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, ClosureSizeProfileData, 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.eval_closure_size();
  64         wbcx.visit_fake_reads_map();
  65         wbcx.visit_closures();
  66         wbcx.visit_liberated_fn_sigs();
  67         wbcx.visit_fru_field_types();
  68         wbcx.visit_opaque_types(body.value.span);
  69         wbcx.visit_coercion_casts();
  70         wbcx.visit_user_provided_tys();
  71         wbcx.visit_user_provided_sigs();
  72         wbcx.visit_generator_interior_types();
  73
  74         let used_trait_imports =
  75             mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports);
  76         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  77         wbcx.typeck_results.used_trait_imports = used_trait_imports;
  78
  79         wbcx.typeck_results.treat_byte_string_as_slice =
  80             mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice);
  81
  82         if self.is_tainted_by_errors() {
  83             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
  84             wbcx.typeck_results.tainted_by_errors = Some(ErrorReported);
  85         }
  86
  87         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  88
  89         self.tcx.arena.alloc(wbcx.typeck_results)
  90     }
  91 }
  92
  93 ///////////////////////////////////////////////////////////////////////////
  94 // The Writeback context. This visitor walks the HIR, checking the
  95 // fn-specific typeck results to find references to types or regions. It
  96 // resolves those regions to remove inference variables and writes the
  97 // final result back into the master typeck results in the tcx. Here and
  98 // there, it applies a few ad-hoc checks that were not convenient to
  99 // do elsewhere.
 100
 101 struct WritebackCx<'cx, 'tcx> {
 102     fcx: &'cx FnCtxt<'cx, 'tcx>,
 103
 104     typeck_results: ty::TypeckResults<'tcx>,
 105
 106     body: &'tcx hir::Body<'tcx>,
 107
 108     rustc_dump_user_substs: bool,
 109 }
 110
 111 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 112     fn new(
 113         fcx: &'cx FnCtxt<'cx, 'tcx>,
 114         body: &'tcx hir::Body<'tcx>,
 115         rustc_dump_user_substs: bool,
 116     ) -> WritebackCx<'cx, 'tcx> {
 117         let owner = body.id().hir_id.owner;
 118
 119         WritebackCx {
 120             fcx,
 121             typeck_results: ty::TypeckResults::new(owner),
 122             body,
 123             rustc_dump_user_substs,
 124         }
 125     }
 126
 127     fn tcx(&self) -> TyCtxt<'tcx> {
 128         self.fcx.tcx
 129     }
 130
 131     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 132         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 133         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions(self.tcx()));
 134         self.typeck_results.node_types_mut().insert(hir_id, ty);
 135     }
 136
 137     // Hacky hack: During type-checking, we treat *all* operators
 138     // as potentially overloaded. But then, during writeback, if
 139     // we observe that something like `a+b` is (known to be)
 140     // operating on scalars, we clear the overload.
 141     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 142         match e.kind {
 143             hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, ref inner) => {
 144                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 145                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 146
 147                 if inner_ty.is_scalar() {
 148                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 149                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 150                     typeck_results.node_substs_mut().remove(e.hir_id);
 151                 }
 152             }
 153             hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
 154             | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 155                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 156                 let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty);
 157
 158                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 159                 let rhs_ty = self.fcx.resolve_vars_if_possible(rhs_ty);
 160
 161                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 162                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 163                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 164                     typeck_results.node_substs_mut().remove(e.hir_id);
 165
 166                     match e.kind {
 167                         hir::ExprKind::Binary(..) => {
 168                             if !op.node.is_by_value() {
 169                                 let mut adjustments = typeck_results.adjustments_mut();
 170                                 if let Some(a) = adjustments.get_mut(lhs.hir_id) {
 171                                     a.pop();
 172                                 }
 173                                 if let Some(a) = adjustments.get_mut(rhs.hir_id) {
 174                                     a.pop();
 175                                 }
 176                             }
 177                         }
 178                         hir::ExprKind::AssignOp(..)
