src/librustc_typeck/check/writeback.rs

   1 // Type resolution: the phase that finds all the types in the AST with
   2 // unresolved type variables and replaces "ty_var" types with their
   3 // substitutions.
   4
   5 use crate::check::FnCtxt;
   6 use errors::DiagnosticBuilder;
   7 use rustc::hir;
   8 use rustc::hir::def_id::{DefId, DefIndex};
   9 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  10 use rustc::infer::InferCtxt;
  11 use rustc::ty::adjustment::{Adjust, Adjustment, PointerCast};
  12 use rustc::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder};
  13 use rustc::ty::subst::UnpackedKind;
  14 use rustc::ty::{self, Ty, TyCtxt};
  15 use rustc::util::nodemap::DefIdSet;
  16 use rustc_data_structures::sync::Lrc;
  17 use std::mem;
  18 use syntax_pos::Span;
  19
  20 ///////////////////////////////////////////////////////////////////////////
  21 // Entry point
  22
  23 // During type inference, partially inferred types are
  24 // represented using Type variables (ty::Infer). These don't appear in
  25 // the final TypeckTables since all of the types should have been
  26 // inferred once typeck_tables_of is done.
  27 // When type inference is running however, having to update the typeck
  28 // tables every time a new type is inferred would be unreasonably slow,
  29 // so instead all of the replacement happens at the end in
  30 // resolve_type_vars_in_body, which creates a new TypeTables which
  31 // doesn't contain any inference types.
  32 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  33     pub fn resolve_type_vars_in_body(&self, body: &'gcx hir::Body) -> &'gcx ty::TypeckTables<'gcx> {
  34         let item_id = self.tcx.hir().body_owner(body.id());
  35         let item_def_id = self.tcx.hir().local_def_id(item_id);
  36
  37         // This attribute causes us to dump some writeback information
  38         // in the form of errors, which is used for unit tests.
  39         let rustc_dump_user_substs = self.tcx.has_attr(item_def_id, "rustc_dump_user_substs");
  40
  41         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
  42         for arg in &body.arguments {
  43             wbcx.visit_node_id(arg.pat.span, arg.hir_id);
  44         }
  45         // Type only exists for constants and statics, not functions.
  46         match self.tcx.hir().body_owner_kind(item_id) {
  47             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
  48                 let item_hir_id = self.tcx.hir().node_to_hir_id(item_id);
  49                 wbcx.visit_node_id(body.value.span, item_hir_id);
  50             }
  51             hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
  52         }
  53         wbcx.visit_body(body);
  54         wbcx.visit_upvar_capture_map();
  55         wbcx.visit_upvar_list_map();
  56         wbcx.visit_closures();
  57         wbcx.visit_liberated_fn_sigs();
  58         wbcx.visit_fru_field_types();
  59         wbcx.visit_opaque_types(body.value.span);
  60         wbcx.visit_coercion_casts();
  61         wbcx.visit_free_region_map();
  62         wbcx.visit_user_provided_tys();
  63         wbcx.visit_user_provided_sigs();
  64
  65         let used_trait_imports = mem::replace(
  66             &mut self.tables.borrow_mut().used_trait_imports,
  67             Lrc::new(DefIdSet::default()),
  68         );
  69         debug!(
  70             "used_trait_imports({:?}) = {:?}",
  71             item_def_id, used_trait_imports
  72         );
  73         wbcx.tables.used_trait_imports = used_trait_imports;
  74
  75         wbcx.tables.tainted_by_errors = self.is_tainted_by_errors();
  76
  77         debug!(
  78             "writeback: tables for {:?} are {:#?}",
  79             item_def_id, wbcx.tables
  80         );
  81
  82         self.tcx.alloc_tables(wbcx.tables)
  83     }
  84 }
  85
  86 ///////////////////////////////////////////////////////////////////////////
  87 // The Writeback context. This visitor walks the AST, checking the
  88 // fn-specific tables to find references to types or regions. It
  89 // resolves those regions to remove inference variables and writes the
  90 // final result back into the master tables in the tcx. Here and
  91 // there, it applies a few ad-hoc checks that were not convenient to
  92 // do elsewhere.
