src/librustc_metadata/encoder.rs

   1 use crate::index::Index;
   2 use crate::index_builder::{FromId, IndexBuilder, Untracked};
   3 use crate::isolated_encoder::IsolatedEncoder;
   4 use crate::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 use log::{debug, trace};
  38
  39 use rustc::hir::{self, PatKind};
  40 use rustc::hir::itemlikevisit::ItemLikeVisitor;
  41 use rustc::hir::intravisit::{Visitor, NestedVisitorMap};
  42 use rustc::hir::intravisit;
  43
  44 pub struct EncodeContext<'a, 'tcx: 'a> {
  45     opaque: opaque::Encoder,
  46     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
  47
  48     lazy_state: LazyState,
  49     type_shorthands: FxHashMap<Ty<'tcx>, usize>,
  50     predicate_shorthands: FxHashMap<ty::Predicate<'tcx>, usize>,
  51
  52     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
  53     interpret_allocs_inverse: Vec<interpret::AllocId>,
  54
  55     // This is used to speed up Span encoding.
  56     source_file_cache: Lrc<SourceFile>,
  57 }
  58
  59 macro_rules! encoder_methods {
  60     ($($name:ident($ty:ty);)*) => {
  61         $(fn $name(&mut self, value: $ty) -> Result<(), Self::Error> {
  62             self.opaque.$name(value)
  63         })*
  64     }
  65 }
  66
  67 impl<'a, 'tcx> Encoder for EncodeContext<'a, 'tcx> {
  68     type Error = <opaque::Encoder as Encoder>::Error;
  69
  70     fn emit_unit(&mut self) -> Result<(), Self::Error> {
  71         Ok(())
  72     }
  73
  74     encoder_methods! {
  75         emit_usize(usize);
  76         emit_u128(u128);
  77         emit_u64(u64);
  78         emit_u32(u32);
  79         emit_u16(u16);
  80         emit_u8(u8);
  81
  82         emit_isize(isize);
  83         emit_i128(i128);
  84         emit_i64(i64);
  85         emit_i32(i32);
  86         emit_i16(i16);
  87         emit_i8(i8);
  88
  89         emit_bool(bool);
  90         emit_f64(f64);
  91         emit_f32(f32);
  92         emit_char(char);
  93         emit_str(&str);
  94     }
  95 }
  96
  97 impl<'a, 'tcx, T> SpecializedEncoder<Lazy<T>> for EncodeContext<'a, 'tcx> {
  98     fn specialized_encode(&mut self, lazy: &Lazy<T>) -> Result<(), Self::Error> {
  99         self.emit_lazy_distance(lazy.position, Lazy::<T>::min_size())
 100     }
 101 }
 102
 103 impl<'a, 'tcx, T> SpecializedEncoder<LazySeq<T>> for EncodeContext<'a, 'tcx> {
 104     fn specialized_encode(&mut self, seq: &LazySeq<T>) -> Result<(), Self::Error> {
 105         self.emit_usize(seq.len)?;
 106         if seq.len == 0 {
 107             return Ok(());
 108         }
 109         self.emit_lazy_distance(seq.position, LazySeq::<T>::min_size(seq.len))
 110     }
 111 }
 112
 113 impl<'a, 'tcx> SpecializedEncoder<CrateNum> for EncodeContext<'a, 'tcx> {
 114     #[inline]
 115     fn specialized_encode(&mut self, cnum: &CrateNum) -> Result<(), Self::Error> {
 116         self.emit_u32(cnum.as_u32())
 117     }
 118 }
 119
 120 impl<'a, 'tcx> SpecializedEncoder<DefId> for EncodeContext<'a, 'tcx> {
 121     #[inline]
 122     fn specialized_encode(&mut self, def_id: &DefId) -> Result<(), Self::Error> {
 123         let DefId {
 124             krate,
 125             index,
 126         } = *def_id;
 127
 128         krate.encode(self)?;
 129         index.encode(self)
 130     }
 131 }
 132
 133 impl<'a, 'tcx> SpecializedEncoder<DefIndex> for EncodeContext<'a, 'tcx> {
 134     #[inline]
 135     fn specialized_encode(&mut self, def_index: &DefIndex) -> Result<(), Self::Error> {
 136         self.emit_u32(def_index.as_raw_u32())
 137     }
 138 }
 139
 140 impl<'a, 'tcx> SpecializedEncoder<Span> for EncodeContext<'a, 'tcx> {
 141     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
 142         if span.is_dummy() {
 143             return TAG_INVALID_SPAN.encode(self)
 144         }
 145
 146         let span = span.data();
 147
 148         // The Span infrastructure should make sure that this invariant holds:
 149         debug_assert!(span.lo <= span.hi);
 150
 151         if !self.source_file_cache.contains(span.lo) {
 152             let source_map = self.tcx.sess.source_map();
 153             let source_file_index = source_map.lookup_source_file_idx(span.lo);
 154             self.source_file_cache = source_map.files()[source_file_index].clone();
 155         }
 156
 157         if !self.source_file_cache.contains(span.hi) {
 158             // Unfortunately, macro expansion still sometimes generates Spans
 159             // that malformed in this way.
 160             return TAG_INVALID_SPAN.encode(self)
 161         }
 162
 163         TAG_VALID_SPAN.encode(self)?;
 164         span.lo.encode(self)?;
 165
 166         // Encode length which is usually less than span.hi and profits more
 167         // from the variable-length integer encoding that we use.
 168         let len = span.hi - span.lo;
 169         len.encode(self)
 170
 171         // Don't encode the expansion context.
 172     }
 173 }
 174
 175 impl<'a, 'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'a, 'tcx> {
 176     #[inline]
 177     fn specialized_encode(&mut self, def_id: &LocalDefId) -> Result<(), Self::Error> {
 178         self.specialized_encode(&def_id.to_def_id())
 179     }
 180 }
 181
 182 impl<'a, 'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'a, 'tcx> {
 183     fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
 184         ty_codec::encode_with_shorthand(self, ty, |ecx| &mut ecx.type_shorthands)
 185     }
 186 }
 187
 188 impl<'a, 'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'a, 'tcx> {
 189     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
 190         use std::collections::hash_map::Entry;
 191         let index = match self.interpret_allocs.entry(*alloc_id) {
 192             Entry::Occupied(e) => *e.get(),
 193             Entry::Vacant(e) => {
 194                 let idx = self.interpret_allocs_inverse.len();
 195                 self.interpret_allocs_inverse.push(*alloc_id);
 196                 e.insert(idx);
 197                 idx
 198             },
 199         };
 200
 201         index.encode(self)
 202     }
 203 }
 204
 205 impl<'a, 'tcx> SpecializedEncoder<ty::GenericPredicates<'tcx>> for EncodeContext<'a, 'tcx> {
 206     fn specialized_encode(&mut self,
 207                           predicates: &ty::GenericPredicates<'tcx>)
 208                           -> Result<(), Self::Error> {
 209         ty_codec::encode_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
 210     }
 211 }
 212
 213 impl<'a, 'tcx> SpecializedEncoder<Fingerprint> for EncodeContext<'a, 'tcx> {
 214     fn specialized_encode(&mut self, f: &Fingerprint) -> Result<(), Self::Error> {
 215         f.encode_opaque(&mut self.opaque)
 216     }
 217 }
 218
 219 impl<'a, 'tcx, T: Encodable> SpecializedEncoder<mir::ClearCrossCrate<T>>
 220 for EncodeContext<'a, 'tcx> {
 221     fn specialized_encode(&mut self,
 222                           _: &mir::ClearCrossCrate<T>)
 223                           -> Result<(), Self::Error> {
 224         Ok(())
 225     }
 226 }
 227
 228 impl<'a, 'tcx> TyEncoder for EncodeContext<'a, 'tcx> {
 229     fn position(&self) -> usize {
 230         self.opaque.position()
 231     }
 232 }
 233
 234 impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 235
 236     fn emit_node<F: FnOnce(&mut Self, usize) -> R, R>(&mut self, f: F) -> R {
 237         assert_eq!(self.lazy_state, LazyState::NoNode);
 238         let pos = self.position();
 239         self.lazy_state = LazyState::NodeStart(pos);
 240         let r = f(self, pos);
 241         self.lazy_state = LazyState::NoNode;
 242         r
 243     }
 244
 245     fn emit_lazy_distance(&mut self,
 246                           position: usize,
 247                           min_size: usize)
 248                           -> Result<(), <Self as Encoder>::Error> {
 249         let min_end = position + min_size;
 250         let distance = match self.lazy_state {
 251             LazyState::NoNode => bug!("emit_lazy_distance: outside of a metadata node"),
 252             LazyState::NodeStart(start) => {
 253                 assert!(min_end <= start);
 254                 start - min_end
 255             }
 256             LazyState::Previous(last_min_end) => {
 257                 assert!(
 258                     last_min_end <= position,
 259                     "make sure that the calls to `lazy*` \
 260                     are in the same order as the metadata fields",
 261                 );
 262                 position - last_min_end
 263             }
 264         };
 265         self.lazy_state = LazyState::Previous(min_end);
 266         self.emit_usize(distance)
 267     }
 268
 269     pub fn lazy<T: Encodable>(&mut self, value: &T) -> Lazy<T> {
 270         self.emit_node(|ecx, pos| {
 271             value.encode(ecx).unwrap();
 272
 273             assert!(pos + Lazy::<T>::min_size() <= ecx.position());
 274             Lazy::with_position(pos)
 275         })
 276     }
 277
 278     pub fn lazy_seq<I, T>(&mut self, iter: I) -> LazySeq<T>
 279         where I: IntoIterator<Item = T>,
 280               T: Encodable
 281     {
 282         self.emit_node(|ecx, pos| {
 283             let len = iter.into_iter().map(|value| value.encode(ecx).unwrap()).count();
 284
 285             assert!(pos + LazySeq::<T>::min_size(len) <= ecx.position());
 286             LazySeq::with_position_and_length(pos, len)
 287         })
 288     }
 289
 290     pub fn lazy_seq_ref<'b, I, T>(&mut self, iter: I) -> LazySeq<T>
 291         where I: IntoIterator<Item = &'b T>,
 292               T: 'b + Encodable
 293     {
 294         self.emit_node(|ecx, pos| {
 295             let len = iter.into_iter().map(|value| value.encode(ecx).unwrap()).count();
 296
 297             assert!(pos + LazySeq::<T>::min_size(len) <= ecx.position());
 298             LazySeq::with_position_and_length(pos, len)
 299         })
 300     }
 301
 302     // Encodes something that corresponds to a single DepNode::GlobalMetaData
 303     // and registers the Fingerprint in the `metadata_hashes` map.