 179                             if let Some(a) = typeck_results.adjustments_mut().get_mut(lhs.hir_id) =>
 180                         {
 181                             a.pop();
 182                         }
 183                         _ => {}
 184                     }
 185                 }
 186             }
 187             _ => {}
 188         }
 189     }
 190
 191     // Similar to operators, indexing is always assumed to be overloaded
 192     // Here, correct cases where an indexing expression can be simplified
 193     // to use builtin indexing because the index type is known to be
 194     // usize-ish
 195     fn fix_index_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 196         if let hir::ExprKind::Index(ref base, ref index) = e.kind {
 197             let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 198
 199             // All valid indexing looks like this; might encounter non-valid indexes at this point.
 200             let base_ty = typeck_results
 201                 .expr_ty_adjusted_opt(&base)
 202                 .map(|t| self.fcx.resolve_vars_if_possible(t).kind());
 203             if base_ty.is_none() {
 204                 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
 205                 // that isn't in the type table. We assume more relevant errors have already been
 206                 // emitted, so we delay an ICE if none have. (#64638)
 207                 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
 208             }
 209             if let Some(ty::Ref(_, base_ty, _)) = base_ty {
 210                 let index_ty = typeck_results.expr_ty_adjusted_opt(&index).unwrap_or_else(|| {
 211                     // When encountering `return [0][0]` outside of a `fn` body we would attempt
 212                     // to access an unexistend index. We assume that more relevant errors will
 213                     // already have been emitted, so we only gate on this with an ICE if no
 214                     // error has been emitted. (#64638)
 215                     self.fcx.tcx.ty_error_with_message(
 216                         e.span,
 217                         &format!("bad index {:?} for base: `{:?}`", index, base),
 218                     )
 219                 });
 220                 let index_ty = self.fcx.resolve_vars_if_possible(index_ty);
 221
 222                 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
 223                     // Remove the method call record
 224                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 225                     typeck_results.node_substs_mut().remove(e.hir_id);
 226
 227                     if let Some(a) = typeck_results.adjustments_mut().get_mut(base.hir_id) {
 228                         // Discard the need for a mutable borrow
 229
 230                         // Extra adjustment made when indexing causes a drop
 231                         // of size information - we need to get rid of it
 232                         // Since this is "after" the other adjustment to be
 233                         // discarded, we do an extra `pop()`
 234                         if let Some(Adjustment {
 235                             kind: Adjust::Pointer(PointerCast::Unsize), ..
 236                         }) = a.pop()
 237                         {
 238                             // So the borrow discard actually happens here
 239                             a.pop();
 240                         }
 241                     }
 242                 }
 243             }
 244         }
 245     }
 246 }
 247
 248 ///////////////////////////////////////////////////////////////////////////
 249 // Impl of Visitor for Resolver
 250 //
 251 // This is the master code which walks the AST. It delegates most of
 252 // the heavy lifting to the generic visit and resolve functions
 253 // below. In general, a function is made into a `visitor` if it must
 254 // traffic in node-ids or update typeck results in the type context etc.
