1338         let body_id = self.tcx.hir().body_owned_by(id);
1339         let const_data = self.encode_rendered_const_for_body(body_id);
1340         let qualifs = self.tcx.mir_const_qualif(def_id);
1341
1342         record!(self.per_def.kind[def_id] <- EntryKind::Const(qualifs, const_data));
1343         record!(self.per_def.visibility[def_id] <- ty::Visibility::Public);
1344         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
1345         self.encode_item_type(def_id);
1346         self.encode_generics(def_id);
1347         self.encode_explicit_predicates(def_id);
1348         self.encode_inferred_outlives(def_id);
1349         self.encode_optimized_mir(def_id);
1350         self.encode_promoted_mir(def_id);
1351     }
1352
1353     fn encode_native_libraries(&mut self) -> Lazy<[NativeLibrary]> {
1354         let used_libraries = self.tcx.native_libraries(LOCAL_CRATE);
1355         self.lazy(used_libraries.iter().cloned())
1356     }
1357
1358     fn encode_foreign_modules(&mut self) -> Lazy<[ForeignModule]> {
1359         let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
1360         self.lazy(foreign_modules.iter().cloned())
1361     }
1362
1363     fn encode_proc_macros(&mut self) -> Option<Lazy<[DefIndex]>> {
1364         let is_proc_macro = self.tcx.sess.crate_types.borrow().contains(&CrateType::ProcMacro);
1365         if is_proc_macro {
1366             let tcx = self.tcx;
1367             Some(self.lazy(tcx.hir().krate().items.values().filter_map(|item| {
1368                 if item.attrs.iter().any(|attr| is_proc_macro_attr(attr)) {
1369                     Some(item.hir_id.owner)
1370                 } else {
1371                     None
1372                 }
1373             })))
1374         } else {
1375             None
1376         }
1377     }
1378
1379     fn encode_crate_deps(&mut self) -> Lazy<[CrateDep]> {
1380         let crates = self.tcx.crates();
1381
1382         let mut deps = crates
1383             .iter()
1384             .map(|&cnum| {
1385                 let dep = CrateDep {
1386                     name: self.tcx.original_crate_name(cnum),
1387                     hash: self.tcx.crate_hash(cnum),
1388                     host_hash: self.tcx.crate_host_hash(cnum),
1389                     kind: self.tcx.dep_kind(cnum),
1390                     extra_filename: self.tcx.extra_filename(cnum),
1391                 };
1392                 (cnum, dep)
1393             })
1394             .collect::<Vec<_>>();
1395
1396         deps.sort_by_key(|&(cnum, _)| cnum);
1397
1398         {
1399             // Sanity-check the crate numbers
1400             let mut expected_cnum = 1;
1401             for &(n, _) in &deps {
1402                 assert_eq!(n, CrateNum::new(expected_cnum));
1403                 expected_cnum += 1;
1404             }
1405         }
1406
1407         // We're just going to write a list of crate 'name-hash-version's, with
1408         // the assumption that they are numbered 1 to n.
1409         // FIXME (#2166): This is not nearly enough to support correct versioning
1410         // but is enough to get transitive crate dependencies working.
1411         self.lazy(deps.iter().map(|&(_, ref dep)| dep))
1412     }
1413
1414     fn encode_lib_features(&mut self) -> Lazy<[(ast::Name, Option<ast::Name>)]> {
1415         let tcx = self.tcx;
1416         let lib_features = tcx.lib_features();
1417         self.lazy(lib_features.to_vec())
1418     }
1419
1420     fn encode_diagnostic_items(&mut self) -> Lazy<[(Symbol, DefIndex)]> {
1421         let tcx = self.tcx;
1422         let diagnostic_items = tcx.diagnostic_items(LOCAL_CRATE);
1423         self.lazy(diagnostic_items.iter().map(|(&name, def_id)| (name, def_id.index)))
1424     }
1425
1426     fn encode_lang_items(&mut self) -> Lazy<[(DefIndex, usize)]> {
1427         let tcx = self.tcx;
1428         let lang_items = tcx.lang_items();
1429         let lang_items = lang_items.items().iter();
1430         self.lazy(lang_items.enumerate().filter_map(|(i, &opt_def_id)| {
1431             if let Some(def_id) = opt_def_id {
1432                 if def_id.is_local() {
1433                     return Some((def_id.index, i));
1434                 }
1435             }
1436             None
1437         }))
1438     }
1439
1440     fn encode_lang_items_missing(&mut self) -> Lazy<[lang_items::LangItem]> {
1441         let tcx = self.tcx;
1442         self.lazy(&tcx.lang_items().missing)
1443     }
1444
1445     /// Encodes an index, mapping each trait to its (local) implementations.