  93
  94 struct WritebackCx<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
  95     fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
  96
  97     tables: ty::TypeckTables<'gcx>,
  98
  99     body: &'gcx hir::Body,
 100
 101     rustc_dump_user_substs: bool,
 102 }
 103
 104 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
 105     fn new(
 106         fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
 107         body: &'gcx hir::Body,
 108         rustc_dump_user_substs: bool,
 109     ) -> WritebackCx<'cx, 'gcx, 'tcx> {
 110         let owner = body.id().hir_id;
 111
 112         WritebackCx {
 113             fcx,
 114             tables: ty::TypeckTables::empty(Some(DefId::local(owner.owner))),
 115             body,
 116             rustc_dump_user_substs,
 117         }
 118     }
 119
 120     fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
 121         self.fcx.tcx
 122     }
 123
 124     fn write_ty_to_tables(&mut self, hir_id: hir::HirId, ty: Ty<'gcx>) {
 125         debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
 126         assert!(!ty.needs_infer() && !ty.has_placeholders());
 127         self.tables.node_types_mut().insert(hir_id, ty);
 128     }
 129
 130     // Hacky hack: During type-checking, we treat *all* operators
 131     // as potentially overloaded. But then, during writeback, if
 132     // we observe that something like `a+b` is (known to be)
 133     // operating on scalars, we clear the overload.
 134     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr) {
 135         match e.node {
 136             hir::ExprKind::Unary(hir::UnNeg, ref inner)
 137             | hir::ExprKind::Unary(hir::UnNot, ref inner) => {
 138                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 139                 let inner_ty = self.fcx.resolve_type_vars_if_possible(&inner_ty);
 140
 141                 if inner_ty.is_scalar() {
 142                     let mut tables = self.fcx.tables.borrow_mut();
 143                     tables.type_dependent_defs_mut().remove(e.hir_id);
 144                     tables.node_substs_mut().remove(e.hir_id);
 145                 }
 146             }
 147             hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
 148             | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 149                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 150                 let lhs_ty = self.fcx.resolve_type_vars_if_possible(&lhs_ty);
 151
 152                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 153                 let rhs_ty = self.fcx.resolve_type_vars_if_possible(&rhs_ty);
 154
 155                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 156                     let mut tables = self.fcx.tables.borrow_mut();
 157                     tables.type_dependent_defs_mut().remove(e.hir_id);
 158                     tables.node_substs_mut().remove(e.hir_id);
 159
 160                     match e.node {
 161                         hir::ExprKind::Binary(..) => {
 162                             if !op.node.is_by_value() {
 163                                 let mut adjustments = tables.adjustments_mut();
 164                                 adjustments.get_mut(lhs.hir_id).map(|a| a.pop());
 165                                 adjustments.get_mut(rhs.hir_id).map(|a| a.pop());
 166                             }
 167                         }
 168                         hir::ExprKind::AssignOp(..) => {
 169                             tables
 170                                 .adjustments_mut()
 171                                 .get_mut(lhs.hir_id)
 172                                 .map(|a| a.pop());
 173                         }
 174                         _ => {}
 175                     }
 176                 }
 177             }
 178             _ => {}
 179         }
 180     }
 181
 182     // Similar to operators, indexing is always assumed to be overloaded
 183     // Here, correct cases where an indexing expression can be simplified
 184     // to use builtin indexing because the index type is known to be
 185     // usize-ish
 186     fn fix_index_builtin_expr(&mut self, e: &hir::Expr) {
 187         if let hir::ExprKind::Index(ref base, ref index) = e.node {
 188             let mut tables = self.fcx.tables.borrow_mut();
 189
 190             // All valid indexing looks like this; might encounter non-valid indexes at this point
 191             if let ty::Ref(_, base_ty, _) = tables.expr_ty_adjusted(&base).sty {
 192                 let index_ty = tables.expr_ty_adjusted(&index);
 193                 let index_ty = self.fcx.resolve_type_vars_if_possible(&index_ty);
 194
 195                 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
 196                     // Remove the method call record
 197                     tables.type_dependent_defs_mut().remove(e.hir_id);
 198                     tables.node_substs_mut().remove(e.hir_id);
 199
 200                     tables.adjustments_mut().get_mut(base.hir_id).map(|a| {
 201                         // Discard the need for a mutable borrow
 202                         match a.pop() {
 203                             // Extra adjustment made when indexing causes a drop
 204                             // of size information - we need to get rid of it
 205                             // Since this is "after" the other adjustment to be
 206                             // discarded, we do an extra `pop()`
 207                             Some(Adjustment {
 208                                 kind: Adjust::Pointer(PointerCast::Unsize),
 209                                 ..
