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 use errors::DiagnosticBuilder;
   7 use rustc::hir;
   8 use rustc::hir::def_id::{DefId, DefIndex};
   9 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  10 use rustc::infer::InferCtxt;
  11 use rustc::ty::adjustment::{Adjust, Adjustment, PointerCast};
  12 use rustc::ty::fold::{TypeFoldable, TypeFolder};
  13 use rustc::ty::{self, Ty, TyCtxt};
  14 use rustc::util::nodemap::DefIdSet;
  15 use rustc_data_structures::sync::Lrc;
  16 use std::mem;
  17 use syntax::symbol::sym;
  18 use syntax_pos::Span;
  19
  20 ///////////////////////////////////////////////////////////////////////////
  21 // Entry point
  22
  23 // During type inference, partially inferred types are
  24 // represented using Type variables (ty::Infer). These don't appear in
  25 // the final TypeckTables since all of the types should have been
  26 // inferred once typeck_tables_of is done.
  27 // When type inference is running however, having to update the typeck
  28 // tables every time a new type is inferred would be unreasonably slow,
  29 // so instead all of the replacement happens at the end in
  30 // resolve_type_vars_in_body, which creates a new TypeTables which
  31 // doesn't contain any inference types.
  32 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  33     pub fn resolve_type_vars_in_body(&self, body: &'tcx hir::Body) -> &'tcx ty::TypeckTables<'tcx> {
  34         let item_id = self.tcx.hir().body_owner(body.id());
  35         let item_def_id = self.tcx.hir().local_def_id(item_id);
  36
  37         // This attribute causes us to dump some writeback information
  38         // in the form of errors, which is uSymbolfor unit tests.
  39         let rustc_dump_user_substs = self.tcx.has_attr(item_def_id, sym::rustc_dump_user_substs);
  40
  41         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
  42         for param in &body.params {
  43             wbcx.visit_node_id(param.pat.span, param.hir_id);
  44         }
  45         // Type only exists for constants and statics, not functions.
  46         match self.tcx.hir().body_owner_kind(item_id) {
  47             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
  48                 wbcx.visit_node_id(body.value.span, item_id);
  49             }
  50             hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
  51         }
  52         wbcx.visit_body(body);
  53         wbcx.visit_upvar_capture_map();
  54         wbcx.visit_closures();
  55         wbcx.visit_liberated_fn_sigs();
  56         wbcx.visit_fru_field_types();
  57         wbcx.visit_opaque_types(body.value.span);
  58         wbcx.visit_coercion_casts();
  59         wbcx.visit_free_region_map();
  60         wbcx.visit_user_provided_tys();
  61         wbcx.visit_user_provided_sigs();
  62
  63         let used_trait_imports = mem::replace(
  64             &mut self.tables.borrow_mut().used_trait_imports,
  65             Lrc::new(DefIdSet::default()),
  66         );
  67         debug!(
  68             "used_trait_imports({:?}) = {:?}",
  69             item_def_id, used_trait_imports
  70         );
  71         wbcx.tables.used_trait_imports = used_trait_imports;
  72
  73         wbcx.tables.upvar_list = mem::replace(
  74             &mut self.tables.borrow_mut().upvar_list,
  75             Default::default(),
  76         );
  77
  78         wbcx.tables.tainted_by_errors = self.is_tainted_by_errors();
  79
  80         debug!(
  81             "writeback: tables for {:?} are {:#?}",
  82             item_def_id, wbcx.tables
  83         );
  84
  85         self.tcx.arena.alloc(wbcx.tables)
  86     }
  87 }
  88
  89 ///////////////////////////////////////////////////////////////////////////
  90 // The Writeback context. This visitor walks the AST, checking the
  91 // fn-specific tables 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 tables 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     tables: ty::TypeckTables<'tcx>,
 101
 102     body: &'tcx hir::Body,
 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,
 111         rustc_dump_user_substs: bool,
 112     ) -> WritebackCx<'cx, 'tcx> {
 113         let owner = body.id().hir_id;
 114
 115         WritebackCx {
 116             fcx,
 117             tables: ty::TypeckTables::empty(Some(DefId::local(owner.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_tables(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 128         debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