 255
 256 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
 257     type Map = intravisit::ErasedMap<'tcx>;
 258
 259     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 260         NestedVisitorMap::None
 261     }
 262
 263     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 264         self.fix_scalar_builtin_expr(e);
 265         self.fix_index_builtin_expr(e);
 266
 267         self.visit_node_id(e.span, e.hir_id);
 268
 269         match e.kind {
 270             hir::ExprKind::Closure(_, _, body, _, _) => {
 271                 let body = self.fcx.tcx.hir().body(body);
 272                 for param in body.params {
 273                     self.visit_node_id(e.span, param.hir_id);
 274                 }
 275
 276                 self.visit_body(body);
 277             }
 278             hir::ExprKind::Struct(_, fields, _) => {
 279                 for field in fields {
 280                     self.visit_field_id(field.hir_id);
 281                 }
 282             }
 283             hir::ExprKind::Field(..) => {
 284                 self.visit_field_id(e.hir_id);
 285             }
 286             _ => {}
 287         }
 288
 289         intravisit::walk_expr(self, e);
 290     }
 291
 292     fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
 293         self.visit_node_id(b.span, b.hir_id);
 294         intravisit::walk_block(self, b);
 295     }
 296
 297     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 298         match p.kind {
 299             hir::PatKind::Binding(..) => {
 300                 let typeck_results = self.fcx.typeck_results.borrow();
 301                 if let Some(bm) =
 302                     typeck_results.extract_binding_mode(self.tcx().sess, p.hir_id, p.span)
 303                 {
 304                     self.typeck_results.pat_binding_modes_mut().insert(p.hir_id, bm);
 305                 }
 306             }
 307             hir::PatKind::Struct(_, fields, _) => {
 308                 for field in fields {
 309                     self.visit_field_id(field.hir_id);
 310                 }
 311             }
 312             _ => {}
 313         };
 314
 315         self.visit_pat_adjustments(p.span, p.hir_id);
 316
 317         self.visit_node_id(p.span, p.hir_id);
 318         intravisit::walk_pat(self, p);
 319     }
 320
 321     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 322         intravisit::walk_local(self, l);
 323         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 324         let var_ty = self.resolve(var_ty, &l.span);
 325         self.write_ty_to_typeck_results(l.hir_id, var_ty);
 326     }
 327
 328     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
 329         intravisit::walk_ty(self, hir_ty);
 330         let ty = self.fcx.node_ty(hir_ty.hir_id);
 331         let ty = self.resolve(ty, &hir_ty.span);
 332         self.write_ty_to_typeck_results(hir_ty.hir_id, ty);
 333     }
 334
 335     fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
 336         intravisit::walk_inf(self, inf);
 337         // Ignore cases where the inference is a const.
 338         if let Some(ty) = self.fcx.node_ty_opt(inf.hir_id) {
 339             let ty = self.resolve(ty, &inf.span);
 340             self.write_ty_to_typeck_results(inf.hir_id, ty);
 341         }
 342     }
 343 }
 344
 345 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 346     fn eval_closure_size(&mut self) {
 347         let mut res: FxHashMap<DefId, ClosureSizeProfileData<'tcx>> = Default::default();
 348         for (closure_def_id, data) in self.fcx.typeck_results.borrow().closure_size_eval.iter() {
 349             let closure_hir_id =
 350                 self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local());
 351
 352             let data = self.resolve(*data, &closure_hir_id);
 353
 354             res.insert(*closure_def_id, data);
 355         }
 356
 357         self.typeck_results.closure_size_eval = res;
 358     }
 359     fn visit_min_capture_map(&mut self) {
 360         let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher(
 361             self.fcx.typeck_results.borrow().closure_min_captures.len(),
 362             Default::default(),
 363         );
 364         for (closure_def_id, root_min_captures) in
 365             self.fcx.typeck_results.borrow().closure_min_captures.iter()
 366         {
 367             let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher(
 368                 root_min_captures.len(),
 369                 Default::default(),
 370             );
 371             for (var_hir_id, min_list) in root_min_captures.iter() {
 372                 let min_list_wb = min_list
 373                     .iter()
 374                     .map(|captured_place| {
 375                         let locatable = captured_place.info.path_expr_id.unwrap_or_else(|| {
 376                             self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local())
 377                         });
 378
 379                         self.resolve(captured_place.clone(), &locatable)
 380                     })
 381                     .collect();
 382                 root_var_map_wb.insert(*var_hir_id, min_list_wb);
 383             }
 384             min_captures_wb.insert(*closure_def_id, root_var_map_wb);
 385         }
 386
 387         self.typeck_results.closure_min_captures = min_captures_wb;
 388     }
 389
 390     fn visit_fake_reads_map(&mut self) {
 391         let mut resolved_closure_fake_reads: FxHashMap<
