compiler/rustc_typeck/src/check/writeback.rs

   1 // Type resolution: the phase that finds all the types in the AST with
   2 // unresolved type variables and replaces "ty_var" types with their
   3 // substitutions.
   4
   5 use crate::check::FnCtxt;
   6
   7 use rustc_data_structures::stable_map::FxHashMap;
   8 use rustc_errors::ErrorReported;
   9 use rustc_hir as hir;
  10 use rustc_hir::def_id::DefId;
  11 use rustc_hir::intravisit::{self, Visitor};
  12 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
  13 use rustc_infer::infer::InferCtxt;
  14 use rustc_middle::hir::place::Place as HirPlace;
  15 use rustc_middle::mir::FakeReadCause;
  16 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
  17 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
  18 use rustc_middle::ty::{self, ClosureSizeProfileData, Ty, TyCtxt};
  19 use rustc_span::symbol::sym;
  20 use rustc_span::Span;
  21
  22 use std::mem;
  23
  24 ///////////////////////////////////////////////////////////////////////////
  25 // Entry point
  26
  27 // During type inference, partially inferred types are
  28 // represented using Type variables (ty::Infer). These don't appear in
  29 // the final TypeckResults since all of the types should have been
  30 // inferred once typeck is done.
  31 // When type inference is running however, having to update the typeck
  32 // typeck results every time a new type is inferred would be unreasonably slow,
  33 // so instead all of the replacement happens at the end in
  34 // resolve_type_vars_in_body, which creates a new TypeTables which
  35 // doesn't contain any inference types.
  36 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  37     pub fn resolve_type_vars_in_body(
  38         &self,
  39         body: &'tcx hir::Body<'tcx>,
  40     ) -> &'tcx ty::TypeckResults<'tcx> {
  41         let item_id = self.tcx.hir().body_owner(body.id());
  42         let item_def_id = self.tcx.hir().local_def_id(item_id);
  43
  44         // This attribute causes us to dump some writeback information
  45         // in the form of errors, which is used for unit tests.
  46         let rustc_dump_user_substs =
  47             self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs);
  48
  49         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
  50         for param in body.params {
  51             wbcx.visit_node_id(param.pat.span, param.hir_id);
  52         }
  53         // Type only exists for constants and statics, not functions.
  54         match self.tcx.hir().body_owner_kind(item_id) {
  55             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
  56                 wbcx.visit_node_id(body.value.span, item_id);
  57             }
  58             hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
  59         }
  60         wbcx.visit_body(body);
  61         wbcx.visit_min_capture_map();
  62         wbcx.eval_closure_size();
  63         wbcx.visit_fake_reads_map();
  64         wbcx.visit_closures();
  65         wbcx.visit_liberated_fn_sigs();
  66         wbcx.visit_fru_field_types();
  67         wbcx.visit_opaque_types();
  68         wbcx.visit_coercion_casts();
  69         wbcx.visit_user_provided_tys();
  70         wbcx.visit_user_provided_sigs();
  71         wbcx.visit_generator_interior_types();
  72
  73         let used_trait_imports =
  74             mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports);
  75         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  76         wbcx.typeck_results.used_trait_imports = used_trait_imports;
  77
  78         wbcx.typeck_results.treat_byte_string_as_slice =
  79             mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice);
  80
  81         if self.is_tainted_by_errors() {
  82             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
  83             wbcx.typeck_results.tainted_by_errors = Some(ErrorReported);
  84         }
  85
  86         debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results);
  87
  88         self.tcx.arena.alloc(wbcx.typeck_results)
  89     }
  90 }
  91
  92 ///////////////////////////////////////////////////////////////////////////
  93 // The Writeback context. This visitor walks the HIR, checking the
  94 // fn-specific typeck results to find references to types or regions. It
  95 // resolves those regions to remove inference variables and writes the
  96 // final result back into the master typeck results in the tcx. Here and
  97 // there, it applies a few ad-hoc checks that were not convenient to
  98 // do elsewhere.
