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::ErrorGuaranteed;
   9 use rustc_hir as hir;
  10 use rustc_hir::def_id::DefId;
  11 use rustc_hir::intravisit::{self, 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
  22 use std::mem;
  23 use std::ops::ControlFlow;
  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 used 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_def_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();
  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 `ErrorGuaranteed` from where the error was emitted.
  84             wbcx.typeck_results.tainted_by_errors =
  85                 Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
  86         }
  87
  88         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  89
  90         self.tcx.arena.alloc(wbcx.typeck_results)
  91     }
  92 }
  93
  94 ///////////////////////////////////////////////////////////////////////////
  95 // The Writeback context. This visitor walks the HIR, checking the
  96 // fn-specific typeck results to find references to types or regions. It
  97 // resolves those regions to remove inference variables and writes the
  98 // final result back into the master typeck results in the tcx. Here and
  99 // there, it applies a few ad-hoc checks that were not convenient to
 100 // do elsewhere.
 101
 102 struct WritebackCx<'cx, 'tcx> {
 103     fcx: &'cx FnCtxt<'cx, 'tcx>,
 104
 105     typeck_results: ty::TypeckResults<'tcx>,
 106
 107     body: &'tcx hir::Body<'tcx>,
 108
 109     rustc_dump_user_substs: bool,
 110 }
 111
 112 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 113     fn new(
 114         fcx: &'cx FnCtxt<'cx, 'tcx>,
 115         body: &'tcx hir::Body<'tcx>,
 116         rustc_dump_user_substs: bool,
 117     ) -> WritebackCx<'cx, 'tcx> {
 118         let owner = body.id().hir_id.owner;
 119
 120         WritebackCx {
 121             fcx,
 122             typeck_results: ty::TypeckResults::new(owner),
 123             body,
 124             rustc_dump_user_substs,
 125         }
 126     }
 127
 128     fn tcx(&self) -> TyCtxt<'tcx> {
 129         self.fcx.tcx
 130     }
 131
 132     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 133         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 134         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
 135         self.typeck_results.node_types_mut().insert(hir_id, ty);
 136     }
 137
 138     // Hacky hack: During type-checking, we treat *all* operators
 139     // as potentially overloaded. But then, during writeback, if
 140     // we observe that something like `a+b` is (known to be)
 141     // operating on scalars, we clear the overload.
 142     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 143         match e.kind {
 144             hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, inner) => {
 145                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 146                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 147
 148                 if inner_ty.is_scalar() {
 149                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 150                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 151                     typeck_results.node_substs_mut().remove(e.hir_id);
 152                 }
 153             }
 154             hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, 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 nonexistent 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     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 258         self.fix_scalar_builtin_expr(e);
 259         self.fix_index_builtin_expr(e);
 260
 261         self.visit_node_id(e.span, e.hir_id);
 262
 263         match e.kind {
 264             hir::ExprKind::Closure(_, _, body, _, _) => {
 265                 let body = self.fcx.tcx.hir().body(body);
 266                 for param in body.params {
 267                     self.visit_node_id(e.span, param.hir_id);
 268                 }
 269
 270                 self.visit_body(body);
 271             }
 272             hir::ExprKind::Struct(_, fields, _) => {
 273                 for field in fields {
 274                     self.visit_field_id(field.hir_id);
 275                 }
 276             }
 277             hir::ExprKind::Field(..) => {
 278                 self.visit_field_id(e.hir_id);
 279             }
 280             hir::ExprKind::ConstBlock(anon_const) => {
 281                 self.visit_node_id(e.span, anon_const.hir_id);
 282
 283                 let body = self.tcx().hir().body(anon_const.body);
 284                 self.visit_body(body);
 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 mut diag in errors_buffer.drain(..) {
 471                 self.tcx().sess.diagnostic().emit_diagnostic(&mut 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     #[instrument(skip(self), level = "debug")]
 501     fn visit_opaque_types(&mut self) {
 502         let opaque_types =
 503             self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
 504         for (opaque_type_key, decl) in opaque_types {
 505             let hidden_type = match decl.origin {
 506                 hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => {
 507                     let ty = self.resolve(decl.hidden_type.ty, &decl.hidden_type.span);
 508                     struct RecursionChecker {
 509                         def_id: DefId,
 510                     }
