src/librustc_metadata/encoder.rs

   1 use crate::index::Index;
   2 use crate::schema::*;
   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;
   9 use rustc::hir::map::definitions::DefPathTable;
  10 use rustc_data_structures::fingerprint::Fingerprint;
  11 use rustc::middle::dependency_format::Linkage;
  12 use rustc::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel,
  13                                       metadata_symbol_name};
  14 use rustc::middle::lang_items;
  15 use rustc::mir::{self, interpret};
  16 use rustc::traits::specialization_graph;
  17 use rustc::ty::{self, Ty, TyCtxt, ReprOptions, SymbolName};
  18 use rustc::ty::codec::{self as ty_codec, TyEncoder};
  19 use rustc::ty::layout::VariantIdx;
  20
  21 use rustc::session::config::{self, CrateType};
  22 use rustc::util::nodemap::FxHashMap;
  23
  24 use rustc_data_structures::stable_hasher::StableHasher;
  25 use rustc_serialize::{Encodable, Encoder, SpecializedEncoder, opaque};
  26
  27 use std::hash::Hash;
  28 use std::path::Path;
  29 use rustc_data_structures::sync::Lrc;
  30 use std::u32;
  31 use syntax::ast;
  32 use syntax::attr;
  33 use syntax::source_map::Spanned;
  34 use syntax::symbol::{kw, sym};
  35 use syntax_pos::{self, FileName, SourceFile, Span};
  36 use log::{debug, trace};
  37
  38 use rustc::hir::{self, PatKind};
  39 use rustc::hir::itemlikevisit::ItemLikeVisitor;
  40 use rustc::hir::intravisit::{Visitor, NestedVisitorMap};
  41 use rustc::hir::intravisit;
  42
  43 pub struct EncodeContext<'tcx> {
  44     opaque: opaque::Encoder,
  45     pub tcx: TyCtxt<'tcx>,
  46
  47     entries_index: Index<'tcx>,
  48
  49     lazy_state: LazyState,
  50     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
  51     predicate_shorthands: FxHashMap<ty::Predicate<'tcx>, usize>,
  52
  53     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
  54     interpret_allocs_inverse: Vec<interpret::AllocId>,
  55
  56     // This is used to speed up Span encoding.
  57     source_file_cache: Lrc<SourceFile>,
  58 }
  59
  60 macro_rules! encoder_methods {
  61     ($($name:ident($ty:ty);)*) => {
  62         $(fn $name(&mut self, value: $ty) -> Result<(), Self::Error> {
  63             self.opaque.$name(value)
  64         })*
  65     }
  66 }
  67
  68 impl<'tcx> Encoder for EncodeContext<'tcx> {
  69     type Error = <opaque::Encoder as Encoder>::Error;
  70
  71     fn emit_unit(&mut self) -> Result<(), Self::Error> {
  72         Ok(())
  73     }
  74
  75     encoder_methods! {
  76         emit_usize(usize);
  77         emit_u128(u128);
  78         emit_u64(u64);
  79         emit_u32(u32);
  80         emit_u16(u16);
  81         emit_u8(u8);
  82
  83         emit_isize(isize);
  84         emit_i128(i128);
  85         emit_i64(i64);
  86         emit_i32(i32);
  87         emit_i16(i16);
  88         emit_i8(i8);
  89
  90         emit_bool(bool);
  91         emit_f64(f64);
  92         emit_f32(f32);
  93         emit_char(char);
  94         emit_str(&str);
  95     }
  96 }
  97
  98 impl<'tcx, T> SpecializedEncoder<Lazy<T>> for EncodeContext<'tcx> {
  99     fn specialized_encode(&mut self, lazy: &Lazy<T>) -> Result<(), Self::Error> {
 100         self.emit_lazy_distance(lazy.position, Lazy::<T>::min_size())
 101     }
 102 }
 103
 104 impl<'tcx, T> SpecializedEncoder<LazySeq<T>> for EncodeContext<'tcx> {
 105     fn specialized_encode(&mut self, seq: &LazySeq<T>) -> Result<(), Self::Error> {
 106         self.emit_usize(seq.len)?;
 107         if seq.len == 0 {
 108             return Ok(());
 109         }
 110         self.emit_lazy_distance(seq.position, LazySeq::<T>::min_size(seq.len))
 111     }
 112 }
 113
 114 impl<'tcx> SpecializedEncoder<CrateNum> for EncodeContext<'tcx> {
 115     #[inline]
 116     fn specialized_encode(&mut self, cnum: &CrateNum) -> Result<(), Self::Error> {
 117         self.emit_u32(cnum.as_u32())
 118     }
 119 }
 120
 121 impl<'tcx> SpecializedEncoder<DefId> for EncodeContext<'tcx> {
 122     #[inline]
 123     fn specialized_encode(&mut self, def_id: &DefId) -> Result<(), Self::Error> {
 124         let DefId {
 125             krate,
 126             index,
 127         } = *def_id;
 128
 129         krate.encode(self)?;
 130         index.encode(self)
 131     }
 132 }
 133
 134 impl<'tcx> SpecializedEncoder<DefIndex> for EncodeContext<'tcx> {
 135     #[inline]
 136     fn specialized_encode(&mut self, def_index: &DefIndex) -> Result<(), Self::Error> {
 137         self.emit_u32(def_index.as_u32())
 138     }
 139 }
 140
 141 impl<'tcx> SpecializedEncoder<Span> for EncodeContext<'tcx> {
 142     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
 143         if span.is_dummy() {
 144             return TAG_INVALID_SPAN.encode(self)
 145         }
 146
 147         let span = span.data();
 148
 149         // The Span infrastructure should make sure that this invariant holds:
 150         debug_assert!(span.lo <= span.hi);
 151
 152         if !self.source_file_cache.contains(span.lo) {
 153             let source_map = self.tcx.sess.source_map();
 154             let source_file_index = source_map.lookup_source_file_idx(span.lo);
 155             self.source_file_cache = source_map.files()[source_file_index].clone();
 156         }
 157
 158         if !self.source_file_cache.contains(span.hi) {
 159             // Unfortunately, macro expansion still sometimes generates Spans
 160             // that malformed in this way.
 161             return TAG_INVALID_SPAN.encode(self)
 162         }
 163
 164         TAG_VALID_SPAN.encode(self)?;
 165         span.lo.encode(self)?;
 166
 167         // Encode length which is usually less than span.hi and profits more
 168         // from the variable-length integer encoding that we use.
 169         let len = span.hi - span.lo;
 170         len.encode(self)
 171
 172         // Don't encode the expansion context.
 173     }
 174 }
 175
 176 impl<'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'tcx> {
 177     #[inline]
 178     fn specialized_encode(&mut self, def_id: &LocalDefId) -> Result<(), Self::Error> {
 179         self.specialized_encode(&def_id.to_def_id())
 180     }
 181 }
 182
 183 impl<'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'tcx> {
 184     fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
 185         ty_codec::encode_with_shorthand(self, ty, |ecx| &mut ecx.type_shorthands)
 186     }
 187 }
 188
 189 impl<'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'tcx> {
 190     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
 191         use std::collections::hash_map::Entry;
 192         let index = match self.interpret_allocs.entry(*alloc_id) {
 193             Entry::Occupied(e) => *e.get(),
 194             Entry::Vacant(e) => {
 195                 let idx = self.interpret_allocs_inverse.len();
 196                 self.interpret_allocs_inverse.push(*alloc_id);
 197                 e.insert(idx);
 198                 idx
 199             },
 200         };
 201
 202         index.encode(self)
 203     }
 204 }
 205
 206 impl<'tcx> SpecializedEncoder<ty::GenericPredicates<'tcx>> for EncodeContext<'tcx> {
 207     fn specialized_encode(&mut self,
 208                           predicates: &ty::GenericPredicates<'tcx>)
 209                           -> Result<(), Self::Error> {
 210         ty_codec::encode_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
 211     }
 212 }
 213
 214 impl<'tcx> SpecializedEncoder<Fingerprint> for EncodeContext<'tcx> {
 215     fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> {
 216         f.encode_opaque(&mut self.opaque)
 217     }
 218 }
 219
 220 impl<'tcx, T: Encodable> SpecializedEncoder<mir::ClearCrossCrate<T>> for EncodeContext<'tcx> {
 221     fn specialized_encode(&mut self,
 222                           _: &mir::ClearCrossCrate<T>)
 223                           -> Result<(), Self::Error> {
 224         Ok(())
 225     }
 226 }
 227
 228 impl<'tcx> TyEncoder for EncodeContext<'tcx> {
 229     fn position(&self) -> usize {
 230         self.opaque.position()
 231     }
 232 }
 233
 234 impl<'tcx> EncodeContext<'tcx> {
 235     fn emit_node<F: FnOnce(&mut Self, usize) -> R, R>(&mut self, f: F) -> R {
 236         assert_eq!(self.lazy_state, LazyState::NoNode);
 237         let pos = self.position();
 238         self.lazy_state = LazyState::NodeStart(pos);
 239         let r = f(self, pos);
 240         self.lazy_state = LazyState::NoNode;
 241         r
 242     }
 243
 244     fn emit_lazy_distance(&mut self,
 245                           position: usize,
 246                           min_size: usize)
 247                           -> Result<(), <Self as Encoder>::Error> {
 248         let min_end = position + min_size;
 249         let distance = match self.lazy_state {
 250             LazyState::NoNode => bug!("emit_lazy_distance: outside of a metadata node"),
 251             LazyState::NodeStart(start) => {
 252                 assert!(min_end <= start);
 253                 start - min_end
 254             }
 255             LazyState::Previous(last_min_end) => {
 256                 assert!(
 257                     last_min_end <= position,
 258                     "make sure that the calls to `lazy*` \
 259                     are in the same order as the metadata fields",
 260                 );
 261                 position - last_min_end
 262             }
 263         };
 264         self.lazy_state = LazyState::Previous(min_end);
 265         self.emit_usize(distance)
 266     }
 267
 268     pub fn lazy<T: Encodable>(&mut self, value: &T) -> Lazy<T> {
 269         self.emit_node(|ecx, pos| {
 270             value.encode(ecx).unwrap();
 271
 272             assert!(pos + Lazy::<T>::min_size() <= ecx.position());
 273             Lazy::with_position(pos)
 274         })
 275     }
 276
 277     pub fn lazy_seq<I, T>(&mut self, iter: I) -> LazySeq<T>
 278         where I: IntoIterator<Item = T>,
 279               T: Encodable
 280     {
 281         self.emit_node(|ecx, pos| {
 282             let len = iter.into_iter().map(|value| value.encode(ecx).unwrap()).count();
 283
 284             assert!(pos + LazySeq::<T>::min_size(len) <= ecx.position());
 285             LazySeq::with_position_and_length(pos, len)
 286         })
 287     }
 288
 289     pub fn lazy_seq_ref<'b, I, T>(&mut self, iter: I) -> LazySeq<T>
 290         where I: IntoIterator<Item = &'b T>,
 291               T: 'b + Encodable
 292     {
 293         self.emit_node(|ecx, pos| {
 294             let len = iter.into_iter().map(|value| value.encode(ecx).unwrap()).count();
 295
 296             assert!(pos + LazySeq::<T>::min_size(len) <= ecx.position());
 297             LazySeq::with_position_and_length(pos, len)
 298         })
 299     }
 300
 301     /// Emit the data for a `DefId` to the metadata. The function to
 302     /// emit the data is `op`, and it will be given `data` as
 303     /// arguments. This `record` function will call `op` to generate
 304     /// the `Entry` (which may point to other encoded information)
 305     /// and will then record the `Lazy<Entry>` for use in the index.
