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
5 use crate::check::FnCtxt;
7 use rustc_data_structures::sync::Lrc;
8 use rustc_errors::ErrorReported;
10 use rustc_hir::def_id::DefIdSet;
11 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
12 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
13 use rustc_infer::infer::InferCtxt;
14 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
15 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
16 use rustc_middle::ty::{self, Ty, TyCtxt};
17 use rustc_span::symbol::sym;
19 use rustc_trait_selection::opaque_types::InferCtxtExt;
23 ///////////////////////////////////////////////////////////////////////////
26 // During type inference, partially inferred types are
27 // represented using Type variables (ty::Infer). These don't appear in
28 // the final TypeckTables since all of the types should have been
29 // inferred once typeck_tables_of is done.
30 // When type inference is running however, having to update the typeck
31 // tables every time a new type is inferred would be unreasonably slow,
32 // so instead all of the replacement happens at the end in
33 // resolve_type_vars_in_body, which creates a new TypeTables which
34 // doesn't contain any inference types.
35 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
36 pub fn resolve_type_vars_in_body(
38 body: &'tcx hir::Body<'tcx>,
39 ) -> &'tcx ty::TypeckTables<'tcx> {
40 let item_id = self.tcx.hir().body_owner(body.id());
41 let item_def_id = self.tcx.hir().local_def_id(item_id);
43 // This attribute causes us to dump some writeback information
44 // in the form of errors, which is uSymbol for unit tests.
45 let rustc_dump_user_substs =
46 self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs);
48 let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
49 for param in body.params {
50 wbcx.visit_node_id(param.pat.span, param.hir_id);
52 // Type only exists for constants and statics, not functions.
53 match self.tcx.hir().body_owner_kind(item_id) {
54 hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
55 wbcx.visit_node_id(body.value.span, item_id);
57 hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (),
59 wbcx.visit_body(body);
60 wbcx.visit_upvar_capture_map();
61 wbcx.visit_closures();
62 wbcx.visit_liberated_fn_sigs();
63 wbcx.visit_fru_field_types();
64 wbcx.visit_opaque_types(body.value.span);
65 wbcx.visit_coercion_casts();
66 wbcx.visit_user_provided_tys();
67 wbcx.visit_user_provided_sigs();
68 wbcx.visit_generator_interior_types();
70 let used_trait_imports = mem::replace(
71 &mut self.tables.borrow_mut().used_trait_imports,
72 Lrc::new(DefIdSet::default()),
74 debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
75 wbcx.tables.used_trait_imports = used_trait_imports;
77 wbcx.tables.upvar_list =
78 mem::replace(&mut self.tables.borrow_mut().upvar_list, Default::default());
80 if self.is_tainted_by_errors() {
81 // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
82 wbcx.tables.tainted_by_errors = Some(ErrorReported);
85 debug!("writeback: tables for {:?} are {:#?}", item_def_id, wbcx.tables);
87 self.tcx.arena.alloc(wbcx.tables)
91 ///////////////////////////////////////////////////////////////////////////
92 // The Writeback context. This visitor walks the AST, checking the
93 // fn-specific tables 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 tables in the tcx. Here and
96 // there, it applies a few ad-hoc checks that were not convenient to
99 struct WritebackCx<'cx, 'tcx> {
100 fcx: &'cx FnCtxt<'cx, 'tcx>,
102 tables: ty::TypeckTables<'tcx>,
104 body: &'tcx hir::Body<'tcx>,
106 rustc_dump_user_substs: bool,
109 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
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;
119 tables: ty::TypeckTables::empty(Some(owner)),
121 rustc_dump_user_substs,
125 fn tcx(&self) -> TyCtxt<'tcx> {
129 fn write_ty_to_tables(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
130 debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
131 assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions());
132 self.tables.node_types_mut().insert(hir_id, ty);
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<'_>) {
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);
145 if inner_ty.is_scalar() {
146 let mut tables = self.fcx.tables.borrow_mut();
147 tables.type_dependent_defs_mut().remove(e.hir_id);
148 tables.node_substs_mut().remove(e.hir_id);
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);
156 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
157 let rhs_ty = self.fcx.resolve_vars_if_possible(&rhs_ty);
159 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
160 let mut tables = self.fcx.tables.borrow_mut();
161 tables.type_dependent_defs_mut().remove(e.hir_id);
162 tables.node_substs_mut().remove(e.hir_id);
165 hir::ExprKind::Binary(..) => {
166 if !op.node.is_by_value() {
167 let mut adjustments = tables.adjustments_mut();
168 if let Some(a) = adjustments.get_mut(lhs.hir_id) {
171 if let Some(a) = adjustments.get_mut(rhs.hir_id) {
176 hir::ExprKind::AssignOp(..) => {
177 if let Some(a) = tables.adjustments_mut().get_mut(lhs.hir_id) {
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
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 tables = self.fcx.tables.borrow_mut();
197 // All valid indexing looks like this; might encounter non-valid indexes at this point.
