compiler/rustc_typeck/src/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
   7 use rustc_data_structures::stable_map::FxHashMap;
   8 use rustc_errors::ErrorReported;
   9 use rustc_hir as hir;
  10 use rustc_hir::def_id::DefId;
  11 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  12 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
  13 use rustc_infer::infer::InferCtxt;
  14 use rustc_middle::hir::place::Place as HirPlace;
  15 use rustc_middle::mir::FakeReadCause;
  16 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
  17 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
  18 use rustc_middle::ty::{self, Ty, TyCtxt};
  19 use rustc_span::symbol::sym;
  20 use rustc_span::Span;
  21 use rustc_trait_selection::opaque_types::InferCtxtExt;
  22
  23 use std::mem;
  24
  25 ///////////////////////////////////////////////////////////////////////////
  26 // Entry point
  27
  28 // During type inference, partially inferred types are
  29 // represented using Type variables (ty::Infer). These don't appear in
  30 // the final TypeckResults since all of the types should have been
  31 // inferred once typeck is done.
  32 // When type inference is running however, having to update the typeck
  33 // typeck results every time a new type is inferred would be unreasonably slow,
  34 // so instead all of the replacement happens at the end in
  35 // resolve_type_vars_in_body, which creates a new TypeTables which
  36 // doesn't contain any inference types.
  37 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  38     pub fn resolve_type_vars_in_body(
  39         &self,
  40         body: &'tcx hir::Body<'tcx>,
  41     ) -> &'tcx ty::TypeckResults<'tcx> {
  42         let item_id = self.tcx.hir().body_owner(body.id());
  43         let item_def_id = self.tcx.hir().local_def_id(item_id);
  44
  45         // This attribute causes us to dump some writeback information
  46         // in the form of errors, which is uSymbol for unit tests.
  47         let rustc_dump_user_substs =
  48             self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs);
  49
  50         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
  51         for param in body.params {
  52             wbcx.visit_node_id(param.pat.span, param.hir_id);
  53         }
  54         // Type only exists for constants and statics, not functions.
  55         match self.tcx.hir().body_owner_kind(item_id) {
  56             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
  57                 wbcx.visit_node_id(body.value.span, item_id);
  58             }
  59             hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
  60         }
  61         wbcx.visit_body(body);
  62         wbcx.visit_min_capture_map();
  63         wbcx.visit_fake_reads_map();
  64         wbcx.visit_closures();
  65         wbcx.visit_liberated_fn_sigs();
  66         wbcx.visit_fru_field_types();
  67         wbcx.visit_opaque_types(body.value.span);
  68         wbcx.visit_coercion_casts();
  69         wbcx.visit_user_provided_tys();
  70         wbcx.visit_user_provided_sigs();
  71         wbcx.visit_generator_interior_types();
  72
  73         let used_trait_imports =
  74             mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports);
  75         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  76         wbcx.typeck_results.used_trait_imports = used_trait_imports;
  77
  78         wbcx.typeck_results.treat_byte_string_as_slice =
  79             mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice);
  80
  81         if self.is_tainted_by_errors() {
  82             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
  83             wbcx.typeck_results.tainted_by_errors = Some(ErrorReported);
  84         }
  85
  86         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  87
  88         self.tcx.arena.alloc(wbcx.typeck_results)
  89     }
  90 }
  91
  92 ///////////////////////////////////////////////////////////////////////////
  93 // The Writeback context. This visitor walks the HIR, checking the
  94 // fn-specific typeck results to find references to types or regions. It
  95 // resolves those regions to remove inference variables and writes the
  96 // final result back into the master typeck results in the tcx. Here and
  97 // there, it applies a few ad-hoc checks that were not convenient to
  98 // do elsewhere.