  99
 100 struct WritebackCx<'cx, 'tcx> {
 101     fcx: &'cx FnCtxt<'cx, 'tcx>,
 102
 103     typeck_results: ty::TypeckResults<'tcx>,
 104
 105     body: &'tcx hir::Body<'tcx>,
 106
 107     rustc_dump_user_substs: bool,
 108 }
 109
 110 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 111     fn new(
 112         fcx: &'cx FnCtxt<'cx, 'tcx>,
 113         body: &'tcx hir::Body<'tcx>,
 114         rustc_dump_user_substs: bool,
 115     ) -> WritebackCx<'cx, 'tcx> {
 116         let owner = body.id().hir_id.owner;
 117
 118         WritebackCx {
 119             fcx,
 120             typeck_results: ty::TypeckResults::new(owner),
 121             body,
 122             rustc_dump_user_substs,
 123         }
 124     }
 125
 126     fn tcx(&self) -> TyCtxt<'tcx> {
 127         self.fcx.tcx
 128     }
 129
 130     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
 131         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
 132         assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
 133         self.typeck_results.node_types_mut().insert(hir_id, ty);
 134     }
 135
 136     // Hacky hack: During type-checking, we treat *all* operators
 137     // as potentially overloaded. But then, during writeback, if
 138     // we observe that something like `a+b` is (known to be)
 139     // operating on scalars, we clear the overload.
 140     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) {
 141         match e.kind {
 142             hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, inner) => {
 143                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 144                 let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty);
 145
 146                 if inner_ty.is_scalar() {
 147                     let mut typeck_results = self.fcx.typeck_results.borrow_mut();
 148                     typeck_results.type_dependent_defs_mut().remove(e.hir_id);
 149                     typeck_results.node_substs_mut().remove(e.hir_id);
 150                 }
 151             }
 152             hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, 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                         {
 179                             a.pop();
 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     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 256         self.fix_scalar_builtin_expr(e);
 257         self.fix_index_builtin_expr(e);
 258
 259         self.visit_node_id(e.span, e.hir_id);
 260
 261         match e.kind {
 262             hir::ExprKind::Closure(_, _, body, _, _) => {
 263                 let body = self.fcx.tcx.hir().body(body);
 264                 for param in body.params {
 265                     self.visit_node_id(e.span, param.hir_id);
 266                 }
 267
 268                 self.visit_body(body);
 269             }
 270             hir::ExprKind::Struct(_, fields, _) => {
 271                 for field in fields {
 272                     self.visit_field_id(field.hir_id);
 273                 }
 274             }
 275             hir::ExprKind::Field(..) => {
 276                 self.visit_field_id(e.hir_id);
 277             }
 278             hir::ExprKind::ConstBlock(anon_const) => {
 279                 self.visit_node_id(e.span, anon_const.hir_id);
 280
 281                 let body = self.tcx().hir().body(anon_const.body);
 282                 self.visit_body(body);
 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     fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
 334         intravisit::walk_inf(self, inf);
 335         // Ignore cases where the inference is a const.
 336         if let Some(ty) = self.fcx.node_ty_opt(inf.hir_id) {
 337             let ty = self.resolve(ty, &inf.span);
 338             self.write_ty_to_typeck_results(inf.hir_id, ty);
 339         }
 340     }
 341 }
 342
 343 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 344     fn eval_closure_size(&mut self) {
 345         let mut res: FxHashMap<DefId, ClosureSizeProfileData<'tcx>> = Default::default();
 346         for (closure_def_id, data) in self.fcx.typeck_results.borrow().closure_size_eval.iter() {
 347             let closure_hir_id =
 348                 self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local());
 349
 350             let data = self.resolve(*data, &closure_hir_id);
 351
 352             res.insert(*closure_def_id, data);
 353         }
 354
 355         self.typeck_results.closure_size_eval = res;
 356     }
 357     fn visit_min_capture_map(&mut self) {
 358         let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher(
 359             self.fcx.typeck_results.borrow().closure_min_captures.len(),
 360             Default::default(),
 361         );
 362         for (closure_def_id, root_min_captures) in
 363             self.fcx.typeck_results.borrow().closure_min_captures.iter()
 364         {
 365             let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher(
 366                 root_min_captures.len(),
 367                 Default::default(),
 368             );
 369             for (var_hir_id, min_list) in root_min_captures.iter() {
 370                 let min_list_wb = min_list
 371                     .iter()
 372                     .map(|captured_place| {
 373                         let locatable = captured_place.info.path_expr_id.unwrap_or_else(|| {
 374                             self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local())
 375                         });
 376
 377                         self.resolve(captured_place.clone(), &locatable)
 378                     })
 379                     .collect();
 380                 root_var_map_wb.insert(*var_hir_id, min_list_wb);
 381             }
 382             min_captures_wb.insert(*closure_def_id, root_var_map_wb);
 383         }
 384
 385         self.typeck_results.closure_min_captures = min_captures_wb;
 386     }
 387
 388     fn visit_fake_reads_map(&mut self) {
 389         let mut resolved_closure_fake_reads: FxHashMap<
 390             DefId,
