src/librustc_metadata/encoder.rs

   1 use index::Index;
   2 use index_builder::{FromId, IndexBuilder, Untracked};
   3 use isolated_encoder::IsolatedEncoder;
   4 use schema::*;
   5
   6 use rustc::middle::cstore::{LinkagePreference, NativeLibrary,
   7                             EncodedMetadata, ForeignModule};
   8 use rustc::hir::def::CtorKind;
   9 use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefIndex, DefId, LocalDefId, LOCAL_CRATE};
  10 use rustc::hir::map::definitions::DefPathTable;
  11 use rustc_data_structures::fingerprint::Fingerprint;
  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, ReprOptions, 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_serialize::{Encodable, Encoder, SpecializedEncoder, opaque};
  27
  28 use std::hash::Hash;
  29 use std::path::Path;
  30 use rustc_data_structures::sync::Lrc;
  31 use std::u32;
  32 use syntax::ast::{self, CRATE_NODE_ID};
  33 use syntax::attr;
  34 use syntax::source_map::Spanned;
  35 use syntax::symbol::keywords;
  36 use syntax_pos::{self, hygiene, FileName, SourceFile, Span};
  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<'a, 'tcx: 'a> {
  44     opaque: opaque::Encoder,
  45     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
  46
  47     lazy_state: LazyState,
  48     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
  49     predicate_shorthands: FxHashMap<ty::Predicate<'tcx>, usize>,
  50
  51     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
  52     interpret_allocs_inverse: Vec<interpret::AllocId>,
  53
  54     // This is used to speed up Span encoding.
  55     source_file_cache: Lrc<SourceFile>,
  56 }
  57
  58 macro_rules! encoder_methods {
  59     ($($name:ident($ty:ty);)*) => {
  60         $(fn $name(&mut self, value: $ty) -> Result<(), Self::Error> {
  61             self.opaque.$name(value)
  62         })*
  63     }
  64 }
  65
  66 impl<'a, 'tcx> Encoder for EncodeContext<'a, 'tcx> {
  67     type Error = <opaque::Encoder as Encoder>::Error;
  68
  69     fn emit_unit(&mut self) -> Result<(), Self::Error> {
  70         Ok(())
  71     }
  72
  73     encoder_methods! {
  74         emit_usize(usize);
  75         emit_u128(u128);
  76         emit_u64(u64);
  77         emit_u32(u32);
  78         emit_u16(u16);
  79         emit_u8(u8);
  80
  81         emit_isize(isize);
  82         emit_i128(i128);
  83         emit_i64(i64);
  84         emit_i32(i32);
  85         emit_i16(i16);
  86         emit_i8(i8);
  87
  88         emit_bool(bool);
  89         emit_f64(f64);
  90         emit_f32(f32);
  91         emit_char(char);
  92         emit_str(&str);
  93     }
  94 }
  95
  96 impl<'a, 'tcx, T> SpecializedEncoder<Lazy<T>> for EncodeContext<'a, 'tcx> {
  97     fn specialized_encode(&mut self, lazy: &Lazy<T>) -> Result<(), Self::Error> {
  98         self.emit_lazy_distance(lazy.position, Lazy::<T>::min_size())
  99     }
 100 }
 101
 102 impl<'a, 'tcx, T> SpecializedEncoder<LazySeq<T>> for EncodeContext<'a, 'tcx> {
 103     fn specialized_encode(&mut self, seq: &LazySeq<T>) -> Result<(), Self::Error> {
 104         self.emit_usize(seq.len)?;
 105         if seq.len == 0 {
 106             return Ok(());
 107         }
 108         self.emit_lazy_distance(seq.position, LazySeq::<T>::min_size(seq.len))
 109     }
 110 }
 111
 112 impl<'a, 'tcx> SpecializedEncoder<CrateNum> for EncodeContext<'a, 'tcx> {
 113     #[inline]
 114     fn specialized_encode(&mut self, cnum: &CrateNum) -> Result<(), Self::Error> {
 115         self.emit_u32(cnum.as_u32())
 116     }
 117 }
 118
 119 impl<'a, 'tcx> SpecializedEncoder<DefId> for EncodeContext<'a, 'tcx> {
 120     #[inline]
 121     fn specialized_encode(&mut self, def_id: &DefId) -> Result<(), Self::Error> {
 122         let DefId {
 123             krate,
 124             index,
 125         } = *def_id;
 126
 127         krate.encode(self)?;
 128         index.encode(self)
 129     }
 130 }
 131
 132 impl<'a, 'tcx> SpecializedEncoder<DefIndex> for EncodeContext<'a, 'tcx> {
 133     #[inline]
 134     fn specialized_encode(&mut self, def_index: &DefIndex) -> Result<(), Self::Error> {
 135         self.emit_u32(def_index.as_raw_u32())
 136     }
 137 }
 138
 139 impl<'a, 'tcx> SpecializedEncoder<Span> for EncodeContext<'a, 'tcx> {
 140     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
 141         if span.is_dummy() {
 142             return TAG_INVALID_SPAN.encode(self)
 143         }
 144
 145         let span = span.data();
 146
 147         // The Span infrastructure should make sure that this invariant holds:
 148         debug_assert!(span.lo <= span.hi);
 149
 150         if !self.source_file_cache.contains(span.lo) {
 151             let source_map = self.tcx.sess.source_map();
 152             let source_file_index = source_map.lookup_source_file_idx(span.lo);
 153             self.source_file_cache = source_map.files()[source_file_index].clone();
 154         }
 155
 156         if !self.source_file_cache.contains(span.hi) {
 157             // Unfortunately, macro expansion still sometimes generates Spans
 158             // that malformed in this way.
 159             return TAG_INVALID_SPAN.encode(self)
 160         }
 161
 162         TAG_VALID_SPAN.encode(self)?;
 163         span.lo.encode(self)?;
 164
 165         // Encode length which is usually less than span.hi and profits more
 166         // from the variable-length integer encoding that we use.
 167         let len = span.hi - span.lo;
 168         len.encode(self)
 169
 170         // Don't encode the expansion context.
 171     }
 172 }
 173
 174 impl<'a, 'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'a, 'tcx> {
 175     #[inline]
 176     fn specialized_encode(&mut self, def_id: &LocalDefId) -> Result<(), Self::Error> {
 177         self.specialized_encode(&def_id.to_def_id())
 178     }
 179 }
 180
 181 impl<'a, 'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'a, 'tcx> {
 182     fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
 183         ty_codec::encode_with_shorthand(self, ty, |ecx| &mut ecx.type_shorthands)
 184     }
 185 }
 186
 187 impl<'a, 'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'a, 'tcx> {
 188     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
 189         use std::collections::hash_map::Entry;
 190         let index = match self.interpret_allocs.entry(*alloc_id) {
 191             Entry::Occupied(e) => *e.get(),
 192             Entry::Vacant(e) => {
 193                 let idx = self.interpret_allocs_inverse.len();
 194                 self.interpret_allocs_inverse.push(*alloc_id);
 195                 e.insert(idx);
 196                 idx
 197             },
 198         };
 199
 200         index.encode(self)
 201     }
 202 }
 203
 204 impl<'a, 'tcx> SpecializedEncoder<ty::GenericPredicates<'tcx>> for EncodeContext<'a, 'tcx> {
 205     fn specialized_encode(&mut self,
 206                           predicates: &ty::GenericPredicates<'tcx>)
 207                           -> Result<(), Self::Error> {
 208         ty_codec::encode_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
 209     }
 210 }
 211
 212 impl<'a, 'tcx> SpecializedEncoder<Fingerprint> for EncodeContext<'a, 'tcx> {
 213     fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> {
 214         f.encode_opaque(&mut self.opaque)
 215     }
 216 }
 217
 218 impl<'a, 'tcx, T: Encodable> SpecializedEncoder<mir::ClearCrossCrate<T>>
 219 for EncodeContext<'a, 'tcx> {
 220     fn specialized_encode(&mut self,
 221                           _: &mir::ClearCrossCrate<T>)
 222                           -> Result<(), Self::Error> {
 223         Ok(())
 224     }
 225 }
 226
 227 impl<'a, 'tcx> TyEncoder for EncodeContext<'a, 'tcx> {
 228     fn position(&self) -> usize {
 229         self.opaque.position()
 230     }
 231 }
 232
 233 impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 234
 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     // Encodes something that corresponds to a single DepNode::GlobalMetaData
 302     // and registers the Fingerprint in the `metadata_hashes` map.