1446     fn encode_impls(&mut self) -> Lazy<[TraitImpls]> {
1447         debug!("EncodeContext::encode_impls()");
1448         let tcx = self.tcx;
1449         let mut visitor = ImplVisitor {
1450             tcx,
1451             impls: FxHashMap::default(),
1452         };
1453         tcx.hir().krate().visit_all_item_likes(&mut visitor);
1454
1455         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
1456
1457         // Bring everything into deterministic order for hashing
1458         all_impls.sort_by_cached_key(|&(trait_def_id, _)| {
1459             tcx.def_path_hash(trait_def_id)
1460         });
1461
1462         let all_impls: Vec<_> = all_impls
1463             .into_iter()
1464             .map(|(trait_def_id, mut impls)| {
1465                 // Bring everything into deterministic order for hashing
1466                 impls.sort_by_cached_key(|&def_index| {
1467                     tcx.hir().definitions().def_path_hash(def_index)
1468                 });
1469
1470                 TraitImpls {
1471                     trait_id: (trait_def_id.krate.as_u32(), trait_def_id.index),
1472                     impls: self.lazy(&impls),
1473                 }
1474             })
1475             .collect();
1476
1477         self.lazy(&all_impls)
1478     }
1479
1480     // Encodes all symbols exported from this crate into the metadata.
1481     //
1482     // This pass is seeded off the reachability list calculated in the
1483     // middle::reachable module but filters out items that either don't have a
1484     // symbol associated with them (they weren't translated) or if they're an FFI
1485     // definition (as that's not defined in this crate).
1486     fn encode_exported_symbols(&mut self,
1487                                exported_symbols: &[(ExportedSymbol<'tcx>, SymbolExportLevel)])
1488                                -> Lazy<[(ExportedSymbol<'tcx>, SymbolExportLevel)]> {
1489         // The metadata symbol name is special. It should not show up in
1490         // downstream crates.
1491         let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
1492
1493         self.lazy(exported_symbols
1494             .iter()
1495             .filter(|&&(ref exported_symbol, _)| {
1496                 match *exported_symbol {
1497                     ExportedSymbol::NoDefId(symbol_name) => {
1498                         symbol_name != metadata_symbol_name
1499                     },
1500                     _ => true,
1501                 }
1502             })
1503             .cloned())
1504     }
1505
1506     fn encode_dylib_dependency_formats(&mut self) -> Lazy<[Option<LinkagePreference>]> {
1507         let formats = self.tcx.dependency_formats(LOCAL_CRATE);
1508         for (ty, arr) in formats.iter() {
1509             if *ty != config::CrateType::Dylib {
1510                 continue;
1511             }
1512             return self.lazy(arr.iter().map(|slot| {
1513                 match *slot {
1514                     Linkage::NotLinked |
1515                     Linkage::IncludedFromDylib => None,
1516
1517                     Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
1518                     Linkage::Static => Some(LinkagePreference::RequireStatic),
1519                 }
1520             }));
1521         }
1522         Lazy::empty()
1523     }
1524
1525     fn encode_info_for_foreign_item(
1526         &mut self,
1527         def_id: DefId,
1528         nitem: &hir::ForeignItem,
1529     )  {
1530         let tcx = self.tcx;
1531
1532         debug!("EncodeContext::encode_info_for_foreign_item({:?})", def_id);
1533
1534         record!(self.per_def.kind[def_id] <- match nitem.kind {
1535             hir::ForeignItemKind::Fn(_, ref names, _) => {
1536                 let data = FnData {
