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