compiler/rustc_hir_typeck/src/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::FnCtxt;
   6 use hir::def_id::LocalDefId;
   7 use rustc_data_structures::fx::FxHashMap;
   8 use rustc_errors::ErrorGuaranteed;
   9 use rustc_hir as hir;
  10 use rustc_hir::intravisit::{self, Visitor};
  11 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
  12 use rustc_infer::infer::InferCtxt;
  13 use rustc_middle::hir::place::Place as HirPlace;
  14 use rustc_middle::mir::FakeReadCause;
  15 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
  16 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
  17 use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable};
  18 use rustc_middle::ty::TypeckResults;
  19 use rustc_middle::ty::{self, ClosureSizeProfileData, Ty, TyCtxt};
  20 use rustc_span::symbol::sym;
  21 use rustc_span::Span;
  22
  23 use std::mem;
  24 use std::ops::ControlFlow;
  25
  26 ///////////////////////////////////////////////////////////////////////////
  27 // Entry point
  28
  29 // During type inference, partially inferred types are
  30 // represented using Type variables (ty::Infer). These don't appear in
  31 // the final TypeckResults since all of the types should have been
  32 // inferred once typeck is done.
  33 // When type inference is running however, having to update the typeck
  34 // typeck results every time a new type is inferred would be unreasonably slow,
  35 // so instead all of the replacement happens at the end in
  36 // resolve_type_vars_in_body, which creates a new TypeTables which
  37 // doesn't contain any inference types.
  38 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  39     pub fn resolve_type_vars_in_body(
  40         &self,
  41         body: &'tcx hir::Body<'tcx>,
  42     ) -> &'tcx ty::TypeckResults<'tcx> {
  43         let item_id = self.tcx.hir().body_owner(body.id());
  44         let item_def_id = self.tcx.hir().local_def_id(item_id);
  45
  46         // This attribute causes us to dump some writeback information
  47         // in the form of errors, which is used for unit tests.
  48         let rustc_dump_user_substs =
  49             self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs);
  50
  51         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
  52         for param in body.params {
  53             wbcx.visit_node_id(param.pat.span, param.hir_id);
  54         }
  55         // Type only exists for constants and statics, not functions.
  56         match self.tcx.hir().body_owner_kind(item_def_id) {
  57             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
  58                 wbcx.visit_node_id(body.value.span, item_id);
  59             }
  60             hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
  61         }
  62         wbcx.visit_body(body);
  63         wbcx.visit_min_capture_map();
  64         wbcx.eval_closure_size();
  65         wbcx.visit_fake_reads_map();
  66         wbcx.visit_closures();
  67         wbcx.visit_liberated_fn_sigs();
  68         wbcx.visit_fru_field_types();
  69         wbcx.visit_opaque_types();
  70         wbcx.visit_coercion_casts();
  71         wbcx.visit_user_provided_tys();
  72         wbcx.visit_user_provided_sigs();
  73         wbcx.visit_generator_interior_types();
  74
  75         wbcx.typeck_results.rvalue_scopes =
  76             mem::take(&mut self.typeck_results.borrow_mut().rvalue_scopes);
  77
  78         let used_trait_imports =
  79             mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports);
  80         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  81         wbcx.typeck_results.used_trait_imports = used_trait_imports;
  82
  83         wbcx.typeck_results.treat_byte_string_as_slice =
  84             mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice);
  85
  86         if let Some(e) = self.tainted_by_errors() {
  87             wbcx.typeck_results.tainted_by_errors = Some(e);
  88         }
  89
  90         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  91
  92         self.tcx.arena.alloc(wbcx.typeck_results)
  93     }
  94 }
  95
  96 ///////////////////////////////////////////////////////////////////////////
  97 // The Writeback context. This visitor walks the HIR, checking the
  98 // fn-specific typeck results to find references to types or regions. It
  99 // resolves those regions to remove inference variables and writes the
 100 // final result back into the master typeck results in the tcx. Here and
 101 // there, it applies a few ad-hoc checks that were not convenient to
 102 // do elsewhere.