 210                             }) => {
 211                                 // So the borrow discard actually happens here
 212                                 a.pop();
 213                             }
 214                             _ => {}
 215                         }
 216                     });
 217                 }
 218             }
 219         }
 220     }
 221 }
 222
 223 ///////////////////////////////////////////////////////////////////////////
 224 // Impl of Visitor for Resolver
 225 //
 226 // This is the master code which walks the AST. It delegates most of
 227 // the heavy lifting to the generic visit and resolve functions
 228 // below. In general, a function is made into a `visitor` if it must
 229 // traffic in node-ids or update tables in the type context etc.
 230
 231 impl<'cx, 'gcx, 'tcx> Visitor<'gcx> for WritebackCx<'cx, 'gcx, 'tcx> {
 232     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
 233         NestedVisitorMap::None
 234     }
 235
 236     fn visit_expr(&mut self, e: &'gcx hir::Expr) {
 237         self.fix_scalar_builtin_expr(e);
 238         self.fix_index_builtin_expr(e);
 239
 240         self.visit_node_id(e.span, e.hir_id);
 241
 242         match e.node {
 243             hir::ExprKind::Closure(_, _, body, _, _) => {
 244                 let body = self.fcx.tcx.hir().body(body);
 245                 for arg in &body.arguments {
 246                     self.visit_node_id(e.span, arg.hir_id);
 247                 }
 248
 249                 self.visit_body(body);
 250             }
 251             hir::ExprKind::Struct(_, ref fields, _) => {
 252                 for field in fields {
 253                     self.visit_field_id(field.hir_id);
 254                 }
 255             }
 256             hir::ExprKind::Field(..) => {
 257                 self.visit_field_id(e.hir_id);
 258             }
 259             _ => {}
 260         }
 261
 262         intravisit::walk_expr(self, e);
 263     }
 264
 265     fn visit_block(&mut self, b: &'gcx hir::Block) {
 266         self.visit_node_id(b.span, b.hir_id);
 267         intravisit::walk_block(self, b);
 268     }
 269
 270     fn visit_pat(&mut self, p: &'gcx hir::Pat) {
 271         match p.node {
 272             hir::PatKind::Binding(..) => {
 273                 if let Some(&bm) = self.fcx.tables.borrow().pat_binding_modes().get(p.hir_id) {
 274                     self.tables.pat_binding_modes_mut().insert(p.hir_id, bm);
 275                 } else {
 276                     self.tcx()
 277                         .sess
 278                         .delay_span_bug(p.span, "missing binding mode");
 279                 }
 280             }
 281             hir::PatKind::Struct(_, ref fields, _) => {
 282                 for field in fields {
 283                     self.visit_field_id(field.node.hir_id);
 284                 }
 285             }
 286             _ => {}
 287         };
 288
 289         self.visit_pat_adjustments(p.span, p.hir_id);
 290
 291         self.visit_node_id(p.span, p.hir_id);
 292         intravisit::walk_pat(self, p);
 293     }
 294
 295     fn visit_local(&mut self, l: &'gcx hir::Local) {
 296         intravisit::walk_local(self, l);
 297         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 298         let var_ty = self.resolve(&var_ty, &l.span);
 299         self.write_ty_to_tables(l.hir_id, var_ty);
 300     }
 301
 302     fn visit_ty(&mut self, hir_ty: &'gcx hir::Ty) {
 303         intravisit::walk_ty(self, hir_ty);
 304         let ty = self.fcx.node_ty(hir_ty.hir_id);
 305         let ty = self.resolve(&ty, &hir_ty.span);
 306         self.write_ty_to_tables(hir_ty.hir_id, ty);
 307     }
 308
 309     fn visit_argument_source(&mut self, s: &'gcx hir::ArgSource) {
 310         match s {
 311             // Don't visit the pattern in `ArgSource::AsyncFn`, it contains a pattern which has
 312             // a `NodeId` w/out a type, as it is only used for getting the name of the original
 313             // pattern for diagnostics where only an `hir::Arg` is present.
 314             hir::ArgSource::AsyncFn(..) => {},
 315             _ => intravisit::walk_argument_source(self, s),
 316         }
 317     }
 318 }
 319