 392             DefId,
 393             Vec<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>,
 394         > = Default::default();
 395         for (closure_def_id, fake_reads) in
 396             self.fcx.typeck_results.borrow().closure_fake_reads.iter()
 397         {
 398             let mut resolved_fake_reads = Vec::<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>::new();
 399             for (place, cause, hir_id) in fake_reads.iter() {
 400                 let locatable =
 401                     self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local());
 402
 403                 let resolved_fake_read = self.resolve(place.clone(), &locatable);
 404                 resolved_fake_reads.push((resolved_fake_read, *cause, *hir_id));
 405             }
 406             resolved_closure_fake_reads.insert(*closure_def_id, resolved_fake_reads);
 407         }
 408         self.typeck_results.closure_fake_reads = resolved_closure_fake_reads;
 409     }
 410
 411     fn visit_closures(&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         for (id, origin) in fcx_typeck_results.closure_kind_origins().iter() {
 417             let hir_id = hir::HirId { owner: common_hir_owner, local_id: *id };
 418             let place_span = origin.0;
 419             let place = self.resolve(origin.1.clone(), &place_span);
 420             self.typeck_results.closure_kind_origins_mut().insert(hir_id, (place_span, place));
 421         }
 422     }
 423
 424     fn visit_coercion_casts(&mut self) {
 425         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 426         let fcx_coercion_casts = fcx_typeck_results.coercion_casts();
 427         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 428
 429         for local_id in fcx_coercion_casts {
 430             self.typeck_results.set_coercion_cast(*local_id);
 431         }
 432     }
 433
 434     fn visit_user_provided_tys(&mut self) {
 435         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 436         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 437         let common_hir_owner = fcx_typeck_results.hir_owner;
 438
 439         let mut errors_buffer = Vec::new();
 440         for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() {
 441             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 442
 443             if cfg!(debug_assertions) && c_ty.needs_infer() {
 444                 span_bug!(
 445                     hir_id.to_span(self.fcx.tcx),
 446                     "writeback: `{:?}` has inference variables",
 447                     c_ty
 448                 );
 449             };
 450
 451             self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty);
 452
 453             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 454                 if self.rustc_dump_user_substs {
 455                     // This is a unit-testing mechanism.
 456                     let span = self.tcx().hir().span(hir_id);
 457                     // We need to buffer the errors in order to guarantee a consistent
 458                     // order when emitting them.
 459                     let err = self
 460                         .tcx()
 461                         .sess
 462                         .struct_span_err(span, &format!("user substs: {:?}", user_substs));
 463                     err.buffer(&mut errors_buffer);
 464                 }
 465             }
 466         }
 467
 468         if !errors_buffer.is_empty() {
 469             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 470             for diag in errors_buffer.drain(..) {
 471                 self.tcx().sess.diagnostic().emit_diagnostic(&diag);
 472             }
 473         }
 474     }
 475
 476     fn visit_user_provided_sigs(&mut self) {
 477         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 478         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 479
 480         for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() {
 481             if cfg!(debug_assertions) && c_sig.needs_infer() {
 482                 span_bug!(
 483                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 484                     "writeback: `{:?}` has inference variables",
 485                     c_sig
 486                 );
 487             };
 488
 489             self.typeck_results.user_provided_sigs.insert(def_id, *c_sig);
 490         }
 491     }
 492
 493     fn visit_generator_interior_types(&mut self) {
 494         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 495         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 496         self.typeck_results.generator_interior_types =
 497             fcx_typeck_results.generator_interior_types.clone();
 498     }
 499
 500     fn visit_opaque_types(&mut self, span: Span) {
 501         let opaque_types = self.fcx.infcx.inner.borrow().opaque_types.clone();
 502         for (opaque_type_key, opaque_defn) in opaque_types {
 503             let hir_id =
 504                 self.tcx().hir().local_def_id_to_hir_id(opaque_type_key.def_id.expect_local());
 505             let instantiated_ty = self.resolve(opaque_defn.concrete_ty, &hir_id);
 506
 507             debug_assert!(!instantiated_ty.has_escaping_bound_vars());
 508
 509             let opaque_type_key = self.fcx.fully_resolve(opaque_type_key).unwrap();
 510
 511             // Prevent:
 512             // * `fn foo<T>() -> Foo<T>`
 513             // * `fn foo<T: Bound + Other>() -> Foo<T>`
 514             // from being defining.