 306     // FIXME(eddyb) remove this.
 307     pub fn record<DATA>(&mut self,
 308                         id: DefId,
 309                         op: impl FnOnce(&mut Self, DATA) -> Entry<'tcx>,
 310                         data: DATA)
 311     {
 312         assert!(id.is_local());
 313
 314         let entry = op(self, data);
 315         let entry = self.lazy(&entry);
 316         self.entries_index.record(id, entry);
 317     }
 318
 319     fn encode_info_for_items(&mut self) {
 320         let krate = self.tcx.hir().krate();
 321         let vis = Spanned { span: syntax_pos::DUMMY_SP, node: hir::VisibilityKind::Public };
 322         self.record(DefId::local(CRATE_DEF_INDEX),
 323                      EncodeContext::encode_info_for_mod,
 324                      (hir::CRATE_HIR_ID, &krate.module, &krate.attrs, &vis));
 325         krate.visit_all_item_likes(&mut self.as_deep_visitor());
 326         for macro_def in &krate.exported_macros {
 327             self.visit_macro_def(macro_def);
 328         }
 329     }
 330
 331     fn encode_def_path_table(&mut self) -> Lazy<DefPathTable> {
 332         let definitions = self.tcx.hir().definitions();
 333         self.lazy(definitions.def_path_table())
 334     }
 335
 336     fn encode_source_map(&mut self) -> LazySeq<syntax_pos::SourceFile> {
 337         let source_map = self.tcx.sess.source_map();
 338         let all_source_files = source_map.files();
 339
 340         let (working_dir, _cwd_remapped) = self.tcx.sess.working_dir.clone();
 341
 342         let adapted = all_source_files.iter()
 343             .filter(|source_file| {
 344                 // No need to re-export imported source_files, as any downstream
 345                 // crate will import them from their original source.
 346                 !source_file.is_imported()
 347             })
 348             .map(|source_file| {
 349                 match source_file.name {
 350                     // This path of this SourceFile has been modified by
 351                     // path-remapping, so we use it verbatim (and avoid
 352                     // cloning the whole map in the process).
 353                     _  if source_file.name_was_remapped => source_file.clone(),
 354
 355                     // Otherwise expand all paths to absolute paths because
 356                     // any relative paths are potentially relative to a
 357                     // wrong directory.
 358                     FileName::Real(ref name) => {
 359                         let mut adapted = (**source_file).clone();
 360                         adapted.name = Path::new(&working_dir).join(name).into();
 361                         adapted.name_hash = {
 362                             let mut hasher: StableHasher<u128> = StableHasher::new();
 363                             adapted.name.hash(&mut hasher);
 364                             hasher.finish()
 365                         };
 366                         Lrc::new(adapted)
 367                     },
 368
 369                     // expanded code, not from a file
 370                     _ => source_file.clone(),
 371                 }
 372             })
 373             .collect::<Vec<_>>();
 374
 375         self.lazy_seq_ref(adapted.iter().map(|rc| &**rc))
 376     }
 377
 378     fn encode_crate_root(&mut self) -> Lazy<CrateRoot<'tcx>> {
 379         let mut i = self.position();
 380
 381         let crate_deps = self.encode_crate_deps();
 382         let dylib_dependency_formats = self.encode_dylib_dependency_formats();
 383         let dep_bytes = self.position() - i;
 384
 385         // Encode the lib features.
 386         i = self.position();
 387         let lib_features = self.encode_lib_features();
 388         let lib_feature_bytes = self.position() - i;
 389
 390         // Encode the language items.
 391         i = self.position();
 392         let lang_items = self.encode_lang_items();
 393         let lang_items_missing = self.encode_lang_items_missing();
 394         let lang_item_bytes = self.position() - i;
 395
 396         // Encode the native libraries used
 397         i = self.position();
 398         let native_libraries = self.encode_native_libraries();
 399         let native_lib_bytes = self.position() - i;
 400
 401         let foreign_modules = self.encode_foreign_modules();
 402
 403         // Encode source_map
 404         i = self.position();
 405         let source_map = self.encode_source_map();
 406         let source_map_bytes = self.position() - i;
 407
 408         // Encode DefPathTable
 409         i = self.position();
 410         let def_path_table = self.encode_def_path_table();
 411         let def_path_table_bytes = self.position() - i;
 412
 413         // Encode the def IDs of impls, for coherence checking.
 414         i = self.position();
 415         let impls = self.encode_impls();
 416         let impl_bytes = self.position() - i;
 417
 418         // Encode exported symbols info.
 419         i = self.position();
 420         let exported_symbols = self.tcx.exported_symbols(LOCAL_CRATE);
 421         let exported_symbols = self.encode_exported_symbols(&exported_symbols);
 422         let exported_symbols_bytes = self.position() - i;
 423
 424         let tcx = self.tcx;
 425
 426         // Encode the items.
 427         i = self.position();
 428         self.encode_info_for_items();
 429         let item_bytes = self.position() - i;
 430
 431         // Encode the allocation index
 432         let interpret_alloc_index = {
 433             let mut interpret_alloc_index = Vec::new();
 434             let mut n = 0;
 435             trace!("beginning to encode alloc ids");
 436             loop {
 437                 let new_n = self.interpret_allocs_inverse.len();
 438                 // if we have found new ids, serialize those, too
 439                 if n == new_n {
 440                     // otherwise, abort
 441                     break;
 442                 }
 443                 trace!("encoding {} further alloc ids", new_n - n);
 444                 for idx in n..new_n {
 445                     let id = self.interpret_allocs_inverse[idx];
 446                     let pos = self.position() as u32;
 447                     interpret_alloc_index.push(pos);
 448                     interpret::specialized_encode_alloc_id(
 449                         self,
 450                         tcx,
 451                         id,
 452                     ).unwrap();
 453                 }
 454                 n = new_n;
 455             }
 456             self.lazy_seq(interpret_alloc_index)
 457         };
 458
 459         i = self.position();
 460         let entries_index = self.entries_index.write_index(&mut self.opaque);
 461         let entries_index_bytes = self.position() - i;
 462
 463         let attrs = tcx.hir().krate_attrs();
 464         let is_proc_macro = tcx.sess.crate_types.borrow().contains(&CrateType::ProcMacro);
 465         let has_default_lib_allocator = attr::contains_name(&attrs, sym::default_lib_allocator);
 466         let has_global_allocator = *tcx.sess.has_global_allocator.get();
 467         let has_panic_handler = *tcx.sess.has_panic_handler.try_get().unwrap_or(&false);
 468
 469         let root = self.lazy(&CrateRoot {
 470             name: tcx.crate_name(LOCAL_CRATE),
 471             extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
 472             triple: tcx.sess.opts.target_triple.clone(),
 473             hash: tcx.crate_hash(LOCAL_CRATE),
 474             disambiguator: tcx.sess.local_crate_disambiguator(),
 475             panic_strategy: tcx.sess.panic_strategy(),
 476             edition: tcx.sess.edition(),
 477             has_global_allocator: has_global_allocator,
 478             has_panic_handler: has_panic_handler,
 479             has_default_lib_allocator: has_default_lib_allocator,
 480             plugin_registrar_fn: tcx.plugin_registrar_fn(LOCAL_CRATE).map(|id| id.index),
 481             proc_macro_decls_static: if is_proc_macro {
 482                 let id = tcx.proc_macro_decls_static(LOCAL_CRATE).unwrap();
 483                 Some(id.index)
 484             } else {
 485                 None
 486             },
 487             proc_macro_stability: if is_proc_macro {
 488                 tcx.lookup_stability(DefId::local(CRATE_DEF_INDEX)).map(|stab| stab.clone())
 489             } else {
 490                 None
 491             },
 492             compiler_builtins: attr::contains_name(&attrs, sym::compiler_builtins),
 493             needs_allocator: attr::contains_name(&attrs, sym::needs_allocator),
 494             needs_panic_runtime: attr::contains_name(&attrs, sym::needs_panic_runtime),
 495             no_builtins: attr::contains_name(&attrs, sym::no_builtins),
 496             panic_runtime: attr::contains_name(&attrs, sym::panic_runtime),
 497             profiler_runtime: attr::contains_name(&attrs, sym::profiler_runtime),
 498             sanitizer_runtime: attr::contains_name(&attrs, sym::sanitizer_runtime),
 499             symbol_mangling_version: tcx.sess.opts.debugging_opts.symbol_mangling_version,
 500
 501             crate_deps,
 502             dylib_dependency_formats,
 503             lib_features,
 504             lang_items,
 505             lang_items_missing,
 506             native_libraries,
 507             foreign_modules,
 508             source_map,
 509             def_path_table,
 510             impls,
 511             exported_symbols,
 512             interpret_alloc_index,
 513             entries_index,
 514         });
 515
 516         let total_bytes = self.position();
 517
 518         if self.tcx.sess.meta_stats() {
 519             let mut zero_bytes = 0;
 520             for e in self.opaque.data.iter() {
 521                 if *e == 0 {
 522                     zero_bytes += 1;
 523                 }
 524             }
 525
 526             println!("metadata stats:");
 527             println!("             dep bytes: {}", dep_bytes);
 528             println!("     lib feature bytes: {}", lib_feature_bytes);
 529             println!("       lang item bytes: {}", lang_item_bytes);
 530             println!("          native bytes: {}", native_lib_bytes);
 531             println!("         source_map bytes: {}", source_map_bytes);
 532             println!("            impl bytes: {}", impl_bytes);
 533             println!("    exp. symbols bytes: {}", exported_symbols_bytes);
 534             println!("  def-path table bytes: {}", def_path_table_bytes);
 535             println!("            item bytes: {}", item_bytes);
 536             println!("   entries index bytes: {}", entries_index_bytes);
 537             println!("            zero bytes: {}", zero_bytes);
 538             println!("           total bytes: {}", total_bytes);
 539         }
 540
 541         root
 542     }
 543 }
 544
 545 impl EncodeContext<'tcx> {
 546     fn encode_variances_of(&mut self, def_id: DefId) -> LazySeq<ty::Variance> {
 547         debug!("EncodeContext::encode_variances_of({:?})", def_id);
 548         let tcx = self.tcx;
 549         self.lazy_seq_ref(&tcx.variances_of(def_id)[..])