 320 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
 321     fn visit_upvar_capture_map(&mut self) {
 322         for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
 323             let new_upvar_capture = match *upvar_capture {
 324                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 325                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 326                     let r = upvar_borrow.region;
 327                     let r = self.resolve(&r, &upvar_id.var_path.hir_id);
 328                     ty::UpvarCapture::ByRef(ty::UpvarBorrow {
 329                         kind: upvar_borrow.kind,
 330                         region: r,
 331                     })
 332                 }
 333             };
 334             debug!(
 335                 "Upvar capture for {:?} resolved to {:?}",
 336                 upvar_id, new_upvar_capture
 337             );
 338             self.tables
 339                 .upvar_capture_map
 340                 .insert(*upvar_id, new_upvar_capture);
 341         }
 342     }
 343
 344     /// Runs through the function context's upvar list map and adds the same to
 345     /// the TypeckTables. upvarlist is a hashmap of the list of upvars referred
 346     /// to in a closure..
 347     fn visit_upvar_list_map(&mut self) {
 348         for (closure_def_id, upvar_list) in self.fcx.tables.borrow().upvar_list.iter() {
 349             debug!(
 350                 "UpvarIDs captured by closure {:?} are: {:?}",
 351                 closure_def_id, upvar_list
 352             );
 353             self.tables
 354                 .upvar_list
 355                 .insert(*closure_def_id, upvar_list.to_vec());
 356         }
 357     }
 358
 359     fn visit_closures(&mut self) {
 360         let fcx_tables = self.fcx.tables.borrow();
 361         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 362         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 363
 364         for (&id, &origin) in fcx_tables.closure_kind_origins().iter() {
 365             let hir_id = hir::HirId {
 366                 owner: common_local_id_root.index,
 367                 local_id: id,
 368             };
 369             self.tables
 370                 .closure_kind_origins_mut()
 371                 .insert(hir_id, origin);
 372         }
 373     }
 374
 375     fn visit_coercion_casts(&mut self) {
 376         let fcx_tables = self.fcx.tables.borrow();
 377         let fcx_coercion_casts = fcx_tables.coercion_casts();
 378         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 379
 380         for local_id in fcx_coercion_casts {
 381             self.tables.set_coercion_cast(*local_id);
 382         }
 383     }
 384
 385     fn visit_free_region_map(&mut self) {
 386         let free_region_map = self.tcx()
 387             .lift_to_global(&self.fcx.tables.borrow().free_region_map);
 388         let free_region_map = free_region_map.expect("all regions in free-region-map are global");
 389         self.tables.free_region_map = free_region_map;
 390     }
 391
 392     fn visit_user_provided_tys(&mut self) {
 393         let fcx_tables = self.fcx.tables.borrow();
 394         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 395         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 396
 397         let mut errors_buffer = Vec::new();
 398         for (&local_id, c_ty) in fcx_tables.user_provided_types().iter() {
 399             let hir_id = hir::HirId {
 400                 owner: common_local_id_root.index,
 401                 local_id,
 402             };
 403
 404             let c_ty = if let Some(c_ty) = self.tcx().lift_to_global(c_ty) {
 405                 c_ty
 406             } else {
 407                 span_bug!(
 408                     hir_id.to_span(self.fcx.tcx),
 409                     "writeback: `{:?}` missing from the global type context",
 410                     c_ty
 411                 );
 412             };
 413
 414             self.tables
 415                 .user_provided_types_mut()
 416                 .insert(hir_id, c_ty.clone());
 417
 418             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 419                 if self.rustc_dump_user_substs {
 420                     // This is a unit-testing mechanism.