 129         assert!(!ty.needs_infer() && !ty.has_placeholders());
 130         self.tables.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.node {
 139             hir::ExprKind::Unary(hir::UnNeg, ref inner)
 140             | hir::ExprKind::Unary(hir::UnNot, ref inner) => {
 141                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 142                 let inner_ty = self.fcx.resolve_vars_if_possible(&inner_ty);
 143
 144                 if inner_ty.is_scalar() {
 145                     let mut tables = self.fcx.tables.borrow_mut();
 146                     tables.type_dependent_defs_mut().remove(e.hir_id);
 147                     tables.node_substs_mut().remove(e.hir_id);
 148                 }
 149             }
 150             hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
 151             | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 152                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 153                 let lhs_ty = self.fcx.resolve_vars_if_possible(&lhs_ty);
 154
 155                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 156                 let rhs_ty = self.fcx.resolve_vars_if_possible(&rhs_ty);
 157
 158                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 159                     let mut tables = self.fcx.tables.borrow_mut();
 160                     tables.type_dependent_defs_mut().remove(e.hir_id);
 161                     tables.node_substs_mut().remove(e.hir_id);
 162
 163                     match e.node {
 164                         hir::ExprKind::Binary(..) => {
 165                             if !op.node.is_by_value() {
 166                                 let mut adjustments = tables.adjustments_mut();
 167                                 adjustments.get_mut(lhs.hir_id).map(|a| a.pop());
 168                                 adjustments.get_mut(rhs.hir_id).map(|a| a.pop());
 169                             }
 170                         }
 171                         hir::ExprKind::AssignOp(..) => {
 172                             tables
 173                                 .adjustments_mut()
 174                                 .get_mut(lhs.hir_id)
 175                                 .map(|a| a.pop());
 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.node {
 191             let mut tables = self.fcx.tables.borrow_mut();
 192
 193             // All valid indexing looks like this; might encounter non-valid indexes at this point
 194             if let ty::Ref(_, base_ty, _) = tables.expr_ty_adjusted(&base).sty {
 195                 let index_ty = tables.expr_ty_adjusted(&index);
 196                 let index_ty = self.fcx.resolve_vars_if_possible(&index_ty);
 197
 198                 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
 199                     // Remove the method call record
 200                     tables.type_dependent_defs_mut().remove(e.hir_id);
 201                     tables.node_substs_mut().remove(e.hir_id);
 202
 203                     tables.adjustments_mut().get_mut(base.hir_id).map(|a| {
 204                         // Discard the need for a mutable borrow
 205                         match a.pop() {
 206                             // Extra adjustment made when indexing causes a drop
 207                             // of size information - we need to get rid of it
 208                             // Since this is "after" the other adjustment to be
 209                             // discarded, we do an extra `pop()`
 210                             Some(Adjustment {
 211                                 kind: Adjust::Pointer(PointerCast::Unsize),
 212                                 ..
 213                             }) => {
 214                                 // So the borrow discard actually happens here
 215                                 a.pop();
 216                             }
 217                             _ => {}
 218                         }
 219                     });
 220                 }
 221             }
 222         }
 223     }
 224 }
 225
 226 ///////////////////////////////////////////////////////////////////////////
 227 // Impl of Visitor for Resolver
 228 //
 229 // This is the master code which walks the AST. It delegates most of
 230 // the heavy lifting to the generic visit and resolve functions
 231 // below. In general, a function is made into a `visitor` if it must
 232 // traffic in node-ids or update tables in the type context etc.
