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