 511                     impl<'tcx> ty::TypeVisitor<'tcx> for RecursionChecker {
 512                         type BreakTy = ();
 513                         fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
 514                             if let ty::Opaque(def_id, _) = *t.kind() {
 515                                 if def_id == self.def_id {
 516                                     return ControlFlow::Break(());
 517                                 }
 518                             }
 519                             t.super_visit_with(self)
 520                         }
 521                     }
 522                     if ty
 523                         .visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id })
 524                         .is_break()
 525                     {
 526                         return;
 527                     }
 528                     Some(ty)
 529                 }
 530                 hir::OpaqueTyOrigin::TyAlias => None,
 531             };
 532             self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type);
 533         }
 534     }
 535
 536     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 537         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 538         {
 539             self.typeck_results.field_indices_mut().insert(hir_id, index);
 540         }
 541     }
 542
 543     #[instrument(skip(self, span), level = "debug")]
 544     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 545         // Export associated path extensions and method resolutions.
 546         if let Some(def) =
 547             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 548         {
 549             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 550         }
 551
 552         // Resolve any borrowings for the node with id `node_id`
 553         self.visit_adjustments(span, hir_id);
 554
 555         // Resolve the type of the node with id `node_id`
 556         let n_ty = self.fcx.node_ty(hir_id);
 557         let n_ty = self.resolve(n_ty, &span);
 558         self.write_ty_to_typeck_results(hir_id, n_ty);
 559         debug!(?n_ty);
 560
 561         // Resolve any substitutions
 562         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 563             let substs = self.resolve(substs, &span);
 564             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 565             assert!(!substs.needs_infer() && !substs.has_placeholders());
 566             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 567         }
 568     }
 569
 570     #[instrument(skip(self, span), level = "debug")]
 571     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 572         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 573         match adjustment {
 574             None => {
 575                 debug!("no adjustments for node");
 576             }
 577
 578             Some(adjustment) => {
 579                 let resolved_adjustment = self.resolve(adjustment, &span);
 580                 debug!(?resolved_adjustment);
 581                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 582             }
 583         }
 584     }
 585
 586     #[instrument(skip(self, span), level = "debug")]
 587     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 588         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 589         match adjustment {
 590             None => {
 591                 debug!("no pat_adjustments for node");
 592             }
 593
 594             Some(adjustment) => {
 595                 let resolved_adjustment = self.resolve(adjustment, &span);
 596                 debug!(?resolved_adjustment);
 597                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 598             }
 599         }
 600     }
 601
 602     fn visit_liberated_fn_sigs(&mut self) {
 603         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 604         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 605         let common_hir_owner = fcx_typeck_results.hir_owner;
 606
 607         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 608             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 609             let fn_sig = self.resolve(fn_sig, &hir_id);
 610             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 611         }
 612     }
 613
 614     fn visit_fru_field_types(&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, ftys) in fcx_typeck_results.fru_field_types().iter() {
 620             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 621             let ftys = self.resolve(ftys.clone(), &hir_id);
 622             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 623         }
 624     }
 625
 626     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 627     where
 628         T: TypeFoldable<'tcx>,
 629     {
 630         let mut resolver = Resolver::new(self.fcx, span, self.body);
 631         let x = x.fold_with(&mut resolver);
 632         if cfg!(debug_assertions) && x.needs_infer() {
 633             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 634         }
 635
 636         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 637         // to mark the `TypeckResults` as tainted in that case, so that downstream
 638         // users of the typeck results don't produce extra errors, or worse, ICEs.
 639         if resolver.replaced_with_error {
 640             // FIXME(eddyb) keep track of `ErrorGuaranteed` from where the error was emitted.