 233
 234 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
 235     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 236         NestedVisitorMap::None
 237     }
 238
 239     fn visit_expr(&mut self, e: &'tcx hir::Expr) {
 240         self.fix_scalar_builtin_expr(e);
 241         self.fix_index_builtin_expr(e);
 242
 243         self.visit_node_id(e.span, e.hir_id);
 244
 245         match e.node {
 246             hir::ExprKind::Closure(_, _, body, _, _) => {
 247                 let body = self.fcx.tcx.hir().body(body);
 248                 for param in &body.params {
 249                     self.visit_node_id(e.span, param.hir_id);
 250                 }
 251
 252                 self.visit_body(body);
 253             }
 254             hir::ExprKind::Struct(_, ref fields, _) => {
 255                 for field in fields {
 256                     self.visit_field_id(field.hir_id);
 257                 }
 258             }
 259             hir::ExprKind::Field(..) => {
 260                 self.visit_field_id(e.hir_id);
 261             }
 262             _ => {}
 263         }
 264
 265         intravisit::walk_expr(self, e);
 266     }
 267
 268     fn visit_block(&mut self, b: &'tcx hir::Block) {
 269         self.visit_node_id(b.span, b.hir_id);
 270         intravisit::walk_block(self, b);
 271     }
 272
 273     fn visit_pat(&mut self, p: &'tcx hir::Pat) {
 274         match p.node {
 275             hir::PatKind::Binding(..) => {
 276                 if let Some(&bm) = self.fcx.tables.borrow().pat_binding_modes().get(p.hir_id) {
 277                     self.tables.pat_binding_modes_mut().insert(p.hir_id, bm);
 278                 } else {
 279                     self.tcx()
 280                         .sess
 281                         .delay_span_bug(p.span, "missing binding mode");
 282                 }
 283             }
 284             hir::PatKind::Struct(_, ref fields, _) => {
 285                 for field in fields {
 286                     self.visit_field_id(field.hir_id);
 287                 }
 288             }
 289             _ => {}
 290         };
 291
 292         self.visit_pat_adjustments(p.span, p.hir_id);
 293
 294         self.visit_node_id(p.span, p.hir_id);
 295         intravisit::walk_pat(self, p);
 296     }
 297
 298     fn visit_local(&mut self, l: &'tcx hir::Local) {
 299         intravisit::walk_local(self, l);
 300         let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
 301         let var_ty = self.resolve(&var_ty, &l.span);
 302         self.write_ty_to_tables(l.hir_id, var_ty);
 303     }
 304
 305     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty) {
 306         intravisit::walk_ty(self, hir_ty);
 307         let ty = self.fcx.node_ty(hir_ty.hir_id);
 308         let ty = self.resolve(&ty, &hir_ty.span);
 309         self.write_ty_to_tables(hir_ty.hir_id, ty);
 310     }
 311 }
 312
 313 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 314     fn visit_upvar_capture_map(&mut self) {
 315         for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
 316             let new_upvar_capture = match *upvar_capture {
 317                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 318                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 319                     let r = upvar_borrow.region;
 320                     let r = self.resolve(&r, &upvar_id.var_path.hir_id);
 321                     ty::UpvarCapture::ByRef(ty::UpvarBorrow {
 322                         kind: upvar_borrow.kind,
 323                         region: r,
 324                     })
 325                 }
 326             };
 327             debug!(
 328                 "Upvar capture for {:?} resolved to {:?}",
 329                 upvar_id, new_upvar_capture
 330             );
 331             self.tables
 332                 .upvar_capture_map
 333                 .insert(*upvar_id, new_upvar_capture);
 334         }
 335     }
 336
 337     fn visit_closures(&mut self) {
 338         let fcx_tables = self.fcx.tables.borrow();
 339         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 340         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 341
 342         for (&id, &origin) in fcx_tables.closure_kind_origins().iter() {
 343             let hir_id = hir::HirId {
 344                 owner: common_local_id_root.index,
 345                 local_id: id,
 346             };
 347             self.tables
 348                 .closure_kind_origins_mut()
 349                 .insert(hir_id, origin);
 350         }
 351     }
 352
 353     fn visit_coercion_casts(&mut self) {
 354         let fcx_tables = self.fcx.tables.borrow();
 355         let fcx_coercion_casts = fcx_tables.coercion_casts();
 356         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 357
 358         for local_id in fcx_coercion_casts {
 359             self.tables.set_coercion_cast(*local_id);
 360         }
 361     }
 362
 363     fn visit_free_region_map(&mut self) {
 364         self.tables.free_region_map = self.fcx.tables.borrow().free_region_map.clone();
 365         debug_assert!(!self.tables.free_region_map.elements().any(|r| r.has_local_value()));
 366     }
 367
 368     fn visit_user_provided_tys(&mut self) {
 369         let fcx_tables = self.fcx.tables.borrow();