 421                     let span = self.tcx().hir().span_by_hir_id(hir_id);
 422                     // We need to buffer the errors in order to guarantee a consistent
 423                     // order when emitting them.
 424                     let err = self.tcx().sess.struct_span_err(
 425                         span,
 426                         &format!("user substs: {:?}", user_substs)
 427                     );
 428                     err.buffer(&mut errors_buffer);
 429                 }
 430             }
 431         }
 432
 433         if !errors_buffer.is_empty() {
 434             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 435             for diag in errors_buffer.drain(..) {
 436                 DiagnosticBuilder::new_diagnostic(self.tcx().sess.diagnostic(), diag).emit();
 437             }
 438         }
 439     }
 440
 441     fn visit_user_provided_sigs(&mut self) {
 442         let fcx_tables = self.fcx.tables.borrow();
 443         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 444
 445         for (&def_id, c_sig) in fcx_tables.user_provided_sigs.iter() {
 446             let c_sig = if let Some(c_sig) = self.tcx().lift_to_global(c_sig) {
 447                 c_sig
 448             } else {
 449                 span_bug!(
 450                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 451                     "writeback: `{:?}` missing from the global type context",
 452                     c_sig
 453                 );
 454             };
 455
 456             self.tables
 457                 .user_provided_sigs
 458                 .insert(def_id, c_sig.clone());
 459         }
 460     }
 461
 462     fn visit_opaque_types(&mut self, span: Span) {
 463         for (&def_id, opaque_defn) in self.fcx.opaque_types.borrow().iter() {
 464             let hir_id = self.tcx().hir().as_local_hir_id(def_id).unwrap();
 465             let instantiated_ty = self.resolve(&opaque_defn.concrete_ty, &hir_id);
 466
 467             let generics = self.tcx().generics_of(def_id);
 468
 469             let definition_ty = if generics.parent.is_some() {
 470                 // impl trait
 471                 self.fcx.infer_opaque_definition_from_instantiation(
 472                     def_id,
 473                     opaque_defn,
 474                     instantiated_ty,
 475                 )
 476             } else {
 477                 // prevent
 478                 // * `fn foo<T>() -> Foo<T>`
 479                 // * `fn foo<T: Bound + Other>() -> Foo<T>`
 480                 // from being defining
 481
 482                 // Also replace all generic params with the ones from the existential type
 483                 // definition so
 484                 // ```rust
 485                 // existential type Foo<T>: 'static;
 486                 // fn foo<U>() -> Foo<U> { .. }
 487                 // ```
 488                 // figures out the concrete type with `U`, but the stored type is with `T`
 489                 instantiated_ty.fold_with(&mut BottomUpFolder {
 490                     tcx: self.tcx().global_tcx(),
 491                     fldop: |ty| {
 492                         trace!("checking type {:?}", ty);
 493                         // find a type parameter
 494                         if let ty::Param(..) = ty.sty {
 495                             // look it up in the substitution list
 496                             assert_eq!(opaque_defn.substs.len(), generics.params.len());
 497                             for (subst, param) in opaque_defn.substs.iter().zip(&generics.params) {
 498                                 if let UnpackedKind::Type(subst) = subst.unpack() {
 499                                     if subst == ty {
 500                                         // found it in the substitution list, replace with the
 501                                         // parameter from the existential type
 502                                         return self.tcx()
 503                                             .global_tcx()
 504                                             .mk_ty_param(param.index, param.name);
 505                                     }
 506                                 }
 507                             }
 508                             self.tcx()
 509                                 .sess
 510                                 .struct_span_err(
 511                                     span,
 512                                     &format!(
 513                                         "type parameter `{}` is part of concrete type but not used \
 514                                          in parameter list for existential type",
 515                                         ty,
 516                                     ),
 517                                 )
 518                                 .emit();
 519                             return self.tcx().types.err;