198 let base_ty = tables.expr_ty_adjusted_opt(&base).map(|t| &t.kind);
199 if base_ty.is_none() {
200 // When encountering `return [0][0]` outside of a `fn` body we can encounter a base
201 // that isn't in the type table. We assume more relevant errors have already been
202 // emitted, so we delay an ICE if none have. (#64638)
203 self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base));
205 if let Some(ty::Ref(_, base_ty, _)) = base_ty {
206 let index_ty = tables.expr_ty_adjusted_opt(&index).unwrap_or_else(|| {
207 // When encountering `return [0][0]` outside of a `fn` body we would attempt
208 // to access an unexistend index. We assume that more relevant errors will
209 // already have been emitted, so we only gate on this with an ICE if no
210 // error has been emitted. (#64638)
211 self.tcx().sess.delay_span_bug(
213 &format!("bad index {:?} for base: `{:?}`", index, base),
215 self.fcx.tcx.types.err
217 let index_ty = self.fcx.resolve_vars_if_possible(&index_ty);
219 if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
220 // Remove the method call record
221 tables.type_dependent_defs_mut().remove(e.hir_id);
222 tables.node_substs_mut().remove(e.hir_id);
224 if let Some(a) = tables.adjustments_mut().get_mut(base.hir_id) {
225 // Discard the need for a mutable borrow
227 // Extra adjustment made when indexing causes a drop
228 // of size information - we need to get rid of it
229 // Since this is "after" the other adjustment to be
230 // discarded, we do an extra `pop()`
231 if let Some(Adjustment {
232 kind: Adjust::Pointer(PointerCast::Unsize), ..
235 // So the borrow discard actually happens here
245 ///////////////////////////////////////////////////////////////////////////
246 // Impl of Visitor for Resolver
248 // This is the master code which walks the AST. It delegates most of
249 // the heavy lifting to the generic visit and resolve functions
250 // below. In general, a function is made into a `visitor` if it must
251 // traffic in node-ids or update tables in the type context etc.
253 impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> {
254 type Map = intravisit::ErasedMap<'tcx>;
256 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
257 NestedVisitorMap::None
260 fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
261 self.fix_scalar_builtin_expr(e);
262 self.fix_index_builtin_expr(e);
264 self.visit_node_id(e.span, e.hir_id);
267 hir::ExprKind::Closure(_, _, body, _, _) => {
268 let body = self.fcx.tcx.hir().body(body);
269 for param in body.params {
270 self.visit_node_id(e.span, param.hir_id);
273 self.visit_body(body);
275 hir::ExprKind::Struct(_, fields, _) => {
276 for field in fields {
277 self.visit_field_id(field.hir_id);
280 hir::ExprKind::Field(..) => {
281 self.visit_field_id(e.hir_id);
286 intravisit::walk_expr(self, e);
289 fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
290 self.visit_node_id(b.span, b.hir_id);
291 intravisit::walk_block(self, b);
294 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
296 hir::PatKind::Binding(..) => {
297 let tables = self.fcx.tables.borrow();
298 if let Some(bm) = tables.extract_binding_mode(self.tcx().sess, p.hir_id, p.span) {
299 self.tables.pat_binding_modes_mut().insert(p.hir_id, bm);
302 hir::PatKind::Struct(_, fields, _) => {
303 for field in fields {
304 self.visit_field_id(field.hir_id);
310 self.visit_pat_adjustments(p.span, p.hir_id);
312 self.visit_node_id(p.span, p.hir_id);
313 intravisit::walk_pat(self, p);
316 fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
317 intravisit::walk_local(self, l);
318 let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty;
319 let var_ty = self.resolve(&var_ty, &l.span);
320 self.write_ty_to_tables(l.hir_id, var_ty);
323 fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