 370         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 371         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 372
 373         let mut errors_buffer = Vec::new();
 374         for (&local_id, c_ty) in fcx_tables.user_provided_types().iter() {
 375             let hir_id = hir::HirId {
 376                 owner: common_local_id_root.index,
 377                 local_id,
 378             };
 379
 380             if cfg!(debug_assertions) && c_ty.has_local_value() {
 381                 span_bug!(
 382                     hir_id.to_span(self.fcx.tcx),
 383                     "writeback: `{:?}` is a local value",
 384                     c_ty
 385                 );
 386             };
 387
 388             self.tables
 389                 .user_provided_types_mut()
 390                 .insert(hir_id, c_ty.clone());
 391
 392             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 393                 if self.rustc_dump_user_substs {
 394                     // This is a unit-testing mechanism.
 395                     let span = self.tcx().hir().span(hir_id);
 396                     // We need to buffer the errors in order to guarantee a consistent
 397                     // order when emitting them.
 398                     let err = self.tcx().sess.struct_span_err(
 399                         span,
 400                         &format!("user substs: {:?}", user_substs)
 401                     );
 402                     err.buffer(&mut errors_buffer);
 403                 }
 404             }
 405         }
 406
 407         if !errors_buffer.is_empty() {
 408             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 409             for diag in errors_buffer.drain(..) {
 410                 DiagnosticBuilder::new_diagnostic(self.tcx().sess.diagnostic(), diag).emit();
 411             }
 412         }
 413     }
 414
 415     fn visit_user_provided_sigs(&mut self) {
 416         let fcx_tables = self.fcx.tables.borrow();
 417         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 418
 419         for (&def_id, c_sig) in fcx_tables.user_provided_sigs.iter() {
 420             if cfg!(debug_assertions) && c_sig.has_local_value() {
 421                 span_bug!(
 422                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 423                     "writeback: `{:?}` is a local value",
 424                     c_sig
 425                 );
 426             };
 427
 428             self.tables
 429                 .user_provided_sigs
 430                 .insert(def_id, c_sig.clone());
 431         }
 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).unwrap();
 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, opaque_defn, instantiated_ty, span);
 455
 456             let mut skip_add = false;
 457
 458             if let ty::Opaque(defin_ty_def_id, _substs) = definition_ty.sty {
 459                 if def_id == defin_ty_def_id {
 460                     debug!("Skipping adding concrete definition for opaque type {:?} {:?}",
 461                            opaque_defn, defin_ty_def_id);
 462                     skip_add = true;
 463                 }
 464             }
 465
 466             if !opaque_defn.substs.has_local_value() {
 467                 // We only want to add an entry into `concrete_opaque_types`
 468                 // if we actually found a defining usage of this opaque type.
 469                 // Otherwise, we do nothing - we'll either find a defining usage
 470                 // in some other location, or we'll end up emitting an error due
 471                 // to the lack of defining usage
 472                 if !skip_add {
 473                     let new = ty::ResolvedOpaqueTy {
 474                         concrete_type: definition_ty,
 475                         substs: opaque_defn.substs,
 476                     };
 477
 478                     let old = self.tables
 479                         .concrete_opaque_types
 480                         .insert(def_id, new);
 481                     if let Some(old) = old {
 482                         if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
 483                             span_bug!(
 484                                 span,
 485                                 "visit_opaque_types tried to write different types for the same \
 486                                 opaque type: {:?}, {:?}, {:?}, {:?}",
 487                                 def_id,
 488                                 definition_ty,
 489                                 opaque_defn,
 490                                 old,
 491                             );
 492                         }
 493                     }
 494                 }
 495             } else {
 496                 self.tcx().sess.delay_span_bug(
 497                     span,
 498                     "`opaque_defn` is a local value",
 499                 );
 500             }
 501         }
 502     }
 503
 504     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 505         if let Some(index) = self.fcx
 506             .tables
 507             .borrow_mut()
 508             .field_indices_mut()
 509             .remove(hir_id)
 510         {
 511             self.tables.field_indices_mut().insert(hir_id, index);
 512         }
 513     }
 514
 515     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 516         // Export associated path extensions and method resolutions.