 303     pub fn tracked<'x, DATA, R>(&'x mut self,
 304                                 op: fn(&mut IsolatedEncoder<'x, 'a, 'tcx>, DATA) -> R,
 305                                 data: DATA)
 306                                 -> R {
 307         op(&mut IsolatedEncoder::new(self), data)
 308     }
 309
 310     fn encode_info_for_items(&mut self) -> Index {
 311         let krate = self.tcx.hir().krate();
 312         let mut index = IndexBuilder::new(self);
 313         let vis = Spanned { span: syntax_pos::DUMMY_SP, node: hir::VisibilityKind::Public };
 314         index.record(DefId::local(CRATE_DEF_INDEX),
 315                      IsolatedEncoder::encode_info_for_mod,
 316                      FromId(CRATE_NODE_ID, (&krate.module, &krate.attrs, &vis)));
 317         let mut visitor = EncodeVisitor { index };
 318         krate.visit_all_item_likes(&mut visitor.as_deep_visitor());
 319         for macro_def in &krate.exported_macros {
 320             visitor.visit_macro_def(macro_def);
 321         }
 322         visitor.index.into_items()
 323     }
 324
 325     fn encode_def_path_table(&mut self) -> Lazy<DefPathTable> {
 326         let definitions = self.tcx.hir().definitions();
 327         self.lazy(definitions.def_path_table())
 328     }
 329
 330     fn encode_source_map(&mut self) -> LazySeq<syntax_pos::SourceFile> {
 331         let source_map = self.tcx.sess.source_map();
 332         let all_source_files = source_map.files();
 333
 334         let (working_dir, _cwd_remapped) = self.tcx.sess.working_dir.clone();
 335
 336         let adapted = all_source_files.iter()
 337             .filter(|source_file| {
 338                 // No need to re-export imported source_files, as any downstream
 339                 // crate will import them from their original source.
 340                 !source_file.is_imported()
 341             })
 342             .map(|source_file| {
 343                 match source_file.name {
 344                     // This path of this SourceFile has been modified by
 345                     // path-remapping, so we use it verbatim (and avoid
 346                     // cloning the whole map in the process).
 347                     _  if source_file.name_was_remapped => source_file.clone(),
 348
 349                     // Otherwise expand all paths to absolute paths because
 350                     // any relative paths are potentially relative to a
 351                     // wrong directory.
 352                     FileName::Real(ref name) => {
 353                         let mut adapted = (**source_file).clone();
 354                         adapted.name = Path::new(&working_dir).join(name).into();
 355                         adapted.name_hash = {
 356                             let mut hasher: StableHasher<u128> = StableHasher::new();
 357                             adapted.name.hash(&mut hasher);
 358                             hasher.finish()
 359                         };
 360                         Lrc::new(adapted)
 361                     },
 362
 363                     // expanded code, not from a file
 364                     _ => source_file.clone(),
 365                 }
 366             })
 367             .collect::<Vec<_>>();
 368
 369         self.lazy_seq_ref(adapted.iter().map(|rc| &**rc))
 370     }
 371
 372     fn encode_crate_root(&mut self) -> Lazy<CrateRoot> {
 373         let mut i = self.position();
 374
 375         let crate_deps = self.tracked(IsolatedEncoder::encode_crate_deps, ());
 376         let dylib_dependency_formats = self.tracked(
 377             IsolatedEncoder::encode_dylib_dependency_formats,
 378             ());
 379         let dep_bytes = self.position() - i;
 380
 381         // Encode the lib features.
 382         i = self.position();
 383         let lib_features = self.tracked(IsolatedEncoder::encode_lib_features, ());
 384         let lib_feature_bytes = self.position() - i;
 385
 386         // Encode the language items.
 387         i = self.position();
 388         let lang_items = self.tracked(IsolatedEncoder::encode_lang_items, ());
 389         let lang_items_missing = self.tracked(
 390             IsolatedEncoder::encode_lang_items_missing,
 391             ());
 392         let lang_item_bytes = self.position() - i;
 393
 394         // Encode the native libraries used
 395         i = self.position();
 396         let native_libraries = self.tracked(
 397             IsolatedEncoder::encode_native_libraries,
 398             ());
 399         let native_lib_bytes = self.position() - i;
 400
 401         let foreign_modules = self.tracked(
 402             IsolatedEncoder::encode_foreign_modules,
 403             ());
 404
 405         // Encode source_map
 406         i = self.position();
 407         let source_map = self.encode_source_map();
 408         let source_map_bytes = self.position() - i;
 409
 410         // Encode DefPathTable
 411         i = self.position();
 412         let def_path_table = self.encode_def_path_table();
 413         let def_path_table_bytes = self.position() - i;
 414
 415         // Encode the def IDs of impls, for coherence checking.
 416         i = self.position();
 417         let impls = self.tracked(IsolatedEncoder::encode_impls, ());
 418         let impl_bytes = self.position() - i;
 419
 420         // Encode exported symbols info.
 421         i = self.position();
 422         let exported_symbols = self.tcx.exported_symbols(LOCAL_CRATE);
 423         let exported_symbols = self.tracked(
 424             IsolatedEncoder::encode_exported_symbols,
 425             &exported_symbols);
 426         let exported_symbols_bytes = self.position() - i;
 427
 428         let tcx = self.tcx;
 429
 430         // Encode the items.
 431         i = self.position();
 432         let items = self.encode_info_for_items();
 433         let item_bytes = self.position() - i;
 434
 435         // Encode the allocation index
 436         let interpret_alloc_index = {
 437             let mut interpret_alloc_index = Vec::new();
 438             let mut n = 0;
 439             trace!("beginning to encode alloc ids");
 440             loop {
 441                 let new_n = self.interpret_allocs_inverse.len();
 442                 // if we have found new ids, serialize those, too
 443                 if n == new_n {
 444                     // otherwise, abort
 445                     break;
 446                 }
 447                 trace!("encoding {} further alloc ids", new_n - n);
 448                 for idx in n..new_n {
 449                     let id = self.interpret_allocs_inverse[idx];
 450                     let pos = self.position() as u32;
 451                     interpret_alloc_index.push(pos);
 452                     interpret::specialized_encode_alloc_id(
 453                         self,
 454                         tcx,
 455                         id,
 456                     ).unwrap();
 457                 }
 458                 n = new_n;
 459             }
 460             self.lazy_seq(interpret_alloc_index)
 461         };
 462
 463         // Index the items
 464         i = self.position();
 465         let index = items.write_index(&mut self.opaque);
 466         let index_bytes = self.position() - i;
 467
 468         let attrs = tcx.hir().krate_attrs();
 469         let is_proc_macro = tcx.sess.crate_types.borrow().contains(&CrateType::ProcMacro);
 470         let has_default_lib_allocator = attr::contains_name(&attrs, "default_lib_allocator");
 471         let has_global_allocator = *tcx.sess.has_global_allocator.get();
 472         let has_panic_handler = *tcx.sess.has_panic_handler.try_get().unwrap_or(&false);
 473
 474         let root = self.lazy(&CrateRoot {
 475             name: tcx.crate_name(LOCAL_CRATE),
 476             extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
 477             triple: tcx.sess.opts.target_triple.clone(),
 478             hash: tcx.crate_hash(LOCAL_CRATE),
 479             disambiguator: tcx.sess.local_crate_disambiguator(),
 480             panic_strategy: tcx.sess.panic_strategy(),
 481             edition: hygiene::default_edition(),
 482             has_global_allocator: has_global_allocator,
 483             has_panic_handler: has_panic_handler,
 484             has_default_lib_allocator: has_default_lib_allocator,
 485             plugin_registrar_fn: tcx.sess
 486                 .plugin_registrar_fn
 487                 .get()
 488                 .map(|id| tcx.hir().local_def_id(id).index),
 489             proc_macro_decls_static: if is_proc_macro {
 490                 let id = tcx.sess.proc_macro_decls_static.get().unwrap();
 491                 Some(tcx.hir().local_def_id(id).index)
 492             } else {
 493                 None
 494             },
 495
 496             compiler_builtins: attr::contains_name(&attrs, "compiler_builtins"),
 497             needs_allocator: attr::contains_name(&attrs, "needs_allocator"),
 498             needs_panic_runtime: attr::contains_name(&attrs, "needs_panic_runtime"),
 499             no_builtins: attr::contains_name(&attrs, "no_builtins"),
 500             panic_runtime: attr::contains_name(&attrs, "panic_runtime"),
 501             profiler_runtime: attr::contains_name(&attrs, "profiler_runtime"),
 502             sanitizer_runtime: attr::contains_name(&attrs, "sanitizer_runtime"),
 503
 504             crate_deps,
 505             dylib_dependency_formats,
 506             lib_features,
 507             lang_items,
 508             lang_items_missing,
 509             native_libraries,
 510             foreign_modules,
 511             source_map,
 512             def_path_table,
 513             impls,
 514             exported_symbols,
 515             interpret_alloc_index,
 516             index,
 517         });
 518
 519         let total_bytes = self.position();
 520
 521         if self.tcx.sess.meta_stats() {
 522             let mut zero_bytes = 0;
 523             for e in self.opaque.data.iter() {
 524                 if *e == 0 {
 525                     zero_bytes += 1;
 526                 }
 527             }
 528
 529             println!("metadata stats:");
 530             println!("             dep bytes: {}", dep_bytes);
 531             println!("     lib feature bytes: {}", lib_feature_bytes);
 532             println!("       lang item bytes: {}", lang_item_bytes);
 533             println!("          native bytes: {}", native_lib_bytes);
 534             println!("         source_map bytes: {}", source_map_bytes);
 535             println!("            impl bytes: {}", impl_bytes);
 536             println!("    exp. symbols bytes: {}", exported_symbols_bytes);
 537             println!("  def-path table bytes: {}", def_path_table_bytes);
 538             println!("            item bytes: {}", item_bytes);
 539             println!("           index bytes: {}", index_bytes);
 540             println!("            zero bytes: {}", zero_bytes);
 541             println!("           total bytes: {}", total_bytes);
 542         }
 543
 544         root
 545     }
 546 }
 547
 548 // These are methods for encoding various things. They are meant to be used with
 549 // IndexBuilder::record() and EncodeContext::tracked(). They actually
 550 // would not have to be methods of IsolatedEncoder (free standing functions
 551 // taking IsolatedEncoder as first argument would be just fine) but by making
 552 // them methods we don't have to repeat the lengthy `<'a, 'b: 'a, 'tcx: 'b>`
 553 // clause again and again.