 103
 104 struct WritebackCx<'cx, 'tcx> {
 105     fcx: &'cx FnCtxt<'cx, 'tcx>,
 106
 107     typeck_results: ty::TypeckResults<'tcx>,
 108
 109     body: &'tcx hir::Body<'tcx>,
 110
 111     rustc_dump_user_substs: bool,
 112 }
 113
 114 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 115     fn new(
 116         fcx: &'cx FnCtxt<'cx, 'tcx>,
 117         body: &'tcx hir::Body<'tcx>,
 118         rustc_dump_user_substs: bool,
 119     ) -> WritebackCx<'cx, 'tcx> {
 120         let owner = body.id().hir_id.owner;
 121
 122         WritebackCx {
 123             fcx,
 124             typeck_results: ty::TypeckResults::new(owner),
 125             body,
 126             rustc_dump_user_substs,
 127         }
 128     }
 129
 130     fn tcx(&self) -> TyCtxt<'tcx> {
 131         self.fcx.tcx
 132     }
 133
 134     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 135         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 136         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
 137         self.typeck_results.node_types_mut().insert(hir_id, ty);
 138     }
 139
 140     // Hacky hack: During type-checking, we treat *all* operators
 141     // as potentially overloaded. But then, during writeback, if
 142     // we observe that something like `a+b` is (known to be)
 143     // operating on scalars, we clear the overload.
 144     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 145         match e.kind {
 146             hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, inner) => {
 147                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 148                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 149
 150                 if inner_ty.is_scalar() {
 151                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 152                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 153                     typeck_results.node_substs_mut().remove(e.hir_id);
 154                 }
 155             }
 156             hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, rhs) => {
 157                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 158                 let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty);
 159
 160                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 161                 let rhs_ty = self.fcx.resolve_vars_if_possible(rhs_ty);
 162
 163                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 164                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 165                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 166                     typeck_results.node_substs_mut().remove(e.hir_id);
 167
 168                     match e.kind {
 169                         hir::ExprKind::Binary(..) => {
 170                             if !op.node.is_by_value() {
 171                                 let mut adjustments = typeck_results.adjustments_mut();
 172                                 if let Some(a) = adjustments.get_mut(lhs.hir_id) {
 173                                     a.pop();
 174                                 }
 175                                 if let Some(a) = adjustments.get_mut(rhs.hir_id) {
 176                                     a.pop();
 177                                 }
 178                             }
 179                         }
 180                         hir::ExprKind::AssignOp(..)
 181                             if let Some(a) = typeck_results.adjustments_mut().get_mut(lhs.hir_id) =>
 182                         {
 183                             a.pop();
 184                         }
 185                         _ => {}
 186                     }
 187                 }
 188             }
 189             _ => {}
 190         }
 191     }
 192
 193     // (ouz-a 1005988): Normally `[T] : std::ops::Index<usize>` should be normalized
 194     // into [T] but currently `Where` clause stops the normalization process for it,
 195     // here we compare types of expr and base in a code without `Where` clause they would be equal
 196     // if they are not we don't modify the expr, hence we bypass the ICE
 197     fn is_builtin_index(
 198         &mut self,
 199         typeck_results: &TypeckResults<'tcx>,
 200         e: &hir::Expr<'_>,
 201         base_ty: Ty<'tcx>,
 202         index_ty: Ty<'tcx>,
 203     ) -> bool {
 204         if let Some(elem_ty) = base_ty.builtin_index() {
 205             let Some(exp_ty) = typeck_results.expr_ty_opt(e) else {return false;};
 206             let resolved_exp_ty = self.resolve(exp_ty, &e.span);
 207
 208             elem_ty == resolved_exp_ty && index_ty == self.fcx.tcx.types.usize
 209         } else {
 210             false
 211         }
 212     }
 213
 214     // Similar to operators, indexing is always assumed to be overloaded
 215     // Here, correct cases where an indexing expression can be simplified
 216     // to use builtin indexing because the index type is known to be
 217     // usize-ish
 218     fn fix_index_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 219         if let hir::ExprKind::Index(ref base, ref index) = e.kind {
 220             let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 221
 222             // All valid indexing looks like this; might encounter non-valid indexes at this point.