 391             Vec<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>,
 392         > = Default::default();
 393         for (closure_def_id, fake_reads) in
 394             self.fcx.typeck_results.borrow().closure_fake_reads.iter()
 395         {
 396             let mut resolved_fake_reads = Vec::<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>::new();
 397             for (place, cause, hir_id) in fake_reads.iter() {
 398                 let locatable =
 399                     self.tcx().hir().local_def_id_to_hir_id(closure_def_id.expect_local());
 400
 401                 let resolved_fake_read = self.resolve(place.clone(), &locatable);
 402                 resolved_fake_reads.push((resolved_fake_read, *cause, *hir_id));
 403             }
 404             resolved_closure_fake_reads.insert(*closure_def_id, resolved_fake_reads);
 405         }
 406         self.typeck_results.closure_fake_reads = resolved_closure_fake_reads;
 407     }
 408
 409     fn visit_closures(&mut self) {
 410         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 411         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 412         let common_hir_owner = fcx_typeck_results.hir_owner;
 413
 414         for (id, origin) in fcx_typeck_results.closure_kind_origins().iter() {
 415             let hir_id = hir::HirId { owner: common_hir_owner, local_id: *id };
 416             let place_span = origin.0;
 417             let place = self.resolve(origin.1.clone(), &place_span);
 418             self.typeck_results.closure_kind_origins_mut().insert(hir_id, (place_span, place));
 419         }
 420     }
 421
 422     fn visit_coercion_casts(&mut self) {
 423         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 424         let fcx_coercion_casts = fcx_typeck_results.coercion_casts();
 425         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 426
 427         for local_id in fcx_coercion_casts {
 428             self.typeck_results.set_coercion_cast(*local_id);
 429         }
 430     }
 431
 432     fn visit_user_provided_tys(&mut self) {
 433         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 434         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 435         let common_hir_owner = fcx_typeck_results.hir_owner;
 436
 437         let mut errors_buffer = Vec::new();
 438         for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() {
 439             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 440
 441             if cfg!(debug_assertions) && c_ty.needs_infer() {
 442                 span_bug!(
 443                     hir_id.to_span(self.fcx.tcx),
 444                     "writeback: `{:?}` has inference variables",
 445                     c_ty
 446                 );
 447             };
 448
 449             self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty);
 450
 451             if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
 452                 if self.rustc_dump_user_substs {
 453                     // This is a unit-testing mechanism.
 454                     let span = self.tcx().hir().span(hir_id);
 455                     // We need to buffer the errors in order to guarantee a consistent
 456                     // order when emitting them.
 457                     let err = self
 458                         .tcx()
 459                         .sess
 460                         .struct_span_err(span, &format!("user substs: {:?}", user_substs));
 461                     err.buffer(&mut errors_buffer);
 462                 }
 463             }
 464         }
 465
 466         if !errors_buffer.is_empty() {
 467             errors_buffer.sort_by_key(|diag| diag.span.primary_span());
 468             for diag in errors_buffer.drain(..) {
 469                 self.tcx().sess.diagnostic().emit_diagnostic(&diag);
 470             }
 471         }
 472     }
 473
 474     fn visit_user_provided_sigs(&mut self) {
 475         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 476         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 477
 478         for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() {
 479             if cfg!(debug_assertions) && c_sig.needs_infer() {
 480                 span_bug!(
 481                     self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
 482                     "writeback: `{:?}` has inference variables",
 483                     c_sig
 484                 );
 485             };
 486
 487             self.typeck_results.user_provided_sigs.insert(def_id, *c_sig);
 488         }
 489     }
 490
 491     fn visit_generator_interior_types(&mut self) {
 492         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 493         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 494         self.typeck_results.generator_interior_types =
 495             fcx_typeck_results.generator_interior_types.clone();
 496     }
 497
 498     #[instrument(skip(self), level = "debug")]
 499     fn visit_opaque_types(&mut self) {
 500         let opaque_types =
 501             self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
 502         for (opaque_type_key, decl) in opaque_types {
 503             let hidden_type = match decl.origin {
 504                 hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => {
 505                     Some(self.resolve(decl.hidden_type.ty, &decl.hidden_type.span))
 506                 }
 507                 hir::OpaqueTyOrigin::TyAlias => None,
 508             };
 509             self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type);
 510         }
 511     }
 512
 513     fn visit_field_id(&mut self, hir_id: hir::HirId) {
 514         if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id)
 515         {
 516             self.typeck_results.field_indices_mut().insert(hir_id, index);
 517         }
 518     }
 519
 520     #[instrument(skip(self, span), level = "debug")]
 521     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 522         // Export associated path extensions and method resolutions.