1537                     asyncness: hir::IsAsync::NotAsync,
1538                     constness: if self.tcx.is_const_fn_raw(def_id) {
1539                         hir::Constness::Const
1540                     } else {
1541                         hir::Constness::NotConst
1542                     },
1543                     param_names: self.encode_fn_param_names(names),
1544                 };
1545                 EntryKind::ForeignFn(self.lazy(data))
1546             }
1547             hir::ForeignItemKind::Static(_, hir::Mutability::Mutable) =>
1548                 EntryKind::ForeignMutStatic,
1549             hir::ForeignItemKind::Static(_, hir::Mutability::Immutable) =>
1550                 EntryKind::ForeignImmStatic,
1551             hir::ForeignItemKind::Type => EntryKind::ForeignType,
1552         });
1553         record!(self.per_def.visibility[def_id] <-
1554             ty::Visibility::from_hir(&nitem.vis, nitem.hir_id, self.tcx));
1555         record!(self.per_def.span[def_id] <- nitem.span);
1556         record!(self.per_def.attributes[def_id] <- &nitem.attrs);
1557         self.encode_stability(def_id);
1558         self.encode_const_stability(def_id);
1559         self.encode_deprecation(def_id);
1560         self.encode_item_type(def_id);
1561         if let hir::ForeignItemKind::Fn(..) = nitem.kind {
1562             record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
1563             self.encode_variances_of(def_id);
1564         }
1565         self.encode_generics(def_id);
1566         self.encode_explicit_predicates(def_id);
1567         self.encode_inferred_outlives(def_id);
1568     }
1569 }
1570
1571 // FIXME(eddyb) make metadata encoding walk over all definitions, instead of HIR.
1572 impl Visitor<'tcx> for EncodeContext<'tcx> {
1573     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1574         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
1575     }
1576     fn visit_expr(&mut self, ex: &'tcx hir::Expr) {
1577         intravisit::walk_expr(self, ex);
1578         self.encode_info_for_expr(ex);
1579     }
1580     fn visit_anon_const(&mut self, c: &'tcx AnonConst) {
1581         intravisit::walk_anon_const(self, c);
1582         let def_id = self.tcx.hir().local_def_id(c.hir_id);
1583         self.encode_info_for_anon_const(def_id);
1584     }
1585     fn visit_item(&mut self, item: &'tcx hir::Item) {
1586         intravisit::walk_item(self, item);
1587         let def_id = self.tcx.hir().local_def_id(item.hir_id);
1588         match item.kind {
1589             hir::ItemKind::ExternCrate(_) |
1590             hir::ItemKind::Use(..) => {} // ignore these
1591             _ => self.encode_info_for_item(def_id, item),
1592         }
1593         self.encode_addl_info_for_item(item);
1594     }
1595     fn visit_foreign_item(&mut self, ni: &'tcx hir::ForeignItem) {
1596         intravisit::walk_foreign_item(self, ni);
1597         let def_id = self.tcx.hir().local_def_id(ni.hir_id);
1598         self.encode_info_for_foreign_item(def_id, ni);
1599     }
1600     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
1601         intravisit::walk_generics(self, generics);
1602         self.encode_info_for_generics(generics);
1603     }
1604     fn visit_macro_def(&mut self, macro_def: &'tcx hir::MacroDef) {
1605         self.encode_info_for_macro_def(macro_def);
1606     }
1607 }
1608
1609 impl EncodeContext<'tcx> {
1610     fn encode_fields(&mut self, adt_def_id: DefId) {
1611         let def = self.tcx.adt_def(adt_def_id);
1612         for (variant_index, variant) in def.variants.iter_enumerated() {
1613             for (field_index, _field) in variant.fields.iter().enumerate() {
1614                 // FIXME(eddyb) `adt_def_id` is leftover from incremental isolation,
1615                 // pass `def`, `variant` or `field` instead.