 550     }
 551
 552     fn encode_item_type(&mut self, def_id: DefId) -> Lazy<Ty<'tcx>> {
 553         let tcx = self.tcx;
 554         let ty = tcx.type_of(def_id);
 555         debug!("EncodeContext::encode_item_type({:?}) => {:?}", def_id, ty);
 556         self.lazy(&ty)
 557     }
 558
 559     fn encode_enum_variant_info(
 560         &mut self,
 561         (enum_did, index): (DefId, VariantIdx),
 562     ) -> Entry<'tcx> {
 563         let tcx = self.tcx;
 564         let def = tcx.adt_def(enum_did);
 565         let variant = &def.variants[index];
 566         let def_id = variant.def_id;
 567         debug!("EncodeContext::encode_enum_variant_info({:?})", def_id);
 568
 569         let data = VariantData {
 570             ctor_kind: variant.ctor_kind,
 571             discr: variant.discr,
 572             // FIXME(eddyb) deduplicate these with `encode_enum_variant_ctor`.
 573             ctor: variant.ctor_def_id.map(|did| did.index),
 574             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 575                 variant.ctor_def_id.map(|ctor_def_id| self.lazy(&tcx.fn_sig(ctor_def_id)))
 576             } else {
 577                 None
 578             },
 579         };
 580
 581         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
 582         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 583
 584         Entry {
 585             kind: EntryKind::Variant(self.lazy(&data)),
 586             visibility: self.lazy(&ty::Visibility::from_hir(enum_vis, enum_id, tcx)),
 587             span: self.lazy(&tcx.def_span(def_id)),
 588             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
 589             children: self.lazy_seq(variant.fields.iter().map(|f| {
 590                 assert!(f.did.is_local());
 591                 f.did.index
 592             })),
 593             stability: self.encode_stability(def_id),
 594             deprecation: self.encode_deprecation(def_id),
 595
 596             ty: Some(self.encode_item_type(def_id)),
 597             inherent_impls: LazySeq::empty(),
 598             variances: if variant.ctor_kind == CtorKind::Fn {
 599                 self.encode_variances_of(def_id)
 600             } else {
 601                 LazySeq::empty()
 602             },
 603             generics: Some(self.encode_generics(def_id)),
 604             predicates: Some(self.encode_predicates(def_id)),
 605             predicates_defined_on: None,
 606
 607             mir: self.encode_optimized_mir(def_id),
 608         }
 609     }
 610
 611     fn encode_enum_variant_ctor(
 612         &mut self,
 613         (enum_did, index): (DefId, VariantIdx),
 614     ) -> Entry<'tcx> {
 615         let tcx = self.tcx;
 616         let def = tcx.adt_def(enum_did);
 617         let variant = &def.variants[index];
 618         let def_id = variant.ctor_def_id.unwrap();
 619         debug!("EncodeContext::encode_enum_variant_ctor({:?})", def_id);
 620
 621         let data = VariantData {
 622             ctor_kind: variant.ctor_kind,
 623             discr: variant.discr,
 624             ctor: Some(def_id.index),
 625             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 626                 Some(self.lazy(&tcx.fn_sig(def_id)))
 627             } else {
 628                 None
 629             }
 630         };
 631
 632         // Variant constructors have the same visibility as the parent enums, unless marked as
 633         // non-exhaustive, in which case they are lowered to `pub(crate)`.
 634         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
 635         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 636         let mut ctor_vis = ty::Visibility::from_hir(enum_vis, enum_id, tcx);
 637         if variant.is_field_list_non_exhaustive() && ctor_vis == ty::Visibility::Public {
 638             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 639         }
 640
 641         Entry {
 642             kind: EntryKind::Variant(self.lazy(&data)),
 643             visibility: self.lazy(&ctor_vis),
 644             span: self.lazy(&tcx.def_span(def_id)),
 645             attributes: LazySeq::empty(),
 646             children: LazySeq::empty(),
 647             stability: self.encode_stability(def_id),
 648             deprecation: self.encode_deprecation(def_id),
 649
 650             ty: Some(self.encode_item_type(def_id)),
 651             inherent_impls: LazySeq::empty(),
 652             variances: if variant.ctor_kind == CtorKind::Fn {
 653                 self.encode_variances_of(def_id)
 654             } else {
 655                 LazySeq::empty()
 656             },
 657             generics: Some(self.encode_generics(def_id)),
 658             predicates: Some(self.encode_predicates(def_id)),
 659             predicates_defined_on: None,
 660
 661             mir: self.encode_optimized_mir(def_id),
 662         }
 663     }
 664
 665     fn encode_info_for_mod(
 666         &mut self,
 667         (id, md, attrs, vis): (hir::HirId, &hir::Mod, &[ast::Attribute], &hir::Visibility),
 668     ) -> Entry<'tcx> {
 669         let tcx = self.tcx;
 670         let def_id = tcx.hir().local_def_id(id);
 671         debug!("EncodeContext::encode_info_for_mod({:?})", def_id);
 672
 673         let data = ModData {
 674             reexports: match tcx.module_exports(def_id) {
 675                 Some(exports) => self.lazy_seq_ref(exports),
 676                 _ => LazySeq::empty(),
 677             },
 678         };
 679
 680         Entry {
 681             kind: EntryKind::Mod(self.lazy(&data)),
 682             visibility: self.lazy(&ty::Visibility::from_hir(vis, id, tcx)),
 683             span: self.lazy(&tcx.def_span(def_id)),
 684             attributes: self.encode_attributes(attrs),
 685             children: self.lazy_seq(md.item_ids.iter().map(|item_id| {
 686                 tcx.hir().local_def_id(item_id.id).index
 687             })),
 688             stability: self.encode_stability(def_id),
 689             deprecation: self.encode_deprecation(def_id),
 690
 691             ty: None,
 692             inherent_impls: LazySeq::empty(),
 693             variances: LazySeq::empty(),
 694             generics: None,
 695             predicates: None,
 696             predicates_defined_on: None,
 697
 698             mir: None
 699         }
 700     }
 701
 702     fn encode_field(
 703         &mut self,
 704         (adt_def_id, variant_index, field_index): (DefId, VariantIdx, usize),
 705     ) -> Entry<'tcx> {
 706         let tcx = self.tcx;
 707         let variant = &tcx.adt_def(adt_def_id).variants[variant_index];
 708         let field = &variant.fields[field_index];
 709
 710         let def_id = field.did;
 711         debug!("EncodeContext::encode_field({:?})", def_id);
 712
 713         let variant_id = tcx.hir().as_local_hir_id(variant.def_id).unwrap();
 714         let variant_data = tcx.hir().expect_variant_data(variant_id);
 715
 716         Entry {
 717             kind: EntryKind::Field,
 718             visibility: self.lazy(&field.vis),
 719             span: self.lazy(&tcx.def_span(def_id)),
 720             attributes: self.encode_attributes(&variant_data.fields()[field_index].attrs),
 721             children: LazySeq::empty(),
 722             stability: self.encode_stability(def_id),
 723             deprecation: self.encode_deprecation(def_id),
 724
 725             ty: Some(self.encode_item_type(def_id)),
 726             inherent_impls: LazySeq::empty(),
 727             variances: LazySeq::empty(),
 728             generics: Some(self.encode_generics(def_id)),
 729             predicates: Some(self.encode_predicates(def_id)),
 730             predicates_defined_on: None,
 731
 732             mir: None,
 733         }
 734     }
 735
 736     fn encode_struct_ctor(&mut self, (adt_def_id, def_id): (DefId, DefId)) -> Entry<'tcx> {
 737         debug!("EncodeContext::encode_struct_ctor({:?})", def_id);
 738         let tcx = self.tcx;
 739         let adt_def = tcx.adt_def(adt_def_id);
 740         let variant = adt_def.non_enum_variant();
 741
 742         let data = VariantData {
 743             ctor_kind: variant.ctor_kind,
 744             discr: variant.discr,
 745             ctor: Some(def_id.index),
 746             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 747                 Some(self.lazy(&tcx.fn_sig(def_id)))
 748             } else {
 749                 None
 750             }
 751         };
 752
 753         let struct_id = tcx.hir().as_local_hir_id(adt_def_id).unwrap();
 754         let struct_vis = &tcx.hir().expect_item(struct_id).vis;
 755         let mut ctor_vis = ty::Visibility::from_hir(struct_vis, struct_id, tcx);
 756         for field in &variant.fields {
 757             if ctor_vis.is_at_least(field.vis, tcx) {
 758                 ctor_vis = field.vis;
 759             }
 760         }
 761
 762         // If the structure is marked as non_exhaustive then lower the visibility
 763         // to within the crate.
