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