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_min_capture_map();
  59         wbcx.visit_upvar_capture_map();
  60         wbcx.visit_closures();
  61         wbcx.visit_liberated_fn_sigs();
  62         wbcx.visit_fru_field_types();
  63         wbcx.visit_opaque_types(body.value.span);
  64         wbcx.visit_coercion_casts();
  65         wbcx.visit_user_provided_tys();
  66         wbcx.visit_user_provided_sigs();
  67         wbcx.visit_generator_interior_types();
  68
  69         let used_trait_imports =
  70             mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports);
  71         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  72         wbcx.typeck_results.used_trait_imports = used_trait_imports;
  73
  74         wbcx.typeck_results.treat_byte_string_as_slice =
  75             mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice);
  76
  77         wbcx.typeck_results.closure_captures =
  78             mem::take(&mut self.typeck_results.borrow_mut().closure_captures);
  79
  80         if self.is_tainted_by_errors() {
  81             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
  82             wbcx.typeck_results.tainted_by_errors = Some(ErrorReported);
  83         }
  84
  85         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  86
  87         self.tcx.arena.alloc(wbcx.typeck_results)
  88     }
  89 }
  90
  91 ///////////////////////////////////////////////////////////////////////////
  92 // The Writeback context. This visitor walks the HIR, checking the
  93 // fn-specific typeck results to find references to types or regions. It
  94 // resolves those regions to remove inference variables and writes the
  95 // final result back into the master typeck results in the tcx. Here and
  96 // there, it applies a few ad-hoc checks that were not convenient to
  97 // do elsewhere.
  98
  99 struct WritebackCx<'cx, 'tcx> {
 100     fcx: &'cx FnCtxt<'cx, 'tcx>,
 101
 102     typeck_results: ty::TypeckResults<'tcx>,
 103
 104     body: &'tcx hir::Body<'tcx>,
 105
 106     rustc_dump_user_substs: bool,
 107 }
 108
 109 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 110     fn new(
 111         fcx: &'cx FnCtxt<'cx, 'tcx>,
 112         body: &'tcx hir::Body<'tcx>,
 113         rustc_dump_user_substs: bool,
 114     ) -> WritebackCx<'cx, 'tcx> {
 115         let owner = body.id().hir_id.owner;
 116
 117         WritebackCx {
 118             fcx,
 119             typeck_results: ty::TypeckResults::new(owner),
 120             body,
 121             rustc_dump_user_substs,
 122         }
 123     }
 124
 125     fn tcx(&self) -> TyCtxt<'tcx> {
 126         self.fcx.tcx
 127     }
 128
 129     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 130         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 131         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
 132         self.typeck_results.node_types_mut().insert(hir_id, ty);
 133     }
 134
 135     // Hacky hack: During type-checking, we treat *all* operators
 136     // as potentially overloaded. But then, during writeback, if
 137     // we observe that something like `a+b` is (known to be)
 138     // operating on scalars, we clear the overload.
 139     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 140         match e.kind {
 141             hir::ExprKind::Unary(hir::UnOp::UnNeg | hir::UnOp::UnNot, ref inner) => {
 142                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 143                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 144
 145                 if inner_ty.is_scalar() {
 146                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 147                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 148                     typeck_results.node_substs_mut().remove(e.hir_id);
 149                 }
 150             }
 151             hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
 152             | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 153                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 154                 let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty);
 155
 156                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 157                 let rhs_ty = self.fcx.resolve_vars_if_possible(rhs_ty);
 158
 159                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 160                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 161                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 162                     typeck_results.node_substs_mut().remove(e.hir_id);
 163
 164                     match e.kind {
 165                         hir::ExprKind::Binary(..) => {
 166                             if !op.node.is_by_value() {
 167                                 let mut adjustments = typeck_results.adjustments_mut();
 168                                 if let Some(a) = adjustments.get_mut(lhs.hir_id) {
 169                                     a.pop();
 170                                 }
 171                                 if let Some(a) = adjustments.get_mut(rhs.hir_id) {
 172                                     a.pop();
 173                                 }
 174                             }
 175                         }
 176                         hir::ExprKind::AssignOp(..) => {
 177                             if let Some(a) = typeck_results.adjustments_mut().get_mut(lhs.hir_id) {
 178                                 a.pop();
 179                             }
 180                         }
 181                         _ => {}
 182                     }
 183                 }
 184             }
 185             _ => {}
 186         }
 187     }
 188
 189     // Similar to operators, indexing is always assumed to be overloaded
 190     // Here, correct cases where an indexing expression can be simplified
 191     // to use builtin indexing because the index type is known to be
 192     // usize-ish
 193     fn fix_index_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 194         if let hir::ExprKind::Index(ref base, ref index) = e.kind {
 195             let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 196
 197             // All valid indexing looks like this; might encounter non-valid indexes at this point.