 304     pub fn tracked<'x, DATA, R>(&'x mut self,
 305                                 op: fn(&mut IsolatedEncoder<'x, 'a, 'tcx>, DATA) -> R,
 306                                 data: DATA)
 307                                 -> R {
 308         op(&mut IsolatedEncoder::new(self), data)
 309     }
 310
 311     fn encode_info_for_items(&mut self) -> Index {
 312         let krate = self.tcx.hir().krate();
 313         let mut index = IndexBuilder::new(self);
 314         let vis = Spanned { span: syntax_pos::DUMMY_SP, node: hir::VisibilityKind::Public };
 315         index.record(DefId::local(CRATE_DEF_INDEX),
 316                      IsolatedEncoder::encode_info_for_mod,
 317                      FromId(CRATE_NODE_ID, (&krate.module, &krate.attrs, &vis)));
 318         let mut visitor = EncodeVisitor { index };
 319         krate.visit_all_item_likes(&mut visitor.as_deep_visitor());
 320         for macro_def in &krate.exported_macros {
 321             visitor.visit_macro_def(macro_def);
 322         }
 323         visitor.index.into_items()
 324     }
 325
 326     fn encode_def_path_table(&mut self) -> Lazy<DefPathTable> {
 327         let definitions = self.tcx.hir().definitions();
 328         self.lazy(definitions.def_path_table())
 329     }
 330
 331     fn encode_source_map(&mut self) -> LazySeq<syntax_pos::SourceFile> {
 332         let source_map = self.tcx.sess.source_map();
 333         let all_source_files = source_map.files();
 334
 335         let (working_dir, _cwd_remapped) = self.tcx.sess.working_dir.clone();
 336
 337         let adapted = all_source_files.iter()
 338             .filter(|source_file| {
 339                 // No need to re-export imported source_files, as any downstream
 340                 // crate will import them from their original source.
 341                 !source_file.is_imported()
 342             })
 343             .map(|source_file| {
 344                 match source_file.name {
 345                     // This path of this SourceFile has been modified by
 346                     // path-remapping, so we use it verbatim (and avoid
 347                     // cloning the whole map in the process).
 348                     _  if source_file.name_was_remapped => source_file.clone(),
 349
 350                     // Otherwise expand all paths to absolute paths because
 351                     // any relative paths are potentially relative to a
 352                     // wrong directory.
 353                     FileName::Real(ref name) => {
 354                         let mut adapted = (**source_file).clone();
 355                         adapted.name = Path::new(&working_dir).join(name).into();
 356                         adapted.name_hash = {
 357                             let mut hasher: StableHasher<u128> = StableHasher::new();
 358                             adapted.name.hash(&mut hasher);
 359                             hasher.finish()
 360                         };
 361                         Lrc::new(adapted)
 362                     },
 363
 364                     // expanded code, not from a file
 365                     _ => source_file.clone(),
 366                 }
 367             })
 368             .collect::<Vec<_>>();
 369
 370         self.lazy_seq_ref(adapted.iter().map(|rc| &**rc))
 371     }
 372
 373     fn encode_crate_root(&mut self) -> Lazy<CrateRoot> {
 374         let mut i = self.position();
 375
 376         let crate_deps = self.tracked(IsolatedEncoder::encode_crate_deps, ());
 377         let dylib_dependency_formats = self.tracked(
 378             IsolatedEncoder::encode_dylib_dependency_formats,
 379             ());
 380         let dep_bytes = self.position() - i;
 381
 382         // Encode the lib features.
 383         i = self.position();
 384         let lib_features = self.tracked(IsolatedEncoder::encode_lib_features, ());
 385         let lib_feature_bytes = self.position() - i;
 386
 387         // Encode the language items.
 388         i = self.position();
 389         let lang_items = self.tracked(IsolatedEncoder::encode_lang_items, ());
 390         let lang_items_missing = self.tracked(
 391             IsolatedEncoder::encode_lang_items_missing,
 392             ());
 393         let lang_item_bytes = self.position() - i;
 394
 395         // Encode the native libraries used
 396         i = self.position();
 397         let native_libraries = self.tracked(
 398             IsolatedEncoder::encode_native_libraries,
 399             ());
 400         let native_lib_bytes = self.position() - i;
 401
 402         let foreign_modules = self.tracked(
 403             IsolatedEncoder::encode_foreign_modules,
 404             ());
 405
 406         // Encode source_map
 407         i = self.position();
 408         let source_map = self.encode_source_map();
 409         let source_map_bytes = self.position() - i;
 410
 411         // Encode DefPathTable
 412         i = self.position();
 413         let def_path_table = self.encode_def_path_table();
 414         let def_path_table_bytes = self.position() - i;
 415
 416         // Encode the def IDs of impls, for coherence checking.
 417         i = self.position();
 418         let impls = self.tracked(IsolatedEncoder::encode_impls, ());
 419         let impl_bytes = self.position() - i;
 420
 421         // Encode exported symbols info.
 422         i = self.position();
 423         let exported_symbols = self.tcx.exported_symbols(LOCAL_CRATE);
 424         let exported_symbols = self.tracked(
 425             IsolatedEncoder::encode_exported_symbols,
 426             &exported_symbols);
 427         let exported_symbols_bytes = self.position() - i;
 428
 429         let tcx = self.tcx;
 430
 431         // Encode the items.
 432         i = self.position();
 433         let items = self.encode_info_for_items();
 434         let item_bytes = self.position() - i;
 435
 436         // Encode the allocation index
 437         let interpret_alloc_index = {
 438             let mut interpret_alloc_index = Vec::new();
 439             let mut n = 0;
 440             trace!("beginning to encode alloc ids");
 441             loop {
 442                 let new_n = self.interpret_allocs_inverse.len();
 443                 // if we have found new ids, serialize those, too
 444                 if n == new_n {
 445                     // otherwise, abort
 446                     break;
 447                 }
 448                 trace!("encoding {} further alloc ids", new_n - n);
 449                 for idx in n..new_n {
 450                     let id = self.interpret_allocs_inverse[idx];
 451                     let pos = self.position() as u32;
 452                     interpret_alloc_index.push(pos);
 453                     interpret::specialized_encode_alloc_id(
 454                         self,
 455                         tcx,
 456                         id,
 457                     ).unwrap();
 458                 }
 459                 n = new_n;
 460             }
 461             self.lazy_seq(interpret_alloc_index)
 462         };
 463
 464         // Index the items
 465         i = self.position();
 466         let index = items.write_index(&mut self.opaque);
 467         let index_bytes = self.position() - i;
 468
 469         let attrs = tcx.hir().krate_attrs();
 470         let is_proc_macro = tcx.sess.crate_types.borrow().contains(&CrateType::ProcMacro);
 471         let has_default_lib_allocator = attr::contains_name(&attrs, "default_lib_allocator");
 472         let has_global_allocator = *tcx.sess.has_global_allocator.get();
 473         let has_panic_handler = *tcx.sess.has_panic_handler.try_get().unwrap_or(&false);
 474
 475         let root = self.lazy(&CrateRoot {
 476             name: tcx.crate_name(LOCAL_CRATE),
 477             extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
 478             triple: tcx.sess.opts.target_triple.clone(),
 479             hash: tcx.crate_hash(LOCAL_CRATE),
 480             disambiguator: tcx.sess.local_crate_disambiguator(),
 481             panic_strategy: tcx.sess.panic_strategy(),
 482             edition: hygiene::default_edition(),
 483             has_global_allocator: has_global_allocator,
 484             has_panic_handler: has_panic_handler,
 485             has_default_lib_allocator: has_default_lib_allocator,
 486             plugin_registrar_fn: tcx.plugin_registrar_fn(LOCAL_CRATE).map(|id| id.index),
 487             proc_macro_decls_static: if is_proc_macro {
 488                 let id = tcx.proc_macro_decls_static(LOCAL_CRATE).unwrap();
 489                 Some(id.index)
 490             } else {
 491                 None
 492             },
 493
 494             compiler_builtins: attr::contains_name(&attrs, "compiler_builtins"),
 495             needs_allocator: attr::contains_name(&attrs, "needs_allocator"),
 496             needs_panic_runtime: attr::contains_name(&attrs, "needs_panic_runtime"),
 497             no_builtins: attr::contains_name(&attrs, "no_builtins"),
 498             panic_runtime: attr::contains_name(&attrs, "panic_runtime"),
 499             profiler_runtime: attr::contains_name(&attrs, "profiler_runtime"),
 500             sanitizer_runtime: attr::contains_name(&attrs, "sanitizer_runtime"),
 501
 502             crate_deps,
 503             dylib_dependency_formats,
 504             lib_features,
 505             lang_items,
 506             lang_items_missing,
 507             native_libraries,
 508             foreign_modules,
 509             source_map,
 510             def_path_table,
 511             impls,
 512             exported_symbols,
 513             interpret_alloc_index,
 514             index,
 515         });
 516
 517         let total_bytes = self.position();
 518
 519         if self.tcx.sess.meta_stats() {
 520             let mut zero_bytes = 0;
 521             for e in self.opaque.data.iter() {
 522                 if *e == 0 {
 523                     zero_bytes += 1;
 524                 }
 525             }
 526
 527             println!("metadata stats:");
 528             println!("             dep bytes: {}", dep_bytes);
 529             println!("     lib feature bytes: {}", lib_feature_bytes);
 530             println!("       lang item bytes: {}", lang_item_bytes);
 531             println!("          native bytes: {}", native_lib_bytes);
 532             println!("         source_map bytes: {}", source_map_bytes);
 533             println!("            impl bytes: {}", impl_bytes);
 534             println!("    exp. symbols bytes: {}", exported_symbols_bytes);
 535             println!("  def-path table bytes: {}", def_path_table_bytes);
 536             println!("            item bytes: {}", item_bytes);
 537             println!("           index bytes: {}", index_bytes);
 538             println!("            zero bytes: {}", zero_bytes);
 539             println!("           total bytes: {}", total_bytes);
 540         }
 541
 542         root
 543     }
 544 }
 545
 546 // These are methods for encoding various things. They are meant to be used with
 547 // IndexBuilder::record() and EncodeContext::tracked(). They actually
 548 // would not have to be methods of IsolatedEncoder (free standing functions
 549 // taking IsolatedEncoder as first argument would be just fine) but by making
 550 // them methods we don't have to repeat the lengthy `<'a, 'b: 'a, 'tcx: 'b>`
 551 // clause again and again.