 554 impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
 555     fn encode_variances_of(&mut self, def_id: DefId) -> LazySeq<ty::Variance> {
 556         debug!("IsolatedEncoder::encode_variances_of({:?})", def_id);
 557         let tcx = self.tcx;
 558         self.lazy_seq_from_slice(&tcx.variances_of(def_id))
 559     }
 560
 561     fn encode_item_type(&mut self, def_id: DefId) -> Lazy<Ty<'tcx>> {
 562         let tcx = self.tcx;
 563         let ty = tcx.type_of(def_id);
 564         debug!("IsolatedEncoder::encode_item_type({:?}) => {:?}", def_id, ty);
 565         self.lazy(&ty)
 566     }
 567
 568     /// Encode data for the given variant of the given ADT. The
 569     /// index of the variant is untracked: this is ok because we
 570     /// will have to lookup the adt-def by its id, and that gives us
 571     /// the right to access any information in the adt-def (including,
 572     /// e.g., the length of the various vectors).
 573     fn encode_enum_variant_info(&mut self,
 574                                 (enum_did, Untracked(index)): (DefId, Untracked<VariantIdx>))
 575                                 -> Entry<'tcx> {
 576         let tcx = self.tcx;
 577         let def = tcx.adt_def(enum_did);
 578         let variant = &def.variants[index];
 579         let def_id = variant.did;
 580         debug!("IsolatedEncoder::encode_enum_variant_info({:?})", def_id);
 581
 582         let data = VariantData {
 583             ctor_kind: variant.ctor_kind,
 584             discr: variant.discr,
 585             struct_ctor: None,
 586             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 587                 Some(self.lazy(&tcx.fn_sig(def_id)))
 588             } else {
 589                 None
 590             }
 591         };
 592
 593         let enum_id = tcx.hir().as_local_node_id(enum_did).unwrap();
 594         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 595
 596         Entry {
 597             kind: EntryKind::Variant(self.lazy(&data)),
 598             visibility: self.lazy(&ty::Visibility::from_hir(enum_vis, enum_id, tcx)),
 599             span: self.lazy(&tcx.def_span(def_id)),
 600             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
 601             children: self.lazy_seq(variant.fields.iter().map(|f| {
 602                 assert!(f.did.is_local());
 603                 f.did.index
 604             })),
 605             stability: self.encode_stability(def_id),
 606             deprecation: self.encode_deprecation(def_id),
 607
 608             ty: Some(self.encode_item_type(def_id)),
 609             inherent_impls: LazySeq::empty(),
 610             variances: if variant.ctor_kind == CtorKind::Fn {
 611                 self.encode_variances_of(def_id)
 612             } else {
 613                 LazySeq::empty()
 614             },
 615             generics: Some(self.encode_generics(def_id)),
 616             predicates: Some(self.encode_predicates(def_id)),
 617             predicates_defined_on: None,
 618
 619             mir: self.encode_optimized_mir(def_id),
 620         }
 621     }
 622
 623     fn encode_info_for_mod(&mut self,
 624                            FromId(id, (md, attrs, vis)): FromId<(&hir::Mod,
 625                                                                  &[ast::Attribute],
 626                                                                  &hir::Visibility)>)
 627                            -> Entry<'tcx> {
 628         let tcx = self.tcx;
 629         let def_id = tcx.hir().local_def_id(id);
 630         debug!("IsolatedEncoder::encode_info_for_mod({:?})", def_id);
 631
 632         let data = ModData {
 633             reexports: match tcx.module_exports(def_id) {
 634                 Some(ref exports) => self.lazy_seq_from_slice(exports.as_slice()),
 635                 _ => LazySeq::empty(),
 636             },
 637         };
 638
 639         Entry {
 640             kind: EntryKind::Mod(self.lazy(&data)),
 641             visibility: self.lazy(&ty::Visibility::from_hir(vis, id, tcx)),
 642             span: self.lazy(&tcx.def_span(def_id)),
 643             attributes: self.encode_attributes(attrs),
 644             children: self.lazy_seq(md.item_ids.iter().map(|item_id| {
 645                 tcx.hir().local_def_id(item_id.id).index
 646             })),
 647             stability: self.encode_stability(def_id),
 648             deprecation: self.encode_deprecation(def_id),
 649
 650             ty: None,
 651             inherent_impls: LazySeq::empty(),
 652             variances: LazySeq::empty(),
 653             generics: None,
 654             predicates: None,
 655             predicates_defined_on: None,
 656
 657             mir: None
 658         }
 659     }
 660
 661     /// Encode data for the given field of the given variant of the
 662     /// given ADT. The indices of the variant/field are untracked:
 663     /// this is ok because we will have to lookup the adt-def by its
 664     /// id, and that gives us the right to access any information in
 665     /// the adt-def (including, e.g., the length of the various
 666     /// vectors).
 667     fn encode_field(&mut self,
 668                     (adt_def_id, Untracked((variant_index, field_index))): (DefId,
 669                                                                             Untracked<(VariantIdx,
 670                                                                                        usize)>))
 671                     -> Entry<'tcx> {
 672         let tcx = self.tcx;
 673         let variant = &tcx.adt_def(adt_def_id).variants[variant_index];
 674         let field = &variant.fields[field_index];
 675
 676         let def_id = field.did;
 677         debug!("IsolatedEncoder::encode_field({:?})", def_id);
 678
 679         let variant_id = tcx.hir().as_local_node_id(variant.did).unwrap();
 680         let variant_data = tcx.hir().expect_variant_data(variant_id);
 681
 682         Entry {
 683             kind: EntryKind::Field,
 684             visibility: self.lazy(&field.vis),
 685             span: self.lazy(&tcx.def_span(def_id)),
 686             attributes: self.encode_attributes(&variant_data.fields()[field_index].attrs),
 687             children: LazySeq::empty(),
 688             stability: self.encode_stability(def_id),
 689             deprecation: self.encode_deprecation(def_id),
 690
 691             ty: Some(self.encode_item_type(def_id)),
 692             inherent_impls: LazySeq::empty(),
 693             variances: LazySeq::empty(),
 694             generics: Some(self.encode_generics(def_id)),
 695             predicates: Some(self.encode_predicates(def_id)),
 696             predicates_defined_on: None,
 697
 698             mir: None,
 699         }
 700     }
 701
 702     fn encode_struct_ctor(&mut self, (adt_def_id, def_id): (DefId, DefId)) -> Entry<'tcx> {
 703         debug!("IsolatedEncoder::encode_struct_ctor({:?})", def_id);
 704         let tcx = self.tcx;
 705         let adt_def = tcx.adt_def(adt_def_id);
 706         let variant = adt_def.non_enum_variant();
 707
 708         let data = VariantData {
 709             ctor_kind: variant.ctor_kind,
 710             discr: variant.discr,
 711             struct_ctor: Some(def_id.index),
 712             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 713                 Some(self.lazy(&tcx.fn_sig(def_id)))
 714             } else {
 715                 None
 716             }
 717         };
 718
 719         let struct_id = tcx.hir().as_local_node_id(adt_def_id).unwrap();
 720         let struct_vis = &tcx.hir().expect_item(struct_id).vis;
 721         let mut ctor_vis = ty::Visibility::from_hir(struct_vis, struct_id, tcx);
 722         for field in &variant.fields {
 723             if ctor_vis.is_at_least(field.vis, tcx) {
 724                 ctor_vis = field.vis;
 725             }
 726         }
 727
 728         // If the structure is marked as non_exhaustive then lower the visibility
 729         // to within the crate.