1616                 self.encode_field(adt_def_id, variant_index, field_index);
1617             }
1618         }
1619     }
1620
1621     fn encode_info_for_generics(&mut self, generics: &hir::Generics) {
1622         for param in &generics.params {
1623             let def_id = self.tcx.hir().local_def_id(param.hir_id);
1624             match param.kind {
1625                 GenericParamKind::Lifetime { .. } => continue,
1626                 GenericParamKind::Type { ref default, .. } => {
1627                     self.encode_info_for_generic_param(
1628                         def_id,
1629                         EntryKind::TypeParam,
1630                         default.is_some(),
1631                     );
1632                 }
1633                 GenericParamKind::Const { .. } => {
1634                     self.encode_info_for_generic_param(def_id, EntryKind::ConstParam, true);
1635                 }
1636             }
1637         }
1638     }
1639
1640     fn encode_info_for_expr(&mut self, expr: &hir::Expr) {
1641         match expr.kind {
1642             hir::ExprKind::Closure(..) => {
1643                 let def_id = self.tcx.hir().local_def_id(expr.hir_id);
1644                 self.encode_info_for_closure(def_id);
1645             }
1646             _ => {}
1647         }
1648     }
1649
1650     /// In some cases, along with the item itself, we also
1651     /// encode some sub-items. Usually we want some info from the item
1652     /// so it's easier to do that here then to wait until we would encounter
1653     /// normally in the visitor walk.
1654     fn encode_addl_info_for_item(&mut self, item: &hir::Item) {
1655         let def_id = self.tcx.hir().local_def_id(item.hir_id);
1656         match item.kind {
1657             hir::ItemKind::Static(..) |
1658             hir::ItemKind::Const(..) |
1659             hir::ItemKind::Fn(..) |
1660             hir::ItemKind::Mod(..) |
1661             hir::ItemKind::ForeignMod(..) |
1662             hir::ItemKind::GlobalAsm(..) |
1663             hir::ItemKind::ExternCrate(..) |
1664             hir::ItemKind::Use(..) |
1665             hir::ItemKind::TyAlias(..) |
1666             hir::ItemKind::OpaqueTy(..) |
1667             hir::ItemKind::TraitAlias(..) => {
1668                 // no sub-item recording needed in these cases
1669             }
1670             hir::ItemKind::Enum(..) => {
1671                 self.encode_fields(def_id);
1672
1673                 let def = self.tcx.adt_def(def_id);
1674                 for (i, variant) in def.variants.iter_enumerated() {
1675                     // FIXME(eddyb) `def_id` is leftover from incremental isolation,
1676                     // pass `def` or `variant` instead.
1677                     self.encode_enum_variant_info(def_id, i);
1678
1679                     // FIXME(eddyb) `def_id` is leftover from incremental isolation,
1680                     // pass `def`, `variant` or `ctor_def_id` instead.
1681                     if let Some(_ctor_def_id) = variant.ctor_def_id {
1682                         self.encode_enum_variant_ctor(def_id, i);
1683                     }
1684                 }
1685             }
1686             hir::ItemKind::Struct(ref struct_def, _) => {
1687                 self.encode_fields(def_id);
1688
1689                 // If the struct has a constructor, encode it.