 515
 516             // Also replace all generic params with the ones from the opaque type
 517             // definition so that
 518             // ```rust
 519             // type Foo<T> = impl Baz + 'static;
 520             // fn foo<U>() -> Foo<U> { .. }
 521             // ```
 522             // figures out the concrete type with `U`, but the stored type is with `T`.
 523
 524             // FIXME: why are we calling this here? This seems too early, and duplicated.
 525             let definition_ty = self.fcx.infer_opaque_definition_from_instantiation(
 526                 opaque_type_key,
 527                 instantiated_ty,
 528                 span,
 529             );
 530
 531             let mut skip_add = false;
 532
 533             if let ty::Opaque(definition_ty_def_id, _substs) = *definition_ty.kind() {
 534                 if opaque_defn.origin == hir::OpaqueTyOrigin::TyAlias {
 535                     if opaque_type_key.def_id == definition_ty_def_id {
 536                         debug!(
 537                             "skipping adding concrete definition for opaque type {:?} {:?}",
 538                             opaque_defn, opaque_type_key.def_id
 539                         );
 540                         skip_add = true;
 541                     }
 542                 }
 543             }
 544
 545             if opaque_type_key.substs.needs_infer() {
 546                 span_bug!(span, "{:#?} has inference variables", opaque_type_key.substs)
 547             }
 548
 549             // We only want to add an entry into `concrete_opaque_types`
 550             // if we actually found a defining usage of this opaque type.
 551             // Otherwise, we do nothing - we'll either find a defining usage
 552             // in some other location, or we'll end up emitting an error due
 553             // to the lack of defining usage
 554             if !skip_add {
 555                 self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id);
 556             }
 557         }
 558     }
 559
 560     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 561         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 562         {
 563             self.typeck_results.field_indices_mut().insert(hir_id, index);
 564         }
 565     }
 566
 567     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 568         // Export associated path extensions and method resolutions.
 569         if let Some(def) =
 570             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 571         {
 572             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 573         }
 574
 575         // Resolve any borrowings for the node with id `node_id`
 576         self.visit_adjustments(span, hir_id);
 577
 578         // Resolve the type of the node with id `node_id`
 579         let n_ty = self.fcx.node_ty(hir_id);
 580         let n_ty = self.resolve(n_ty, &span);
 581         self.write_ty_to_typeck_results(hir_id, n_ty);
 582         debug!("node {:?} has type {:?}", hir_id, n_ty);
 583
 584         // Resolve any substitutions
 585         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 586             let substs = self.resolve(substs, &span);
 587             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 588             assert!(!substs.needs_infer() && !substs.has_placeholders());
 589             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 590         }
 591     }
 592
 593     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 594         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 595         match adjustment {
 596             None => {
 597                 debug!("no adjustments for node {:?}", hir_id);
 598             }
 599
 600             Some(adjustment) => {
 601                 let resolved_adjustment = self.resolve(adjustment, &span);
 602                 debug!("adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 603                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 604             }
 605         }
 606     }
 607
 608     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 609         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 610         match adjustment {
 611             None => {
 612                 debug!("no pat_adjustments for node {:?}", hir_id);
 613             }
 614
 615             Some(adjustment) => {
 616                 let resolved_adjustment = self.resolve(adjustment, &span);
 617                 debug!("pat_adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 618                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 619             }
 620         }
 621     }
 622
 623     fn visit_liberated_fn_sigs(&mut self) {
 624         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 625         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 626         let common_hir_owner = fcx_typeck_results.hir_owner;
 627
 628         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 629             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 630             let fn_sig = self.resolve(fn_sig, &hir_id);
 631             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 632         }
 633     }
 634
 635     fn visit_fru_field_types(&mut self) {
 636         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 637         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 638         let common_hir_owner = fcx_typeck_results.hir_owner;
 639
 640         for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() {
 641             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 642             let ftys = self.resolve(ftys.clone(), &hir_id);
 643             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 644         }
 645     }
 646
 647     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 648     where
 649         T: TypeFoldable<'tcx>,
 650     {
 651         let mut resolver = Resolver::new(self.fcx, span, self.body);
 652         let x = x.fold_with(&mut resolver);
 653         if cfg!(debug_assertions) && x.needs_infer() {
 654             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 655         }
 656
 657         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 658         // to mark the `TypeckResults` as tainted in that case, so that downstream
 659         // users of the typeck results don't produce extra errors, or worse, ICEs.