 730         if adt_def.non_enum_variant().is_field_list_non_exhaustive() &&
 731             ctor_vis == ty::Visibility::Public
 732         {
 733             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 734         }
 735
 736         let repr_options = get_repr_options(&tcx, adt_def_id);
 737
 738         Entry {
 739             kind: EntryKind::Struct(self.lazy(&data), repr_options),
 740             visibility: self.lazy(&ctor_vis),
 741             span: self.lazy(&tcx.def_span(def_id)),
 742             attributes: LazySeq::empty(),
 743             children: LazySeq::empty(),
 744             stability: self.encode_stability(def_id),
 745             deprecation: self.encode_deprecation(def_id),
 746
 747             ty: Some(self.encode_item_type(def_id)),
 748             inherent_impls: LazySeq::empty(),
 749             variances: if variant.ctor_kind == CtorKind::Fn {
 750                 self.encode_variances_of(def_id)
 751             } else {
 752                 LazySeq::empty()
 753             },
 754             generics: Some(self.encode_generics(def_id)),
 755             predicates: Some(self.encode_predicates(def_id)),
 756             predicates_defined_on: None,
 757
 758             mir: self.encode_optimized_mir(def_id),
 759         }
 760     }
 761
 762     fn encode_generics(&mut self, def_id: DefId) -> Lazy<ty::Generics> {
 763         debug!("IsolatedEncoder::encode_generics({:?})", def_id);
 764         let tcx = self.tcx;
 765         self.lazy(tcx.generics_of(def_id))
 766     }
 767
 768     fn encode_predicates(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 769         debug!("IsolatedEncoder::encode_predicates({:?})", def_id);
 770         let tcx = self.tcx;
 771         self.lazy(&tcx.predicates_of(def_id))
 772     }
 773
 774     fn encode_predicates_defined_on(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 775         debug!("IsolatedEncoder::encode_predicates_defined_on({:?})", def_id);
 776         let tcx = self.tcx;
 777         self.lazy(&tcx.predicates_defined_on(def_id))
 778     }
 779
 780     fn encode_info_for_trait_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 781         debug!("IsolatedEncoder::encode_info_for_trait_item({:?})", def_id);
 782         let tcx = self.tcx;
 783
 784         let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
 785         let ast_item = tcx.hir().expect_trait_item(node_id);
 786         let trait_item = tcx.associated_item(def_id);
 787
 788         let container = match trait_item.defaultness {
 789             hir::Defaultness::Default { has_value: true } =>
 790                 AssociatedContainer::TraitWithDefault,
 791             hir::Defaultness::Default { has_value: false } =>
 792                 AssociatedContainer::TraitRequired,
 793             hir::Defaultness::Final =>
 794                 span_bug!(ast_item.span, "traits cannot have final items"),
 795         };
 796
 797         let kind = match trait_item.kind {
 798             ty::AssociatedKind::Const => {
 799                 let const_qualif =
 800                     if let hir::TraitItemKind::Const(_, Some(body)) = ast_item.node {
 801                         self.const_qualif(0, body)
 802                     } else {
 803                         ConstQualif { mir: 0, ast_promotable: false }
 804                     };
 805
 806                 let rendered =
 807                     hir::print::to_string(self.tcx.hir(), |s| s.print_trait_item(ast_item));
 808                 let rendered_const = self.lazy(&RenderedConst(rendered));
 809
 810                 EntryKind::AssociatedConst(container, const_qualif, rendered_const)
 811             }
 812             ty::AssociatedKind::Method => {
 813                 let fn_data = if let hir::TraitItemKind::Method(_, ref m) = ast_item.node {
 814                     let arg_names = match *m {
 815                         hir::TraitMethod::Required(ref names) => {
 816                             self.encode_fn_arg_names(names)
 817                         }
 818                         hir::TraitMethod::Provided(body) => {
 819                             self.encode_fn_arg_names_for_body(body)
 820                         }
 821                     };
 822                     FnData {
 823                         constness: hir::Constness::NotConst,
 824                         arg_names,
 825                         sig: self.lazy(&tcx.fn_sig(def_id)),
 826                     }
 827                 } else {
 828                     bug!()
 829                 };
 830                 EntryKind::Method(self.lazy(&MethodData {
 831                     fn_data,
 832                     container,
 833                     has_self: trait_item.method_has_self_argument,
 834                 }))
 835             }
 836             ty::AssociatedKind::Type => EntryKind::AssociatedType(container),
 837             ty::AssociatedKind::Existential =>
 838                 span_bug!(ast_item.span, "existential type in trait"),
 839         };
 840
 841         Entry {
 842             kind,
 843             visibility: self.lazy(&trait_item.vis),
 844             span: self.lazy(&ast_item.span),
 845             attributes: self.encode_attributes(&ast_item.attrs),
 846             children: LazySeq::empty(),
 847             stability: self.encode_stability(def_id),
 848             deprecation: self.encode_deprecation(def_id),
 849
 850             ty: match trait_item.kind {
 851                 ty::AssociatedKind::Const |
 852                 ty::AssociatedKind::Method => {
 853                     Some(self.encode_item_type(def_id))
 854                 }
 855                 ty::AssociatedKind::Type => {
 856                     if trait_item.defaultness.has_value() {
 857                         Some(self.encode_item_type(def_id))
 858                     } else {
 859                         None
 860                     }
 861                 }
 862                 ty::AssociatedKind::Existential => unreachable!(),
 863             },
 864             inherent_impls: LazySeq::empty(),
 865             variances: if trait_item.kind == ty::AssociatedKind::Method {
 866                 self.encode_variances_of(def_id)
 867             } else {
 868                 LazySeq::empty()
 869             },
 870             generics: Some(self.encode_generics(def_id)),
 871             predicates: Some(self.encode_predicates(def_id)),
 872             predicates_defined_on: None,
 873
 874             mir: self.encode_optimized_mir(def_id),
 875         }
 876     }
 877
 878     fn metadata_output_only(&self) -> bool {
 879         // MIR optimisation can be skipped when we're just interested in the metadata.
 880         !self.tcx.sess.opts.output_types.should_codegen()
 881     }
 882
 883     fn const_qualif(&self, mir: u8, body_id: hir::BodyId) -> ConstQualif {
 884         let body_owner_def_id = self.tcx.hir().body_owner_def_id(body_id);
 885         let ast_promotable = self.tcx.const_is_rvalue_promotable_to_static(body_owner_def_id);
 886
 887         ConstQualif { mir, ast_promotable }
 888     }
 889
 890     fn encode_info_for_impl_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 891         debug!("IsolatedEncoder::encode_info_for_impl_item({:?})", def_id);
 892         let tcx = self.tcx;
 893
 894         let node_id = self.tcx.hir().as_local_node_id(def_id).unwrap();
 895         let ast_item = self.tcx.hir().expect_impl_item(node_id);
 896         let impl_item = self.tcx.associated_item(def_id);
 897
 898         let container = match impl_item.defaultness {
 899             hir::Defaultness::Default { has_value: true } => AssociatedContainer::ImplDefault,
 900             hir::Defaultness::Final => AssociatedContainer::ImplFinal,
 901             hir::Defaultness::Default { has_value: false } =>
 902                 span_bug!(ast_item.span, "impl items always have values (currently)"),
 903         };
 904
 905         let kind = match impl_item.kind {
 906             ty::AssociatedKind::Const => {
 907                 if let hir::ImplItemKind::Const(_, body_id) = ast_item.node {
 908                     let mir = self.tcx.at(ast_item.span).mir_const_qualif(def_id).0;
 909
 910                     EntryKind::AssociatedConst(container,
 911                         self.const_qualif(mir, body_id),
 912                         self.encode_rendered_const_for_body(body_id))
 913                 } else {
 914                     bug!()
 915                 }
 916             }
 917             ty::AssociatedKind::Method => {
 918                 let fn_data = if let hir::ImplItemKind::Method(ref sig, body) = ast_item.node {
 919                     FnData {
 920                         constness: sig.header.constness,
 921                         arg_names: self.encode_fn_arg_names_for_body(body),
 922                         sig: self.lazy(&tcx.fn_sig(def_id)),
 923                     }
 924                 } else {
 925                     bug!()
 926                 };
 927                 EntryKind::Method(self.lazy(&MethodData {
 928                     fn_data,
 929                     container,
 930                     has_self: impl_item.method_has_self_argument,
 931                 }))
 932             }
 933             ty::AssociatedKind::Existential => EntryKind::AssociatedExistential(container),
 934             ty::AssociatedKind::Type => EntryKind::AssociatedType(container)
 935         };
 936
 937         let mir =
 938             match ast_item.node {
 939                 hir::ImplItemKind::Const(..) => true,
 940                 hir::ImplItemKind::Method(ref sig, _) => {
 941                     let generics = self.tcx.generics_of(def_id);
 942                     let needs_inline = (generics.requires_monomorphization(self.tcx) ||
 943                                         tcx.codegen_fn_attrs(def_id).requests_inline()) &&
 944                                         !self.metadata_output_only();
 945                     let is_const_fn = sig.header.constness == hir::Constness::Const;
 946                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
 947                     needs_inline || is_const_fn || always_encode_mir
 948                 },
 949                 hir::ImplItemKind::Existential(..) |
 950                 hir::ImplItemKind::Type(..) => false,
 951             };
 952
 953         Entry {
 954             kind,
 955             visibility: self.lazy(&impl_item.vis),
 956             span: self.lazy(&ast_item.span),
 957             attributes: self.encode_attributes(&ast_item.attrs),
 958             children: LazySeq::empty(),
 959             stability: self.encode_stability(def_id),
 960             deprecation: self.encode_deprecation(def_id),
 961
 962             ty: Some(self.encode_item_type(def_id)),
 963             inherent_impls: LazySeq::empty(),
 964             variances: if impl_item.kind == ty::AssociatedKind::Method {
 965                 self.encode_variances_of(def_id)
 966             } else {
 967                 LazySeq::empty()
 968             },
 969             generics: Some(self.encode_generics(def_id)),
 970             predicates: Some(self.encode_predicates(def_id)),
 971             predicates_defined_on: None,
 972
 973             mir: if mir { self.encode_optimized_mir(def_id) } else { None },
 974         }
 975     }
 976
 977     fn encode_fn_arg_names_for_body(&mut self, body_id: hir::BodyId)
 978                                     -> LazySeq<ast::Name> {
 979         self.tcx.dep_graph.with_ignore(|| {
 980             let body = self.tcx.hir().body(body_id);
 981             self.lazy_seq(body.arguments.iter().map(|arg| {
 982                 match arg.pat.node {
 983                     PatKind::Binding(_, _, ident, _) => ident.name,
 984                     _ => keywords::Invalid.name(),
 985                 }
 986             }))
 987         })
 988     }
 989
 990     fn encode_fn_arg_names(&mut self, param_names: &[ast::Ident]) -> LazySeq<ast::Name> {
 991         self.lazy_seq(param_names.iter().map(|ident| ident.name))
 992     }
 993
 994     fn encode_optimized_mir(&mut self, def_id: DefId) -> Option<Lazy<mir::Mir<'tcx>>> {
 995         debug!("EntryBuilder::encode_mir({:?})", def_id);
 996         if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id) {
 997             let mir = self.tcx.optimized_mir(def_id);
 998             Some(self.lazy(&mir))
 999         } else {
1000             None
1001         }
1002     }
1003
1004     // Encodes the inherent implementations of a structure, enumeration, or trait.