1690                 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
1691                     let ctor_def_id = self.tcx.hir().local_def_id(ctor_hir_id);
1692                     self.encode_struct_ctor(def_id, ctor_def_id);
1693                 }
1694             }
1695             hir::ItemKind::Union(..) => {
1696                 self.encode_fields(def_id);
1697             }
1698             hir::ItemKind::Impl(..) => {
1699                 for &trait_item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1700                     self.encode_info_for_impl_item(trait_item_def_id);
1701                 }
1702             }
1703             hir::ItemKind::Trait(..) => {
1704                 for &item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1705                     self.encode_info_for_trait_item(item_def_id);
1706                 }
1707             }
1708         }
1709     }
1710 }
1711
1712 struct ImplVisitor<'tcx> {
1713     tcx: TyCtxt<'tcx>,
1714     impls: FxHashMap<DefId, Vec<DefIndex>>,
1715 }
1716
1717 impl<'tcx, 'v> ItemLikeVisitor<'v> for ImplVisitor<'tcx> {
1718     fn visit_item(&mut self, item: &hir::Item) {
1719         if let hir::ItemKind::Impl(..) = item.kind {
1720             let impl_id = self.tcx.hir().local_def_id(item.hir_id);
1721             if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_id) {
1722                 self.impls
1723                     .entry(trait_ref.def_id)
1724                     .or_default()
1725                     .push(impl_id.index);
1726             }
1727         }
1728     }
1729
1730     fn visit_trait_item(&mut self, _trait_item: &'v hir::TraitItem) {}
1731
1732     fn visit_impl_item(&mut self, _impl_item: &'v hir::ImplItem) {
1733         // handled in `visit_item` above
1734     }
1735 }
1736
1737 // NOTE(eddyb) The following comment was preserved for posterity, even
1738 // though it's no longer relevant as EBML (which uses nested & tagged
1739 // "documents") was replaced with a scheme that can't go out of bounds.
1740 //
1741 // And here we run into yet another obscure archive bug: in which metadata
1742 // loaded from archives may have trailing garbage bytes. Awhile back one of
1743 // our tests was failing sporadically on the macOS 64-bit builders (both nopt
1744 // and opt) by having ebml generate an out-of-bounds panic when looking at
1745 // metadata.
1746 //
1747 // Upon investigation it turned out that the metadata file inside of an rlib
1748 // (and ar archive) was being corrupted. Some compilations would generate a
1749 // metadata file which would end in a few extra bytes, while other
1750 // compilations would not have these extra bytes appended to the end. These
1751 // extra bytes were interpreted by ebml as an extra tag, so they ended up
1752 // being interpreted causing the out-of-bounds.
1753 //
1754 // The root cause of why these extra bytes were appearing was never
1755 // discovered, and in the meantime the solution we're employing is to insert
1756 // the length of the metadata to the start of the metadata. Later on this
1757 // will allow us to slice the metadata to the precise length that we just
1758 // generated regardless of trailing bytes that end up in it.
1759
1760 pub(super) fn encode_metadata(tcx: TyCtxt<'_>) -> EncodedMetadata {
1761     let mut encoder = opaque::Encoder::new(vec![]);
1762     encoder.emit_raw_bytes(METADATA_HEADER);
1763
1764     // Will be filled with the root position after encoding everything.
1765     encoder.emit_raw_bytes(&[0, 0, 0, 0]);
1766
1767     // Since encoding metadata is not in a query, and nothing is cached,
1768     // there's no need to do dep-graph tracking for any of it.
1769     let (root, mut result) = tcx.dep_graph.with_ignore(move || {
1770         let mut ecx = EncodeContext {
1771             opaque: encoder,
1772             tcx,
1773             per_def: Default::default(),
1774             lazy_state: LazyState::NoNode,
1775             type_shorthands: Default::default(),
1776             predicate_shorthands: Default::default(),
1777             source_file_cache: tcx.sess.source_map().files()[0].clone(),
1778             interpret_allocs: Default::default(),
1779             interpret_allocs_inverse: Default::default(),
1780         };
1781
1782         // Encode the rustc version string in a predictable location.
1783         rustc_version().encode(&mut ecx).unwrap();
1784
1785         // Encode all the entries and extra information in the crate,
1786         // culminating in the `CrateRoot` which points to all of it.
1787         let root = ecx.encode_crate_root();
1788         (root, ecx.opaque.into_inner())
1789     });
1790
1791     // Encode the root position.
1792     let header = METADATA_HEADER.len();
1793     let pos = root.position.get();
1794     result[header + 0] = (pos >> 24) as u8;
1795     result[header + 1] = (pos >> 16) as u8;
1796     result[header + 2] = (pos >> 8) as u8;
1797     result[header + 3] = (pos >> 0) as u8;
1798
1799     EncodedMetadata { raw_data: result }
1800 }