 552 impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
 553     fn encode_variances_of(&mut self, def_id: DefId) -> LazySeq<ty::Variance> {
 554         debug!("IsolatedEncoder::encode_variances_of({:?})", def_id);
 555         let tcx = self.tcx;
 556         self.lazy_seq_from_slice(&tcx.variances_of(def_id))
 557     }
 558
 559     fn encode_item_type(&mut self, def_id: DefId) -> Lazy<Ty<'tcx>> {
 560         let tcx = self.tcx;
 561         let ty = tcx.type_of(def_id);
 562         debug!("IsolatedEncoder::encode_item_type({:?}) => {:?}", def_id, ty);
 563         self.lazy(&ty)
 564     }
 565
 566     /// Encode data for the given variant of the given ADT. The
 567     /// index of the variant is untracked: this is ok because we
 568     /// will have to lookup the adt-def by its id, and that gives us
 569     /// the right to access any information in the adt-def (including,
 570     /// e.g., the length of the various vectors).
 571     fn encode_enum_variant_info(&mut self,
 572                                 (enum_did, Untracked(index)): (DefId, Untracked<VariantIdx>))
 573                                 -> Entry<'tcx> {
 574         let tcx = self.tcx;
 575         let def = tcx.adt_def(enum_did);
 576         let variant = &def.variants[index];
 577         let def_id = variant.did;
 578         debug!("IsolatedEncoder::encode_enum_variant_info({:?})", def_id);
 579
 580         let data = VariantData {
 581             ctor_kind: variant.ctor_kind,
 582             discr: variant.discr,
 583             struct_ctor: None,
 584             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 585                 Some(self.lazy(&tcx.fn_sig(def_id)))
 586             } else {
 587                 None
 588             }
 589         };
 590
 591         let enum_id = tcx.hir().as_local_node_id(enum_did).unwrap();
 592         let enum_vis = &tcx.hir().expect_item(enum_id).vis;
 593
 594         Entry {
 595             kind: EntryKind::Variant(self.lazy(&data)),
 596             visibility: self.lazy(&ty::Visibility::from_hir(enum_vis, enum_id, tcx)),
 597             span: self.lazy(&tcx.def_span(def_id)),
 598             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
 599             children: self.lazy_seq(variant.fields.iter().map(|f| {
 600                 assert!(f.did.is_local());
 601                 f.did.index
 602             })),
 603             stability: self.encode_stability(def_id),
 604             deprecation: self.encode_deprecation(def_id),
 605
 606             ty: Some(self.encode_item_type(def_id)),
 607             inherent_impls: LazySeq::empty(),
 608             variances: if variant.ctor_kind == CtorKind::Fn {
 609                 self.encode_variances_of(def_id)
 610             } else {
 611                 LazySeq::empty()
 612             },
 613             generics: Some(self.encode_generics(def_id)),
 614             predicates: Some(self.encode_predicates(def_id)),
 615             predicates_defined_on: None,
 616
 617             mir: self.encode_optimized_mir(def_id),
 618         }
 619     }
 620
 621     fn encode_info_for_mod(&mut self,
 622                            FromId(id, (md, attrs, vis)): FromId<(&hir::Mod,
 623                                                                  &[ast::Attribute],
 624                                                                  &hir::Visibility)>)
 625                            -> Entry<'tcx> {
 626         let tcx = self.tcx;
 627         let def_id = tcx.hir().local_def_id(id);
 628         debug!("IsolatedEncoder::encode_info_for_mod({:?})", def_id);
 629
 630         let data = ModData {
 631             reexports: match tcx.module_exports(def_id) {
 632                 Some(ref exports) => self.lazy_seq_from_slice(exports.as_slice()),
 633                 _ => LazySeq::empty(),
 634             },
 635         };
 636
 637         Entry {
 638             kind: EntryKind::Mod(self.lazy(&data)),
 639             visibility: self.lazy(&ty::Visibility::from_hir(vis, id, tcx)),
 640             span: self.lazy(&tcx.def_span(def_id)),
 641             attributes: self.encode_attributes(attrs),
 642             children: self.lazy_seq(md.item_ids.iter().map(|item_id| {
 643                 tcx.hir().local_def_id(item_id.id).index
 644             })),
 645             stability: self.encode_stability(def_id),
 646             deprecation: self.encode_deprecation(def_id),
 647
 648             ty: None,
 649             inherent_impls: LazySeq::empty(),
 650             variances: LazySeq::empty(),
 651             generics: None,
 652             predicates: None,
 653             predicates_defined_on: None,
 654
 655             mir: None
 656         }
 657     }
 658
 659     /// Encode data for the given field of the given variant of the
 660     /// given ADT. The indices of the variant/field are untracked:
 661     /// this is ok because we will have to lookup the adt-def by its
 662     /// id, and that gives us the right to access any information in
 663     /// the adt-def (including, e.g., the length of the various
 664     /// vectors).
 665     fn encode_field(&mut self,
 666                     (adt_def_id, Untracked((variant_index, field_index))): (DefId,
 667                                                                             Untracked<(VariantIdx,
 668                                                                                        usize)>))
 669                     -> Entry<'tcx> {
 670         let tcx = self.tcx;
 671         let variant = &tcx.adt_def(adt_def_id).variants[variant_index];
 672         let field = &variant.fields[field_index];
 673
 674         let def_id = field.did;
 675         debug!("IsolatedEncoder::encode_field({:?})", def_id);
 676
 677         let variant_id = tcx.hir().as_local_node_id(variant.did).unwrap();
 678         let variant_data = tcx.hir().expect_variant_data(variant_id);
 679
 680         Entry {
 681             kind: EntryKind::Field,
 682             visibility: self.lazy(&field.vis),
 683             span: self.lazy(&tcx.def_span(def_id)),
 684             attributes: self.encode_attributes(&variant_data.fields()[field_index].attrs),
 685             children: LazySeq::empty(),
 686             stability: self.encode_stability(def_id),
 687             deprecation: self.encode_deprecation(def_id),
 688
 689             ty: Some(self.encode_item_type(def_id)),
 690             inherent_impls: LazySeq::empty(),
 691             variances: LazySeq::empty(),
 692             generics: Some(self.encode_generics(def_id)),
 693             predicates: Some(self.encode_predicates(def_id)),
 694             predicates_defined_on: None,
 695
 696             mir: None,
 697         }
 698     }
 699
 700     fn encode_struct_ctor(&mut self, (adt_def_id, def_id): (DefId, DefId)) -> Entry<'tcx> {
 701         debug!("IsolatedEncoder::encode_struct_ctor({:?})", def_id);
 702         let tcx = self.tcx;
 703         let adt_def = tcx.adt_def(adt_def_id);
 704         let variant = adt_def.non_enum_variant();
 705
 706         let data = VariantData {
 707             ctor_kind: variant.ctor_kind,
 708             discr: variant.discr,
 709             struct_ctor: Some(def_id.index),
 710             ctor_sig: if variant.ctor_kind == CtorKind::Fn {
 711                 Some(self.lazy(&tcx.fn_sig(def_id)))
 712             } else {
 713                 None
 714             }
 715         };
 716
 717         let struct_id = tcx.hir().as_local_node_id(adt_def_id).unwrap();
 718         let struct_vis = &tcx.hir().expect_item(struct_id).vis;
 719         let mut ctor_vis = ty::Visibility::from_hir(struct_vis, struct_id, tcx);
 720         for field in &variant.fields {
 721             if ctor_vis.is_at_least(field.vis, tcx) {
 722                 ctor_vis = field.vis;
 723             }
 724         }
 725
 726         // If the structure is marked as non_exhaustive then lower the visibility
 727         // to within the crate.