1005     fn encode_inherent_implementations(&mut self, def_id: DefId) -> LazySeq<DefIndex> {
1006         debug!("IsolatedEncoder::encode_inherent_implementations({:?})", def_id);
1007         let implementations = self.tcx.inherent_impls(def_id);
1008         if implementations.is_empty() {
1009             LazySeq::empty()
1010         } else {
1011             self.lazy_seq(implementations.iter().map(|&def_id| {
1012                 assert!(def_id.is_local());
1013                 def_id.index
1014             }))
1015         }
1016     }
1017
1018     fn encode_stability(&mut self, def_id: DefId) -> Option<Lazy<attr::Stability>> {
1019         debug!("IsolatedEncoder::encode_stability({:?})", def_id);
1020         self.tcx.lookup_stability(def_id).map(|stab| self.lazy(stab))
1021     }
1022
1023     fn encode_deprecation(&mut self, def_id: DefId) -> Option<Lazy<attr::Deprecation>> {
1024         debug!("IsolatedEncoder::encode_deprecation({:?})", def_id);
1025         self.tcx.lookup_deprecation(def_id).map(|depr| self.lazy(&depr))
1026     }
1027
1028     fn encode_rendered_const_for_body(&mut self, body_id: hir::BodyId) -> Lazy<RenderedConst> {
1029         let body = self.tcx.hir().body(body_id);
1030         let rendered = hir::print::to_string(self.tcx.hir(), |s| s.print_expr(&body.value));
1031         let rendered_const = &RenderedConst(rendered);
1032         self.lazy(rendered_const)
1033     }
1034
1035     fn encode_info_for_item(&mut self, (def_id, item): (DefId, &'tcx hir::Item)) -> Entry<'tcx> {
1036         let tcx = self.tcx;
1037
1038         debug!("IsolatedEncoder::encode_info_for_item({:?})", def_id);
1039
1040         let kind = match item.node {
1041             hir::ItemKind::Static(_, hir::MutMutable, _) => EntryKind::MutStatic,
1042             hir::ItemKind::Static(_, hir::MutImmutable, _) => EntryKind::ImmStatic,
1043             hir::ItemKind::Const(_, body_id) => {
1044                 let mir = tcx.at(item.span).mir_const_qualif(def_id).0;
1045                 EntryKind::Const(
1046                     self.const_qualif(mir, body_id),
1047                     self.encode_rendered_const_for_body(body_id)
1048                 )
1049             }
1050             hir::ItemKind::Fn(_, header, .., body) => {
1051                 let data = FnData {
1052                     constness: header.constness,
1053                     arg_names: self.encode_fn_arg_names_for_body(body),
1054                     sig: self.lazy(&tcx.fn_sig(def_id)),
1055                 };
1056
1057                 EntryKind::Fn(self.lazy(&data))
1058             }
1059             hir::ItemKind::Mod(ref m) => {
1060                 return self.encode_info_for_mod(FromId(item.id, (m, &item.attrs, &item.vis)));
1061             }
1062             hir::ItemKind::ForeignMod(_) => EntryKind::ForeignMod,
1063             hir::ItemKind::GlobalAsm(..) => EntryKind::GlobalAsm,
1064             hir::ItemKind::Ty(..) => EntryKind::Type,
1065             hir::ItemKind::Existential(..) => EntryKind::Existential,
1066             hir::ItemKind::Enum(..) => EntryKind::Enum(get_repr_options(&tcx, def_id)),
1067             hir::ItemKind::Struct(ref struct_def, _) => {
1068                 let variant = tcx.adt_def(def_id).non_enum_variant();
1069
1070                 // Encode def_ids for each field and method
1071                 // for methods, write all the stuff get_trait_method
1072                 // needs to know
1073                 let struct_ctor = if !struct_def.is_struct() {
1074                     Some(tcx.hir().local_def_id(struct_def.id()).index)
1075                 } else {
1076                     None
1077                 };
1078
1079                 let repr_options = get_repr_options(&tcx, def_id);
1080
1081                 EntryKind::Struct(self.lazy(&VariantData {
1082                     ctor_kind: variant.ctor_kind,
1083                     discr: variant.discr,
1084                     struct_ctor,
1085                     ctor_sig: None,
1086                 }), repr_options)
1087             }
1088             hir::ItemKind::Union(..) => {
1089                 let variant = tcx.adt_def(def_id).non_enum_variant();
1090                 let repr_options = get_repr_options(&tcx, def_id);
1091
1092                 EntryKind::Union(self.lazy(&VariantData {
1093                     ctor_kind: variant.ctor_kind,
1094                     discr: variant.discr,
1095                     struct_ctor: None,
1096                     ctor_sig: None,
1097                 }), repr_options)
1098             }
1099             hir::ItemKind::Impl(_, polarity, defaultness, ..) => {
1100                 let trait_ref = tcx.impl_trait_ref(def_id);
1101                 let parent = if let Some(trait_ref) = trait_ref {
1102                     let trait_def = tcx.trait_def(trait_ref.def_id);
1103                     trait_def.ancestors(tcx, def_id).nth(1).and_then(|node| {
1104                         match node {
1105                             specialization_graph::Node::Impl(parent) => Some(parent),
1106                             _ => None,
1107                         }
1108                     })
1109                 } else {
1110                     None
1111                 };
1112
1113                 // if this is an impl of `CoerceUnsized`, create its
1114                 // "unsized info", else just store None
1115                 let coerce_unsized_info =
1116                     trait_ref.and_then(|t| {
1117                         if Some(t.def_id) == tcx.lang_items().coerce_unsized_trait() {
1118                             Some(tcx.at(item.span).coerce_unsized_info(def_id))
1119                         } else {
1120                             None
1121                         }
1122                     });
1123
1124                 let data = ImplData {
1125                     polarity,
1126                     defaultness,
1127                     parent_impl: parent,
1128                     coerce_unsized_info,
1129                     trait_ref: trait_ref.map(|trait_ref| self.lazy(&trait_ref)),
1130                 };
1131
1132                 EntryKind::Impl(self.lazy(&data))
1133             }
1134             hir::ItemKind::Trait(..) |
1135             hir::ItemKind::TraitAlias(..) => {
1136                 let trait_def = tcx.trait_def(def_id);
1137                 let data = TraitData {
1138                     unsafety: trait_def.unsafety,
1139                     paren_sugar: trait_def.paren_sugar,
1140                     has_auto_impl: tcx.trait_is_auto(def_id),
1141                     is_marker: trait_def.is_marker,
1142                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
1143                 };
1144
1145                 EntryKind::Trait(self.lazy(&data))
1146             }
1147             hir::ItemKind::ExternCrate(_) |
1148             hir::ItemKind::Use(..) => bug!("cannot encode info for item {:?}", item),
1149         };
1150
1151         Entry {
1152             kind,
1153             visibility: self.lazy(&ty::Visibility::from_hir(&item.vis, item.id, tcx)),
1154             span: self.lazy(&item.span),
1155             attributes: self.encode_attributes(&item.attrs),
1156             children: match item.node {
1157                 hir::ItemKind::ForeignMod(ref fm) => {
1158                     self.lazy_seq(fm.items
1159                         .iter()
1160                         .map(|foreign_item| tcx.hir().local_def_id(foreign_item.id).index))
1161                 }
1162                 hir::ItemKind::Enum(..) => {
1163                     let def = self.tcx.adt_def(def_id);
1164                     self.lazy_seq(def.variants.iter().map(|v| {
1165                         assert!(v.did.is_local());
1166                         v.did.index
1167                     }))
1168                 }
1169                 hir::ItemKind::Struct(..) |
1170                 hir::ItemKind::Union(..) => {
1171                     let def = self.tcx.adt_def(def_id);
1172                     self.lazy_seq(def.non_enum_variant().fields.iter().map(|f| {
1173                         assert!(f.did.is_local());
1174                         f.did.index
1175                     }))
1176                 }
1177                 hir::ItemKind::Impl(..) |
1178                 hir::ItemKind::Trait(..) => {
1179                     self.lazy_seq(tcx.associated_item_def_ids(def_id).iter().map(|&def_id| {
1180                         assert!(def_id.is_local());
1181                         def_id.index
1182                     }))
1183                 }
1184                 _ => LazySeq::empty(),
1185             },
1186             stability: self.encode_stability(def_id),
1187             deprecation: self.encode_deprecation(def_id),
1188
1189             ty: match item.node {
1190                 hir::ItemKind::Static(..) |
1191                 hir::ItemKind::Const(..) |
1192                 hir::ItemKind::Fn(..) |
1193                 hir::ItemKind::Ty(..) |
1194                 hir::ItemKind::Existential(..) |
1195                 hir::ItemKind::Enum(..) |
1196                 hir::ItemKind::Struct(..) |
1197                 hir::ItemKind::Union(..) |
1198                 hir::ItemKind::Impl(..) => Some(self.encode_item_type(def_id)),
1199                 _ => None,
1200             },
1201             inherent_impls: self.encode_inherent_implementations(def_id),
1202             variances: match item.node {
1203                 hir::ItemKind::Enum(..) |
1204                 hir::ItemKind::Struct(..) |
1205                 hir::ItemKind::Union(..) |
1206                 hir::ItemKind::Fn(..) => self.encode_variances_of(def_id),
1207                 _ => LazySeq::empty(),
1208             },
1209             generics: match item.node {
1210                 hir::ItemKind::Static(..) |
1211                 hir::ItemKind::Const(..) |
1212                 hir::ItemKind::Fn(..) |
1213                 hir::ItemKind::Ty(..) |
1214                 hir::ItemKind::Enum(..) |
1215                 hir::ItemKind::Struct(..) |
1216                 hir::ItemKind::Union(..) |
1217                 hir::ItemKind::Impl(..) |
1218                 hir::ItemKind::Existential(..) |
1219                 hir::ItemKind::Trait(..) => Some(self.encode_generics(def_id)),
1220                 _ => None,
1221             },
1222             predicates: match item.node {
1223                 hir::ItemKind::Static(..) |
1224                 hir::ItemKind::Const(..) |
1225                 hir::ItemKind::Fn(..) |
1226                 hir::ItemKind::Ty(..) |
1227                 hir::ItemKind::Enum(..) |
1228                 hir::ItemKind::Struct(..) |
1229                 hir::ItemKind::Union(..) |
1230                 hir::ItemKind::Impl(..) |
1231                 hir::ItemKind::Existential(..) |
1232                 hir::ItemKind::Trait(..) => Some(self.encode_predicates(def_id)),
1233                 _ => None,
1234             },
1235
1236             // The only time that `predicates_defined_on` is used (on
1237             // an external item) is for traits, during chalk lowering,
1238             // so only encode it in that case as an efficiency
1239             // hack. (No reason not to expand it in the future if
1240             // necessary.)