 520                         }
 521                         ty
 522                     },
 523                     reg_op: |region| {
 524                         match region {
 525                             // ignore static regions
 526                             ty::ReStatic => region,
 527                             _ => {
 528                                 trace!("checking {:?}", region);
 529                                 for (subst, p) in opaque_defn.substs.iter().zip(&generics.params) {
 530                                     if let UnpackedKind::Lifetime(subst) = subst.unpack() {
 531                                         if subst == region {
 532                                             // found it in the substitution list, replace with the
 533                                             // parameter from the existential type
 534                                             let reg = ty::EarlyBoundRegion {
 535                                                 def_id: p.def_id,
 536                                                 index: p.index,
 537                                                 name: p.name,
 538                                             };
 539                                             trace!("replace {:?} with {:?}", region, reg);
 540                                             return self.tcx()
 541                                                 .global_tcx()
 542                                                 .mk_region(ty::ReEarlyBound(reg));
 543                                         }
 544                                     }
 545                                 }
 546                                 trace!("opaque_defn: {:#?}", opaque_defn);
 547                                 trace!("generics: {:#?}", generics);
 548                                 self.tcx()
 549                                     .sess
 550                                     .struct_span_err(
 551                                         span,
 552                                         "non-defining existential type use in defining scope",
 553                                     )
 554                                     .span_label(
 555                                         span,
 556                                         format!(
 557                                             "lifetime `{}` is part of concrete type but not used \
 558                                              in parameter list of existential type",
 559                                             region,
 560                                         ),
 561                                     )
 562                                     .emit();
 563                                 self.tcx().global_tcx().mk_region(ty::ReStatic)
 564                             }
 565                         }
 566                     },
 567                 })
 568             };
 569
 570             if let ty::Opaque(defin_ty_def_id, _substs) = definition_ty.sty {
 571                 if def_id == defin_ty_def_id {
 572                     // Concrete type resolved to the existential type itself
 573                     // Force a cycle error
 574                     // FIXME(oli-obk): we could just not insert it into `concrete_existential_types`
 575                     // which simply would make this use not a defining use.
 576                     self.tcx().at(span).type_of(defin_ty_def_id);
 577                 }
 578             }
 579
 580             let new = ty::ResolvedOpaqueTy {
 581                 concrete_type: definition_ty,
 582                 substs: self.tcx().lift_to_global(&opaque_defn.substs).unwrap(),
 583             };
 584
 585             let old = self.tables
 586                 .concrete_existential_types
 587                 .insert(def_id, new);
 588             if let Some(old) = old {
 589                 if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
 590                     span_bug!(
 591                         span,
 592                         "visit_opaque_types tried to write \
 593                         different types for the same existential type: {:?}, {:?}, {:?}, {:?}",
 594                         def_id,
 595                         definition_ty,
 596                         opaque_defn,
 597                         old,
 598                     );
 599                 }
 600             }
 601         }
 602     }
 603
 604     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 605         if let Some(index) = self.fcx
 606             .tables
 607             .borrow_mut()
 608             .field_indices_mut()
 609             .remove(hir_id)
 610         {
 611             self.tables.field_indices_mut().insert(hir_id, index);
 612         }
 613     }
 614
 615     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 616         // Export associated path extensions and method resolutions.