 223             let base_ty = typeck_results
 224                 .expr_ty_adjusted_opt(base)
 225                 .map(|t| self.fcx.resolve_vars_if_possible(t).kind());
 226             if base_ty.is_none() {
 227                 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
 228                 // that isn't in the type table. We assume more relevant errors have already been
 229                 // emitted, so we delay an ICE if none have. (#64638)
 230                 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
 231             }
 232             if let Some(ty::Ref(_, base_ty, _)) = base_ty {
 233                 let index_ty = typeck_results.expr_ty_adjusted_opt(index).unwrap_or_else(|| {
 234                     // When encountering `return [0][0]` outside of a `fn` body we would attempt
 235                     // to access an nonexistent index. We assume that more relevant errors will
 236                     // already have been emitted, so we only gate on this with an ICE if no
 237                     // error has been emitted. (#64638)
 238                     self.fcx.tcx.ty_error_with_message(
 239                         e.span,
 240                         &format!("bad index {:?} for base: `{:?}`", index, base),
 241                     )
 242                 });
 243                 let index_ty = self.fcx.resolve_vars_if_possible(index_ty);
 244                 let resolved_base_ty = self.resolve(*base_ty, &base.span);
 245
 246                 if self.is_builtin_index(&typeck_results, e, resolved_base_ty, index_ty) {
 247                     // Remove the method call record
 248                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 249                     typeck_results.node_substs_mut().remove(e.hir_id);
 250
 251                     if let Some(a) = typeck_results.adjustments_mut().get_mut(base.hir_id) {
 252                         // Discard the need for a mutable borrow
 253
 254                         // Extra adjustment made when indexing causes a drop
 255                         // of size information - we need to get rid of it
 256                         // Since this is "after" the other adjustment to be
 257                         // discarded, we do an extra `pop()`
 258                         if let Some(Adjustment {
 259                             kind: Adjust::Pointer(PointerCast::Unsize), ..
 260                         }) = a.pop()
 261                         {
 262                             // So the borrow discard actually happens here
 263                             a.pop();
 264                         }
 265                     }
 266                 }
 267             }
 268         }
 269     }
 270 }
 271
 272 ///////////////////////////////////////////////////////////////////////////
 273 // Impl of Visitor for Resolver
 274 //
 275 // This is the master code which walks the AST. It delegates most of
 276 // the heavy lifting to the generic visit and resolve functions
 277 // below. In general, a function is made into a `visitor` if it must
 278 // traffic in node-ids or update typeck results in the type context etc.
 279
 280 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
 281     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 282         self.fix_scalar_builtin_expr(e);
 283         self.fix_index_builtin_expr(e);
 284
 285         match e.kind {
 286             hir::ExprKind::Closure(&hir::Closure { body, .. }) => {
 287                 let body = self.fcx.tcx.hir().body(body);
 288                 for param in body.params {
 289                     self.visit_node_id(e.span, param.hir_id);
 290                 }
 291
 292                 self.visit_body(body);
 293             }
 294             hir::ExprKind::Struct(_, fields, _) => {
 295                 for field in fields {
 296                     self.visit_field_id(field.hir_id);
 297                 }
 298             }
 299             hir::ExprKind::Field(..) => {
 300                 self.visit_field_id(e.hir_id);
 301             }
 302             hir::ExprKind::ConstBlock(anon_const) => {
 303                 self.visit_node_id(e.span, anon_const.hir_id);
 304
 305                 let body = self.tcx().hir().body(anon_const.body);
 306                 self.visit_body(body);
 307             }
 308             _ => {}
 309         }
 310
 311         self.visit_node_id(e.span, e.hir_id);
 312         intravisit::walk_expr(self, e);
 313     }
 314
 315     fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
 316         match &p.kind {
 317             hir::GenericParamKind::Lifetime { .. } => {
 318                 // Nothing to write back here
 319             }
 320             hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => {
 321                 self.tcx().sess.delay_span_bug(p.span, format!("unexpected generic param: {p:?}"));
 322             }
 323         }
 324     }
 325
 326     fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
 327         self.visit_node_id(b.span, b.hir_id);
 328         intravisit::walk_block(self, b);