 198             let base_ty = typeck_results
 199                 .expr_ty_adjusted_opt(&base)
 200                 .map(|t| self.fcx.resolve_vars_if_possible(t).kind());
 201             if base_ty.is_none() {
 202                 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
 203                 // that isn't in the type table. We assume more relevant errors have already been
 204                 // emitted, so we delay an ICE if none have. (#64638)
 205                 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
 206             }
 207             if let Some(ty::Ref(_, base_ty, _)) = base_ty {
 208                 let index_ty = typeck_results.expr_ty_adjusted_opt(&index).unwrap_or_else(|| {
 209                     // When encountering `return [0][0]` outside of a `fn` body we would attempt
 210                     // to access an unexistend index. We assume that more relevant errors will
 211                     // already have been emitted, so we only gate on this with an ICE if no
 212                     // error has been emitted. (#64638)
 213                     self.fcx.tcx.ty_error_with_message(
 214                         e.span,
 215                         &format!("bad index {:?} for base: `{:?}`", index, base),
 216                     )
 217                 });
 218                 let index_ty = self.fcx.resolve_vars_if_possible(index_ty);
 219
 220                 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
 221                     // Remove the method call record
 222                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 223                     typeck_results.node_substs_mut().remove(e.hir_id);
 224
 225                     if let Some(a) = typeck_results.adjustments_mut().get_mut(base.hir_id) {
 226                         // Discard the need for a mutable borrow
 227
 228                         // Extra adjustment made when indexing causes a drop
 229                         // of size information - we need to get rid of it
 230                         // Since this is "after" the other adjustment to be
 231                         // discarded, we do an extra `pop()`
 232                         if let Some(Adjustment {
 233                             kind: Adjust::Pointer(PointerCast::Unsize), ..
 234                         }) = a.pop()
 235                         {
 236                             // So the borrow discard actually happens here
 237                             a.pop();
 238                         }
 239                     }
 240                 }
 241             }
 242         }
 243     }
 244 }
 245
 246 ///////////////////////////////////////////////////////////////////////////
 247 // Impl of Visitor for Resolver
 248 //
 249 // This is the master code which walks the AST. It delegates most of
 250 // the heavy lifting to the generic visit and resolve functions
 251 // below. In general, a function is made into a `visitor` if it must
 252 // traffic in node-ids or update typeck results in the type context etc.
 253
 254 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
 255     type Map = intravisit::ErasedMap<'tcx>;
 256
 257     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 258         NestedVisitorMap::None
 259     }
 260
 261     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 262         self.fix_scalar_builtin_expr(e);
 263         self.fix_index_builtin_expr(e);
 264
 265         self.visit_node_id(e.span, e.hir_id);
 266
 267         match e.kind {
 268             hir::ExprKind::Closure(_, _, body, _, _) => {
 269                 let body = self.fcx.tcx.hir().body(body);
 270                 for param in body.params {
 271                     self.visit_node_id(e.span, param.hir_id);
 272                 }
 273
 274                 self.visit_body(body);
 275             }
 276             hir::ExprKind::Struct(_, fields, _) => {
 277                 for field in fields {
 278                     self.visit_field_id(field.hir_id);
 279                 }
 280             }
 281             hir::ExprKind::Field(..) => {
 282                 self.visit_field_id(e.hir_id);
 283             }
 284             _ => {}
 285         }
 286
 287         intravisit::walk_expr(self, e);
 288     }
 289
 290     fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
 291         self.visit_node_id(b.span, b.hir_id);
 292         intravisit::walk_block(self, b);
 293     }
 294
 295     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 296         match p.kind {
 297             hir::PatKind::Binding(..) => {
 298                 let typeck_results = self.fcx.typeck_results.borrow();
 299                 if let Some(bm) =
 300                     typeck_results.extract_binding_mode(self.tcx().sess, p.hir_id, p.span)
 301                 {
 302                     self.typeck_results.pat_binding_modes_mut().insert(p.hir_id, bm);
 303                 }
 304             }
 305             hir::PatKind::Struct(_, fields, _) => {
 306                 for field in fields {
 307                     self.visit_field_id(field.hir_id);
 308                 }
 309             }
 310             _ => {}
 311         };
 312
 313         self.visit_pat_adjustments(p.span, p.hir_id);