 641             self.typeck_results.tainted_by_errors =
 642                 Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
 643         }
 644
 645         x
 646     }
 647 }
 648
 649 crate trait Locatable {
 650     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 651 }
 652
 653 impl Locatable for Span {
 654     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 655         *self
 656     }
 657 }
 658
 659 impl Locatable for hir::HirId {
 660     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 661         tcx.hir().span(*self)
 662     }
 663 }
 664
 665 /// The Resolver. This is the type folding engine that detects
 666 /// unresolved types and so forth.
 667 struct Resolver<'cx, 'tcx> {
 668     tcx: TyCtxt<'tcx>,
 669     infcx: &'cx InferCtxt<'cx, 'tcx>,
 670     span: &'cx dyn Locatable,
 671     body: &'tcx hir::Body<'tcx>,
 672
 673     /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
 674     replaced_with_error: bool,
 675 }
 676
 677 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 678     fn new(
 679         fcx: &'cx FnCtxt<'cx, 'tcx>,
 680         span: &'cx dyn Locatable,
 681         body: &'tcx hir::Body<'tcx>,
 682     ) -> Resolver<'cx, 'tcx> {
 683         Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false }
 684     }
 685
 686     fn report_type_error(&self, t: Ty<'tcx>) {
 687         if !self.tcx.sess.has_errors().is_some() {
 688             self.infcx
 689                 .emit_inference_failure_err(
 690                     Some(self.body.id()),
 691                     self.span.to_span(self.tcx),
 692                     t.into(),
 693                     vec![],
 694                     E0282,
 695                 )
 696                 .emit();
 697         }
 698     }
 699
 700     fn report_const_error(&self, c: ty::Const<'tcx>) {
 701         if self.tcx.sess.has_errors().is_none() {
 702             self.infcx
 703                 .emit_inference_failure_err(
 704                     Some(self.body.id()),
 705                     self.span.to_span(self.tcx),
 706                     c.into(),
 707                     vec![],
 708                     E0282,
 709                 )
 710                 .emit();
 711         }
 712     }
 713 }
 714
 715 struct EraseEarlyRegions<'tcx> {
 716     tcx: TyCtxt<'tcx>,
 717 }
 718
 719 impl<'tcx> TypeFolder<'tcx> for EraseEarlyRegions<'tcx> {
 720     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
 721         self.tcx
 722     }
 723     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
 724         if ty.has_type_flags(ty::TypeFlags::HAS_FREE_REGIONS) {
 725             ty.super_fold_with(self)
 726         } else {
 727             ty
 728         }
 729     }
 730     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 731         if r.is_late_bound() { r } else { self.tcx.lifetimes.re_erased }
 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) => {
 743                 // Do not anonymize late-bound regions
 744                 // (e.g. keep `for<'a>` named `for<'a>`).
 745                 // This allows NLL to generate error messages that
 746                 // refer to the higher-ranked lifetime names written by the user.
 747                 EraseEarlyRegions { tcx: self.infcx.tcx }.fold_ty(t)
 748             }
 749             Err(_) => {
 750                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 751                 self.report_type_error(t);
 752                 self.replaced_with_error = true;
 753                 self.tcx().ty_error()
 754             }
 755         }
 756     }
 757
 758     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 759         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 760         self.tcx.lifetimes.re_erased
 761     }
 762
 763     fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
 764         match self.infcx.fully_resolve(ct) {
 765             Ok(ct) => self.infcx.tcx.erase_regions(ct),
 766             Err(_) => {
 767                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 768                 self.report_const_error(ct);
 769                 self.replaced_with_error = true;
 770                 self.tcx().const_error(ct.ty())
 771             }
 772         }
 773     }
 774 }
 775
 776 ///////////////////////////////////////////////////////////////////////////
 777 // During type check, we store promises with the result of trait
 778 // lookup rather than the actual results (because the results are not
 779 // necessarily available immediately). These routines unwind the
 780 // promises. It is expected that we will have already reported any
 781 // errors that may be encountered, so if the promises store an error,
 782 // a dummy result is returned.