 764         if adt_def.non_enum_variant().is_field_list_non_exhaustive() &&
 765             ctor_vis == ty::Visibility::Public
 766         {
 767             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 768         }
 769
 770         let repr_options = get_repr_options(tcx, adt_def_id);
 771
 772         Entry {
 773             kind: EntryKind::Struct(self.lazy(&data), repr_options),
 774             visibility: self.lazy(&ctor_vis),
 775             span: self.lazy(&tcx.def_span(def_id)),
 776             attributes: LazySeq::empty(),
 777             children: LazySeq::empty(),
 778             stability: self.encode_stability(def_id),
 779             deprecation: self.encode_deprecation(def_id),
 780
 781             ty: Some(self.encode_item_type(def_id)),
 782             inherent_impls: LazySeq::empty(),
 783             variances: if variant.ctor_kind == CtorKind::Fn {
 784                 self.encode_variances_of(def_id)
 785             } else {
 786                 LazySeq::empty()
 787             },
 788             generics: Some(self.encode_generics(def_id)),
 789             predicates: Some(self.encode_predicates(def_id)),
 790             predicates_defined_on: None,
 791
 792             mir: self.encode_optimized_mir(def_id),
 793         }
 794     }
 795
 796     fn encode_generics(&mut self, def_id: DefId) -> Lazy<ty::Generics> {
 797         debug!("EncodeContext::encode_generics({:?})", def_id);
 798         let tcx = self.tcx;
 799         self.lazy(tcx.generics_of(def_id))
 800     }
 801
 802     fn encode_predicates(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 803         debug!("EncodeContext::encode_predicates({:?})", def_id);
 804         let tcx = self.tcx;
 805         self.lazy(&tcx.predicates_of(def_id))
 806     }
 807
 808     fn encode_predicates_defined_on(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 809         debug!("EncodeContext::encode_predicates_defined_on({:?})", def_id);
 810         let tcx = self.tcx;
 811         self.lazy(&tcx.predicates_defined_on(def_id))
 812     }
 813
 814     fn encode_info_for_trait_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 815         debug!("EncodeContext::encode_info_for_trait_item({:?})", def_id);
 816         let tcx = self.tcx;
 817
 818         let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 819         let ast_item = tcx.hir().expect_trait_item(hir_id);
 820         let trait_item = tcx.associated_item(def_id);
 821
 822         let container = match trait_item.defaultness {
 823             hir::Defaultness::Default { has_value: true } =>
 824                 AssocContainer::TraitWithDefault,
 825             hir::Defaultness::Default { has_value: false } =>
 826                 AssocContainer::TraitRequired,
 827             hir::Defaultness::Final =>
 828                 span_bug!(ast_item.span, "traits cannot have final items"),
 829         };
 830
 831         let kind = match trait_item.kind {
 832             ty::AssocKind::Const => {
 833                 let const_qualif =
 834                     if let hir::TraitItemKind::Const(_, Some(body)) = ast_item.node {
 835                         self.const_qualif(0, body)
 836                     } else {
 837                         ConstQualif { mir: 0, ast_promotable: false }
 838                     };
 839
 840                 let rendered =
 841                     hir::print::to_string(self.tcx.hir(), |s| s.print_trait_item(ast_item));
 842                 let rendered_const = self.lazy(&RenderedConst(rendered));
 843
 844                 EntryKind::AssocConst(container, const_qualif, rendered_const)
 845             }
 846             ty::AssocKind::Method => {
 847                 let fn_data = if let hir::TraitItemKind::Method(_, ref m) = ast_item.node {
 848                     let arg_names = match *m {
 849                         hir::TraitMethod::Required(ref names) => {
 850                             self.encode_fn_arg_names(names)
 851                         }
 852                         hir::TraitMethod::Provided(body) => {
 853                             self.encode_fn_arg_names_for_body(body)
 854                         }
 855                     };
 856                     FnData {
 857                         constness: hir::Constness::NotConst,
 858                         arg_names,
 859                         sig: self.lazy(&tcx.fn_sig(def_id)),
 860                     }
 861                 } else {
 862                     bug!()
 863                 };
 864                 EntryKind::Method(self.lazy(&MethodData {
 865                     fn_data,
 866                     container,
 867                     has_self: trait_item.method_has_self_argument,
 868                 }))
 869             }
 870             ty::AssocKind::Type => EntryKind::AssocType(container),
 871             ty::AssocKind::OpaqueTy => span_bug!(ast_item.span, "opaque type in trait"),
 872         };
 873
 874         Entry {
 875             kind,
 876             visibility: self.lazy(&trait_item.vis),
 877             span: self.lazy(&ast_item.span),
 878             attributes: self.encode_attributes(&ast_item.attrs),
 879             children: LazySeq::empty(),
 880             stability: self.encode_stability(def_id),
 881             deprecation: self.encode_deprecation(def_id),
 882
 883             ty: match trait_item.kind {
 884                 ty::AssocKind::Const |
 885                 ty::AssocKind::Method => {
 886                     Some(self.encode_item_type(def_id))
 887                 }
 888                 ty::AssocKind::Type => {
 889                     if trait_item.defaultness.has_value() {
 890                         Some(self.encode_item_type(def_id))
 891                     } else {
 892                         None
 893                     }
 894                 }
 895                 ty::AssocKind::OpaqueTy => unreachable!(),
 896             },
 897             inherent_impls: LazySeq::empty(),
 898             variances: if trait_item.kind == ty::AssocKind::Method {
 899                 self.encode_variances_of(def_id)
 900             } else {
 901                 LazySeq::empty()
 902             },
 903             generics: Some(self.encode_generics(def_id)),
 904             predicates: Some(self.encode_predicates(def_id)),
 905             predicates_defined_on: None,
 906
 907             mir: self.encode_optimized_mir(def_id),
 908         }
 909     }
 910
 911     fn metadata_output_only(&self) -> bool {
 912         // MIR optimisation can be skipped when we're just interested in the metadata.
 913         !self.tcx.sess.opts.output_types.should_codegen()
 914     }
 915
 916     fn const_qualif(&self, mir: u8, body_id: hir::BodyId) -> ConstQualif {
 917         let body_owner_def_id = self.tcx.hir().body_owner_def_id(body_id);
 918         let ast_promotable = self.tcx.const_is_rvalue_promotable_to_static(body_owner_def_id);
 919
 920         ConstQualif { mir, ast_promotable }
 921     }
 922
 923     fn encode_info_for_impl_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 924         debug!("EncodeContext::encode_info_for_impl_item({:?})", def_id);
 925         let tcx = self.tcx;
 926
 927         let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
 928         let ast_item = self.tcx.hir().expect_impl_item(hir_id);
 929         let impl_item = self.tcx.associated_item(def_id);
 930
 931         let container = match impl_item.defaultness {
 932             hir::Defaultness::Default { has_value: true } => AssocContainer::ImplDefault,
 933             hir::Defaultness::Final => AssocContainer::ImplFinal,
 934             hir::Defaultness::Default { has_value: false } =>
 935                 span_bug!(ast_item.span, "impl items always have values (currently)"),
 936         };
 937
 938         let kind = match impl_item.kind {
 939             ty::AssocKind::Const => {
 940                 if let hir::ImplItemKind::Const(_, body_id) = ast_item.node {
 941                     let mir = self.tcx.at(ast_item.span).mir_const_qualif(def_id).0;
 942
 943                     EntryKind::AssocConst(container,
 944                         self.const_qualif(mir, body_id),
 945                         self.encode_rendered_const_for_body(body_id))
 946                 } else {
 947                     bug!()
 948                 }
 949             }
 950             ty::AssocKind::Method => {
 951                 let fn_data = if let hir::ImplItemKind::Method(ref sig, body) = ast_item.node {
 952                     FnData {
 953                         constness: sig.header.constness,
 954                         arg_names: self.encode_fn_arg_names_for_body(body),
 955                         sig: self.lazy(&tcx.fn_sig(def_id)),
 956                     }
 957                 } else {
 958                     bug!()
 959                 };
 960                 EntryKind::Method(self.lazy(&MethodData {
 961                     fn_data,
 962                     container,
 963                     has_self: impl_item.method_has_self_argument,
 964                 }))
 965             }
 966             ty::AssocKind::OpaqueTy => EntryKind::AssocOpaqueTy(container),
 967             ty::AssocKind::Type => EntryKind::AssocType(container)
 968         };
 969
 970         let mir =
 971             match ast_item.node {
 972                 hir::ImplItemKind::Const(..) => true,
 973                 hir::ImplItemKind::Method(ref sig, _) => {
 974                     let generics = self.tcx.generics_of(def_id);
 975                     let needs_inline = (generics.requires_monomorphization(self.tcx) ||
 976                                         tcx.codegen_fn_attrs(def_id).requests_inline()) &&
 977                                         !self.metadata_output_only();
 978                     let is_const_fn = sig.header.constness == hir::Constness::Const;
 979                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
 980                     needs_inline || is_const_fn || always_encode_mir
 981                 },
 982                 hir::ImplItemKind::OpaqueTy(..) |
 983                 hir::ImplItemKind::TyAlias(..) => false,
 984             };
 985
 986         Entry {
 987             kind,
 988             visibility: self.lazy(&impl_item.vis),
 989             span: self.lazy(&ast_item.span),
 990             attributes: self.encode_attributes(&ast_item.attrs),
 991             children: LazySeq::empty(),
 992             stability: self.encode_stability(def_id),
 993             deprecation: self.encode_deprecation(def_id),
 994
 995             ty: Some(self.encode_item_type(def_id)),
 996             inherent_impls: LazySeq::empty(),
 997             variances: if impl_item.kind == ty::AssocKind::Method {
 998                 self.encode_variances_of(def_id)
 999             } else {
1000                 LazySeq::empty()
1001             },
1002             generics: Some(self.encode_generics(def_id)),
1003             predicates: Some(self.encode_predicates(def_id)),
1004             predicates_defined_on: None,
1005
1006             mir: if mir { self.encode_optimized_mir(def_id) } else { None },
1007         }
1008     }
1009
1010     fn encode_fn_arg_names_for_body(&mut self, body_id: hir::BodyId)
1011                                     -> LazySeq<ast::Name> {
1012         self.tcx.dep_graph.with_ignore(|| {
1013             let body = self.tcx.hir().body(body_id);
1014             self.lazy_seq(body.arguments.iter().map(|arg| {
1015                 match arg.pat.node {
1016                     PatKind::Binding(_, _, ident, _) => ident.name,
1017                     _ => kw::Invalid,
1018                 }
1019             }))
1020         })
1021     }
1022
1023     fn encode_fn_arg_names(&mut self, param_names: &[ast::Ident]) -> LazySeq<ast::Name> {
1024         self.lazy_seq(param_names.iter().map(|ident| ident.name))
1025     }
1026
1027     fn encode_optimized_mir(&mut self, def_id: DefId) -> Option<Lazy<mir::Body<'tcx>>> {
1028         debug!("EntryBuilder::encode_mir({:?})", def_id);
1029         if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id) {
1030             let mir = self.tcx.optimized_mir(def_id);
1031             Some(self.lazy(&mir))
1032         } else {
1033             None
1034         }
1035     }
1036
1037     // Encodes the inherent implementations of a structure, enumeration, or trait.