 728         if adt_def.non_enum_variant().is_field_list_non_exhaustive() &&
 729             ctor_vis == ty::Visibility::Public
 730         {
 731             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 732         }
 733
 734         let repr_options = get_repr_options(&tcx, adt_def_id);
 735
 736         Entry {
 737             kind: EntryKind::Struct(self.lazy(&data), repr_options),
 738             visibility: self.lazy(&ctor_vis),
 739             span: self.lazy(&tcx.def_span(def_id)),
 740             attributes: LazySeq::empty(),
 741             children: LazySeq::empty(),
 742             stability: self.encode_stability(def_id),
 743             deprecation: self.encode_deprecation(def_id),
 744
 745             ty: Some(self.encode_item_type(def_id)),
 746             inherent_impls: LazySeq::empty(),
 747             variances: if variant.ctor_kind == CtorKind::Fn {
 748                 self.encode_variances_of(def_id)
 749             } else {
 750                 LazySeq::empty()
 751             },
 752             generics: Some(self.encode_generics(def_id)),
 753             predicates: Some(self.encode_predicates(def_id)),
 754             predicates_defined_on: None,
 755
 756             mir: self.encode_optimized_mir(def_id),
 757         }
 758     }
 759
 760     fn encode_generics(&mut self, def_id: DefId) -> Lazy<ty::Generics> {
 761         debug!("IsolatedEncoder::encode_generics({:?})", def_id);
 762         let tcx = self.tcx;
 763         self.lazy(tcx.generics_of(def_id))
 764     }
 765
 766     fn encode_predicates(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 767         debug!("IsolatedEncoder::encode_predicates({:?})", def_id);
 768         let tcx = self.tcx;
 769         self.lazy(&tcx.predicates_of(def_id))
 770     }
 771
 772     fn encode_predicates_defined_on(&mut self, def_id: DefId) -> Lazy<ty::GenericPredicates<'tcx>> {
 773         debug!("IsolatedEncoder::encode_predicates_defined_on({:?})", def_id);
 774         let tcx = self.tcx;
 775         self.lazy(&tcx.predicates_defined_on(def_id))
 776     }
 777
 778     fn encode_info_for_trait_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 779         debug!("IsolatedEncoder::encode_info_for_trait_item({:?})", def_id);
 780         let tcx = self.tcx;
 781
 782         let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
 783         let ast_item = tcx.hir().expect_trait_item(node_id);
 784         let trait_item = tcx.associated_item(def_id);
 785
 786         let container = match trait_item.defaultness {
 787             hir::Defaultness::Default { has_value: true } =>
 788                 AssociatedContainer::TraitWithDefault,
 789             hir::Defaultness::Default { has_value: false } =>
 790                 AssociatedContainer::TraitRequired,
 791             hir::Defaultness::Final =>
 792                 span_bug!(ast_item.span, "traits cannot have final items"),
 793         };
 794
 795         let kind = match trait_item.kind {
 796             ty::AssociatedKind::Const => {
 797                 let const_qualif =
 798                     if let hir::TraitItemKind::Const(_, Some(body)) = ast_item.node {
 799                         self.const_qualif(0, body)
 800                     } else {
 801                         ConstQualif { mir: 0, ast_promotable: false }
 802                     };
 803
 804                 let rendered =
 805                     hir::print::to_string(self.tcx.hir(), |s| s.print_trait_item(ast_item));
 806                 let rendered_const = self.lazy(&RenderedConst(rendered));
 807
 808                 EntryKind::AssociatedConst(container, const_qualif, rendered_const)
 809             }
 810             ty::AssociatedKind::Method => {
 811                 let fn_data = if let hir::TraitItemKind::Method(_, ref m) = ast_item.node {
 812                     let arg_names = match *m {
 813                         hir::TraitMethod::Required(ref names) => {
 814                             self.encode_fn_arg_names(names)
 815                         }
 816                         hir::TraitMethod::Provided(body) => {
 817                             self.encode_fn_arg_names_for_body(body)
 818                         }
 819                     };
 820                     FnData {
 821                         constness: hir::Constness::NotConst,
 822                         arg_names,
 823                         sig: self.lazy(&tcx.fn_sig(def_id)),
 824                     }
 825                 } else {
 826                     bug!()
 827                 };
 828                 EntryKind::Method(self.lazy(&MethodData {
 829                     fn_data,
 830                     container,
 831                     has_self: trait_item.method_has_self_argument,
 832                 }))
 833             }
 834             ty::AssociatedKind::Type => EntryKind::AssociatedType(container),
 835             ty::AssociatedKind::Existential =>
 836                 span_bug!(ast_item.span, "existential type in trait"),
 837         };
 838
 839         Entry {
 840             kind,
 841             visibility: self.lazy(&trait_item.vis),
 842             span: self.lazy(&ast_item.span),
 843             attributes: self.encode_attributes(&ast_item.attrs),
 844             children: LazySeq::empty(),
 845             stability: self.encode_stability(def_id),
 846             deprecation: self.encode_deprecation(def_id),
 847
 848             ty: match trait_item.kind {
 849                 ty::AssociatedKind::Const |
 850                 ty::AssociatedKind::Method => {
 851                     Some(self.encode_item_type(def_id))
 852                 }
 853                 ty::AssociatedKind::Type => {
 854                     if trait_item.defaultness.has_value() {
 855                         Some(self.encode_item_type(def_id))
 856                     } else {
 857                         None
 858                     }
 859                 }
 860                 ty::AssociatedKind::Existential => unreachable!(),
 861             },
 862             inherent_impls: LazySeq::empty(),
 863             variances: if trait_item.kind == ty::AssociatedKind::Method {
 864                 self.encode_variances_of(def_id)
 865             } else {
 866                 LazySeq::empty()
 867             },
 868             generics: Some(self.encode_generics(def_id)),
 869             predicates: Some(self.encode_predicates(def_id)),
 870             predicates_defined_on: None,
 871
 872             mir: self.encode_optimized_mir(def_id),
 873         }
 874     }
 875
 876     fn metadata_output_only(&self) -> bool {
 877         // MIR optimisation can be skipped when we're just interested in the metadata.
 878         !self.tcx.sess.opts.output_types.should_codegen()
 879     }
 880
 881     fn const_qualif(&self, mir: u8, body_id: hir::BodyId) -> ConstQualif {
 882         let body_owner_def_id = self.tcx.hir().body_owner_def_id(body_id);
 883         let ast_promotable = self.tcx.const_is_rvalue_promotable_to_static(body_owner_def_id);
 884
 885         ConstQualif { mir, ast_promotable }
 886     }
 887
 888     fn encode_info_for_impl_item(&mut self, def_id: DefId) -> Entry<'tcx> {
 889         debug!("IsolatedEncoder::encode_info_for_impl_item({:?})", def_id);
 890         let tcx = self.tcx;
 891
 892         let node_id = self.tcx.hir().as_local_node_id(def_id).unwrap();
 893         let ast_item = self.tcx.hir().expect_impl_item(node_id);
 894         let impl_item = self.tcx.associated_item(def_id);
 895
 896         let container = match impl_item.defaultness {
 897             hir::Defaultness::Default { has_value: true } => AssociatedContainer::ImplDefault,
 898             hir::Defaultness::Final => AssociatedContainer::ImplFinal,
 899             hir::Defaultness::Default { has_value: false } =>
 900                 span_bug!(ast_item.span, "impl items always have values (currently)"),
 901         };
 902
 903         let kind = match impl_item.kind {
 904             ty::AssociatedKind::Const => {
 905                 if let hir::ImplItemKind::Const(_, body_id) = ast_item.node {
 906                     let mir = self.tcx.at(ast_item.span).mir_const_qualif(def_id).0;
 907
 908                     EntryKind::AssociatedConst(container,
 909                         self.const_qualif(mir, body_id),
 910                         self.encode_rendered_const_for_body(body_id))
 911                 } else {
 912                     bug!()
 913                 }
 914             }
 915             ty::AssociatedKind::Method => {
 916                 let fn_data = if let hir::ImplItemKind::Method(ref sig, body) = ast_item.node {
 917                     FnData {
 918                         constness: sig.header.constness,
 919                         arg_names: self.encode_fn_arg_names_for_body(body),
 920                         sig: self.lazy(&tcx.fn_sig(def_id)),
 921                     }
 922                 } else {
 923                     bug!()
 924                 };
 925                 EntryKind::Method(self.lazy(&MethodData {
 926                     fn_data,
 927                     container,
 928                     has_self: impl_item.method_has_self_argument,
 929                 }))
 930             }
 931             ty::AssociatedKind::Existential => EntryKind::AssociatedExistential(container),
 932             ty::AssociatedKind::Type => EntryKind::AssociatedType(container)
 933         };
 934
 935         let mir =
 936             match ast_item.node {
 937                 hir::ImplItemKind::Const(..) => true,
 938                 hir::ImplItemKind::Method(ref sig, _) => {
 939                     let generics = self.tcx.generics_of(def_id);
 940                     let needs_inline = (generics.requires_monomorphization(self.tcx) ||
 941                                         tcx.codegen_fn_attrs(def_id).requests_inline()) &&
 942                                         !self.metadata_output_only();
 943                     let is_const_fn = sig.header.constness == hir::Constness::Const;
 944                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
 945                     needs_inline || is_const_fn || always_encode_mir
 946                 },
 947                 hir::ImplItemKind::Existential(..) |
 948                 hir::ImplItemKind::Type(..) => false,
 949             };
 950
 951         Entry {
 952             kind,
 953             visibility: self.lazy(&impl_item.vis),
 954             span: self.lazy(&ast_item.span),
 955             attributes: self.encode_attributes(&ast_item.attrs),
 956             children: LazySeq::empty(),
 957             stability: self.encode_stability(def_id),
 958             deprecation: self.encode_deprecation(def_id),
 959
 960             ty: Some(self.encode_item_type(def_id)),
 961             inherent_impls: LazySeq::empty(),
 962             variances: if impl_item.kind == ty::AssociatedKind::Method {
 963                 self.encode_variances_of(def_id)
 964             } else {
 965                 LazySeq::empty()
 966             },
 967             generics: Some(self.encode_generics(def_id)),
 968             predicates: Some(self.encode_predicates(def_id)),
 969             predicates_defined_on: None,
 970
 971             mir: if mir { self.encode_optimized_mir(def_id) } else { None },
 972         }
 973     }
 974
 975     fn encode_fn_arg_names_for_body(&mut self, body_id: hir::BodyId)
 976                                     -> LazySeq<ast::Name> {
 977         self.tcx.dep_graph.with_ignore(|| {
 978             let body = self.tcx.hir().body(body_id);
 979             self.lazy_seq(body.arguments.iter().map(|arg| {
 980                 match arg.pat.node {
 981                     PatKind::Binding(_, _, _, ident, _) => ident.name,
 982                     _ => keywords::Invalid.name(),
 983                 }
 984             }))
 985         })
 986     }
 987
 988     fn encode_fn_arg_names(&mut self, param_names: &[ast::Ident]) -> LazySeq<ast::Name> {
 989         self.lazy_seq(param_names.iter().map(|ident| ident.name))
 990     }
 991
 992     fn encode_optimized_mir(&mut self, def_id: DefId) -> Option<Lazy<mir::Mir<'tcx>>> {
 993         debug!("EntryBuilder::encode_mir({:?})", def_id);
 994         if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id) {
 995             let mir = self.tcx.optimized_mir(def_id);
 996             Some(self.lazy(&mir))
 997         } else {
 998             None
 999         }
1000     }
1001
1002     // Encodes the inherent implementations of a structure, enumeration, or trait.