 329     }
 330
 331     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 332         match p.kind {
 333             hir::PatKind::Binding(..) => {
 334                 let typeck_results = self.fcx.typeck_results.borrow();
 335                 if let Some(bm) =
 336                     typeck_results.extract_binding_mode(self.tcx().sess, p.hir_id, p.span)
 337                 {
 338                     self.typeck_results.pat_binding_modes_mut().insert(p.hir_id, bm);
 339                 }
 340             }
 341             hir::PatKind::Struct(_, fields, _) => {
 342                 for field in fields {
 343                     self.visit_field_id(field.hir_id);
 344                 }
 345             }
 346             _ => {}
 347         };
 348
 349         self.visit_pat_adjustments(p.span, p.hir_id);
 350
 351         self.visit_node_id(p.span, p.hir_id);
 352         intravisit::walk_pat(self, p);
 353     }
 354
 355     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 356         intravisit::walk_local(self, l);
 357         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 358         let var_ty = self.resolve(var_ty, &l.span);
 359         self.write_ty_to_typeck_results(l.hir_id, var_ty);
 360     }
 361
 362     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
 363         intravisit::walk_ty(self, hir_ty);
 364         // If there are type checking errors, Type privacy pass will stop,
 365         // so we may not get the type from hid_id, see #104513
 366         if let Some(ty) = self.fcx.node_ty_opt(hir_ty.hir_id) {
 367             let ty = self.resolve(ty, &hir_ty.span);
 368             self.write_ty_to_typeck_results(hir_ty.hir_id, ty);
 369         }
 370     }
 371
 372     fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
 373         intravisit::walk_inf(self, inf);
 374         // Ignore cases where the inference is a const.
 375         if let Some(ty) = self.fcx.node_ty_opt(inf.hir_id) {
 376             let ty = self.resolve(ty, &inf.span);
 377             self.write_ty_to_typeck_results(inf.hir_id, ty);
 378         }
 379     }
 380 }
 381
 382 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 383     fn eval_closure_size(&mut self) {
 384         let mut res: FxHashMap<LocalDefId, ClosureSizeProfileData<'tcx>> = Default::default();
 385         for (&closure_def_id, data) in self.fcx.typeck_results.borrow().closure_size_eval.iter() {
 386             let closure_hir_id = self.tcx().hir().local_def_id_to_hir_id(closure_def_id);
 387
 388             let data = self.resolve(*data, &closure_hir_id);
 389
 390             res.insert(closure_def_id, data);
 391         }
 392
 393         self.typeck_results.closure_size_eval = res;
 394     }
 395     fn visit_min_capture_map(&mut self) {
 396         let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher(
 397             self.fcx.typeck_results.borrow().closure_min_captures.len(),
 398             Default::default(),
 399         );
 400         for (&closure_def_id, root_min_captures) in
 401             self.fcx.typeck_results.borrow().closure_min_captures.iter()
 402         {
 403             let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher(
 404                 root_min_captures.len(),
 405                 Default::default(),
 406             );
 407             for (var_hir_id, min_list) in root_min_captures.iter() {
 408                 let min_list_wb = min_list
 409                     .iter()
 410                     .map(|captured_place| {
 411                         let locatable = captured_place.info.path_expr_id.unwrap_or_else(|| {
 412                             self.tcx().hir().local_def_id_to_hir_id(closure_def_id)
 413                         });
 414
 415                         self.resolve(captured_place.clone(), &locatable)
 416                     })
 417                     .collect();
 418                 root_var_map_wb.insert(*var_hir_id, min_list_wb);
 419             }
 420             min_captures_wb.insert(closure_def_id, root_var_map_wb);
 421         }
 422
 423         self.typeck_results.closure_min_captures = min_captures_wb;
 424     }
 425
 426     fn visit_fake_reads_map(&mut self) {
 427         let mut resolved_closure_fake_reads: FxHashMap<
 428             LocalDefId,
 429             Vec<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>,
 430         > = Default::default();
 431         for (&closure_def_id, fake_reads) in
 432             self.fcx.typeck_results.borrow().closure_fake_reads.iter()
 433         {
 434             let mut resolved_fake_reads = Vec::<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>::new();
 435             for (place, cause, hir_id) in fake_reads.iter() {
 436                 let locatable = self.tcx().hir().local_def_id_to_hir_id(closure_def_id);
 437
 438                 let resolved_fake_read = self.resolve(place.clone(), &locatable);
 439                 resolved_fake_reads.push((resolved_fake_read, *cause, *hir_id));
 440             }