 523         if let Some(def) =
 524             self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id)
 525         {
 526             self.typeck_results.type_dependent_defs_mut().insert(hir_id, def);
 527         }
 528
 529         // Resolve any borrowings for the node with id `node_id`
 530         self.visit_adjustments(span, hir_id);
 531
 532         // Resolve the type of the node with id `node_id`
 533         let n_ty = self.fcx.node_ty(hir_id);
 534         let n_ty = self.resolve(n_ty, &span);
 535         self.write_ty_to_typeck_results(hir_id, n_ty);
 536         debug!(?n_ty);
 537
 538         // Resolve any substitutions
 539         if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
 540             let substs = self.resolve(substs, &span);
 541             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 542             assert!(!substs.needs_infer() && !substs.has_placeholders());
 543             self.typeck_results.node_substs_mut().insert(hir_id, substs);
 544         }
 545     }
 546
 547     #[instrument(skip(self, span), level = "debug")]
 548     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 549         let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id);
 550         match adjustment {
 551             None => {
 552                 debug!("no adjustments for node");
 553             }
 554
 555             Some(adjustment) => {
 556                 let resolved_adjustment = self.resolve(adjustment, &span);
 557                 debug!(?resolved_adjustment);
 558                 self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment);
 559             }
 560         }
 561     }
 562
 563     #[instrument(skip(self, span), level = "debug")]
 564     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 565         let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id);
 566         match adjustment {
 567             None => {
 568                 debug!("no pat_adjustments for node");
 569             }
 570
 571             Some(adjustment) => {
 572                 let resolved_adjustment = self.resolve(adjustment, &span);
 573                 debug!(?resolved_adjustment);
 574                 self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
 575             }
 576         }
 577     }
 578
 579     fn visit_liberated_fn_sigs(&mut self) {
 580         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 581         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 582         let common_hir_owner = fcx_typeck_results.hir_owner;
 583
 584         for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() {
 585             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 586             let fn_sig = self.resolve(fn_sig, &hir_id);
 587             self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
 588         }
 589     }
 590
 591     fn visit_fru_field_types(&mut self) {
 592         let fcx_typeck_results = self.fcx.typeck_results.borrow();
 593         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 594         let common_hir_owner = fcx_typeck_results.hir_owner;
 595
 596         for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() {
 597             let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 598             let ftys = self.resolve(ftys.clone(), &hir_id);
 599             self.typeck_results.fru_field_types_mut().insert(hir_id, ftys);
 600         }
 601     }
 602
 603     fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T
 604     where
 605         T: TypeFoldable<'tcx>,
 606     {
 607         let mut resolver = Resolver::new(self.fcx, span, self.body);
 608         let x = x.fold_with(&mut resolver);
 609         if cfg!(debug_assertions) && x.needs_infer() {
 610             span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
 611         }
 612
 613         // We may have introduced e.g. `ty::Error`, if inference failed, make sure
 614         // to mark the `TypeckResults` as tainted in that case, so that downstream
 615         // users of the typeck results don't produce extra errors, or worse, ICEs.