1003     fn encode_inherent_implementations(&mut self, def_id: DefId) -> LazySeq<DefIndex> {
1004         debug!("IsolatedEncoder::encode_inherent_implementations({:?})", def_id);
1005         let implementations = self.tcx.inherent_impls(def_id);
1006         if implementations.is_empty() {
1007             LazySeq::empty()
1008         } else {
1009             self.lazy_seq(implementations.iter().map(|&def_id| {
1010                 assert!(def_id.is_local());
1011                 def_id.index
1012             }))
1013         }
1014     }
1015
1016     fn encode_stability(&mut self, def_id: DefId) -> Option<Lazy<attr::Stability>> {
1017         debug!("IsolatedEncoder::encode_stability({:?})", def_id);
1018         self.tcx.lookup_stability(def_id).map(|stab| self.lazy(stab))
1019     }
1020
1021     fn encode_deprecation(&mut self, def_id: DefId) -> Option<Lazy<attr::Deprecation>> {
1022         debug!("IsolatedEncoder::encode_deprecation({:?})", def_id);
1023         self.tcx.lookup_deprecation(def_id).map(|depr| self.lazy(&depr))
1024     }
1025
1026     fn encode_rendered_const_for_body(&mut self, body_id: hir::BodyId) -> Lazy<RenderedConst> {
1027         let body = self.tcx.hir().body(body_id);
1028         let rendered = hir::print::to_string(self.tcx.hir(), |s| s.print_expr(&body.value));
1029         let rendered_const = &RenderedConst(rendered);
1030         self.lazy(rendered_const)
1031     }
1032
1033     fn encode_info_for_item(&mut self, (def_id, item): (DefId, &'tcx hir::Item)) -> Entry<'tcx> {
1034         let tcx = self.tcx;
1035
1036         debug!("IsolatedEncoder::encode_info_for_item({:?})", def_id);
1037
1038         let kind = match item.node {
1039             hir::ItemKind::Static(_, hir::MutMutable, _) => EntryKind::MutStatic,
1040             hir::ItemKind::Static(_, hir::MutImmutable, _) => EntryKind::ImmStatic,
1041             hir::ItemKind::Const(_, body_id) => {
1042                 let mir = tcx.at(item.span).mir_const_qualif(def_id).0;
1043                 EntryKind::Const(
1044                     self.const_qualif(mir, body_id),
1045                     self.encode_rendered_const_for_body(body_id)
1046                 )
1047             }
1048             hir::ItemKind::Fn(_, header, .., body) => {
1049                 let data = FnData {
1050                     constness: header.constness,
1051                     arg_names: self.encode_fn_arg_names_for_body(body),
1052                     sig: self.lazy(&tcx.fn_sig(def_id)),
1053                 };
1054
1055                 EntryKind::Fn(self.lazy(&data))
1056             }
1057             hir::ItemKind::Mod(ref m) => {
1058                 return self.encode_info_for_mod(FromId(item.id, (m, &item.attrs, &item.vis)));
1059             }
1060             hir::ItemKind::ForeignMod(_) => EntryKind::ForeignMod,
1061             hir::ItemKind::GlobalAsm(..) => EntryKind::GlobalAsm,
1062             hir::ItemKind::Ty(..) => EntryKind::Type,
1063             hir::ItemKind::Existential(..) => EntryKind::Existential,
1064             hir::ItemKind::Enum(..) => EntryKind::Enum(get_repr_options(&tcx, def_id)),
1065             hir::ItemKind::Struct(ref struct_def, _) => {
1066                 let variant = tcx.adt_def(def_id).non_enum_variant();
1067
1068                 // Encode def_ids for each field and method
1069                 // for methods, write all the stuff get_trait_method
1070                 // needs to know
1071                 let struct_ctor = if !struct_def.is_struct() {
1072                     Some(tcx.hir().local_def_id(struct_def.id()).index)
1073                 } else {
1074                     None
1075                 };
1076
1077                 let repr_options = get_repr_options(&tcx, def_id);
1078
1079                 EntryKind::Struct(self.lazy(&VariantData {
1080                     ctor_kind: variant.ctor_kind,
1081                     discr: variant.discr,
1082                     struct_ctor,
1083                     ctor_sig: None,
1084                 }), repr_options)
1085             }
1086             hir::ItemKind::Union(..) => {
1087                 let variant = tcx.adt_def(def_id).non_enum_variant();
1088                 let repr_options = get_repr_options(&tcx, def_id);
1089
1090                 EntryKind::Union(self.lazy(&VariantData {
1091                     ctor_kind: variant.ctor_kind,
1092                     discr: variant.discr,
1093                     struct_ctor: None,
1094                     ctor_sig: None,
1095                 }), repr_options)
1096             }
1097             hir::ItemKind::Impl(_, polarity, defaultness, ..) => {
1098                 let trait_ref = tcx.impl_trait_ref(def_id);
1099                 let parent = if let Some(trait_ref) = trait_ref {
1100                     let trait_def = tcx.trait_def(trait_ref.def_id);
1101                     trait_def.ancestors(tcx, def_id).nth(1).and_then(|node| {
1102                         match node {
1103                             specialization_graph::Node::Impl(parent) => Some(parent),
1104                             _ => None,
1105                         }
1106                     })
1107                 } else {
1108                     None
1109                 };
1110
1111                 // if this is an impl of `CoerceUnsized`, create its
1112                 // "unsized info", else just store None
1113                 let coerce_unsized_info =
1114                     trait_ref.and_then(|t| {
1115                         if Some(t.def_id) == tcx.lang_items().coerce_unsized_trait() {
1116                             Some(tcx.at(item.span).coerce_unsized_info(def_id))
1117                         } else {
1118                             None
1119                         }
1120                     });
1121
1122                 let data = ImplData {
1123                     polarity,
1124                     defaultness,
1125                     parent_impl: parent,
1126                     coerce_unsized_info,
1127                     trait_ref: trait_ref.map(|trait_ref| self.lazy(&trait_ref)),
1128                 };
1129
1130                 EntryKind::Impl(self.lazy(&data))
1131             }
1132             hir::ItemKind::Trait(..) => {
1133                 let trait_def = tcx.trait_def(def_id);
1134                 let data = TraitData {
1135                     unsafety: trait_def.unsafety,
1136                     paren_sugar: trait_def.paren_sugar,
1137                     has_auto_impl: tcx.trait_is_auto(def_id),
1138                     is_marker: trait_def.is_marker,
1139                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
1140                 };
1141
1142                 EntryKind::Trait(self.lazy(&data))
1143             }
1144             hir::ItemKind::TraitAlias(..) => {
1145                 let data = TraitAliasData {
1146                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
1147                 };
1148
1149                 EntryKind::TraitAlias(self.lazy(&data))
1150             }
1151             hir::ItemKind::ExternCrate(_) |
1152             hir::ItemKind::Use(..) => bug!("cannot encode info for item {:?}", item),
1153         };
1154
1155         Entry {
1156             kind,
1157             visibility: self.lazy(&ty::Visibility::from_hir(&item.vis, item.id, tcx)),
1158             span: self.lazy(&item.span),
1159             attributes: self.encode_attributes(&item.attrs),
1160             children: match item.node {
1161                 hir::ItemKind::ForeignMod(ref fm) => {
1162                     self.lazy_seq(fm.items
1163                         .iter()
1164                         .map(|foreign_item| tcx.hir().local_def_id(foreign_item.id).index))
1165                 }
1166                 hir::ItemKind::Enum(..) => {
1167                     let def = self.tcx.adt_def(def_id);
1168                     self.lazy_seq(def.variants.iter().map(|v| {
1169                         assert!(v.did.is_local());
1170                         v.did.index
1171                     }))
1172                 }
1173                 hir::ItemKind::Struct(..) |
1174                 hir::ItemKind::Union(..) => {
1175                     let def = self.tcx.adt_def(def_id);
1176                     self.lazy_seq(def.non_enum_variant().fields.iter().map(|f| {
1177                         assert!(f.did.is_local());
1178                         f.did.index
1179                     }))
1180                 }
1181                 hir::ItemKind::Impl(..) |
1182                 hir::ItemKind::Trait(..) => {
1183                     self.lazy_seq(tcx.associated_item_def_ids(def_id).iter().map(|&def_id| {
1184                         assert!(def_id.is_local());
1185                         def_id.index
1186                     }))
1187                 }
1188                 _ => LazySeq::empty(),
1189             },
1190             stability: self.encode_stability(def_id),
1191             deprecation: self.encode_deprecation(def_id),
1192
1193             ty: match item.node {
1194                 hir::ItemKind::Static(..) |
1195                 hir::ItemKind::Const(..) |
1196                 hir::ItemKind::Fn(..) |
1197                 hir::ItemKind::Ty(..) |
1198                 hir::ItemKind::Existential(..) |
1199                 hir::ItemKind::Enum(..) |
1200                 hir::ItemKind::Struct(..) |
1201                 hir::ItemKind::Union(..) |