 441             resolved_closure_fake_reads.insert(closure_def_id, resolved_fake_reads);
 442         }
 443         self.typeck_results.closure_fake_reads = resolved_closure_fake_reads;
 444     }
 445
 446     fn visit_closures(&mut self) {
 447         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 448         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 449         let common_hir_owner = fcx_typeck_results.hir_owner;
 450
 451         for (id, origin) in fcx_typeck_results.closure_kind_origins().iter() {
 452             let hir_id = hir::HirId { owner: common_hir_owner, local_id: *id };
 453             let place_span = origin.0;
 454             let place = self.resolve(origin.1.clone(), &place_span);
 455             self.typeck_results.closure_kind_origins_mut().insert(hir_id, (place_span, place));
 456         }
 457     }
 458
 459     fn visit_coercion_casts(&mut self) {
 460         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 461         let fcx_coercion_casts = fcx_typeck_results.coercion_casts();
 462         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 463
 464         for local_id in fcx_coercion_casts {
 465             self.typeck_results.set_coercion_cast(*local_id);
 466         }
 467     }
 468
 469     fn visit_user_provided_tys(&mut self) {
 470         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 471         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 472         let common_hir_owner = fcx_typeck_results.hir_owner;
 473
 474         let mut errors_buffer = Vec::new();
 475         for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() {
 476             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 477
 478             if cfg!(debug_assertions) && c_ty.needs_infer() {
 479                 span_bug!(
 480                     hir_id.to_span(self.fcx.tcx),
 481                     "writeback: `{:?}` has inference variables",
 482                     c_ty
 483                 );
 484             };
 485
 486             self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty);
 487
 488             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 489                 if self.rustc_dump_user_substs {
 490                     // This is a unit-testing mechanism.
 491                     let span = self.tcx().hir().span(hir_id);
 492                     // We need to buffer the errors in order to guarantee a consistent
 493                     // order when emitting them.
 494                     let err = self
 495                         .tcx()
 496                         .sess
 497                         .struct_span_err(span, &format!("user substs: {:?}", user_substs));
 498                     err.buffer(&mut errors_buffer);
 499                 }
 500             }
 501         }
 502
 503         if !errors_buffer.is_empty() {
 504             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 505             for mut diag in errors_buffer {
 506                 self.tcx().sess.diagnostic().emit_diagnostic(&mut diag);
 507             }
 508         }
 509     }
 510
 511     fn visit_user_provided_sigs(&mut self) {
 512         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 513         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 514
 515         for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() {
 516             if cfg!(debug_assertions) && c_sig.needs_infer() {
 517                 span_bug!(
 518                     self.fcx.tcx.def_span(def_id),
 519                     "writeback: `{:?}` has inference variables",
 520                     c_sig
 521                 );
 522             };
 523
 524             self.typeck_results.user_provided_sigs.insert(def_id, *c_sig);
 525         }
 526     }
 527
 528     fn visit_generator_interior_types(&mut self) {
 529         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 530         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 531         self.typeck_results.generator_interior_types =
 532             fcx_typeck_results.generator_interior_types.clone();
 533     }
 534
 535     #[instrument(skip(self), level = "debug")]
 536     fn visit_opaque_types(&mut self) {
 537         let opaque_types = self.fcx.infcx.take_opaque_types();
 538         for (opaque_type_key, decl) in opaque_types {
 539             let hidden_type = self.resolve(decl.hidden_type, &decl.hidden_type.span);
 540             let opaque_type_key = self.resolve(opaque_type_key, &decl.hidden_type.span);
 541
 542             struct RecursionChecker {
 543                 def_id: LocalDefId,
 544             }
 545             impl<'tcx> ty::TypeVisitor<'tcx> for RecursionChecker {
 546                 type BreakTy = ();
 547                 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
 548                     if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *t.kind() {
 549                         if def_id == self.def_id.to_def_id() {
 550                             return ControlFlow::Break(());
 551                         }
 552                     }