324 intravisit::walk_ty(self, hir_ty);
325 let ty = self.fcx.node_ty(hir_ty.hir_id);
326 let ty = self.resolve(&ty, &hir_ty.span);
327 self.write_ty_to_tables(hir_ty.hir_id, ty);
331 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
332 fn visit_upvar_capture_map(&mut self) {
333 for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
334 let new_upvar_capture = match *upvar_capture {
335 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
336 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
337 ty::UpvarCapture::ByRef(ty::UpvarBorrow {
338 kind: upvar_borrow.kind,
339 region: self.tcx().lifetimes.re_erased,
343 debug!("Upvar capture for {:?} resolved to {:?}", upvar_id, new_upvar_capture);
344 self.tables.upvar_capture_map.insert(*upvar_id, new_upvar_capture);
348 fn visit_closures(&mut self) {
349 let fcx_tables = self.fcx.tables.borrow();
350 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
351 let common_hir_owner = fcx_tables.hir_owner.unwrap();
353 for (&id, &origin) in fcx_tables.closure_kind_origins().iter() {
354 let hir_id = hir::HirId { owner: common_hir_owner, local_id: id };
355 self.tables.closure_kind_origins_mut().insert(hir_id, origin);
359 fn visit_coercion_casts(&mut self) {
360 let fcx_tables = self.fcx.tables.borrow();
361 let fcx_coercion_casts = fcx_tables.coercion_casts();
362 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
364 for local_id in fcx_coercion_casts {
365 self.tables.set_coercion_cast(*local_id);
369 fn visit_user_provided_tys(&mut self) {
370 let fcx_tables = self.fcx.tables.borrow();
371 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
372 let common_hir_owner = fcx_tables.hir_owner.unwrap();
374 let mut errors_buffer = Vec::new();
375 for (&local_id, c_ty) in fcx_tables.user_provided_types().iter() {
376 let hir_id = hir::HirId { owner: common_hir_owner, local_id };
378 if cfg!(debug_assertions) && c_ty.needs_infer() {
380 hir_id.to_span(self.fcx.tcx),
381 "writeback: `{:?}` has inference variables",
386 self.tables.user_provided_types_mut().insert(hir_id, *c_ty);
388 if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
389 if self.rustc_dump_user_substs {
390 // This is a unit-testing mechanism.
391 let span = self.tcx().hir().span(hir_id);
392 // We need to buffer the errors in order to guarantee a consistent
393 // order when emitting them.
397 .struct_span_err(span, &format!("user substs: {:?}", user_substs));
398 err.buffer(&mut errors_buffer);
403 if !errors_buffer.is_empty() {
404 errors_buffer.sort_by_key(|diag| diag.span.primary_span());
405 for diag in errors_buffer.drain(..) {
406 self.tcx().sess.diagnostic().emit_diagnostic(&diag);
411 fn visit_user_provided_sigs(&mut self) {
412 let fcx_tables = self.fcx.tables.borrow();
413 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
415 for (&def_id, c_sig) in fcx_tables.user_provided_sigs.iter() {
416 if cfg!(debug_assertions) && c_sig.needs_infer() {
418 self.fcx.tcx.hir().span_if_local(def_id).unwrap(),
419 "writeback: `{:?}` has inference variables",
424 self.tables.user_provided_sigs.insert(def_id, *c_sig);
428 fn visit_generator_interior_types(&mut self) {
429 let fcx_tables = self.fcx.tables.borrow();
430 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
431 self.tables.generator_interior_types = fcx_tables.generator_interior_types.clone();
434 fn visit_opaque_types(&mut self, span: Span) {
435 for (&def_id, opaque_defn) in self.fcx.opaque_types.borrow().iter() {
436 let hir_id = self.tcx().hir().as_local_hir_id(def_id.expect_local());
437 let instantiated_ty = self.resolve(&opaque_defn.concrete_ty, &hir_id);
439 debug_assert!(!instantiated_ty.has_escaping_bound_vars());
442 // * `fn foo<T>() -> Foo<T>`
443 // * `fn foo<T: Bound + Other>() -> Foo<T>`
444 // from being defining.