1241             predicates_defined_on: match item.node {
1242                 hir::ItemKind::Trait(..) => Some(self.encode_predicates_defined_on(def_id)),
1243                 _ => None, // not *wrong* for other kinds of items, but not needed
1244             },
1245
1246             mir: match item.node {
1247                 hir::ItemKind::Static(..) => {
1248                     self.encode_optimized_mir(def_id)
1249                 }
1250                 hir::ItemKind::Const(..) => self.encode_optimized_mir(def_id),
1251                 hir::ItemKind::Fn(_, header, ..) => {
1252                     let generics = tcx.generics_of(def_id);
1253                     let needs_inline =
1254                         (generics.requires_monomorphization(tcx) ||
1255                          tcx.codegen_fn_attrs(def_id).requests_inline()) &&
1256                             !self.metadata_output_only();
1257                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
1258                     if needs_inline
1259                         || header.constness == hir::Constness::Const
1260                         || always_encode_mir
1261                     {
1262                         self.encode_optimized_mir(def_id)
1263                     } else {
1264                         None
1265                     }
1266                 }
1267                 _ => None,
1268             },
1269         }
1270     }
1271
1272     /// Serialize the text of exported macros
1273     fn encode_info_for_macro_def(&mut self, macro_def: &hir::MacroDef) -> Entry<'tcx> {
1274         use syntax::print::pprust;
1275         let def_id = self.tcx.hir().local_def_id(macro_def.id);
1276         Entry {
1277             kind: EntryKind::MacroDef(self.lazy(&MacroDef {
1278                 body: pprust::tts_to_string(&macro_def.body.trees().collect::<Vec<_>>()),
1279                 legacy: macro_def.legacy,
1280             })),
1281             visibility: self.lazy(&ty::Visibility::Public),
1282             span: self.lazy(&macro_def.span),
1283             attributes: self.encode_attributes(&macro_def.attrs),
1284             stability: self.encode_stability(def_id),
1285             deprecation: self.encode_deprecation(def_id),
1286
1287             children: LazySeq::empty(),
1288             ty: None,
1289             inherent_impls: LazySeq::empty(),
1290             variances: LazySeq::empty(),
1291             generics: None,
1292             predicates: None,
1293             predicates_defined_on: None,
1294             mir: None,
1295         }
1296     }
1297
1298     fn encode_info_for_ty_param(&mut self,
1299                                 (def_id, Untracked(has_default)): (DefId, Untracked<bool>))
1300                                 -> Entry<'tcx> {
1301         debug!("IsolatedEncoder::encode_info_for_ty_param({:?})", def_id);
1302         let tcx = self.tcx;
1303         Entry {
1304             kind: EntryKind::Type,
1305             visibility: self.lazy(&ty::Visibility::Public),
1306             span: self.lazy(&tcx.def_span(def_id)),
1307             attributes: LazySeq::empty(),
1308             children: LazySeq::empty(),
1309             stability: None,
1310             deprecation: None,
1311
1312             ty: if has_default {
1313                 Some(self.encode_item_type(def_id))
1314             } else {
1315                 None
1316             },
1317             inherent_impls: LazySeq::empty(),
1318             variances: LazySeq::empty(),
1319             generics: None,
1320             predicates: None,
1321             predicates_defined_on: None,
1322
1323             mir: None,
1324         }
1325     }
1326
1327     fn encode_info_for_closure(&mut self, def_id: DefId) -> Entry<'tcx> {
1328         debug!("IsolatedEncoder::encode_info_for_closure({:?})", def_id);
1329         let tcx = self.tcx;
1330
1331         let tables = self.tcx.typeck_tables_of(def_id);
1332         let node_id = self.tcx.hir().as_local_node_id(def_id).unwrap();
1333         let hir_id = self.tcx.hir().node_to_hir_id(node_id);
1334         let kind = match tables.node_id_to_type(hir_id).sty {
1335             ty::Generator(def_id, ..) => {
1336                 let layout = self.tcx.generator_layout(def_id);
1337                 let data = GeneratorData {
1338                     layout: layout.clone(),
1339                 };
1340                 EntryKind::Generator(self.lazy(&data))
1341             }
1342
1343             ty::Closure(def_id, substs) => {
1344                 let sig = substs.closure_sig(def_id, self.tcx);
1345                 let data = ClosureData { sig: self.lazy(&sig) };
1346                 EntryKind::Closure(self.lazy(&data))
1347             }
1348
1349             _ => bug!("closure that is neither generator nor closure")
1350         };
1351
1352         Entry {
1353             kind,
1354             visibility: self.lazy(&ty::Visibility::Public),
1355             span: self.lazy(&tcx.def_span(def_id)),
1356             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
1357             children: LazySeq::empty(),
1358             stability: None,
1359             deprecation: None,
1360
1361             ty: Some(self.encode_item_type(def_id)),
1362             inherent_impls: LazySeq::empty(),
1363             variances: LazySeq::empty(),
1364             generics: Some(self.encode_generics(def_id)),
1365             predicates: None,
1366             predicates_defined_on: None,
1367
1368             mir: self.encode_optimized_mir(def_id),
1369         }
1370     }
1371
1372     fn encode_info_for_anon_const(&mut self, def_id: DefId) -> Entry<'tcx> {
1373         debug!("IsolatedEncoder::encode_info_for_anon_const({:?})", def_id);
1374         let tcx = self.tcx;
1375         let id = tcx.hir().as_local_node_id(def_id).unwrap();
1376         let body_id = tcx.hir().body_owned_by(id);
1377         let const_data = self.encode_rendered_const_for_body(body_id);
1378         let mir = tcx.mir_const_qualif(def_id).0;
1379
1380         Entry {
1381             kind: EntryKind::Const(self.const_qualif(mir, body_id), const_data),
1382             visibility: self.lazy(&ty::Visibility::Public),
1383             span: self.lazy(&tcx.def_span(def_id)),
1384             attributes: LazySeq::empty(),
1385             children: LazySeq::empty(),
1386             stability: None,
1387             deprecation: None,
1388
1389             ty: Some(self.encode_item_type(def_id)),
1390             inherent_impls: LazySeq::empty(),
1391             variances: LazySeq::empty(),
1392             generics: Some(self.encode_generics(def_id)),
1393             predicates: Some(self.encode_predicates(def_id)),
1394             predicates_defined_on: None,
1395
1396             mir: self.encode_optimized_mir(def_id),
1397         }
1398     }
1399
1400     fn encode_attributes(&mut self, attrs: &[ast::Attribute]) -> LazySeq<ast::Attribute> {
1401         // NOTE: This must use lazy_seq_from_slice(), not lazy_seq() because
1402         //       we rely on the HashStable specialization for [Attribute]
1403         //       to properly filter things out.