  99
 100 struct WritebackCx<'cx, 'tcx> {
 101     fcx: &'cx FnCtxt<'cx, 'tcx>,
 102
 103     typeck_results: ty::TypeckResults<'tcx>,
 104
 105     body: &'tcx hir::Body<'tcx>,
 106
 107     rustc_dump_user_substs: bool,
 108 }
 109
 110 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 111     fn new(
 112         fcx: &'cx FnCtxt<'cx, 'tcx>,
 113         body: &'tcx hir::Body<'tcx>,
 114         rustc_dump_user_substs: bool,
 115     ) -> WritebackCx<'cx, 'tcx> {
 116         let owner = body.id().hir_id.owner;
 117
 118         WritebackCx {
 119             fcx,
 120             typeck_results: ty::TypeckResults::new(owner),
 121             body,
 122             rustc_dump_user_substs,
 123         }
 124     }
 125
 126     fn tcx(&self) -> TyCtxt<'tcx> {
 127         self.fcx.tcx
 128     }
 129
 130     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 131         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 132         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
 133         self.typeck_results.node_types_mut().insert(hir_id, ty);
 134     }
 135
 136     // Hacky hack: During type-checking, we treat *all* operators
 137     // as potentially overloaded. But then, during writeback, if
 138     // we observe that something like `a+b` is (known to be)
 139     // operating on scalars, we clear the overload.
 140     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 141         match e.kind {
 142             hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, ref inner) => {
 143                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 144                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 145
 146                 if inner_ty.is_scalar() {
 147                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 148                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 149                     typeck_results.node_substs_mut().remove(e.hir_id);
 150                 }
 151             }
 152             hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
 153             | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 154                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 155                 let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty);
 156
 157                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 158                 let rhs_ty = self.fcx.resolve_vars_if_possible(rhs_ty);
 159
 160                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 161                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 162                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 163                     typeck_results.node_substs_mut().remove(e.hir_id);
 164
 165                     match e.kind {
 166                         hir::ExprKind::Binary(..) => {
 167                             if !op.node.is_by_value() {
 168                                 let mut adjustments = typeck_results.adjustments_mut();
 169                                 if let Some(a) = adjustments.get_mut(lhs.hir_id) {
 170                                     a.pop();
 171                                 }
 172                                 if let Some(a) = adjustments.get_mut(rhs.hir_id) {
 173                                     a.pop();
 174                                 }
 175                             }
 176                         }
 177                         hir::ExprKind::AssignOp(..) => {
 178                             if let Some(a) = typeck_results.adjustments_mut().get_mut(lhs.hir_id) {
 179                                 a.pop();
 180                             }
 181                         }
 182                         _ => {}
 183                     }
 184                 }
 185             }
 186             _ => {}
 187         }
 188     }
 189
 190     // Similar to operators, indexing is always assumed to be overloaded
 191     // Here, correct cases where an indexing expression can be simplified
 192     // to use builtin indexing because the index type is known to be
 193     // usize-ish
 194     fn fix_index_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 195         if let hir::ExprKind::Index(ref base, ref index) = e.kind {
 196             let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 197
 198             // All valid indexing looks like this; might encounter non-valid indexes at this point.
 199             let base_ty = typeck_results
 200                 .expr_ty_adjusted_opt(&base)
 201                 .map(|t| self.fcx.resolve_vars_if_possible(t).kind());
 202             if base_ty.is_none() {
 203                 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
 204                 // that isn't in the type table. We assume more relevant errors have already been
 205                 // emitted, so we delay an ICE if none have. (#64638)
 206                 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
 207             }
 208             if let Some(ty::Ref(_, base_ty, _)) = base_ty {
 209                 let index_ty = typeck_results.expr_ty_adjusted_opt(&index).unwrap_or_else(|| {
 210                     // When encountering `return [0][0]` outside of a `fn` body we would attempt
 211                     // to access an unexistend index. We assume that more relevant errors will
 212                     // already have been emitted, so we only gate on this with an ICE if no
 213                     // error has been emitted. (#64638)
 214                     self.fcx.tcx.ty_error_with_message(
 215                         e.span,
 216                         &format!("bad index {:?} for base: `{:?}`", index, base),
 217                     )
 218                 });
 219                 let index_ty = self.fcx.resolve_vars_if_possible(index_ty);
 220
 221                 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
 222                     // Remove the method call record
 223                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 224                     typeck_results.node_substs_mut().remove(e.hir_id);
 225
 226                     if let Some(a) = typeck_results.adjustments_mut().get_mut(base.hir_id) {
 227                         // Discard the need for a mutable borrow
 228
 229                         // Extra adjustment made when indexing causes a drop
 230                         // of size information - we need to get rid of it
 231                         // Since this is "after" the other adjustment to be
 232                         // discarded, we do an extra `pop()`
 233                         if let Some(Adjustment {
 234                             kind: Adjust::Pointer(PointerCast::Unsize), ..