1202                 hir::ItemKind::Impl(..) => Some(self.encode_item_type(def_id)),
1203                 _ => None,
1204             },
1205             inherent_impls: self.encode_inherent_implementations(def_id),
1206             variances: match item.node {
1207                 hir::ItemKind::Enum(..) |
1208                 hir::ItemKind::Struct(..) |
1209                 hir::ItemKind::Union(..) |
1210                 hir::ItemKind::Fn(..) => self.encode_variances_of(def_id),
1211                 _ => LazySeq::empty(),
1212             },
1213             generics: match item.node {
1214                 hir::ItemKind::Static(..) |
1215                 hir::ItemKind::Const(..) |
1216                 hir::ItemKind::Fn(..) |
1217                 hir::ItemKind::Ty(..) |
1218                 hir::ItemKind::Enum(..) |
1219                 hir::ItemKind::Struct(..) |
1220                 hir::ItemKind::Union(..) |
1221                 hir::ItemKind::Impl(..) |
1222                 hir::ItemKind::Existential(..) |
1223                 hir::ItemKind::Trait(..) => Some(self.encode_generics(def_id)),
1224                 hir::ItemKind::TraitAlias(..) => Some(self.encode_generics(def_id)),
1225                 _ => None,
1226             },
1227             predicates: match item.node {
1228                 hir::ItemKind::Static(..) |
1229                 hir::ItemKind::Const(..) |
1230                 hir::ItemKind::Fn(..) |
1231                 hir::ItemKind::Ty(..) |
1232                 hir::ItemKind::Enum(..) |
1233                 hir::ItemKind::Struct(..) |
1234                 hir::ItemKind::Union(..) |
1235                 hir::ItemKind::Impl(..) |
1236                 hir::ItemKind::Existential(..) |
1237                 hir::ItemKind::Trait(..) |
1238                 hir::ItemKind::TraitAlias(..) => Some(self.encode_predicates(def_id)),
1239                 _ => None,
1240             },
1241
1242             // The only time that `predicates_defined_on` is used (on
1243             // an external item) is for traits, during chalk lowering,
1244             // so only encode it in that case as an efficiency
1245             // hack. (No reason not to expand it in the future if
1246             // necessary.)
1247             predicates_defined_on: match item.node {
1248                 hir::ItemKind::Trait(..) |
1249                 hir::ItemKind::TraitAlias(..) => Some(self.encode_predicates_defined_on(def_id)),
1250                 _ => None, // not *wrong* for other kinds of items, but not needed
1251             },
1252
1253             mir: match item.node {
1254                 hir::ItemKind::Static(..) => {
1255                     self.encode_optimized_mir(def_id)
1256                 }
1257                 hir::ItemKind::Const(..) => self.encode_optimized_mir(def_id),
1258                 hir::ItemKind::Fn(_, header, ..) => {
1259                     let generics = tcx.generics_of(def_id);
1260                     let needs_inline =
1261                         (generics.requires_monomorphization(tcx) ||
1262                          tcx.codegen_fn_attrs(def_id).requests_inline()) &&
1263                             !self.metadata_output_only();
1264                     let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
1265                     if needs_inline
1266                         || header.constness == hir::Constness::Const
1267                         || always_encode_mir
1268                     {
1269                         self.encode_optimized_mir(def_id)
1270                     } else {
1271                         None
1272                     }
1273                 }
1274                 _ => None,
1275             },
1276         }
1277     }
1278
1279     /// Serialize the text of exported macros
1280     fn encode_info_for_macro_def(&mut self, macro_def: &hir::MacroDef) -> Entry<'tcx> {
1281         use syntax::print::pprust;
1282         let def_id = self.tcx.hir().local_def_id(macro_def.id);
1283         Entry {
1284             kind: EntryKind::MacroDef(self.lazy(&MacroDef {
1285                 body: pprust::tts_to_string(&macro_def.body.trees().collect::<Vec<_>>()),
1286                 legacy: macro_def.legacy,
1287             })),
1288             visibility: self.lazy(&ty::Visibility::Public),
1289             span: self.lazy(&macro_def.span),
1290             attributes: self.encode_attributes(&macro_def.attrs),
1291             stability: self.encode_stability(def_id),
1292             deprecation: self.encode_deprecation(def_id),
1293
1294             children: LazySeq::empty(),
1295             ty: None,
1296             inherent_impls: LazySeq::empty(),
1297             variances: LazySeq::empty(),
1298             generics: None,
1299             predicates: None,
1300             predicates_defined_on: None,
1301             mir: None,
1302         }
1303     }
1304
1305     fn encode_info_for_ty_param(&mut self,
1306                                 (def_id, Untracked(has_default)): (DefId, Untracked<bool>))
1307                                 -> Entry<'tcx> {
1308         debug!("IsolatedEncoder::encode_info_for_ty_param({:?})", def_id);
1309         let tcx = self.tcx;
1310         Entry {
1311             kind: EntryKind::Type,
1312             visibility: self.lazy(&ty::Visibility::Public),
1313             span: self.lazy(&tcx.def_span(def_id)),
1314             attributes: LazySeq::empty(),
1315             children: LazySeq::empty(),
1316             stability: None,
1317             deprecation: None,
1318
1319             ty: if has_default {
1320                 Some(self.encode_item_type(def_id))
1321             } else {
1322                 None
1323             },
1324             inherent_impls: LazySeq::empty(),
1325             variances: LazySeq::empty(),
1326             generics: None,
1327             predicates: None,
1328             predicates_defined_on: None,
1329
1330             mir: None,
1331         }
1332     }
1333
1334     fn encode_info_for_closure(&mut self, def_id: DefId) -> Entry<'tcx> {
1335         debug!("IsolatedEncoder::encode_info_for_closure({:?})", def_id);
1336         let tcx = self.tcx;
1337
1338         let tables = self.tcx.typeck_tables_of(def_id);
1339         let node_id = self.tcx.hir().as_local_node_id(def_id).unwrap();
1340         let hir_id = self.tcx.hir().node_to_hir_id(node_id);
1341         let kind = match tables.node_id_to_type(hir_id).sty {
1342             ty::Generator(def_id, ..) => {
1343                 let layout = self.tcx.generator_layout(def_id);
1344                 let data = GeneratorData {
1345                     layout: layout.clone(),
1346                 };
1347                 EntryKind::Generator(self.lazy(&data))
1348             }
1349
1350             ty::Closure(def_id, substs) => {
1351                 let sig = substs.closure_sig(def_id, self.tcx);
1352                 let data = ClosureData { sig: self.lazy(&sig) };
1353                 EntryKind::Closure(self.lazy(&data))
1354             }
1355
1356             _ => bug!("closure that is neither generator nor closure")
1357         };
1358
1359         Entry {
1360             kind,
1361             visibility: self.lazy(&ty::Visibility::Public),
1362             span: self.lazy(&tcx.def_span(def_id)),
1363             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
1364             children: LazySeq::empty(),
1365             stability: None,
1366             deprecation: None,
1367
1368             ty: Some(self.encode_item_type(def_id)),
1369             inherent_impls: LazySeq::empty(),
1370             variances: LazySeq::empty(),
1371             generics: Some(self.encode_generics(def_id)),
1372             predicates: None,
1373             predicates_defined_on: None,
1374
1375             mir: self.encode_optimized_mir(def_id),
1376         }
1377     }
1378
1379     fn encode_info_for_anon_const(&mut self, def_id: DefId) -> Entry<'tcx> {
1380         debug!("IsolatedEncoder::encode_info_for_anon_const({:?})", def_id);
1381         let tcx = self.tcx;
1382         let id = tcx.hir().as_local_node_id(def_id).unwrap();
1383         let body_id = tcx.hir().body_owned_by(id);
1384         let const_data = self.encode_rendered_const_for_body(body_id);
1385         let mir = tcx.mir_const_qualif(def_id).0;
1386
1387         Entry {
1388             kind: EntryKind::Const(self.const_qualif(mir, body_id), const_data),
1389             visibility: self.lazy(&ty::Visibility::Public),
1390             span: self.lazy(&tcx.def_span(def_id)),
1391             attributes: LazySeq::empty(),
1392             children: LazySeq::empty(),
1393             stability: None,
1394             deprecation: None,
1395
1396             ty: Some(self.encode_item_type(def_id)),
1397             inherent_impls: LazySeq::empty(),
1398             variances: LazySeq::empty(),
1399             generics: Some(self.encode_generics(def_id)),
1400             predicates: Some(self.encode_predicates(def_id)),
1401             predicates_defined_on: None,
1402
1403             mir: self.encode_optimized_mir(def_id),
1404         }
1405     }
1406
1407     fn encode_attributes(&mut self, attrs: &[ast::Attribute]) -> LazySeq<ast::Attribute> {
1408         // NOTE: This must use lazy_seq_from_slice(), not lazy_seq() because
1409         //       we rely on the HashStable specialization for [Attribute]
1410         //       to properly filter things out.