 517         if let Some(def) = self.fcx
 518             .tables
 519             .borrow_mut()
 520             .type_dependent_defs_mut()
 521             .remove(hir_id)
 522         {
 523             self.tables.type_dependent_defs_mut().insert(hir_id, def);
 524         }
 525
 526         // Resolve any borrowings for the node with id `node_id`
 527         self.visit_adjustments(span, hir_id);
 528
 529         // Resolve the type of the node with id `node_id`
 530         let n_ty = self.fcx.node_ty(hir_id);
 531         let n_ty = self.resolve(&n_ty, &span);
 532         self.write_ty_to_tables(hir_id, n_ty);
 533         debug!("node {:?} has type {:?}", hir_id, n_ty);
 534
 535         // Resolve any substitutions
 536         if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
 537             let substs = self.resolve(&substs, &span);
 538             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 539             assert!(!substs.needs_infer() && !substs.has_placeholders());
 540             self.tables.node_substs_mut().insert(hir_id, substs);
 541         }
 542     }
 543
 544     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 545         let adjustment = self.fcx
 546             .tables
 547             .borrow_mut()
 548             .adjustments_mut()
 549             .remove(hir_id);
 550         match adjustment {
 551             None => {
 552                 debug!("no adjustments for node {:?}", hir_id);
 553             }
 554
 555             Some(adjustment) => {
 556                 let resolved_adjustment = self.resolve(&adjustment, &span);
 557                 debug!(
 558                     "adjustments for node {:?}: {:?}",
 559                     hir_id, resolved_adjustment
 560                 );
 561                 self.tables
 562                     .adjustments_mut()
 563                     .insert(hir_id, resolved_adjustment);
 564             }
 565         }
 566     }
 567
 568     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 569         let adjustment = self.fcx
 570             .tables
 571             .borrow_mut()
 572             .pat_adjustments_mut()
 573             .remove(hir_id);
 574         match adjustment {
 575             None => {
 576                 debug!("no pat_adjustments for node {:?}", hir_id);
 577             }
 578
 579             Some(adjustment) => {
 580                 let resolved_adjustment = self.resolve(&adjustment, &span);
 581                 debug!(
 582                     "pat_adjustments for node {:?}: {:?}",
 583                     hir_id, resolved_adjustment
 584                 );
 585                 self.tables
 586                     .pat_adjustments_mut()
 587                     .insert(hir_id, resolved_adjustment);
 588             }
 589         }
 590     }
 591
 592     fn visit_liberated_fn_sigs(&mut self) {
 593         let fcx_tables = self.fcx.tables.borrow();
 594         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 595         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 596
 597         for (&local_id, fn_sig) in fcx_tables.liberated_fn_sigs().iter() {
 598             let hir_id = hir::HirId {
 599                 owner: common_local_id_root.index,
 600                 local_id,
 601             };
 602             let fn_sig = self.resolve(fn_sig, &hir_id);
 603             self.tables
 604                 .liberated_fn_sigs_mut()
 605                 .insert(hir_id, fn_sig.clone());
 606         }
 607     }
 608
 609     fn visit_fru_field_types(&mut self) {
 610         let fcx_tables = self.fcx.tables.borrow();
 611         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 612         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 613
 614         for (&local_id, ftys) in fcx_tables.fru_field_types().iter() {
 615             let hir_id = hir::HirId {
 616                 owner: common_local_id_root.index,
 617                 local_id,
 618             };
 619             let ftys = self.resolve(ftys, &hir_id);
 620             self.tables.fru_field_types_mut().insert(hir_id, ftys);
 621         }
 622     }