 553                     t.super_visit_with(self)
 554                 }
 555             }
 556             if hidden_type
 557                 .visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id })
 558                 .is_break()
 559             {
 560                 continue;
 561             }
 562
 563             let hidden_type = hidden_type.remap_generic_params_to_declaration_params(
 564                 opaque_type_key,
 565                 self.fcx.infcx.tcx,
 566                 true,
 567                 decl.origin,
 568             );
 569
 570             self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type);
 571         }
 572     }
 573
 574     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 575         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 576         {
 577             self.typeck_results.field_indices_mut().insert(hir_id, index);
 578         }
 579     }
 580
 581     #[instrument(skip(self, span), level = "debug")]
 582     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 583         // Export associated path extensions and method resolutions.
 584         if let Some(def) =
 585             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 586         {
 587             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 588         }
 589
 590         // Resolve any borrowings for the node with id `node_id`
 591         self.visit_adjustments(span, hir_id);
 592
 593         // Resolve the type of the node with id `node_id`
 594         let n_ty = self.fcx.node_ty(hir_id);
 595         let n_ty = self.resolve(n_ty, &span);
 596         self.write_ty_to_typeck_results(hir_id, n_ty);
 597         debug!(?n_ty);
 598
 599         // Resolve any substitutions
 600         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 601             let substs = self.resolve(substs, &span);
 602             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 603             assert!(!substs.needs_infer() && !substs.has_placeholders());
 604             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 605         }
 606     }
 607
 608     #[instrument(skip(self, span), level = "debug")]
 609     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 610         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 611         match adjustment {
 612             None => {
 613                 debug!("no adjustments for node");
 614             }
 615
 616             Some(adjustment) => {
 617                 let resolved_adjustment = self.resolve(adjustment, &span);
 618                 debug!(?resolved_adjustment);
 619                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 620             }
 621         }
 622     }
 623
 624     #[instrument(skip(self, span), level = "debug")]
 625     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 626         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 627         match adjustment {
 628             None => {
 629                 debug!("no pat_adjustments for node");
 630             }
 631
 632             Some(adjustment) => {
 633                 let resolved_adjustment = self.resolve(adjustment, &span);
 634                 debug!(?resolved_adjustment);
 635                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 636             }
 637         }
 638     }
 639
 640     fn visit_liberated_fn_sigs(&mut self) {
 641         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 642         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 643         let common_hir_owner = fcx_typeck_results.hir_owner;
 644
 645         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 646             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 647             let fn_sig = self.resolve(fn_sig, &hir_id);
 648             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 649         }
 650     }
 651
 652     fn visit_fru_field_types(&mut self) {
 653         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 654         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 655         let common_hir_owner = fcx_typeck_results.hir_owner;
 656
 657         for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() {
 658             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 659             let ftys = self.resolve(ftys.clone(), &hir_id);
 660             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 661         }
 662     }
 663
 664     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 665     where
 666         T: TypeFoldable<'tcx>,
 667     {
 668         let mut resolver = Resolver::new(self.fcx, span, self.body);
 669         let x = x.fold_with(&mut resolver);
 670         if cfg!(debug_assertions) && x.needs_infer() {
 671             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 672         }
 673
 674         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 675         // to mark the `TypeckResults` as tainted in that case, so that downstream
 676         // users of the typeck results don't produce extra errors, or worse, ICEs.