 314
 315         self.visit_node_id(p.span, p.hir_id);
 316         intravisit::walk_pat(self, p);
 317     }
 318
 319     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 320         intravisit::walk_local(self, l);
 321         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 322         let var_ty = self.resolve(var_ty, &l.span);
 323         self.write_ty_to_typeck_results(l.hir_id, var_ty);
 324     }
 325
 326     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
 327         intravisit::walk_ty(self, hir_ty);
 328         let ty = self.fcx.node_ty(hir_ty.hir_id);
 329         let ty = self.resolve(ty, &hir_ty.span);
 330         self.write_ty_to_typeck_results(hir_ty.hir_id, ty);
 331     }
 332 }
 333
 334 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 335     fn visit_min_capture_map(&mut self) {
 336         let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher(
 337             self.fcx.typeck_results.borrow().closure_min_captures.len(),
 338             Default::default(),
 339         );
 340         for (closure_def_id, root_min_captures) in
 341             self.fcx.typeck_results.borrow().closure_min_captures.iter()
 342         {
 343             let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher(
 344                 root_min_captures.len(),
 345                 Default::default(),
 346             );
 347             for (var_hir_id, min_list) in root_min_captures.iter() {
 348                 let min_list_wb = min_list
 349                     .iter()
 350                     .map(|captured_place| {
 351                         let locatable = captured_place.info.expr_id.unwrap_or(
 352                             self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local()),
 353                         );
 354
 355                         self.resolve(captured_place.clone(), &locatable)
 356                     })
 357                     .collect();
 358                 root_var_map_wb.insert(*var_hir_id, min_list_wb);
 359             }
 360             min_captures_wb.insert(*closure_def_id, root_var_map_wb);
 361         }
 362
 363         self.typeck_results.closure_min_captures = min_captures_wb;
 364     }
 365
 366     fn visit_upvar_capture_map(&mut self) {
 367         for (upvar_id, upvar_capture) in self.fcx.typeck_results.borrow().upvar_capture_map.iter() {
 368             let new_upvar_capture = match *upvar_capture {
 369                 ty::UpvarCapture::ByValue(span) => ty::UpvarCapture::ByValue(span),
 370                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 371                     ty::UpvarCapture::ByRef(ty::UpvarBorrow {
 372                         kind: upvar_borrow.kind,
 373                         region: self.tcx().lifetimes.re_erased,
 374                     })
 375                 }
 376             };
 377             debug!("Upvar capture for {:?} resolved to {:?}", upvar_id, new_upvar_capture);
 378             self.typeck_results.upvar_capture_map.insert(*upvar_id, new_upvar_capture);
 379         }
 380     }
 381
 382     fn visit_closures(&mut self) {
 383         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 384         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 385         let common_hir_owner = fcx_typeck_results.hir_owner;
 386
 387         for (&id, &origin) in fcx_typeck_results.closure_kind_origins().iter() {
 388             let hir_id = hir::HirId { owner: common_hir_owner, local_id: id };
 389             self.typeck_results.closure_kind_origins_mut().insert(hir_id, origin);
 390         }
 391     }
 392
 393     fn visit_coercion_casts(&mut self) {
 394         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 395         let fcx_coercion_casts = fcx_typeck_results.coercion_casts();
 396         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 397
 398         for local_id in fcx_coercion_casts {
 399             self.typeck_results.set_coercion_cast(*local_id);
 400         }
 401     }
 402
 403     fn visit_user_provided_tys(&mut self) {
 404         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 405         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 406         let common_hir_owner = fcx_typeck_results.hir_owner;
 407
 408         let mut errors_buffer = Vec::new();
 409         for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() {
 410             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 411
 412             if cfg!(debug_assertions) && c_ty.needs_infer() {
 413                 span_bug!(
 414                     hir_id.to_span(self.fcx.tcx),
 415                     "writeback: `{:?}` has inference variables",
 416                     c_ty
 417                 );
 418             };
 419
 420             self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty);
 421
 422             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 423                 if self.rustc_dump_user_substs {
 424                     // This is a unit-testing mechanism.
 425                     let span = self.tcx().hir().span(hir_id);
 426                     // We need to buffer the errors in order to guarantee a consistent
 427                     // order when emitting them.