 616         if resolver.replaced_with_error {
 617             // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
 618             self.typeck_results.tainted_by_errors = Some(ErrorReported);
 619         }
 620
 621         x
 622     }
 623 }
 624
 625 crate trait Locatable {
 626     fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
 627 }
 628
 629 impl Locatable for Span {
 630     fn to_span(&self, _: TyCtxt<'_>) -> Span {
 631         *self
 632     }
 633 }
 634
 635 impl Locatable for hir::HirId {
 636     fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
 637         tcx.hir().span(*self)
 638     }
 639 }
 640
 641 /// The Resolver. This is the type folding engine that detects
 642 /// unresolved types and so forth.
 643 struct Resolver<'cx, 'tcx> {
 644     tcx: TyCtxt<'tcx>,
 645     infcx: &'cx InferCtxt<'cx, 'tcx>,
 646     span: &'cx dyn Locatable,
 647     body: &'tcx hir::Body<'tcx>,
 648
 649     /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
 650     replaced_with_error: bool,
 651 }
 652
 653 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 654     fn new(
 655         fcx: &'cx FnCtxt<'cx, 'tcx>,
 656         span: &'cx dyn Locatable,
 657         body: &'tcx hir::Body<'tcx>,
 658     ) -> Resolver<'cx, 'tcx> {
 659         Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false }
 660     }
 661
 662     fn report_type_error(&self, t: Ty<'tcx>) {
 663         if !self.tcx.sess.has_errors() {
 664             self.infcx
 665                 .emit_inference_failure_err(
 666                     Some(self.body.id()),
 667                     self.span.to_span(self.tcx),
 668                     t.into(),
 669                     vec![],
 670                     E0282,
 671                 )
 672                 .emit();
 673         }
 674     }
 675
 676     fn report_const_error(&self, c: &'tcx ty::Const<'tcx>) {
 677         if !self.tcx.sess.has_errors() {
 678             self.infcx
 679                 .emit_inference_failure_err(
 680                     Some(self.body.id()),
 681                     self.span.to_span(self.tcx),
 682                     c.into(),
 683                     vec![],
 684                     E0282,
 685                 )
 686                 .emit();
 687         }
 688     }
 689 }
 690
 691 struct EraseEarlyRegions<'tcx> {
 692     tcx: TyCtxt<'tcx>,
 693 }
 694
 695 impl<'tcx> TypeFolder<'tcx> for EraseEarlyRegions<'tcx> {
 696     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
 697         self.tcx
 698     }
 699     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
 700         if ty.has_type_flags(ty::TypeFlags::HAS_FREE_REGIONS) {
 701             ty.super_fold_with(self)
 702         } else {
 703             ty
 704         }
 705     }
 706     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 707         if let ty::ReLateBound(..) = r { r } else { self.tcx.lifetimes.re_erased }
 708     }
 709 }
 710
 711 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 712     fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
 713         self.tcx
 714     }
 715
 716     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 717         match self.infcx.fully_resolve(t) {
 718             Ok(t) => {
 719                 // Do not anonymize late-bound regions
 720                 // (e.g. keep `for<'a>` named `for<'a>`).
 721                 // This allows NLL to generate error messages that
 722                 // refer to the higher-ranked lifetime names written by the user.
 723                 EraseEarlyRegions { tcx: self.infcx.tcx }.fold_ty(t)
 724             }
 725             Err(_) => {
 726                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
 727                 self.report_type_error(t);
 728                 self.replaced_with_error = true;
 729                 self.tcx().ty_error()
 730             }
 731         }
 732     }
 733
 734     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 735         debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
 736         self.tcx.lifetimes.re_erased
 737     }
 738
 739     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
 740         match self.infcx.fully_resolve(ct) {
 741             Ok(ct) => self.infcx.tcx.erase_regions(ct),
 742             Err(_) => {
 743                 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
 744                 self.report_const_error(ct);
 745                 self.replaced_with_error = true;
 746                 self.tcx().const_error(ct.ty)
 747             }
 748         }
 749     }
 750 }
 751
 752 ///////////////////////////////////////////////////////////////////////////
 753 // During type check, we store promises with the result of trait
 754 // lookup rather than the actual results (because the results are not
 755 // necessarily available immediately). These routines unwind the
 756 // promises. It is expected that we will have already reported any
 757 // errors that may be encountered, so if the promises store an error,
 758 // a dummy result is returned.