 623
 624     fn resolve<T>(&self, x: &T, span: &dyn Locatable) -> T
 625     where
 626         T: TypeFoldable<'tcx>,
 627     {
 628         let x = x.fold_with(&mut Resolver::new(self.fcx, span, self.body));
 629         if cfg!(debug_assertions) && x.has_local_value() {
 630             span_bug!(
 631                 span.to_span(self.fcx.tcx),
 632                 "writeback: `{:?}` is a local value",
 633                 x
 634             );
 635         }
 636         x
 637     }
 638 }
 639
 640 trait Locatable {
 641     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 642 }
 643
 644 impl Locatable for Span {
 645     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 646         *self
 647     }
 648 }
 649
 650 impl Locatable for DefIndex {
 651     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 652         let hir_id = tcx.hir().def_index_to_hir_id(*self);
 653         tcx.hir().span(hir_id)
 654     }
 655 }
 656
 657 impl Locatable for hir::HirId {
 658     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 659         tcx.hir().span(*self)
 660     }
 661 }
 662
 663 ///////////////////////////////////////////////////////////////////////////
 664 // The Resolver. This is the type folding engine that detects
 665 // unresolved types and so forth.
 666
 667 struct Resolver<'cx, 'tcx> {
 668     tcx: TyCtxt<'tcx>,
 669     infcx: &'cx InferCtxt<'cx, 'tcx>,
 670     span: &'cx dyn Locatable,
 671     body: &'tcx hir::Body,
 672 }
 673
 674 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 675     fn new(
 676         fcx: &'cx FnCtxt<'cx, 'tcx>,
 677         span: &'cx dyn Locatable,
 678         body: &'tcx hir::Body,
 679     ) -> Resolver<'cx, 'tcx> {
 680         Resolver {
 681             tcx: fcx.tcx,
 682             infcx: fcx,
 683             span,
 684             body,
 685         }
 686     }
 687
 688     fn report_error(&self, t: Ty<'tcx>) {
 689         if !self.tcx.sess.has_errors() {
 690             self.infcx
 691                 .need_type_info_err(Some(self.body.id()), self.span.to_span(self.tcx), t)
 692                 .emit();
 693         }
 694     }
 695 }
 696
 697 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 698     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 699         self.tcx
 700     }
 701
 702     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 703         match self.infcx.fully_resolve(&t) {
 704             Ok(t) => t,
 705             Err(_) => {
 706                 debug!(
 707                     "Resolver::fold_ty: input type `{:?}` not fully resolvable",
 708                     t
 709                 );
 710                 self.report_error(t);
 711                 self.tcx().types.err
 712             }
 713         }
 714     }
 715
 716     // FIXME This should be carefully checked
 717     // We could use `self.report_error` but it doesn't accept a ty::Region, right now.
 718     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 719         self.infcx.fully_resolve(&r).unwrap_or(self.tcx.lifetimes.re_static)
 720     }
 721
 722     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
 723         match self.infcx.fully_resolve(&ct) {
 724             Ok(ct) => ct,
 725             Err(_) => {
 726                 debug!(
 727                     "Resolver::fold_const: input const `{:?}` not fully resolvable",
 728                     ct
 729                 );
 730                 // FIXME: we'd like to use `self.report_error`, but it doesn't yet
 731                 // accept a &'tcx ty::Const.
 732                 self.tcx().consts.err
 733             }
 734         }
 735     }
 736 }
 737
 738 ///////////////////////////////////////////////////////////////////////////
 739 // During type check, we store promises with the result of trait
 740 // lookup rather than the actual results (because the results are not
 741 // necessarily available immediately). These routines unwind the
 742 // promises. It is expected that we will have already reported any
 743 // errors that may be encountered, so if the promises store an error,
 744 // a dummy result is returned.