 235                         }) = a.pop()
 236                         {
 237                             // So the borrow discard actually happens here
 238                             a.pop();
 239                         }
 240                     }
 241                 }
 242             }
 243         }
 244     }
 245 }
 246
 247 ///////////////////////////////////////////////////////////////////////////
 248 // Impl of Visitor for Resolver
 249 //
 250 // This is the master code which walks the AST. It delegates most of
 251 // the heavy lifting to the generic visit and resolve functions
 252 // below. In general, a function is made into a `visitor` if it must
 253 // traffic in node-ids or update typeck results in the type context etc.
 254
 255 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
 256     type Map = intravisit::ErasedMap<'tcx>;
 257
 258     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 259         NestedVisitorMap::None
 260     }
 261
 262     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 263         self.fix_scalar_builtin_expr(e);
 264         self.fix_index_builtin_expr(e);
 265
 266         self.visit_node_id(e.span, e.hir_id);
 267
 268         match e.kind {
 269             hir::ExprKind::Closure(_, _, body, _, _) => {
 270                 let body = self.fcx.tcx.hir().body(body);
 271                 for param in body.params {
 272                     self.visit_node_id(e.span, param.hir_id);
 273                 }
 274
 275                 self.visit_body(body);
 276             }
 277             hir::ExprKind::Struct(_, fields, _) => {
 278                 for field in fields {
 279                     self.visit_field_id(field.hir_id);
 280                 }
 281             }
 282             hir::ExprKind::Field(..) => {
 283                 self.visit_field_id(e.hir_id);
 284             }
 285             _ => {}
 286         }
 287
 288         intravisit::walk_expr(self, e);
 289     }
 290
 291     fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
 292         self.visit_node_id(b.span, b.hir_id);
 293         intravisit::walk_block(self, b);
 294     }
 295
 296     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 297         match p.kind {
 298             hir::PatKind::Binding(..) => {
 299                 let typeck_results = self.fcx.typeck_results.borrow();
 300                 if let Some(bm) =
 301                     typeck_results.extract_binding_mode(self.tcx().sess, p.hir_id, p.span)
 302                 {
 303                     self.typeck_results.pat_binding_modes_mut().insert(p.hir_id, bm);
 304                 }
 305             }
 306             hir::PatKind::Struct(_, fields, _) => {
 307                 for field in fields {
 308                     self.visit_field_id(field.hir_id);
 309                 }
 310             }
 311             _ => {}
 312         };
 313
 314         self.visit_pat_adjustments(p.span, p.hir_id);
 315
 316         self.visit_node_id(p.span, p.hir_id);
 317         intravisit::walk_pat(self, p);
 318     }
 319
 320     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 321         intravisit::walk_local(self, l);
 322         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 323         let var_ty = self.resolve(var_ty, &l.span);
 324         self.write_ty_to_typeck_results(l.hir_id, var_ty);
 325     }
 326
 327     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
 328         intravisit::walk_ty(self, hir_ty);
 329         let ty = self.fcx.node_ty(hir_ty.hir_id);
 330         let ty = self.resolve(ty, &hir_ty.span);
 331         self.write_ty_to_typeck_results(hir_ty.hir_id, ty);
 332     }
 333 }
 334
 335 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 336     fn visit_min_capture_map(&mut self) {
 337         let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher(
 338             self.fcx.typeck_results.borrow().closure_min_captures.len(),
 339             Default::default(),
 340         );
 341         for (closure_def_id, root_min_captures) in
 342             self.fcx.typeck_results.borrow().closure_min_captures.iter()
 343         {
 344             let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher(
 345                 root_min_captures.len(),
 346                 Default::default(),
 347             );
 348             for (var_hir_id, min_list) in root_min_captures.iter() {
 349                 let min_list_wb = min_list
 350                     .iter()
 351                     .map(|captured_place| {
 352                         let locatable = captured_place.info.path_expr_id.unwrap_or_else(|| {
 353                             self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local())
 354                         });
 355
 356                         self.resolve(captured_place.clone(), &locatable)
 357                     })
 358                     .collect();
 359                 root_var_map_wb.insert(*var_hir_id, min_list_wb);
 360             }
 361             min_captures_wb.insert(*closure_def_id, root_var_map_wb);
 362         }
 363
 364         self.typeck_results.closure_min_captures = min_captures_wb;
 365     }
 366
 367     fn visit_fake_reads_map(&mut self) {
 368         let mut resolved_closure_fake_reads: FxHashMap<
 369             DefId,
 370             Vec<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>,