 660         if resolver.replaced_with_error {
 661             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
 662             self.typeck_results.tainted_by_errors = Some(ErrorReported);
 663         }
 664
 665         x
 666     }
 667 }
 668
 669 crate trait Locatable {
 670     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 671 }
 672
 673 impl Locatable for Span {
 674     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 675         *self
 676     }
 677 }
 678
 679 impl Locatable for hir::HirId {
 680     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 681         tcx.hir().span(*self)
 682     }
 683 }
 684
 685 /// The Resolver. This is the type folding engine that detects
 686 /// unresolved types and so forth.
 687 struct Resolver<'cx, 'tcx> {
 688     tcx: TyCtxt<'tcx>,
 689     infcx: &'cx InferCtxt<'cx, 'tcx>,
 690     span: &'cx dyn Locatable,
 691     body: &'tcx hir::Body<'tcx>,
 692
 693     /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
 694     replaced_with_error: bool,
 695 }
 696
 697 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 698     fn new(
 699         fcx: &'cx FnCtxt<'cx, 'tcx>,
 700         span: &'cx dyn Locatable,
 701         body: &'tcx hir::Body<'tcx>,
 702     ) -> Resolver<'cx, 'tcx> {
 703         Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false }
 704     }
 705
 706     fn report_type_error(&self, t: Ty<'tcx>) {
 707         if !self.tcx.sess.has_errors() {
 708             self.infcx
 709                 .emit_inference_failure_err(
 710                     Some(self.body.id()),
 711                     self.span.to_span(self.tcx),
 712                     t.into(),
 713                     vec![],
 714                     E0282,
 715                 )
 716                 .emit();
 717         }
 718     }
 719
 720     fn report_const_error(&self, c: &'tcx ty::Const<'tcx>) {
 721         if !self.tcx.sess.has_errors() {
 722             self.infcx
 723                 .emit_inference_failure_err(
 724                     Some(self.body.id()),
 725                     self.span.to_span(self.tcx),
 726                     c.into(),
 727                     vec![],
 728                     E0282,
 729                 )
 730                 .emit();
 731         }
 732     }
 733 }
 734
 735 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 736     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 737         self.tcx
 738     }
 739
 740     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 741         match self.infcx.fully_resolve(t) {
 742             Ok(t) => self.infcx.tcx.erase_regions(t),
 743             Err(_) => {
 744                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 745                 self.report_type_error(t);
 746                 self.replaced_with_error = true;
 747                 self.tcx().ty_error()
 748             }
 749         }
 750     }
 751
 752     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 753         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 754         self.tcx.lifetimes.re_erased
 755     }
 756
 757     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
 758         match self.infcx.fully_resolve(ct) {
 759             Ok(ct) => self.infcx.tcx.erase_regions(ct),
 760             Err(_) => {
 761                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 762                 self.report_const_error(ct);
 763                 self.replaced_with_error = true;
 764                 self.tcx().const_error(ct.ty)
 765             }
 766         }
 767     }
 768 }
 769
 770 ///////////////////////////////////////////////////////////////////////////
 771 // During type check, we store promises with the result of trait
 772 // lookup rather than the actual results (because the results are not
 773 // necessarily available immediately). These routines unwind the
 774 // promises. It is expected that we will have already reported any
 775 // errors that may be encountered, so if the promises store an error,
 776 // a dummy result is returned.