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