 371         > = Default::default();
 372         for (closure_def_id, fake_reads) in
 373             self.fcx.typeck_results.borrow().closure_fake_reads.iter()
 374         {
 375             let mut resolved_fake_reads = Vec::<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>::new();
 376             for (place, cause, hir_id) in fake_reads.iter() {
 377                 let locatable =
 378                     self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local());
 379
 380                 let resolved_fake_read = self.resolve(place.clone(), &locatable);
 381                 resolved_fake_reads.push((resolved_fake_read, *cause, *hir_id));
 382             }
 383             resolved_closure_fake_reads.insert(*closure_def_id, resolved_fake_reads);
 384         }
 385         self.typeck_results.closure_fake_reads = resolved_closure_fake_reads;
 386     }
 387
 388     fn visit_closures(&mut self) {
 389         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 390         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 391         let common_hir_owner = fcx_typeck_results.hir_owner;
 392
 393         for (id, origin) in fcx_typeck_results.closure_kind_origins().iter() {
 394             let hir_id = hir::HirId { owner: common_hir_owner, local_id: *id };
 395             let place_span = origin.0;
 396             let place = self.resolve(origin.1.clone(), &place_span);
 397             self.typeck_results.closure_kind_origins_mut().insert(hir_id, (place_span, place));
 398         }
 399     }
 400
 401     fn visit_coercion_casts(&mut self) {
 402         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 403         let fcx_coercion_casts = fcx_typeck_results.coercion_casts();
 404         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 405
 406         for local_id in fcx_coercion_casts {
 407             self.typeck_results.set_coercion_cast(*local_id);
 408         }
 409     }
 410
 411     fn visit_user_provided_tys(&mut self) {
 412         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 413         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 414         let common_hir_owner = fcx_typeck_results.hir_owner;
 415
 416         let mut errors_buffer = Vec::new();
 417         for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() {
 418             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 419
 420             if cfg!(debug_assertions) && c_ty.needs_infer() {
 421                 span_bug!(
 422                     hir_id.to_span(self.fcx.tcx),
 423                     "writeback: `{:?}` has inference variables",
 424                     c_ty
 425                 );
 426             };
 427
 428             self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty);
 429
 430             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 431                 if self.rustc_dump_user_substs {
 432                     // This is a unit-testing mechanism.
 433                     let span = self.tcx().hir().span(hir_id);
 434                     // We need to buffer the errors in order to guarantee a consistent
 435                     // order when emitting them.
 436                     let err = self
 437                         .tcx()
 438                         .sess
 439                         .struct_span_err(span, &format!("user substs: {:?}", user_substs));
 440                     err.buffer(&mut errors_buffer);
 441                 }
 442             }
 443         }
 444
 445         if !errors_buffer.is_empty() {
 446             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 447             for diag in errors_buffer.drain(..) {
 448                 self.tcx().sess.diagnostic().emit_diagnostic(&diag);
 449             }
 450         }
 451     }
 452
 453     fn visit_user_provided_sigs(&mut self) {
 454         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 455         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 456
 457         for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() {
 458             if cfg!(debug_assertions) && c_sig.needs_infer() {
 459                 span_bug!(
 460                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 461                     "writeback: `{:?}` has inference variables",
 462                     c_sig
 463                 );
 464             };
 465
 466             self.typeck_results.user_provided_sigs.insert(def_id, *c_sig);
 467         }
 468     }
 469
 470     fn visit_generator_interior_types(&mut self) {
 471         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 472         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 473         self.typeck_results.generator_interior_types =
 474             fcx_typeck_results.generator_interior_types.clone();
 475     }
 476
 477     fn visit_opaque_types(&mut self, span: Span) {
 478         for (&def_id, opaque_defn) in self.fcx.opaque_types.borrow().iter() {
 479             let hir_id = self.tcx().hir().local_def_id_to_hir_id(def_id.expect_local());
 480             let instantiated_ty = self.resolve(opaque_defn.concrete_ty, &hir_id);
 481
 482             debug_assert!(!instantiated_ty.has_escaping_bound_vars());
 483
 484             // Prevent:
 485             // * `fn foo<T>() -> Foo<T>`
 486             // * `fn foo<T: Bound + Other>() -> Foo<T>`
 487             // from being defining.