 428                     let err = self
 429                         .tcx()
 430                         .sess
 431                         .struct_span_err(span, &format!("user substs: {:?}", user_substs));
 432                     err.buffer(&mut errors_buffer);
 433                 }
 434             }
 435         }
 436
 437         if !errors_buffer.is_empty() {
 438             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 439             for diag in errors_buffer.drain(..) {
 440                 self.tcx().sess.diagnostic().emit_diagnostic(&diag);
 441             }
 442         }
 443     }
 444
 445     fn visit_user_provided_sigs(&mut self) {
 446         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 447         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 448
 449         for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() {
 450             if cfg!(debug_assertions) && c_sig.needs_infer() {
 451                 span_bug!(
 452                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 453                     "writeback: `{:?}` has inference variables",
 454                     c_sig
 455                 );
 456             };
 457
 458             self.typeck_results.user_provided_sigs.insert(def_id, *c_sig);
 459         }
 460     }
 461
 462     fn visit_generator_interior_types(&mut self) {
 463         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 464         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 465         self.typeck_results.generator_interior_types =
 466             fcx_typeck_results.generator_interior_types.clone();
 467     }
 468
 469     fn visit_opaque_types(&mut self, span: Span) {
 470         for (&def_id, opaque_defn) in self.fcx.opaque_types.borrow().iter() {
 471             let hir_id = self.tcx().hir().local_def_id_to_hir_id(def_id.expect_local());
 472             let instantiated_ty = self.resolve(opaque_defn.concrete_ty, &hir_id);
 473
 474             debug_assert!(!instantiated_ty.has_escaping_bound_vars());
 475
 476             // Prevent:
 477             // * `fn foo<T>() -> Foo<T>`
 478             // * `fn foo<T: Bound + Other>() -> Foo<T>`
 479             // from being defining.
 480
 481             // Also replace all generic params with the ones from the opaque type
 482             // definition so that
 483             // ```rust
 484             // type Foo<T> = impl Baz + 'static;
 485             // fn foo<U>() -> Foo<U> { .. }
 486             // ```
 487             // figures out the concrete type with `U`, but the stored type is with `T`.
 488             let definition_ty = self.fcx.infer_opaque_definition_from_instantiation(
 489                 def_id,
 490                 opaque_defn.substs,
 491                 instantiated_ty,
 492                 span,
 493             );
 494
 495             let mut skip_add = false;
 496
 497             if let ty::Opaque(defin_ty_def_id, _substs) = *definition_ty.kind() {
 498                 if let hir::OpaqueTyOrigin::Misc = opaque_defn.origin {
 499                     if def_id == defin_ty_def_id {
 500                         debug!(
 501                             "skipping adding concrete definition for opaque type {:?} {:?}",
 502                             opaque_defn, defin_ty_def_id
 503                         );
 504                         skip_add = true;
 505                     }
 506                 }
 507             }
 508
 509             if !opaque_defn.substs.needs_infer() {
 510                 // We only want to add an entry into `concrete_opaque_types`
 511                 // if we actually found a defining usage of this opaque type.
 512                 // Otherwise, we do nothing - we'll either find a defining usage
 513                 // in some other location, or we'll end up emitting an error due
 514                 // to the lack of defining usage
 515                 if !skip_add {
 516                     let new = ty::ResolvedOpaqueTy {
 517                         concrete_type: definition_ty,
 518                         substs: opaque_defn.substs,
 519                     };
 520
 521                     let old = self.typeck_results.concrete_opaque_types.insert(def_id, new);
 522                     if let Some(old) = old {
 523                         if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
 524                             span_bug!(
 525                                 span,
 526                                 "`visit_opaque_types` tried to write different types for the same \
 527                                  opaque type: {:?}, {:?}, {:?}, {:?}",
 528                                 def_id,
 529                                 definition_ty,
 530                                 opaque_defn,
 531                                 old,
 532                             );
 533                         }
 534                     }
 535                 }
 536             } else {
 537                 self.tcx().sess.delay_span_bug(span, "`opaque_defn` has inference variables");
 538             }
 539         }
 540     }
 541
 542     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 543         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 544         {
 545             self.typeck_results.field_indices_mut().insert(hir_id, index);
 546         }
 547     }
 548
 549     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 550         // Export associated path extensions and method resolutions.