1038     fn encode_inherent_implementations(&mut self, def_id: DefId) -> LazySeq<DefIndex> {
1039         debug!("EncodeContext::encode_inherent_implementations({:?})", def_id);
1040         let implementations = self.tcx.inherent_impls(def_id);
1041         if implementations.is_empty() {
1042             LazySeq::empty()
1043         } else {
1044             self.lazy_seq(implementations.iter().map(|&def_id| {
1045                 assert!(def_id.is_local());
1046                 def_id.index
1047             }))
1048         }
1049     }
1050
1051     fn encode_stability(&mut self, def_id: DefId) -> Option<Lazy<attr::Stability>> {
1052         debug!("EncodeContext::encode_stability({:?})", def_id);
1053         self.tcx.lookup_stability(def_id).map(|stab| self.lazy(stab))
1054     }
1055
1056     fn encode_deprecation(&mut self, def_id: DefId) -> Option<Lazy<attr::Deprecation>> {
1057         debug!("EncodeContext::encode_deprecation({:?})", def_id);
1058         self.tcx.lookup_deprecation(def_id).map(|depr| self.lazy(&depr))
1059     }
1060
1061     fn encode_rendered_const_for_body(&mut self, body_id: hir::BodyId) -> Lazy<RenderedConst> {
1062         let body = self.tcx.hir().body(body_id);
1063         let rendered = hir::print::to_string(self.tcx.hir(), |s| s.print_expr(&body.value));
1064         let rendered_const = &RenderedConst(rendered);
1065         self.lazy(rendered_const)
1066     }
1067
1068     fn encode_info_for_item(&mut self, (def_id, item): (DefId, &'tcx hir::Item)) -> Entry<'tcx> {
1069         let tcx = self.tcx;
1070
1071         debug!("EncodeContext::encode_info_for_item({:?})", def_id);
1072
1073         let kind = match item.node {
1074             hir::ItemKind::Static(_, hir::MutMutable, _) => EntryKind::MutStatic,
1075             hir::ItemKind::Static(_, hir::MutImmutable, _) => EntryKind::ImmStatic,
1076             hir::ItemKind::Const(_, body_id) => {
1077                 let mir = tcx.at(item.span).mir_const_qualif(def_id).0;
1078                 EntryKind::Const(
1079                     self.const_qualif(mir, body_id),
1080                     self.encode_rendered_const_for_body(body_id)
1081                 )
1082             }
1083             hir::ItemKind::Fn(_, header, .., body) => {
1084                 let data = FnData {
1085                     constness: header.constness,
1086                     arg_names: self.encode_fn_arg_names_for_body(body),
1087                     sig: self.lazy(&tcx.fn_sig(def_id)),
1088                 };
1089
1090                 EntryKind::Fn(self.lazy(&data))
1091             }
1092             hir::ItemKind::Mod(ref m) => {
1093                 return self.encode_info_for_mod((item.hir_id, m, &item.attrs, &item.vis));
1094             }
1095             hir::ItemKind::ForeignMod(_) => EntryKind::ForeignMod,
1096             hir::ItemKind::GlobalAsm(..) => EntryKind::GlobalAsm,
1097             hir::ItemKind::TyAlias(..) => EntryKind::Type,
1098             hir::ItemKind::OpaqueTy(..) => EntryKind::OpaqueTy,
1099             hir::ItemKind::Enum(..) => EntryKind::Enum(get_repr_options(tcx, def_id)),
1100             hir::ItemKind::Struct(ref struct_def, _) => {
1101                 let variant = tcx.adt_def(def_id).non_enum_variant();
1102
1103                 // Encode def_ids for each field and method
1104                 // for methods, write all the stuff get_trait_method
1105                 // needs to know
1106                 let ctor = struct_def.ctor_hir_id()
1107                     .map(|ctor_hir_id| tcx.hir().local_def_id(ctor_hir_id).index);
1108
1109                 let repr_options = get_repr_options(tcx, def_id);
1110
1111                 EntryKind::Struct(self.lazy(&VariantData {
1112                     ctor_kind: variant.ctor_kind,
1113                     discr: variant.discr,
1114                     ctor,
1115                     ctor_sig: None,
1116                 }), repr_options)
1117             }
1118             hir::ItemKind::Union(..) => {
1119                 let variant = tcx.adt_def(def_id).non_enum_variant();
1120                 let repr_options = get_repr_options(tcx, def_id);
1121
1122                 EntryKind::Union(self.lazy(&VariantData {
1123                     ctor_kind: variant.ctor_kind,
1124                     discr: variant.discr,
1125                     ctor: None,
1126                     ctor_sig: None,
1127                 }), repr_options)
1128             }
1129             hir::ItemKind::Impl(_, polarity, defaultness, ..) => {
1130                 let trait_ref = tcx.impl_trait_ref(def_id);
1131                 let parent = if let Some(trait_ref) = trait_ref {
1132                     let trait_def = tcx.trait_def(trait_ref.def_id);
1133                     trait_def.ancestors(tcx, def_id).nth(1).and_then(|node| {
1134                         match node {
1135                             specialization_graph::Node::Impl(parent) => Some(parent),
1136                             _ => None,
1137                         }
1138                     })
1139                 } else {
1140                     None
1141                 };
1142
1143                 // if this is an impl of `CoerceUnsized`, create its
1144                 // "unsized info", else just store None
1145                 let coerce_unsized_info =
1146                     trait_ref.and_then(|t| {
1147                         if Some(t.def_id) == tcx.lang_items().coerce_unsized_trait() {
1148                             Some(tcx.at(item.span).coerce_unsized_info(def_id))
1149                         } else {
1150                             None
1151                         }
1152                     });
1153
1154                 let data = ImplData {
1155                     polarity,
1156                     defaultness,
1157                     parent_impl: parent,
1158                     coerce_unsized_info,
1159                     trait_ref: trait_ref.map(|trait_ref| self.lazy(&trait_ref)),
1160                 };
1161
1162                 EntryKind::Impl(self.lazy(&data))
1163             }
1164             hir::ItemKind::Trait(..) => {
1165                 let trait_def = tcx.trait_def(def_id);
1166                 let data = TraitData {
1167                     unsafety: trait_def.unsafety,
1168                     paren_sugar: trait_def.paren_sugar,
1169                     has_auto_impl: tcx.trait_is_auto(def_id),
1170                     is_marker: trait_def.is_marker,
1171                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
1172                 };
1173
1174                 EntryKind::Trait(self.lazy(&data))
1175             }
1176             hir::ItemKind::TraitAlias(..) => {
1177                 let data = TraitAliasData {
1178                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
1179                 };
1180
1181                 EntryKind::TraitAlias(self.lazy(&data))
1182             }
1183             hir::ItemKind::ExternCrate(_) |
1184             hir::ItemKind::Use(..) => bug!("cannot encode info for item {:?}", item),
1185         };
1186
1187         Entry {
1188             kind,
1189             visibility: self.lazy(&ty::Visibility::from_hir(&item.vis, item.hir_id, tcx)),
1190             span: self.lazy(&item.span),
1191             attributes: self.encode_attributes(&item.attrs),
1192             children: match item.node {
1193                 hir::ItemKind::ForeignMod(ref fm) => {
1194                     self.lazy_seq(fm.items
1195                         .iter()
1196                         .map(|foreign_item| tcx.hir().local_def_id(
1197                             foreign_item.hir_id).index))
1198                 }
1199                 hir::ItemKind::Enum(..) => {
1200                     let def = self.tcx.adt_def(def_id);
1201                     self.lazy_seq(def.variants.iter().map(|v| {
1202                         assert!(v.def_id.is_local());
1203                         v.def_id.index
1204                     }))
1205                 }
1206                 hir::ItemKind::Struct(..) |
1207                 hir::ItemKind::Union(..) => {
1208                     let def = self.tcx.adt_def(def_id);
1209                     self.lazy_seq(def.non_enum_variant().fields.iter().map(|f| {
1210                         assert!(f.did.is_local());
1211                         f.did.index
1212                     }))
1213                 }
1214                 hir::ItemKind::Impl(..) |
1215                 hir::ItemKind::Trait(..) => {
1216                     self.lazy_seq(tcx.associated_item_def_ids(def_id).iter().map(|&def_id| {
1217                         assert!(def_id.is_local());
1218                         def_id.index
1219                     }))
1220                 }
1221                 _ => LazySeq::empty(),
1222             },
1223             stability: self.encode_stability(def_id),
1224             deprecation: self.encode_deprecation(def_id),
1225
1226             ty: match item.node {
1227                 hir::ItemKind::Static(..) |
1228                 hir::ItemKind::Const(..) |
1229                 hir::ItemKind::Fn(..) |
1230                 hir::ItemKind::TyAlias(..) |
1231                 hir::ItemKind::OpaqueTy(..) |
1232                 hir::ItemKind::Enum(..) |
1233                 hir::ItemKind::Struct(..) |
1234                 hir::ItemKind::Union(..) |
1235                 hir::ItemKind::Impl(..) => Some(self.encode_item_type(def_id)),
1236                 _ => None,
1237             },
1238             inherent_impls: self.encode_inherent_implementations(def_id),
1239             variances: match item.node {
1240                 hir::ItemKind::Enum(..) |
1241                 hir::ItemKind::Struct(..) |
1242                 hir::ItemKind::Union(..) |
1243                 hir::ItemKind::Fn(..) => self.encode_variances_of(def_id),
1244                 _ => LazySeq::empty(),
1245             },
1246             generics: match item.node {
1247                 hir::ItemKind::Static(..) |
1248                 hir::ItemKind::Const(..) |
1249                 hir::ItemKind::Fn(..) |
1250                 hir::ItemKind::TyAlias(..) |
1251                 hir::ItemKind::Enum(..) |
1252                 hir::ItemKind::Struct(..) |
1253                 hir::ItemKind::Union(..) |