 677         if let Some(e) = resolver.replaced_with_error {
 678             self.typeck_results.tainted_by_errors = Some(e);
 679         }
 680
 681         x
 682     }
 683 }
 684
 685 pub(crate) trait Locatable {
 686     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 687 }
 688
 689 impl Locatable for Span {
 690     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 691         *self
 692     }
 693 }
 694
 695 impl Locatable for hir::HirId {
 696     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 697         tcx.hir().span(*self)
 698     }
 699 }
 700
 701 /// The Resolver. This is the type folding engine that detects
 702 /// unresolved types and so forth.
 703 struct Resolver<'cx, 'tcx> {
 704     tcx: TyCtxt<'tcx>,
 705     infcx: &'cx InferCtxt<'tcx>,
 706     span: &'cx dyn Locatable,
 707     body: &'tcx hir::Body<'tcx>,
 708
 709     /// Set to `Some` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
 710     replaced_with_error: Option<ErrorGuaranteed>,
 711 }
 712
 713 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 714     fn new(
 715         fcx: &'cx FnCtxt<'cx, 'tcx>,
 716         span: &'cx dyn Locatable,
 717         body: &'tcx hir::Body<'tcx>,
 718     ) -> Resolver<'cx, 'tcx> {
 719         Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: None }
 720     }
 721
 722     fn report_error(&self, p: impl Into<ty::GenericArg<'tcx>>) -> ErrorGuaranteed {
 723         match self.tcx.sess.has_errors() {
 724             Some(e) => e,
 725             None => self
 726                 .infcx
 727                 .err_ctxt()
 728                 .emit_inference_failure_err(
 729                     Some(self.body.id()),
 730                     self.span.to_span(self.tcx),
 731                     p.into(),
 732                     E0282,
 733                     false,
 734                 )
 735                 .emit(),
 736         }
 737     }
 738 }
 739
 740 struct EraseEarlyRegions<'tcx> {
 741     tcx: TyCtxt<'tcx>,
 742 }
 743
 744 impl<'tcx> TypeFolder<'tcx> for EraseEarlyRegions<'tcx> {
 745     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
 746         self.tcx
 747     }
 748     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
 749         if ty.has_type_flags(ty::TypeFlags::HAS_FREE_REGIONS) {
 750             ty.super_fold_with(self)
 751         } else {
 752             ty
 753         }
 754     }
 755     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 756         if r.is_late_bound() { r } else { self.tcx.lifetimes.re_erased }
 757     }
 758 }
 759
 760 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 761     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 762         self.tcx
 763     }
 764
 765     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 766         match self.infcx.fully_resolve(t) {
 767             Ok(t) => {
 768                 // Do not anonymize late-bound regions
 769                 // (e.g. keep `for<'a>` named `for<'a>`).
 770                 // This allows NLL to generate error messages that
 771                 // refer to the higher-ranked lifetime names written by the user.
 772                 EraseEarlyRegions { tcx: self.tcx }.fold_ty(t)
 773             }
 774             Err(_) => {
 775                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 776                 let e = self.report_error(t);
 777                 self.replaced_with_error = Some(e);
 778                 self.tcx().ty_error_with_guaranteed(e)
 779             }
 780         }
 781     }
 782
 783     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 784         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 785         self.tcx.lifetimes.re_erased
 786     }
 787
 788     fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
 789         match self.infcx.fully_resolve(ct) {
 790             Ok(ct) => self.tcx.erase_regions(ct),
 791             Err(_) => {
 792                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 793                 let e = self.report_error(ct);
 794                 self.replaced_with_error = Some(e);
 795                 self.tcx().const_error_with_guaranteed(ct.ty(), e)
 796             }
 797         }
 798     }
 799 }
 800
 801 ///////////////////////////////////////////////////////////////////////////
 802 // During type check, we store promises with the result of trait
 803 // lookup rather than the actual results (because the results are not
 804 // necessarily available immediately). These routines unwind the
 805 // promises. It is expected that we will have already reported any
 806 // errors that may be encountered, so if the promises store an error,
 807 // a dummy result is returned.