1404         self.lazy_seq_from_slice(attrs)
1405     }
1406
1407     fn encode_native_libraries(&mut self, _: ()) -> LazySeq<NativeLibrary> {
1408         let used_libraries = self.tcx.native_libraries(LOCAL_CRATE);
1409         self.lazy_seq(used_libraries.iter().cloned())
1410     }
1411
1412     fn encode_foreign_modules(&mut self, _: ()) -> LazySeq<ForeignModule> {
1413         let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
1414         self.lazy_seq(foreign_modules.iter().cloned())
1415     }
1416
1417     fn encode_crate_deps(&mut self, _: ()) -> LazySeq<CrateDep> {
1418         let crates = self.tcx.crates();
1419
1420         let mut deps = crates
1421             .iter()
1422             .map(|&cnum| {
1423                 let dep = CrateDep {
1424                     name: self.tcx.original_crate_name(cnum),
1425                     hash: self.tcx.crate_hash(cnum),
1426                     kind: self.tcx.dep_kind(cnum),
1427                     extra_filename: self.tcx.extra_filename(cnum),
1428                 };
1429                 (cnum, dep)
1430             })
1431             .collect::<Vec<_>>();
1432
1433         deps.sort_by_key(|&(cnum, _)| cnum);
1434
1435         {
1436             // Sanity-check the crate numbers
1437             let mut expected_cnum = 1;
1438             for &(n, _) in &deps {
1439                 assert_eq!(n, CrateNum::new(expected_cnum));
1440                 expected_cnum += 1;
1441             }
1442         }
1443
1444         // We're just going to write a list of crate 'name-hash-version's, with
1445         // the assumption that they are numbered 1 to n.
1446         // FIXME (#2166): This is not nearly enough to support correct versioning
1447         // but is enough to get transitive crate dependencies working.
1448         self.lazy_seq_ref(deps.iter().map(|&(_, ref dep)| dep))
1449     }
1450
1451     fn encode_lib_features(&mut self, _: ()) -> LazySeq<(ast::Name, Option<ast::Name>)> {
1452         let tcx = self.tcx;
1453         let lib_features = tcx.lib_features();
1454         self.lazy_seq(lib_features.to_vec())
1455     }
1456
1457     fn encode_lang_items(&mut self, _: ()) -> LazySeq<(DefIndex, usize)> {
1458         let tcx = self.tcx;
1459         let lang_items = tcx.lang_items();
1460         let lang_items = lang_items.items().iter();
1461         self.lazy_seq(lang_items.enumerate().filter_map(|(i, &opt_def_id)| {
1462             if let Some(def_id) = opt_def_id {
1463                 if def_id.is_local() {
1464                     return Some((def_id.index, i));
1465                 }
1466             }
1467             None
1468         }))
1469     }
1470
1471     fn encode_lang_items_missing(&mut self, _: ()) -> LazySeq<lang_items::LangItem> {
1472         let tcx = self.tcx;
1473         self.lazy_seq_ref(&tcx.lang_items().missing)
1474     }
1475
1476     /// Encodes an index, mapping each trait to its (local) implementations.
1477     fn encode_impls(&mut self, _: ()) -> LazySeq<TraitImpls> {
1478         debug!("IsolatedEncoder::encode_impls()");
1479         let tcx = self.tcx;
1480         let mut visitor = ImplVisitor {
1481             tcx,
1482             impls: FxHashMap::default(),
1483         };
1484         tcx.hir().krate().visit_all_item_likes(&mut visitor);
1485
1486         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
1487
1488         // Bring everything into deterministic order for hashing
1489         all_impls.sort_by_cached_key(|&(trait_def_id, _)| {
1490             tcx.def_path_hash(trait_def_id)
1491         });
1492
1493         let all_impls: Vec<_> = all_impls
1494             .into_iter()
1495             .map(|(trait_def_id, mut impls)| {
1496                 // Bring everything into deterministic order for hashing
1497                 impls.sort_by_cached_key(|&def_index| {
1498                     tcx.hir().definitions().def_path_hash(def_index)
1499                 });
1500
1501                 TraitImpls {
1502                     trait_id: (trait_def_id.krate.as_u32(), trait_def_id.index),
1503                     impls: self.lazy_seq_from_slice(&impls[..]),
1504                 }
1505             })
1506             .collect();
1507
1508         self.lazy_seq_from_slice(&all_impls[..])
1509     }
1510
1511     // Encodes all symbols exported from this crate into the metadata.
1512     //
1513     // This pass is seeded off the reachability list calculated in the
1514     // middle::reachable module but filters out items that either don't have a
1515     // symbol associated with them (they weren't translated) or if they're an FFI
1516     // definition (as that's not defined in this crate).
1517     fn encode_exported_symbols(&mut self,
1518                                exported_symbols: &[(ExportedSymbol, SymbolExportLevel)])
1519                                -> EncodedExportedSymbols {
1520         // The metadata symbol name is special. It should not show up in
1521         // downstream crates.
1522         let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
1523
1524         let lazy_seq = self.lazy_seq(exported_symbols
1525             .iter()
1526             .filter(|&&(ref exported_symbol, _)| {
1527                 match *exported_symbol {
1528                     ExportedSymbol::NoDefId(symbol_name) => {
1529                         symbol_name != metadata_symbol_name
1530                     },
1531                     _ => true,
1532                 }
1533             })
1534             .cloned());
1535
1536         EncodedExportedSymbols {
1537             len: lazy_seq.len,
1538             position: lazy_seq.position,
1539         }
1540     }
1541
1542     fn encode_dylib_dependency_formats(&mut self, _: ()) -> LazySeq<Option<LinkagePreference>> {
1543         match self.tcx.sess.dependency_formats.borrow().get(&config::CrateType::Dylib) {
1544             Some(arr) => {
1545                 self.lazy_seq(arr.iter().map(|slot| {
1546                     match *slot {
1547                         Linkage::NotLinked |
1548                         Linkage::IncludedFromDylib => None,
1549
1550                         Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
1551                         Linkage::Static => Some(LinkagePreference::RequireStatic),
1552                     }
1553                 }))
1554             }
1555             None => LazySeq::empty(),
1556         }
1557     }
1558
1559     fn encode_info_for_foreign_item(&mut self,
1560                                     (def_id, nitem): (DefId, &hir::ForeignItem))
1561                                     -> Entry<'tcx> {
1562         let tcx = self.tcx;
1563
1564         debug!("IsolatedEncoder::encode_info_for_foreign_item({:?})", def_id);
1565
1566         let kind = match nitem.node {
1567             hir::ForeignItemKind::Fn(_, ref names, _) => {
1568                 let data = FnData {
1569                     constness: hir::Constness::NotConst,
1570                     arg_names: self.encode_fn_arg_names(names),
1571                     sig: self.lazy(&tcx.fn_sig(def_id)),
1572                 };
1573                 EntryKind::ForeignFn(self.lazy(&data))
1574             }
1575             hir::ForeignItemKind::Static(_, true) => EntryKind::ForeignMutStatic,
1576             hir::ForeignItemKind::Static(_, false) => EntryKind::ForeignImmStatic,
1577             hir::ForeignItemKind::Type => EntryKind::ForeignType,
1578         };
1579
1580         Entry {
1581             kind,
1582             visibility: self.lazy(&ty::Visibility::from_hir(&nitem.vis, nitem.id, tcx)),
1583             span: self.lazy(&nitem.span),
1584             attributes: self.encode_attributes(&nitem.attrs),
1585             children: LazySeq::empty(),
1586             stability: self.encode_stability(def_id),
1587             deprecation: self.encode_deprecation(def_id),
1588
1589             ty: Some(self.encode_item_type(def_id)),
1590             inherent_impls: LazySeq::empty(),
1591             variances: match nitem.node {
1592                 hir::ForeignItemKind::Fn(..) => self.encode_variances_of(def_id),
1593                 _ => LazySeq::empty(),
1594             },
1595             generics: Some(self.encode_generics(def_id)),
1596             predicates: Some(self.encode_predicates(def_id)),
1597             predicates_defined_on: None,
1598
1599             mir: None,
1600         }
1601     }
1602 }
1603
1604 struct EncodeVisitor<'a, 'b: 'a, 'tcx: 'b> {
1605     index: IndexBuilder<'a, 'b, 'tcx>,
1606 }
1607
1608 impl<'a, 'b, 'tcx> Visitor<'tcx> for EncodeVisitor<'a, 'b, 'tcx> {
1609     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1610         NestedVisitorMap::OnlyBodies(&self.index.tcx.hir())
1611     }
1612     fn visit_expr(&mut self, ex: &'tcx hir::Expr) {
1613         intravisit::walk_expr(self, ex);
1614         self.index.encode_info_for_expr(ex);
1615     }
1616     fn visit_item(&mut self, item: &'tcx hir::Item) {
1617         intravisit::walk_item(self, item);
1618         let def_id = self.index.tcx.hir().local_def_id(item.id);
1619         match item.node {
1620             hir::ItemKind::ExternCrate(_) |
1621             hir::ItemKind::Use(..) => (), // ignore these
1622             _ => self.index.record(def_id, IsolatedEncoder::encode_info_for_item, (def_id, item)),
1623         }
1624         self.index.encode_addl_info_for_item(item);
1625     }
1626     fn visit_foreign_item(&mut self, ni: &'tcx hir::ForeignItem) {
1627         intravisit::walk_foreign_item(self, ni);
1628         let def_id = self.index.tcx.hir().local_def_id(ni.id);
1629         self.index.record(def_id,
1630                           IsolatedEncoder::encode_info_for_foreign_item,
1631                           (def_id, ni));
1632     }
1633     fn visit_variant(&mut self,
1634                      v: &'tcx hir::Variant,
1635                      g: &'tcx hir::Generics,
1636                      id: ast::NodeId) {
1637         intravisit::walk_variant(self, v, g, id);
1638
1639         if let Some(ref discr) = v.node.disr_expr {