1254                 hir::ItemKind::Impl(..) |
1255                 hir::ItemKind::OpaqueTy(..) |
1256                 hir::ItemKind::Trait(..) => Some(self.encode_generics(def_id)),
1257                 hir::ItemKind::TraitAlias(..) => Some(self.encode_generics(def_id)),
1258                 _ => None,
1259             },
1260             predicates: match item.node {
1261                 hir::ItemKind::Static(..) |
1262                 hir::ItemKind::Const(..) |
1263                 hir::ItemKind::Fn(..) |
1264                 hir::ItemKind::TyAlias(..) |
1265                 hir::ItemKind::Enum(..) |
1266                 hir::ItemKind::Struct(..) |
1267                 hir::ItemKind::Union(..) |
1268                 hir::ItemKind::Impl(..) |
1269                 hir::ItemKind::OpaqueTy(..) |
1270                 hir::ItemKind::Trait(..) |
1271                 hir::ItemKind::TraitAlias(..) => Some(self.encode_predicates(def_id)),
1272                 _ => None,
1273             },
1274
1275             // The only time that `predicates_defined_on` is used (on
1276             // an external item) is for traits, during chalk lowering,
1277             // so only encode it in that case as an efficiency
1278             // hack. (No reason not to expand it in the future if
1279             // necessary.)
1280             predicates_defined_on: match item.node {
1281                 hir::ItemKind::Trait(..) |
1282                 hir::ItemKind::TraitAlias(..) => Some(self.encode_predicates_defined_on(def_id)),
1283                 _ => None, // not *wrong* for other kinds of items, but not needed
1284             },
1285
1286             mir: match item.node {
1287                 hir::ItemKind::Static(..) => {
1288                     self.encode_optimized_mir(def_id)
1289                 }
1290                 hir::ItemKind::Const(..) => self.encode_optimized_mir(def_id),
1291                 hir::ItemKind::Fn(_, header, ..) => {
1292                     let generics = tcx.generics_of(def_id);
1293                     let needs_inline =
1294                         (generics.requires_monomorphization(tcx) ||
1295                          tcx.codegen_fn_attrs(def_id).requests_inline()) &&
1296                             !self.metadata_output_only();
1297                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
1298                     if needs_inline
1299                         || header.constness == hir::Constness::Const
1300                         || always_encode_mir
1301                     {
1302                         self.encode_optimized_mir(def_id)
1303                     } else {
1304                         None
1305                     }
1306                 }
1307                 _ => None,
1308             },
1309         }
1310     }
1311
1312     /// Serialize the text of exported macros
1313     fn encode_info_for_macro_def(&mut self, macro_def: &hir::MacroDef) -> Entry<'tcx> {
1314         use syntax::print::pprust;
1315         let def_id = self.tcx.hir().local_def_id(macro_def.hir_id);
1316         Entry {
1317             kind: EntryKind::MacroDef(self.lazy(&MacroDef {
1318                 body: pprust::tokens_to_string(macro_def.body.clone()),
1319                 legacy: macro_def.legacy,
1320             })),
1321             visibility: self.lazy(&ty::Visibility::Public),
1322             span: self.lazy(&macro_def.span),
1323             attributes: self.encode_attributes(&macro_def.attrs),
1324             stability: self.encode_stability(def_id),
1325             deprecation: self.encode_deprecation(def_id),
1326
1327             children: LazySeq::empty(),
1328             ty: None,
1329             inherent_impls: LazySeq::empty(),
1330             variances: LazySeq::empty(),
1331             generics: None,
1332             predicates: None,
1333             predicates_defined_on: None,
1334             mir: None,
1335         }
1336     }
1337
1338     fn encode_info_for_generic_param(
1339         &mut self,
1340         def_id: DefId,
1341         entry_kind: EntryKind<'tcx>,
1342         encode_type: bool,
1343     ) -> Entry<'tcx> {
1344         let tcx = self.tcx;
1345         Entry {
1346             kind: entry_kind,
1347             visibility: self.lazy(&ty::Visibility::Public),
1348             span: self.lazy(&tcx.def_span(def_id)),
1349             attributes: LazySeq::empty(),
1350             children: LazySeq::empty(),
1351             stability: None,
1352             deprecation: None,
1353             ty: if encode_type { Some(self.encode_item_type(def_id)) } else { None },
1354             inherent_impls: LazySeq::empty(),
1355             variances: LazySeq::empty(),
1356             generics: None,
1357             predicates: None,
1358             predicates_defined_on: None,
1359
1360             mir: None,
1361         }
1362     }
1363
1364     fn encode_info_for_ty_param(
1365         &mut self,
1366         (def_id, encode_type): (DefId, bool),
1367     ) -> Entry<'tcx> {
1368         debug!("EncodeContext::encode_info_for_ty_param({:?})", def_id);
1369         self.encode_info_for_generic_param(def_id, EntryKind::TypeParam, encode_type)
1370     }
1371
1372     fn encode_info_for_const_param(
1373         &mut self,
1374         def_id: DefId,
1375     ) -> Entry<'tcx> {
1376         debug!("EncodeContext::encode_info_for_const_param({:?})", def_id);
1377         self.encode_info_for_generic_param(def_id, EntryKind::ConstParam, true)
1378     }
1379
1380     fn encode_info_for_closure(&mut self, def_id: DefId) -> Entry<'tcx> {
1381         debug!("EncodeContext::encode_info_for_closure({:?})", def_id);
1382         let tcx = self.tcx;
1383
1384         let tables = self.tcx.typeck_tables_of(def_id);
1385         let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
1386         let kind = match tables.node_type(hir_id).sty {
1387             ty::Generator(def_id, ..) => {
1388                 let layout = self.tcx.generator_layout(def_id);
1389                 let data = GeneratorData {
1390                     layout: layout.clone(),
1391                 };
1392                 EntryKind::Generator(self.lazy(&data))
1393             }
1394
1395             ty::Closure(def_id, substs) => {
1396                 let sig = substs.closure_sig(def_id, self.tcx);
1397                 let data = ClosureData { sig: self.lazy(&sig) };
1398                 EntryKind::Closure(self.lazy(&data))
1399             }
1400
1401             _ => bug!("closure that is neither generator nor closure")
1402         };
1403
1404         Entry {
1405             kind,
1406             visibility: self.lazy(&ty::Visibility::Public),
1407             span: self.lazy(&tcx.def_span(def_id)),
1408             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
1409             children: LazySeq::empty(),
1410             stability: None,
1411             deprecation: None,
1412
1413             ty: Some(self.encode_item_type(def_id)),
1414             inherent_impls: LazySeq::empty(),
1415             variances: LazySeq::empty(),
1416             generics: Some(self.encode_generics(def_id)),
1417             predicates: None,
1418             predicates_defined_on: None,
1419
1420             mir: self.encode_optimized_mir(def_id),
1421         }
1422     }
1423
1424     fn encode_info_for_anon_const(&mut self, def_id: DefId) -> Entry<'tcx> {
1425         debug!("EncodeContext::encode_info_for_anon_const({:?})", def_id);
1426         let tcx = self.tcx;
1427         let id = tcx.hir().as_local_hir_id(def_id).unwrap();
1428         let body_id = tcx.hir().body_owned_by(id);
1429         let const_data = self.encode_rendered_const_for_body(body_id);
1430         let mir = tcx.mir_const_qualif(def_id).0;
1431
1432         Entry {
1433             kind: EntryKind::Const(self.const_qualif(mir, body_id), const_data),
1434             visibility: self.lazy(&ty::Visibility::Public),
1435             span: self.lazy(&tcx.def_span(def_id)),
1436             attributes: LazySeq::empty(),
1437             children: LazySeq::empty(),
1438             stability: None,
1439             deprecation: None,
1440
1441             ty: Some(self.encode_item_type(def_id)),
1442             inherent_impls: LazySeq::empty(),
1443             variances: LazySeq::empty(),
1444             generics: Some(self.encode_generics(def_id)),
1445             predicates: Some(self.encode_predicates(def_id)),
1446             predicates_defined_on: None,
1447
1448             mir: self.encode_optimized_mir(def_id),
1449         }
1450     }
1451
1452     fn encode_attributes(&mut self, attrs: &[ast::Attribute]) -> LazySeq<ast::Attribute> {
1453         self.lazy_seq_ref(attrs)
1454     }
1455
1456     fn encode_native_libraries(&mut self) -> LazySeq<NativeLibrary> {
1457         let used_libraries = self.tcx.native_libraries(LOCAL_CRATE);
1458         self.lazy_seq(used_libraries.iter().cloned())
1459     }
1460
1461     fn encode_foreign_modules(&mut self) -> LazySeq<ForeignModule> {
1462         let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
1463         self.lazy_seq(foreign_modules.iter().cloned())
1464     }
1465
1466     fn encode_crate_deps(&mut self) -> LazySeq<CrateDep> {
1467         let crates = self.tcx.crates();
1468
1469         let mut deps = crates
1470             .iter()
1471             .map(|&cnum| {
1472                 let dep = CrateDep {
1473                     name: self.tcx.original_crate_name(cnum),
1474                     hash: self.tcx.crate_hash(cnum),
1475                     kind: self.tcx.dep_kind(cnum),
1476                     extra_filename: self.tcx.extra_filename(cnum),
1477                 };
1478                 (cnum, dep)
1479             })
1480             .collect::<Vec<_>>();
1481
1482         deps.sort_by_key(|&(cnum, _)| cnum);
1483
1484         {
1485             // Sanity-check the crate numbers
1486             let mut expected_cnum = 1;
1487             for &(n, _) in &deps {
1488                 assert_eq!(n, CrateNum::new(expected_cnum));
1489                 expected_cnum += 1;
1490             }
1491         }
1492
1493         // We're just going to write a list of crate 'name-hash-version's, with
1494         // the assumption that they are numbered 1 to n.