 551         if let Some(def) =
 552             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 553         {
 554             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 555         }
 556
 557         // Resolve any borrowings for the node with id `node_id`
 558         self.visit_adjustments(span, hir_id);
 559
 560         // Resolve the type of the node with id `node_id`
 561         let n_ty = self.fcx.node_ty(hir_id);
 562         let n_ty = self.resolve(n_ty, &span);
 563         self.write_ty_to_typeck_results(hir_id, n_ty);
 564         debug!("node {:?} has type {:?}", hir_id, n_ty);
 565
 566         // Resolve any substitutions
 567         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 568             let substs = self.resolve(substs, &span);
 569             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 570             assert!(!substs.needs_infer() && !substs.has_placeholders());
 571             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 572         }
 573     }
 574
 575     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 576         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 577         match adjustment {
 578             None => {
 579                 debug!("no adjustments for node {:?}", hir_id);
 580             }
 581
 582             Some(adjustment) => {
 583                 let resolved_adjustment = self.resolve(adjustment, &span);
 584                 debug!("adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 585                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 586             }
 587         }
 588     }
 589
 590     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 591         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 592         match adjustment {
 593             None => {
 594                 debug!("no pat_adjustments for node {:?}", hir_id);
 595             }
 596
 597             Some(adjustment) => {
 598                 let resolved_adjustment = self.resolve(adjustment, &span);
 599                 debug!("pat_adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
 600                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 601             }
 602         }
 603     }
 604
 605     fn visit_liberated_fn_sigs(&mut self) {
 606         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 607         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 608         let common_hir_owner = fcx_typeck_results.hir_owner;
 609
 610         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 611             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 612             let fn_sig = self.resolve(fn_sig, &hir_id);
 613             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 614         }
 615     }
 616
 617     fn visit_fru_field_types(&mut self) {
 618         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 619         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 620         let common_hir_owner = fcx_typeck_results.hir_owner;
 621
 622         for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() {
 623             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 624             let ftys = self.resolve(ftys.clone(), &hir_id);
 625             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 626         }
 627     }
 628
 629     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 630     where
 631         T: TypeFoldable<'tcx>,
 632     {
 633         let mut resolver = Resolver::new(self.fcx, span, self.body);
 634         let x = x.fold_with(&mut resolver);
 635         if cfg!(debug_assertions) && x.needs_infer() {
 636             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 637         }
 638
 639         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 640         // to mark the `TypeckResults` as tainted in that case, so that downstream
 641         // users of the typeck results don't produce extra errors, or worse, ICEs.
 642         if resolver.replaced_with_error {
 643             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
 644             self.typeck_results.tainted_by_errors = Some(ErrorReported);
 645         }
 646
 647         x
 648     }
 649 }
 650
 651 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() {
 690             self.infcx
 691                 .emit_inference_failure_err(
 692                     Some(self.body.id()),
 693                     self.span.to_span(self.tcx),
 694                     t.into(),
 695                     E0282,
 696                 )
 697                 .emit();
 698         }
 699     }
 700
 701     fn report_const_error(&self, c: &'tcx ty::Const<'tcx>) {
 702         if !self.tcx.sess.has_errors() {
 703             self.infcx
 704                 .emit_inference_failure_err(
 705                     Some(self.body.id()),
 706                     self.span.to_span(self.tcx),
 707                     c.into(),
 708                     E0282,
 709                 )
 710                 .emit();
 711         }
 712     }
 713 }
 714
 715 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 716     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 717         self.tcx
 718     }
 719
 720     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 721         match self.infcx.fully_resolve(t) {
 722             Ok(t) => self.infcx.tcx.erase_regions(t),
 723             Err(_) => {
 724                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 725                 self.report_type_error(t);
 726                 self.replaced_with_error = true;
 727                 self.tcx().ty_error()
 728             }
 729         }
 730     }
 731
 732     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 733         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 734         self.tcx.lifetimes.re_erased
 735     }
 736
 737     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
 738         match self.infcx.fully_resolve(ct) {
 739             Ok(ct) => self.infcx.tcx.erase_regions(ct),
 740             Err(_) => {
 741                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 742                 self.report_const_error(ct);
 743                 self.replaced_with_error = true;
 744                 self.tcx().const_error(ct.ty)
 745             }
 746         }
 747     }
 748 }
 749
 750 ///////////////////////////////////////////////////////////////////////////
 751 // During type check, we store promises with the result of trait
 752 // lookup rather than the actual results (because the results are not
 753 // necessarily available immediately). These routines unwind the
 754 // promises. It is expected that we will have already reported any
 755 // errors that may be encountered, so if the promises store an error,
 756 // a dummy result is returned.