1640             let def_id = self.index.tcx.hir().local_def_id(discr.id);
1641             self.index.record(def_id, IsolatedEncoder::encode_info_for_anon_const, def_id);
1642         }
1643     }
1644     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
1645         intravisit::walk_generics(self, generics);
1646         self.index.encode_info_for_generics(generics);
1647     }
1648     fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1649         intravisit::walk_ty(self, ty);
1650         self.index.encode_info_for_ty(ty);
1651     }
1652     fn visit_macro_def(&mut self, macro_def: &'tcx hir::MacroDef) {
1653         let def_id = self.index.tcx.hir().local_def_id(macro_def.id);
1654         self.index.record(def_id, IsolatedEncoder::encode_info_for_macro_def, macro_def);
1655     }
1656 }
1657
1658 impl<'a, 'b, 'tcx> IndexBuilder<'a, 'b, 'tcx> {
1659     fn encode_fields(&mut self, adt_def_id: DefId) {
1660         let def = self.tcx.adt_def(adt_def_id);
1661         for (variant_index, variant) in def.variants.iter_enumerated() {
1662             for (field_index, field) in variant.fields.iter().enumerate() {
1663                 self.record(field.did,
1664                             IsolatedEncoder::encode_field,
1665                             (adt_def_id, Untracked((variant_index, field_index))));
1666             }
1667         }
1668     }
1669
1670     fn encode_info_for_generics(&mut self, generics: &hir::Generics) {
1671         for param in &generics.params {
1672             match param.kind {
1673                 hir::GenericParamKind::Lifetime { .. } => {}
1674                 hir::GenericParamKind::Type { ref default, .. } => {
1675                     let def_id = self.tcx.hir().local_def_id(param.id);
1676                     let has_default = Untracked(default.is_some());
1677                     let encode_info = IsolatedEncoder::encode_info_for_ty_param;
1678                     self.record(def_id, encode_info, (def_id, has_default));
1679                 }
1680             }
1681         }
1682     }
1683
1684     fn encode_info_for_ty(&mut self, ty: &hir::Ty) {
1685         match ty.node {
1686             hir::TyKind::Array(_, ref length) => {
1687                 let def_id = self.tcx.hir().local_def_id(length.id);
1688                 self.record(def_id, IsolatedEncoder::encode_info_for_anon_const, def_id);
1689             }
1690             _ => {}
1691         }
1692     }
1693
1694     fn encode_info_for_expr(&mut self, expr: &hir::Expr) {
1695         match expr.node {
1696             hir::ExprKind::Closure(..) => {
1697                 let def_id = self.tcx.hir().local_def_id(expr.id);
1698                 self.record(def_id, IsolatedEncoder::encode_info_for_closure, def_id);
1699             }
1700             _ => {}
1701         }
1702     }
1703
1704     /// In some cases, along with the item itself, we also
1705     /// encode some sub-items. Usually we want some info from the item
1706     /// so it's easier to do that here then to wait until we would encounter
1707     /// normally in the visitor walk.
1708     fn encode_addl_info_for_item(&mut self, item: &hir::Item) {
1709         let def_id = self.tcx.hir().local_def_id(item.id);
1710         match item.node {
1711             hir::ItemKind::Static(..) |
1712             hir::ItemKind::Const(..) |
1713             hir::ItemKind::Fn(..) |
1714             hir::ItemKind::Mod(..) |
1715             hir::ItemKind::ForeignMod(..) |
1716             hir::ItemKind::GlobalAsm(..) |
1717             hir::ItemKind::ExternCrate(..) |
1718             hir::ItemKind::Use(..) |
1719             hir::ItemKind::Ty(..) |
1720             hir::ItemKind::Existential(..) |
1721             hir::ItemKind::TraitAlias(..) => {
1722                 // no sub-item recording needed in these cases
1723             }
1724             hir::ItemKind::Enum(..) => {
1725                 self.encode_fields(def_id);
1726
1727                 let def = self.tcx.adt_def(def_id);
1728                 for (i, variant) in def.variants.iter_enumerated() {
1729                     self.record(variant.did,
1730                                 IsolatedEncoder::encode_enum_variant_info,
1731                                 (def_id, Untracked(i)));
1732                 }
1733             }
1734             hir::ItemKind::Struct(ref struct_def, _) => {
1735                 self.encode_fields(def_id);
1736
1737                 // If the struct has a constructor, encode it.
1738                 if !struct_def.is_struct() {
1739                     let ctor_def_id = self.tcx.hir().local_def_id(struct_def.id());
1740                     self.record(ctor_def_id,
1741                                 IsolatedEncoder::encode_struct_ctor,
1742                                 (def_id, ctor_def_id));
1743                 }
1744             }
1745             hir::ItemKind::Union(..) => {
1746                 self.encode_fields(def_id);
1747             }
1748             hir::ItemKind::Impl(..) => {
1749                 for &trait_item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1750                     self.record(trait_item_def_id,
1751                                 IsolatedEncoder::encode_info_for_impl_item,
1752                                 trait_item_def_id);
1753                 }
1754             }
1755             hir::ItemKind::Trait(..) => {
1756                 for &item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1757                     self.record(item_def_id,
1758                                 IsolatedEncoder::encode_info_for_trait_item,
1759                                 item_def_id);
1760                 }
1761             }
1762         }
1763     }
1764 }
1765
1766 struct ImplVisitor<'a, 'tcx: 'a> {
1767     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1768     impls: FxHashMap<DefId, Vec<DefIndex>>,
1769 }
1770
1771 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for ImplVisitor<'a, 'tcx> {
1772     fn visit_item(&mut self, item: &hir::Item) {
1773         if let hir::ItemKind::Impl(..) = item.node {
1774             let impl_id = self.tcx.hir().local_def_id(item.id);
1775             if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_id) {
1776                 self.impls
1777                     .entry(trait_ref.def_id)
1778                     .or_default()
1779                     .push(impl_id.index);
1780             }
1781         }
1782     }
1783
1784     fn visit_trait_item(&mut self, _trait_item: &'v hir::TraitItem) {}
1785
1786     fn visit_impl_item(&mut self, _impl_item: &'v hir::ImplItem) {
1787         // handled in `visit_item` above
1788     }
1789 }
1790
1791 // NOTE(eddyb) The following comment was preserved for posterity, even
1792 // though it's no longer relevant as EBML (which uses nested & tagged
1793 // "documents") was replaced with a scheme that can't go out of bounds.
1794 //
1795 // And here we run into yet another obscure archive bug: in which metadata
1796 // loaded from archives may have trailing garbage bytes. Awhile back one of
1797 // our tests was failing sporadically on the macOS 64-bit builders (both nopt
1798 // and opt) by having ebml generate an out-of-bounds panic when looking at
1799 // metadata.
1800 //
1801 // Upon investigation it turned out that the metadata file inside of an rlib
1802 // (and ar archive) was being corrupted. Some compilations would generate a
1803 // metadata file which would end in a few extra bytes, while other
1804 // compilations would not have these extra bytes appended to the end. These
1805 // extra bytes were interpreted by ebml as an extra tag, so they ended up
1806 // being interpreted causing the out-of-bounds.
1807 //
1808 // The root cause of why these extra bytes were appearing was never
1809 // discovered, and in the meantime the solution we're employing is to insert
1810 // the length of the metadata to the start of the metadata. Later on this
1811 // will allow us to slice the metadata to the precise length that we just
1812 // generated regardless of trailing bytes that end up in it.
1813
1814 pub fn encode_metadata<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
1815                                  -> EncodedMetadata
1816 {
1817     let mut encoder = opaque::Encoder::new(vec![]);
1818     encoder.emit_raw_bytes(METADATA_HEADER);
1819
1820     // Will be filled with the root position after encoding everything.
1821     encoder.emit_raw_bytes(&[0, 0, 0, 0]);
1822
1823     let (root, mut result) = {
1824         let mut ecx = EncodeContext {
1825             opaque: encoder,
1826             tcx,
1827             lazy_state: LazyState::NoNode,
1828             type_shorthands: Default::default(),
1829             predicate_shorthands: Default::default(),
1830             source_file_cache: tcx.sess.source_map().files()[0].clone(),
1831             interpret_allocs: Default::default(),
1832             interpret_allocs_inverse: Default::default(),
1833         };
1834
1835         // Encode the rustc version string in a predictable location.
1836         rustc_version().encode(&mut ecx).unwrap();
1837
1838         // Encode all the entries and extra information in the crate,
1839         // culminating in the `CrateRoot` which points to all of it.
1840         let root = ecx.encode_crate_root();
1841         (root, ecx.opaque.into_inner())
1842     };
1843
1844     // Encode the root position.
1845     let header = METADATA_HEADER.len();
1846     let pos = root.position;
1847     result[header + 0] = (pos >> 24) as u8;
1848     result[header + 1] = (pos >> 16) as u8;
1849     result[header + 2] = (pos >> 8) as u8;
1850     result[header + 3] = (pos >> 0) as u8;
1851
1852     EncodedMetadata { raw_data: result }
1853 }
1854
1855 pub fn get_repr_options<'a, 'tcx, 'gcx>(tcx: &TyCtxt<'a, 'tcx, 'gcx>, did: DefId) -> ReprOptions {
1856     let ty = tcx.type_of(did);
1857     match ty.sty {
1858         ty::Adt(ref def, _) => return def.repr,
1859         _ => bug!("{} is not an ADT", ty),
1860     }
1861 }