1411         self.lazy_seq_from_slice(attrs)
1412     }
1413
1414     fn encode_native_libraries(&mut self, _: ()) -> LazySeq<NativeLibrary> {
1415         let used_libraries = self.tcx.native_libraries(LOCAL_CRATE);
1416         self.lazy_seq(used_libraries.iter().cloned())
1417     }
1418
1419     fn encode_foreign_modules(&mut self, _: ()) -> LazySeq<ForeignModule> {
1420         let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
1421         self.lazy_seq(foreign_modules.iter().cloned())
1422     }
1423
1424     fn encode_crate_deps(&mut self, _: ()) -> LazySeq<CrateDep> {
1425         let crates = self.tcx.crates();
1426
1427         let mut deps = crates
1428             .iter()
1429             .map(|&cnum| {
1430                 let dep = CrateDep {
1431                     name: self.tcx.original_crate_name(cnum),
1432                     hash: self.tcx.crate_hash(cnum),
1433                     kind: self.tcx.dep_kind(cnum),
1434                     extra_filename: self.tcx.extra_filename(cnum),
1435                 };
1436                 (cnum, dep)
1437             })
1438             .collect::<Vec<_>>();
1439
1440         deps.sort_by_key(|&(cnum, _)| cnum);
1441
1442         {
1443             // Sanity-check the crate numbers
1444             let mut expected_cnum = 1;
1445             for &(n, _) in &deps {
1446                 assert_eq!(n, CrateNum::new(expected_cnum));
1447                 expected_cnum += 1;
1448             }
1449         }
1450
1451         // We're just going to write a list of crate 'name-hash-version's, with
1452         // the assumption that they are numbered 1 to n.
1453         // FIXME (#2166): This is not nearly enough to support correct versioning
1454         // but is enough to get transitive crate dependencies working.
1455         self.lazy_seq_ref(deps.iter().map(|&(_, ref dep)| dep))
1456     }
1457
1458     fn encode_lib_features(&mut self, _: ()) -> LazySeq<(ast::Name, Option<ast::Name>)> {
1459         let tcx = self.tcx;
1460         let lib_features = tcx.lib_features();
1461         self.lazy_seq(lib_features.to_vec())
1462     }
1463
1464     fn encode_lang_items(&mut self, _: ()) -> LazySeq<(DefIndex, usize)> {
1465         let tcx = self.tcx;
1466         let lang_items = tcx.lang_items();
1467         let lang_items = lang_items.items().iter();
1468         self.lazy_seq(lang_items.enumerate().filter_map(|(i, &opt_def_id)| {
1469             if let Some(def_id) = opt_def_id {
1470                 if def_id.is_local() {
1471                     return Some((def_id.index, i));
1472                 }
1473             }
1474             None
1475         }))
1476     }
1477
1478     fn encode_lang_items_missing(&mut self, _: ()) -> LazySeq<lang_items::LangItem> {
1479         let tcx = self.tcx;
1480         self.lazy_seq_ref(&tcx.lang_items().missing)
1481     }
1482
1483     /// Encodes an index, mapping each trait to its (local) implementations.
1484     fn encode_impls(&mut self, _: ()) -> LazySeq<TraitImpls> {
1485         debug!("IsolatedEncoder::encode_impls()");
1486         let tcx = self.tcx;
1487         let mut visitor = ImplVisitor {
1488             tcx,
1489             impls: FxHashMap::default(),
1490         };
1491         tcx.hir().krate().visit_all_item_likes(&mut visitor);
1492
1493         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
1494
1495         // Bring everything into deterministic order for hashing
1496         all_impls.sort_by_cached_key(|&(trait_def_id, _)| {
1497             tcx.def_path_hash(trait_def_id)
1498         });
1499
1500         let all_impls: Vec<_> = all_impls
1501             .into_iter()
1502             .map(|(trait_def_id, mut impls)| {
1503                 // Bring everything into deterministic order for hashing
1504                 impls.sort_by_cached_key(|&def_index| {
1505                     tcx.hir().definitions().def_path_hash(def_index)
1506                 });
1507
1508                 TraitImpls {
1509                     trait_id: (trait_def_id.krate.as_u32(), trait_def_id.index),
1510                     impls: self.lazy_seq_from_slice(&impls[..]),
1511                 }
1512             })
1513             .collect();
1514
1515         self.lazy_seq_from_slice(&all_impls[..])
1516     }
1517
1518     // Encodes all symbols exported from this crate into the metadata.
1519     //
1520     // This pass is seeded off the reachability list calculated in the
1521     // middle::reachable module but filters out items that either don't have a
1522     // symbol associated with them (they weren't translated) or if they're an FFI
1523     // definition (as that's not defined in this crate).
1524     fn encode_exported_symbols(&mut self,
1525                                exported_symbols: &[(ExportedSymbol<'_>, SymbolExportLevel)])
1526                                -> EncodedExportedSymbols {
1527         // The metadata symbol name is special. It should not show up in
1528         // downstream crates.
1529         let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
1530
1531         let lazy_seq = self.lazy_seq(exported_symbols
1532             .iter()
1533             .filter(|&&(ref exported_symbol, _)| {
1534                 match *exported_symbol {
1535                     ExportedSymbol::NoDefId(symbol_name) => {
1536                         symbol_name != metadata_symbol_name
1537                     },
1538                     _ => true,
1539                 }
1540             })
1541             .cloned());
1542
1543         EncodedExportedSymbols {
1544             len: lazy_seq.len,
1545             position: lazy_seq.position,
1546         }
1547     }
1548
1549     fn encode_dylib_dependency_formats(&mut self, _: ()) -> LazySeq<Option<LinkagePreference>> {
1550         match self.tcx.sess.dependency_formats.borrow().get(&config::CrateType::Dylib) {
1551             Some(arr) => {
1552                 self.lazy_seq(arr.iter().map(|slot| {
1553                     match *slot {
1554                         Linkage::NotLinked |
1555                         Linkage::IncludedFromDylib => None,
1556
1557                         Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
1558                         Linkage::Static => Some(LinkagePreference::RequireStatic),
1559                     }
1560                 }))
1561             }
1562             None => LazySeq::empty(),
1563         }
1564     }
1565
1566     fn encode_info_for_foreign_item(&mut self,
1567                                     (def_id, nitem): (DefId, &hir::ForeignItem))
1568                                     -> Entry<'tcx> {
1569         let tcx = self.tcx;
1570
1571         debug!("IsolatedEncoder::encode_info_for_foreign_item({:?})", def_id);
1572
1573         let kind = match nitem.node {
1574             hir::ForeignItemKind::Fn(_, ref names, _) => {
1575                 let data = FnData {
1576                     constness: hir::Constness::NotConst,
1577                     arg_names: self.encode_fn_arg_names(names),
1578                     sig: self.lazy(&tcx.fn_sig(def_id)),
1579                 };
1580                 EntryKind::ForeignFn(self.lazy(&data))
1581             }
1582             hir::ForeignItemKind::Static(_, true) => EntryKind::ForeignMutStatic,
1583             hir::ForeignItemKind::Static(_, false) => EntryKind::ForeignImmStatic,
1584             hir::ForeignItemKind::Type => EntryKind::ForeignType,
1585         };
1586
1587         Entry {
1588             kind,
1589             visibility: self.lazy(&ty::Visibility::from_hir(&nitem.vis, nitem.id, tcx)),
1590             span: self.lazy(&nitem.span),
1591             attributes: self.encode_attributes(&nitem.attrs),
1592             children: LazySeq::empty(),
1593             stability: self.encode_stability(def_id),
1594             deprecation: self.encode_deprecation(def_id),
1595
1596             ty: Some(self.encode_item_type(def_id)),
1597             inherent_impls: LazySeq::empty(),
1598             variances: match nitem.node {
1599                 hir::ForeignItemKind::Fn(..) => self.encode_variances_of(def_id),
1600                 _ => LazySeq::empty(),
1601             },
1602             generics: Some(self.encode_generics(def_id)),
1603             predicates: Some(self.encode_predicates(def_id)),
1604             predicates_defined_on: None,
1605
1606             mir: None,
1607         }
1608     }
1609 }
1610
1611 struct EncodeVisitor<'a, 'b: 'a, 'tcx: 'b> {
1612     index: IndexBuilder<'a, 'b, 'tcx>,
1613 }
1614
1615 impl<'a, 'b, 'tcx> Visitor<'tcx> for EncodeVisitor<'a, 'b, 'tcx> {
1616     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1617         NestedVisitorMap::OnlyBodies(&self.index.tcx.hir())
1618     }
1619     fn visit_expr(&mut self, ex: &'tcx hir::Expr) {
1620         intravisit::walk_expr(self, ex);
1621         self.index.encode_info_for_expr(ex);
1622     }
1623     fn visit_item(&mut self, item: &'tcx hir::Item) {
1624         intravisit::walk_item(self, item);
1625         let def_id = self.index.tcx.hir().local_def_id(item.id);
1626         match item.node {
1627             hir::ItemKind::ExternCrate(_) |
1628             hir::ItemKind::Use(..) => (), // ignore these
1629             _ => self.index.record(def_id, IsolatedEncoder::encode_info_for_item, (def_id, item)),
1630         }
1631         self.index.encode_addl_info_for_item(item);
1632     }
1633     fn visit_foreign_item(&mut self, ni: &'tcx hir::ForeignItem) {
1634         intravisit::walk_foreign_item(self, ni);
1635         let def_id = self.index.tcx.hir().local_def_id(ni.id);
1636         self.index.record(def_id,
1637                           IsolatedEncoder::encode_info_for_foreign_item,
1638                           (def_id, ni));
1639     }
1640     fn visit_variant(&mut self,
1641                      v: &'tcx hir::Variant,
1642                      g: &'tcx hir::Generics,
1643                      id: ast::NodeId) {
1644         intravisit::walk_variant(self, v, g, id);
1645
1646         if let Some(ref discr) = v.node.disr_expr {