 617         if let Some(def) = self.fcx
 618             .tables
 619             .borrow_mut()
 620             .type_dependent_defs_mut()
 621             .remove(hir_id)
 622         {
 623             self.tables.type_dependent_defs_mut().insert(hir_id, def);
 624         }
 625
 626         // Resolve any borrowings for the node with id `node_id`
 627         self.visit_adjustments(span, hir_id);
 628
 629         // Resolve the type of the node with id `node_id`
 630         let n_ty = self.fcx.node_ty(hir_id);
 631         let n_ty = self.resolve(&n_ty, &span);
 632         self.write_ty_to_tables(hir_id, n_ty);
 633         debug!("Node {:?} has type {:?}", hir_id, n_ty);
 634
 635         // Resolve any substitutions
 636         if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
 637             let substs = self.resolve(&substs, &span);
 638             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 639             assert!(!substs.needs_infer() && !substs.has_placeholders());
 640             self.tables.node_substs_mut().insert(hir_id, substs);
 641         }
 642     }
 643
 644     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 645         let adjustment = self.fcx
 646             .tables
 647             .borrow_mut()
 648             .adjustments_mut()
 649             .remove(hir_id);
 650         match adjustment {
 651             None => {
 652                 debug!("No adjustments for node {:?}", hir_id);
 653             }
 654
 655             Some(adjustment) => {
 656                 let resolved_adjustment = self.resolve(&adjustment, &span);
 657                 debug!(
 658                     "Adjustments for node {:?}: {:?}",
 659                     hir_id, resolved_adjustment
 660                 );
 661                 self.tables
 662                     .adjustments_mut()
 663                     .insert(hir_id, resolved_adjustment);
 664             }
 665         }
 666     }
 667
 668     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 669         let adjustment = self.fcx
 670             .tables
 671             .borrow_mut()
 672             .pat_adjustments_mut()
 673             .remove(hir_id);
 674         match adjustment {
 675             None => {
 676                 debug!("No pat_adjustments for node {:?}", hir_id);
 677             }
 678
 679             Some(adjustment) => {
 680                 let resolved_adjustment = self.resolve(&adjustment, &span);
 681                 debug!(
 682                     "pat_adjustments for node {:?}: {:?}",
 683                     hir_id, resolved_adjustment
 684                 );
 685                 self.tables
 686                     .pat_adjustments_mut()
 687                     .insert(hir_id, resolved_adjustment);
 688             }
 689         }
 690     }
 691
 692     fn visit_liberated_fn_sigs(&mut self) {
 693         let fcx_tables = self.fcx.tables.borrow();
 694         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 695         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 696
 697         for (&local_id, fn_sig) in fcx_tables.liberated_fn_sigs().iter() {
 698             let hir_id = hir::HirId {
 699                 owner: common_local_id_root.index,
 700                 local_id,
 701             };
 702             let fn_sig = self.resolve(fn_sig, &hir_id);
 703             self.tables
 704                 .liberated_fn_sigs_mut()
 705                 .insert(hir_id, fn_sig.clone());
 706         }
 707     }
 708
 709     fn visit_fru_field_types(&mut self) {
 710         let fcx_tables = self.fcx.tables.borrow();
 711         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 712         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 713
 714         for (&local_id, ftys) in fcx_tables.fru_field_types().iter() {
 715             let hir_id = hir::HirId {
 716                 owner: common_local_id_root.index,
 717                 local_id,
