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