1647             let def_id = self.index.tcx.hir().local_def_id(discr.id);
1648             self.index.record(def_id, IsolatedEncoder::encode_info_for_anon_const, def_id);
1649         }
1650     }
1651     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
1652         intravisit::walk_generics(self, generics);
1653         self.index.encode_info_for_generics(generics);
1654     }
1655     fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1656         intravisit::walk_ty(self, ty);
1657         self.index.encode_info_for_ty(ty);
1658     }
1659     fn visit_macro_def(&mut self, macro_def: &'tcx hir::MacroDef) {
1660         let def_id = self.index.tcx.hir().local_def_id(macro_def.id);
1661         self.index.record(def_id, IsolatedEncoder::encode_info_for_macro_def, macro_def);
1662     }
1663 }
1664
1665 impl<'a, 'b, 'tcx> IndexBuilder<'a, 'b, 'tcx> {
1666     fn encode_fields(&mut self, adt_def_id: DefId) {
1667         let def = self.tcx.adt_def(adt_def_id);
1668         for (variant_index, variant) in def.variants.iter_enumerated() {
1669             for (field_index, field) in variant.fields.iter().enumerate() {
1670                 self.record(field.did,
1671                             IsolatedEncoder::encode_field,
1672                             (adt_def_id, Untracked((variant_index, field_index))));
1673             }
1674         }
1675     }
1676
1677     fn encode_info_for_generics(&mut self, generics: &hir::Generics) {
1678         for param in &generics.params {
1679             match param.kind {
1680                 hir::GenericParamKind::Lifetime { .. } => {}
1681                 hir::GenericParamKind::Type { ref default, .. } => {
1682                     let def_id = self.tcx.hir().local_def_id(param.id);
1683                     let has_default = Untracked(default.is_some());
1684                     let encode_info = IsolatedEncoder::encode_info_for_ty_param;
1685                     self.record(def_id, encode_info, (def_id, has_default));
1686                 }
1687             }
1688         }
1689     }
1690
1691     fn encode_info_for_ty(&mut self, ty: &hir::Ty) {
1692         match ty.node {
1693             hir::TyKind::Array(_, ref length) => {
1694                 let def_id = self.tcx.hir().local_def_id(length.id);
1695                 self.record(def_id, IsolatedEncoder::encode_info_for_anon_const, def_id);
1696             }
1697             _ => {}
1698         }
1699     }
1700
1701     fn encode_info_for_expr(&mut self, expr: &hir::Expr) {
1702         match expr.node {
1703             hir::ExprKind::Closure(..) => {
1704                 let def_id = self.tcx.hir().local_def_id(expr.id);
1705                 self.record(def_id, IsolatedEncoder::encode_info_for_closure, def_id);
1706             }
1707             _ => {}
1708         }
1709     }
1710
1711     /// In some cases, along with the item itself, we also
1712     /// encode some sub-items. Usually we want some info from the item
1713     /// so it's easier to do that here then to wait until we would encounter
1714     /// normally in the visitor walk.
1715     fn encode_addl_info_for_item(&mut self, item: &hir::Item) {
1716         let def_id = self.tcx.hir().local_def_id(item.id);
1717         match item.node {
1718             hir::ItemKind::Static(..) |
1719             hir::ItemKind::Const(..) |
1720             hir::ItemKind::Fn(..) |
1721             hir::ItemKind::Mod(..) |
1722             hir::ItemKind::ForeignMod(..) |
1723             hir::ItemKind::GlobalAsm(..) |
1724             hir::ItemKind::ExternCrate(..) |
1725             hir::ItemKind::Use(..) |
1726             hir::ItemKind::Ty(..) |
1727             hir::ItemKind::Existential(..) |
1728             hir::ItemKind::TraitAlias(..) => {
1729                 // no sub-item recording needed in these cases
1730             }
1731             hir::ItemKind::Enum(..) => {
1732                 self.encode_fields(def_id);
1733
1734                 let def = self.tcx.adt_def(def_id);
1735                 for (i, variant) in def.variants.iter_enumerated() {
1736                     self.record(variant.did,
1737                                 IsolatedEncoder::encode_enum_variant_info,
1738                                 (def_id, Untracked(i)));
1739                 }
1740             }
1741             hir::ItemKind::Struct(ref struct_def, _) => {
1742                 self.encode_fields(def_id);
1743
1744                 // If the struct has a constructor, encode it.
1745                 if !struct_def.is_struct() {
1746                     let ctor_def_id = self.tcx.hir().local_def_id(struct_def.id());
1747                     self.record(ctor_def_id,
1748                                 IsolatedEncoder::encode_struct_ctor,
1749                                 (def_id, ctor_def_id));
1750                 }
1751             }
1752             hir::ItemKind::Union(..) => {
1753                 self.encode_fields(def_id);
1754             }
1755             hir::ItemKind::Impl(..) => {
1756                 for &trait_item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1757                     self.record(trait_item_def_id,
1758                                 IsolatedEncoder::encode_info_for_impl_item,
1759                                 trait_item_def_id);
1760                 }
1761             }
1762             hir::ItemKind::Trait(..) => {
1763                 for &item_def_id in self.tcx.associated_item_def_ids(def_id).iter() {
1764                     self.record(item_def_id,
1765                                 IsolatedEncoder::encode_info_for_trait_item,
1766                                 item_def_id);
1767                 }
1768             }
1769         }
1770     }
1771 }
1772
1773 struct ImplVisitor<'a, 'tcx: 'a> {
1774     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1775     impls: FxHashMap<DefId, Vec<DefIndex>>,
1776 }
1777
1778 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for ImplVisitor<'a, 'tcx> {
1779     fn visit_item(&mut self, item: &hir::Item) {
1780         if let hir::ItemKind::Impl(..) = item.node {
1781             let impl_id = self.tcx.hir().local_def_id(item.id);
1782             if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_id) {
1783                 self.impls
1784                     .entry(trait_ref.def_id)
1785                     .or_default()
1786                     .push(impl_id.index);
1787             }
1788         }
1789     }
1790
1791     fn visit_trait_item(&mut self, _trait_item: &'v hir::TraitItem) {}
1792
1793     fn visit_impl_item(&mut self, _impl_item: &'v hir::ImplItem) {
1794         // handled in `visit_item` above
1795     }
1796 }
1797
1798 // NOTE(eddyb) The following comment was preserved for posterity, even
1799 // though it's no longer relevant as EBML (which uses nested & tagged
1800 // "documents") was replaced with a scheme that can't go out of bounds.
1801 //
1802 // And here we run into yet another obscure archive bug: in which metadata
1803 // loaded from archives may have trailing garbage bytes. Awhile back one of
1804 // our tests was failing sporadically on the macOS 64-bit builders (both nopt
1805 // and opt) by having ebml generate an out-of-bounds panic when looking at
1806 // metadata.
1807 //
1808 // Upon investigation it turned out that the metadata file inside of an rlib
1809 // (and ar archive) was being corrupted. Some compilations would generate a
1810 // metadata file which would end in a few extra bytes, while other
1811 // compilations would not have these extra bytes appended to the end. These
1812 // extra bytes were interpreted by ebml as an extra tag, so they ended up
1813 // being interpreted causing the out-of-bounds.
1814 //
1815 // The root cause of why these extra bytes were appearing was never
1816 // discovered, and in the meantime the solution we're employing is to insert
1817 // the length of the metadata to the start of the metadata. Later on this
1818 // will allow us to slice the metadata to the precise length that we just
1819 // generated regardless of trailing bytes that end up in it.
1820
1821 pub fn encode_metadata<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
1822                                  -> EncodedMetadata
1823 {
1824     let mut encoder = opaque::Encoder::new(vec![]);
1825     encoder.emit_raw_bytes(METADATA_HEADER);
1826
1827     // Will be filled with the root position after encoding everything.
1828     encoder.emit_raw_bytes(&[0, 0, 0, 0]);
1829
1830     let (root, mut result) = {
1831         let mut ecx = EncodeContext {
1832             opaque: encoder,
1833             tcx,
1834             lazy_state: LazyState::NoNode,
1835             type_shorthands: Default::default(),
1836             predicate_shorthands: Default::default(),
1837             source_file_cache: tcx.sess.source_map().files()[0].clone(),
1838             interpret_allocs: Default::default(),
1839             interpret_allocs_inverse: Default::default(),
1840         };
1841
1842         // Encode the rustc version string in a predictable location.
1843         rustc_version().encode(&mut ecx).unwrap();
1844
1845         // Encode all the entries and extra information in the crate,
1846         // culminating in the `CrateRoot` which points to all of it.
1847         let root = ecx.encode_crate_root();
1848         (root, ecx.opaque.into_inner())
1849     };
1850
1851     // Encode the root position.
1852     let header = METADATA_HEADER.len();
1853     let pos = root.position;
1854     result[header + 0] = (pos >> 24) as u8;
1855     result[header + 1] = (pos >> 16) as u8;
1856     result[header + 2] = (pos >> 8) as u8;
1857     result[header + 3] = (pos >> 0) as u8;
1858
1859     EncodedMetadata { raw_data: result }
1860 }
1861
1862 pub fn get_repr_options<'a, 'tcx, 'gcx>(tcx: &TyCtxt<'a, 'tcx, 'gcx>, did: DefId) -> ReprOptions {
1863     let ty = tcx.type_of(did);
1864     match ty.sty {
1865         ty::Adt(ref def, _) => return def.repr,
1866         _ => bug!("{} is not an ADT", ty),
1867     }
1868 }