 718             };
 719             let ftys = self.resolve(ftys, &hir_id);
 720             self.tables.fru_field_types_mut().insert(hir_id, ftys);
 721         }
 722     }
 723
 724     fn resolve<T>(&self, x: &T, span: &dyn Locatable) -> T::Lifted
 725     where
 726         T: TypeFoldable<'tcx> + ty::Lift<'gcx>,
 727     {
 728         let x = x.fold_with(&mut Resolver::new(self.fcx, span, self.body));
 729         if let Some(lifted) = self.tcx().lift_to_global(&x) {
 730             lifted
 731         } else {
 732             span_bug!(
 733                 span.to_span(self.fcx.tcx),
 734                 "writeback: `{:?}` missing from the global type context",
 735                 x
 736             );
 737         }
 738     }
 739 }
 740
 741 trait Locatable {
 742     fn to_span(&self, tcx: TyCtxt<'_, '_, '_>) -> Span;
 743 }
 744
 745 impl Locatable for Span {
 746     fn to_span(&self, _: TyCtxt<'_, '_, '_>) -> Span {
 747         *self
 748     }
 749 }
 750
 751 impl Locatable for DefIndex {
 752     fn to_span(&self, tcx: TyCtxt<'_, '_, '_>) -> Span {
 753         let hir_id = tcx.hir().def_index_to_hir_id(*self);
 754         tcx.hir().span_by_hir_id(hir_id)
 755     }
 756 }
 757
 758 impl Locatable for hir::HirId {
 759     fn to_span(&self, tcx: TyCtxt<'_, '_, '_>) -> Span {
 760         tcx.hir().span_by_hir_id(*self)
 761     }
 762 }
 763
 764 ///////////////////////////////////////////////////////////////////////////
 765 // The Resolver. This is the type folding engine that detects
 766 // unresolved types and so forth.
 767
 768 struct Resolver<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
 769     tcx: TyCtxt<'cx, 'gcx, 'tcx>,
 770     infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
 771     span: &'cx dyn Locatable,
 772     body: &'gcx hir::Body,
 773 }
 774
 775 impl<'cx, 'gcx, 'tcx> Resolver<'cx, 'gcx, 'tcx> {
 776     fn new(
 777         fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
 778         span: &'cx dyn Locatable,
 779         body: &'gcx hir::Body,
 780     ) -> Resolver<'cx, 'gcx, 'tcx> {
 781         Resolver {
 782             tcx: fcx.tcx,
 783             infcx: fcx,
 784             span,
 785             body,
 786         }
 787     }
 788
 789     fn report_error(&self, t: Ty<'tcx>) {
 790         if !self.tcx.sess.has_errors() {
 791             self.infcx
 792                 .need_type_info_err(Some(self.body.id()), self.span.to_span(self.tcx), t)
 793                 .emit();
 794         }
 795     }
 796 }
 797
 798 impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
 799     fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
 800         self.tcx
 801     }
 802
 803     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 804         match self.infcx.fully_resolve(&t) {
 805             Ok(t) => t,
 806             Err(_) => {
 807                 debug!(
 808                     "Resolver::fold_ty: input type `{:?}` not fully resolvable",
 809                     t
 810                 );
 811                 self.report_error(t);
 812                 self.tcx().types.err
 813             }
 814         }
 815     }
 816
 817     // FIXME This should be carefully checked
 818     // We could use `self.report_error` but it doesn't accept a ty::Region, right now.
 819     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 820         self.infcx.fully_resolve(&r).unwrap_or(self.tcx.types.re_static)
 821     }
 822 }
 823
 824 ///////////////////////////////////////////////////////////////////////////
 825 // During type check, we store promises with the result of trait
 826 // lookup rather than the actual results (because the results are not
 827 // necessarily available immediately). These routines unwind the
 828 // promises. It is expected that we will have already reported any
 829 // errors that may be encountered, so if the promises store an error,
 830 // a dummy result is returned.