1495         // FIXME (#2166): This is not nearly enough to support correct versioning
1496         // but is enough to get transitive crate dependencies working.
1497         self.lazy_seq_ref(deps.iter().map(|&(_, ref dep)| dep))
1498     }
1499
1500     fn encode_lib_features(&mut self) -> LazySeq<(ast::Name, Option<ast::Name>)> {
1501         let tcx = self.tcx;
1502         let lib_features = tcx.lib_features();
1503         self.lazy_seq(lib_features.to_vec())
1504     }
1505
1506     fn encode_lang_items(&mut self) -> LazySeq<(DefIndex, usize)> {
1507         let tcx = self.tcx;
1508         let lang_items = tcx.lang_items();
1509         let lang_items = lang_items.items().iter();
1510         self.lazy_seq(lang_items.enumerate().filter_map(|(i, &opt_def_id)| {
1511             if let Some(def_id) = opt_def_id {
1512                 if def_id.is_local() {
1513                     return Some((def_id.index, i));
1514                 }
1515             }
1516             None
1517         }))
1518     }
1519
1520     fn encode_lang_items_missing(&mut self) -> LazySeq<lang_items::LangItem> {
1521         let tcx = self.tcx;
1522         self.lazy_seq_ref(&tcx.lang_items().missing)
1523     }
1524
1525     /// Encodes an index, mapping each trait to its (local) implementations.
1526     fn encode_impls(&mut self) -> LazySeq<TraitImpls> {
1527         debug!("EncodeContext::encode_impls()");
1528         let tcx = self.tcx;
1529         let mut visitor = ImplVisitor {
1530             tcx,
1531             impls: FxHashMap::default(),
1532         };
1533         tcx.hir().krate().visit_all_item_likes(&mut visitor);
1534
1535         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
1536
1537         // Bring everything into deterministic order for hashing
1538         all_impls.sort_by_cached_key(|&(trait_def_id, _)| {
1539             tcx.def_path_hash(trait_def_id)
1540         });
1541
1542         let all_impls: Vec<_> = all_impls
1543             .into_iter()
1544             .map(|(trait_def_id, mut impls)| {
1545                 // Bring everything into deterministic order for hashing
1546                 impls.sort_by_cached_key(|&def_index| {
1547                     tcx.hir().definitions().def_path_hash(def_index)
1548                 });
1549
1550                 TraitImpls {
1551                     trait_id: (trait_def_id.krate.as_u32(), trait_def_id.index),
1552                     impls: self.lazy_seq_ref(&impls),
1553                 }
1554             })
1555             .collect();
1556
1557         self.lazy_seq_ref(&all_impls)
1558     }
1559
1560     // Encodes all symbols exported from this crate into the metadata.
1561     //
1562     // This pass is seeded off the reachability list calculated in the
1563     // middle::reachable module but filters out items that either don't have a
1564     // symbol associated with them (they weren't translated) or if they're an FFI
1565     // definition (as that's not defined in this crate).
1566     fn encode_exported_symbols(&mut self,
1567                                exported_symbols: &[(ExportedSymbol<'tcx>, SymbolExportLevel)])
1568                                -> LazySeq<(ExportedSymbol<'tcx>, SymbolExportLevel)> {
1569         // The metadata symbol name is special. It should not show up in
1570         // downstream crates.
1571         let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
1572
1573         self.lazy_seq(exported_symbols
1574             .iter()
1575             .filter(|&&(ref exported_symbol, _)| {
1576                 match *exported_symbol {
1577                     ExportedSymbol::NoDefId(symbol_name) => {
1578                         symbol_name != metadata_symbol_name
1579                     },
1580                     _ => true,
1581                 }
1582             })
1583             .cloned())
1584     }
1585
1586     fn encode_dylib_dependency_formats(&mut self) -> LazySeq<Option<LinkagePreference>> {
1587         match self.tcx.sess.dependency_formats.borrow().get(&config::CrateType::Dylib) {
1588             Some(arr) => {
1589                 self.lazy_seq(arr.iter().map(|slot| {
1590                     match *slot {
1591                         Linkage::NotLinked |
1592                         Linkage::IncludedFromDylib => None,
1593
1594                         Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
1595                         Linkage::Static => Some(LinkagePreference::RequireStatic),
1596                     }
1597                 }))
1598             }
1599             None => LazySeq::empty(),
1600         }
1601     }
1602
1603     fn encode_info_for_foreign_item(&mut self,
1604                                     (def_id, nitem): (DefId, &hir::ForeignItem))
1605                                     -> Entry<'tcx> {
1606         let tcx = self.tcx;
1607
1608         debug!("EncodeContext::encode_info_for_foreign_item({:?})", def_id);
1609
1610         let kind = match nitem.node {
1611             hir::ForeignItemKind::Fn(_, ref names, _) => {
1612                 let data = FnData {
1613                     constness: hir::Constness::NotConst,
1614                     arg_names: self.encode_fn_arg_names(names),
1615                     sig: self.lazy(&tcx.fn_sig(def_id)),
1616                 };
1617                 EntryKind::ForeignFn(self.lazy(&data))
1618             }
1619             hir::ForeignItemKind::Static(_, hir::MutMutable) => EntryKind::ForeignMutStatic,
1620             hir::ForeignItemKind::Static(_, hir::MutImmutable) => EntryKind::ForeignImmStatic,
1621             hir::ForeignItemKind::Type => EntryKind::ForeignType,
1622         };
1623
1624         Entry {
1625             kind,
1626             visibility: self.lazy(&ty::Visibility::from_hir(&nitem.vis, nitem.hir_id, tcx)),
1627             span: self.lazy(&nitem.span),
1628             attributes: self.encode_attributes(&nitem.attrs),
1629             children: LazySeq::empty(),
1630             stability: self.encode_stability(def_id),
1631             deprecation: self.encode_deprecation(def_id),
1632
1633             ty: Some(self.encode_item_type(def_id)),
1634             inherent_impls: LazySeq::empty(),
1635             variances: match nitem.node {
1636                 hir::ForeignItemKind::Fn(..) => self.encode_variances_of(def_id),
1637                 _ => LazySeq::empty(),
1638             },
1639             generics: Some(self.encode_generics(def_id)),
1640             predicates: Some(self.encode_predicates(def_id)),
1641             predicates_defined_on: None,
1642
1643             mir: None,
1644         }
1645     }
1646 }
1647
1648 impl Visitor<'tcx> for EncodeContext<'tcx> {
1649     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1650         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
1651     }
1652     fn visit_expr(&mut self, ex: &'tcx hir::Expr) {
1653         intravisit::walk_expr(self, ex);
1654         self.encode_info_for_expr(ex);
1655     }
1656     fn visit_item(&mut self, item: &'tcx hir::Item) {
1657         intravisit::walk_item(self, item);
1658         let def_id = self.tcx.hir().local_def_id(item.hir_id);
1659         match item.node {
1660             hir::ItemKind::ExternCrate(_) |
1661             hir::ItemKind::Use(..) => {} // ignore these
1662             _ => self.record(def_id, EncodeContext::encode_info_for_item, (def_id, item)),
1663         }
1664         self.encode_addl_info_for_item(item);
1665     }
1666     fn visit_foreign_item(&mut self, ni: &'tcx hir::ForeignItem) {
1667         intravisit::walk_foreign_item(self, ni);
1668         let def_id = self.tcx.hir().local_def_id(ni.hir_id);
1669         self.record(def_id,
1670                           EncodeContext::encode_info_for_foreign_item,
1671                           (def_id, ni));
1672     }
1673     fn visit_variant(&mut self,
1674                      v: &'tcx hir::Variant,
1675                      g: &'tcx hir::Generics,
1676                      id: hir::HirId) {
1677         intravisit::walk_variant(self, v, g, id);
1678
1679         if let Some(ref discr) = v.node.disr_expr {
1680             let def_id = self.tcx.hir().local_def_id(discr.hir_id);
1681             self.record(def_id, EncodeContext::encode_info_for_anon_const, def_id);
1682         }
1683     }
1684     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
1685         intravisit::walk_generics(self, generics);
1686         self.encode_info_for_generics(generics);
1687     }
1688     fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1689         intravisit::walk_ty(self, ty);
1690         self.encode_info_for_ty(ty);
1691     }
1692     fn visit_macro_def(&mut self, macro_def: &'tcx hir::MacroDef) {
1693         let def_id = self.tcx.hir().local_def_id(macro_def.hir_id);
1694         self.record(def_id, EncodeContext::encode_info_for_macro_def, macro_def);
1695     }
1696 }
1697
1698 impl EncodeContext<'tcx> {
1699     fn encode_fields(&mut self, adt_def_id: DefId) {
1700         let def = self.tcx.adt_def(adt_def_id);
1701         for (variant_index, variant) in def.variants.iter_enumerated() {
1702             for (field_index, field) in variant.fields.iter().enumerate() {
1703                 self.record(field.did,
1704                             EncodeContext::encode_field,