 488
 489             // Also replace all generic params with the ones from the opaque type
 490             // definition so that
 491             // ```rust
 492             // type Foo<T> = impl Baz + 'static;
 493             // fn foo<U>() -> Foo<U> { .. }
 494             // ```
 495             // figures out the concrete type with `U`, but the stored type is with `T`.
 496             let definition_ty = self.fcx.infer_opaque_definition_from_instantiation(
 497                 def_id,
 498                 opaque_defn.substs,
 499                 instantiated_ty,
 500                 span,
 501             );
 502
 503             let mut skip_add = false;
 504
 505             if let ty::Opaque(defin_ty_def_id, _substs) = *definition_ty.kind() {
 506                 if let hir::OpaqueTyOrigin::Misc | hir::OpaqueTyOrigin::TyAlias = opaque_defn.origin
 507                 {
 508                     if def_id == defin_ty_def_id {
 509                         debug!(
 510                             "skipping adding concrete definition for opaque type {:?} {:?}",
 511                             opaque_defn, defin_ty_def_id
 512                         );
 513                         skip_add = true;
 514                     }
 515                 }
 516             }
 517
 518             if !opaque_defn.substs.needs_infer() {
 519                 // We only want to add an entry into `concrete_opaque_types`
 520                 // if we actually found a defining usage of this opaque type.
 521                 // Otherwise, we do nothing - we'll either find a defining usage
 522                 // in some other location, or we'll end up emitting an error due
 523                 // to the lack of defining usage
 524                 if !skip_add {
 525                     let new = ty::ResolvedOpaqueTy {
 526                         concrete_type: definition_ty,
 527                         substs: opaque_defn.substs,
 528                     };
 529
 530                     let old = self.typeck_results.concrete_opaque_types.insert(def_id, new);
 531                     if let Some(old) = old {
 532                         if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
 533                             span_bug!(
 534                                 span,
 535                                 "`visit_opaque_types` tried to write different types for the same \
 536                                  opaque type: {:?}, {:?}, {:?}, {:?}",
 537                                 def_id,
 538                                 definition_ty,
 539                                 opaque_defn,
 540                                 old,
 541                             );
 542                         }
 543                     }
 544                 }
 545             } else {
 546                 self.tcx().sess.delay_span_bug(span, "`opaque_defn` has inference variables");
 547             }
 548         }
 549     }
 550
 551     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 552         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 553         {
 554             self.typeck_results.field_indices_mut().insert(hir_id, index);
 555         }
 556     }
 557
 558     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 559         // Export associated path extensions and method resolutions.
 560         if let Some(def) =
 561             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 562         {
 563             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 564         }
 565
 566         // Resolve any borrowings for the node with id `node_id`
 567         self.visit_adjustments(span, hir_id);
 568
 569         // Resolve the type of the node with id `node_id`
 570         let n_ty = self.fcx.node_ty(hir_id);
 571         let n_ty = self.resolve(n_ty, &span);
 572         self.write_ty_to_typeck_results(hir_id, n_ty);
 573         debug!("node {:?} has type {:?}", hir_id, n_ty);
 574
 575         // Resolve any substitutions
 576         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 577             let substs = self.resolve(substs, &span);
 578             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 579             assert!(!substs.needs_infer() && !substs.has_placeholders());
 580             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 581         }
 582     }
 583
 584     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 585         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 586         match adjustment {
 587             None => {
 588                 debug!("no adjustments for node {:?}", hir_id);
 589             }
 590
 591             Some(adjustment) => {
 592                 let resolved_adjustment = self.resolve(adjustment, &span);
 593                 debug!("adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 594                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 595             }
 596         }
 597     }
 598
 599     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 600         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 601         match adjustment {
 602             None => {
 603                 debug!("no pat_adjustments for node {:?}", hir_id);
 604             }
 605
 606             Some(adjustment) => {
 607                 let resolved_adjustment = self.resolve(adjustment, &span);
 608                 debug!("pat_adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 609                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 610             }
 611         }
 612     }
 613
 614     fn visit_liberated_fn_sigs(&mut self) {
 615         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 616         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 617         let common_hir_owner = fcx_typeck_results.hir_owner;
 618
 619         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 620             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 621             let fn_sig = self.resolve(fn_sig, &hir_id);
 622             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 623         }
 624     }
 625
 626     fn visit_fru_field_types(&mut self) {
 627         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 628         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 629         let common_hir_owner = fcx_typeck_results.hir_owner;
 630
 631         for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() {
 632             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 633             let ftys = self.resolve(ftys.clone(), &hir_id);
 634             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 635         }
 636     }
 637
 638     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 639     where
 640         T: TypeFoldable<'tcx>,
 641     {
 642         let mut resolver = Resolver::new(self.fcx, span, self.body);
 643         let x = x.fold_with(&mut resolver);
 644         if cfg!(debug_assertions) && x.needs_infer() {
 645             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 646         }
 647
 648         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 649         // to mark the `TypeckResults` as tainted in that case, so that downstream
 650         // users of the typeck results don't produce extra errors, or worse, ICEs.