1705                             (adt_def_id, variant_index, field_index));
1706             }
1707         }
1708     }
1709
1710     fn encode_info_for_generics(&mut self, generics: &hir::Generics) {
1711         for param in &generics.params {
1712             let def_id = self.tcx.hir().local_def_id(param.hir_id);
1713             match param.kind {
1714                 GenericParamKind::Lifetime { .. } => continue,
1715                 GenericParamKind::Type { ref default, .. } => {
1716                     self.record(
1717                         def_id,
1718                         EncodeContext::encode_info_for_ty_param,
1719                         (def_id, default.is_some()),
1720                     );
1721                 }
1722                 GenericParamKind::Const { .. } => {
1723                     self.record(def_id, EncodeContext::encode_info_for_const_param, def_id);
1724                 }
1725             }
1726         }
1727     }
1728
1729     fn encode_info_for_ty(&mut self, ty: &hir::Ty) {
1730         match ty.node {
1731             hir::TyKind::Array(_, ref length) => {
1732                 let def_id = self.tcx.hir().local_def_id(length.hir_id);
1733                 self.record(def_id, EncodeContext::encode_info_for_anon_const, def_id);
1734             }
1735             _ => {}
1736         }
1737     }
1738
1739     fn encode_info_for_expr(&mut self, expr: &hir::Expr) {
1740         match expr.node {
1741             hir::ExprKind::Closure(..) => {
1742                 let def_id = self.tcx.hir().local_def_id(expr.hir_id);
1743                 self.record(def_id, EncodeContext::encode_info_for_closure, def_id);
1744             }
1745             _ => {}
1746         }
1747     }
1748
1749     /// In some cases, along with the item itself, we also
1750     /// encode some sub-items. Usually we want some info from the item
1751     /// so it's easier to do that here then to wait until we would encounter
1752     /// normally in the visitor walk.
1753     fn encode_addl_info_for_item(&mut self, item: &hir::Item) {
1754         let def_id = self.tcx.hir().local_def_id(item.hir_id);
1755         match item.node {
1756             hir::ItemKind::Static(..) |
1757             hir::ItemKind::Const(..) |
1758             hir::ItemKind::Fn(..) |
1759             hir::ItemKind::Mod(..) |
1760             hir::ItemKind::ForeignMod(..) |
1761             hir::ItemKind::GlobalAsm(..) |
1762             hir::ItemKind::ExternCrate(..) |
1763             hir::ItemKind::Use(..) |
1764             hir::ItemKind::TyAlias(..) |
1765             hir::ItemKind::OpaqueTy(..) |
1766             hir::ItemKind::TraitAlias(..) => {
1767                 // no sub-item recording needed in these cases
1768             }
1769             hir::ItemKind::Enum(..) => {
1770                 self.encode_fields(def_id);
1771
1772                 let def = self.tcx.adt_def(def_id);
1773                 for (i, variant) in def.variants.iter_enumerated() {
1774                     self.record(variant.def_id,
1775                                 EncodeContext::encode_enum_variant_info,
1776                                 (def_id, i));
1777
1778                     if let Some(ctor_def_id) = variant.ctor_def_id {
1779                         self.record(ctor_def_id,
1780                                     EncodeContext::encode_enum_variant_ctor,
1781                                     (def_id, i));
1782                     }
1783                 }
1784             }
1785             hir::ItemKind::Struct(ref struct_def, _) => {
1786                 self.encode_fields(def_id);
1787
1788                 // If the struct has a constructor, encode it.
1789                 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
1790                     let ctor_def_id = self.tcx.hir().local_def_id(ctor_hir_id);
1791                     self.record(ctor_def_id,
1792                                 EncodeContext::encode_struct_ctor,
1793                                 (def_id, ctor_def_id));
1794                 }
1795             }
1796             hir::ItemKind::Union(..) => {
1797                 self.encode_fields(def_id);
1798             }
1799             hir::ItemKind::Impl(..) => {
1800                 for &trait_item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1801                     self.record(trait_item_def_id,
1802                                 EncodeContext::encode_info_for_impl_item,
1803                                 trait_item_def_id);
1804                 }
1805             }
1806             hir::ItemKind::Trait(..) => {
1807                 for &item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1808                     self.record(item_def_id,
1809                                 EncodeContext::encode_info_for_trait_item,
1810                                 item_def_id);
1811                 }
1812             }
1813         }
1814     }
1815 }
1816
1817 struct ImplVisitor<'tcx> {
1818     tcx: TyCtxt<'tcx>,
1819     impls: FxHashMap<DefId, Vec<DefIndex>>,
1820 }
1821
1822 impl<'tcx, 'v> ItemLikeVisitor<'v> for ImplVisitor<'tcx> {
1823     fn visit_item(&mut self, item: &hir::Item) {
1824         if let hir::ItemKind::Impl(..) = item.node {
1825             let impl_id = self.tcx.hir().local_def_id(item.hir_id);
1826             if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_id) {
1827                 self.impls
1828                     .entry(trait_ref.def_id)
1829                     .or_default()
1830                     .push(impl_id.index);
1831             }
1832         }
1833     }
1834
1835     fn visit_trait_item(&mut self, _trait_item: &'v hir::TraitItem) {}
1836
1837     fn visit_impl_item(&mut self, _impl_item: &'v hir::ImplItem) {
1838         // handled in `visit_item` above
1839     }
1840 }
1841
1842 // NOTE(eddyb) The following comment was preserved for posterity, even
1843 // though it's no longer relevant as EBML (which uses nested & tagged
1844 // "documents") was replaced with a scheme that can't go out of bounds.
1845 //
1846 // And here we run into yet another obscure archive bug: in which metadata
1847 // loaded from archives may have trailing garbage bytes. Awhile back one of
1848 // our tests was failing sporadically on the macOS 64-bit builders (both nopt
1849 // and opt) by having ebml generate an out-of-bounds panic when looking at
1850 // metadata.
1851 //
1852 // Upon investigation it turned out that the metadata file inside of an rlib
1853 // (and ar archive) was being corrupted. Some compilations would generate a
1854 // metadata file which would end in a few extra bytes, while other
1855 // compilations would not have these extra bytes appended to the end. These
1856 // extra bytes were interpreted by ebml as an extra tag, so they ended up
1857 // being interpreted causing the out-of-bounds.
1858 //
1859 // The root cause of why these extra bytes were appearing was never
1860 // discovered, and in the meantime the solution we're employing is to insert
1861 // the length of the metadata to the start of the metadata. Later on this
1862 // will allow us to slice the metadata to the precise length that we just
1863 // generated regardless of trailing bytes that end up in it.
1864
1865 pub fn encode_metadata(tcx: TyCtxt<'_>) -> EncodedMetadata {
1866     let mut encoder = opaque::Encoder::new(vec![]);
1867     encoder.emit_raw_bytes(METADATA_HEADER);
1868
1869     // Will be filled with the root position after encoding everything.
1870     encoder.emit_raw_bytes(&[0, 0, 0, 0]);
1871
1872     // Since encoding metadata is not in a query, and nothing is cached,
1873     // there's no need to do dep-graph tracking for any of it.
1874     let (root, mut result) = tcx.dep_graph.with_ignore(move || {
1875         let mut ecx = EncodeContext {
1876             opaque: encoder,
1877             tcx,
1878             entries_index: Index::new(tcx.hir().definitions().def_index_count()),
1879             lazy_state: LazyState::NoNode,
1880             type_shorthands: Default::default(),
1881             predicate_shorthands: Default::default(),
1882             source_file_cache: tcx.sess.source_map().files()[0].clone(),
1883             interpret_allocs: Default::default(),
1884             interpret_allocs_inverse: Default::default(),
1885         };
1886
1887         // Encode the rustc version string in a predictable location.
1888         rustc_version().encode(&mut ecx).unwrap();
1889
1890         // Encode all the entries and extra information in the crate,
1891         // culminating in the `CrateRoot` which points to all of it.
1892         let root = ecx.encode_crate_root();
1893         (root, ecx.opaque.into_inner())
1894     });
1895
1896     // Encode the root position.
1897     let header = METADATA_HEADER.len();
1898     let pos = root.position;
1899     result[header + 0] = (pos >> 24) as u8;
1900     result[header + 1] = (pos >> 16) as u8;
1901     result[header + 2] = (pos >> 8) as u8;
1902     result[header + 3] = (pos >> 0) as u8;
1903
1904     EncodedMetadata { raw_data: result }
1905 }
1906
1907 pub fn get_repr_options(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1908     let ty = tcx.type_of(did);
1909     match ty.sty {
1910         ty::Adt(ref def, _) => return def.repr,
1911         _ => bug!("{} is not an ADT", ty),
1912     }
1913 }