 651         if resolver.replaced_with_error {
 652             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
 653             self.typeck_results.tainted_by_errors = Some(ErrorReported);
 654         }
 655
 656         x
 657     }
 658 }
 659
 660 crate trait Locatable {
 661     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 662 }
 663
 664 impl Locatable for Span {
 665     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 666         *self
 667     }
 668 }
 669
 670 impl Locatable for hir::HirId {
 671     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 672         tcx.hir().span(*self)
 673     }
 674 }
 675
 676 /// The Resolver. This is the type folding engine that detects
 677 /// unresolved types and so forth.
 678 struct Resolver<'cx, 'tcx> {
 679     tcx: TyCtxt<'tcx>,
 680     infcx: &'cx InferCtxt<'cx, 'tcx>,
 681     span: &'cx dyn Locatable,
 682     body: &'tcx hir::Body<'tcx>,
 683
 684     /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
 685     replaced_with_error: bool,
 686 }
 687
 688 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 689     fn new(
 690         fcx: &'cx FnCtxt<'cx, 'tcx>,
 691         span: &'cx dyn Locatable,
 692         body: &'tcx hir::Body<'tcx>,
 693     ) -> Resolver<'cx, 'tcx> {
 694         Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false }
 695     }
 696
 697     fn report_type_error(&self, t: Ty<'tcx>) {
 698         if !self.tcx.sess.has_errors() {
 699             self.infcx
 700                 .emit_inference_failure_err(
 701                     Some(self.body.id()),
 702                     self.span.to_span(self.tcx),
 703                     t.into(),
 704                     vec![],
 705                     E0282,
 706                 )
 707                 .emit();
 708         }
 709     }
 710
 711     fn report_const_error(&self, c: &'tcx ty::Const<'tcx>) {
 712         if !self.tcx.sess.has_errors() {
 713             self.infcx
 714                 .emit_inference_failure_err(
 715                     Some(self.body.id()),
 716                     self.span.to_span(self.tcx),
 717                     c.into(),
 718                     vec![],
 719                     E0282,
 720                 )
 721                 .emit();
 722         }
 723     }
 724 }
 725
 726 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 727     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 728         self.tcx
 729     }
 730
 731     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 732         match self.infcx.fully_resolve(t) {
 733             Ok(t) => self.infcx.tcx.erase_regions(t),
 734             Err(_) => {
 735                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 736                 self.report_type_error(t);
 737                 self.replaced_with_error = true;
 738                 self.tcx().ty_error()
 739             }
 740         }
 741     }
 742
 743     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 744         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 745         self.tcx.lifetimes.re_erased
 746     }
 747
 748     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
 749         match self.infcx.fully_resolve(ct) {
 750             Ok(ct) => self.infcx.tcx.erase_regions(ct),
 751             Err(_) => {
 752                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 753                 self.report_const_error(ct);
 754                 self.replaced_with_error = true;
 755                 self.tcx().const_error(ct.ty)
 756             }
 757         }
 758     }
 759 }
 760
 761 ///////////////////////////////////////////////////////////////////////////
 762 // During type check, we store promises with the result of trait
 763 // lookup rather than the actual results (because the results are not
 764 // necessarily available immediately). These routines unwind the
 765 // promises. It is expected that we will have already reported any
 766 // errors that may be encountered, so if the promises store an error,
 767 // a dummy result is returned.