446 // Also replace all generic params with the ones from the opaque type
447 // definition so that
449 // type Foo<T> = impl Baz + 'static;
450 // fn foo<U>() -> Foo<U> { .. }
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(
460 let mut skip_add = false;
462 if let ty::Opaque(defin_ty_def_id, _substs) = definition_ty.kind {
463 if let hir::OpaqueTyOrigin::TypeAlias = opaque_defn.origin {
464 if def_id == defin_ty_def_id {
466 "skipping adding concrete definition for opaque type {:?} {:?}",
467 opaque_defn, defin_ty_def_id
474 if !opaque_defn.substs.needs_infer() {
475 // We only want to add an entry into `concrete_opaque_types`
476 // if we actually found a defining usage of this opaque type.
477 // Otherwise, we do nothing - we'll either find a defining usage
478 // in some other location, or we'll end up emitting an error due
479 // to the lack of defining usage
481 let new = ty::ResolvedOpaqueTy {
482 concrete_type: definition_ty,
483 substs: opaque_defn.substs,
486 let old = self.tables.concrete_opaque_types.insert(def_id, new);
487 if let Some(old) = old {
488 if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
491 "`visit_opaque_types` tried to write different types for the same \
492 opaque type: {:?}, {:?}, {:?}, {:?}",
502 self.tcx().sess.delay_span_bug(span, "`opaque_defn` has inference variables");
507 fn visit_field_id(&mut self, hir_id: hir::HirId) {
508 if let Some(index) = self.fcx.tables.borrow_mut().field_indices_mut().remove(hir_id) {
509 self.tables.field_indices_mut().insert(hir_id, index);
513 fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
514 // Export associated path extensions and method resolutions.
515 if let Some(def) = self.fcx.tables.borrow_mut().type_dependent_defs_mut().remove(hir_id) {
516 self.tables.type_dependent_defs_mut().insert(hir_id, def);
519 // Resolve any borrowings for the node with id `node_id`
520 self.visit_adjustments(span, hir_id);
522 // Resolve the type of the node with id `node_id`
523 let n_ty = self.fcx.node_ty(hir_id);
524 let n_ty = self.resolve(&n_ty, &span);
525 self.write_ty_to_tables(hir_id, n_ty);
526 debug!("node {:?} has type {:?}", hir_id, n_ty);
528 // Resolve any substitutions
529 if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
530 let substs = self.resolve(&substs, &span);
531 debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
532 assert!(!substs.needs_infer() && !substs.has_placeholders());
533 self.tables.node_substs_mut().insert(hir_id, substs);
537 fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
538 let adjustment = self.fcx.tables.borrow_mut().adjustments_mut().remove(hir_id);
541 debug!("no adjustments for node {:?}", hir_id);
544 Some(adjustment) => {
545 let resolved_adjustment = self.resolve(&adjustment, &span);
546 debug!("adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
547 self.tables.adjustments_mut().insert(hir_id, resolved_adjustment);
552 fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
553 let adjustment = self.fcx.tables.borrow_mut().pat_adjustments_mut().remove(hir_id);
556 debug!("no pat_adjustments for node {:?}", hir_id);
559 Some(adjustment) => {
560 let resolved_adjustment = self.resolve(&adjustment, &span);
561 debug!("pat_adjustments for node {:?}: {:?}", hir_id, resolved_adjustment);
562 self.tables.pat_adjustments_mut().insert(hir_id, resolved_adjustment);
567 fn visit_liberated_fn_sigs(&mut self) {
568 let fcx_tables = self.fcx.tables.borrow();
569 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
570 let common_hir_owner = fcx_tables.hir_owner.unwrap();
572 for (&local_id, fn_sig) in fcx_tables.liberated_fn_sigs().iter() {
573 let hir_id = hir::HirId { owner: common_hir_owner, local_id };
574 let fn_sig = self.resolve(fn_sig, &hir_id);
575 self.tables.liberated_fn_sigs_mut().insert(hir_id, fn_sig);
579 fn visit_fru_field_types(&mut self) {
580 let fcx_tables = self.fcx.tables.borrow();
581 assert_eq!(fcx_tables.hir_owner, self.tables.hir_owner);
582 let common_hir_owner = fcx_tables.hir_owner.unwrap();
584 for (&local_id, ftys) in fcx_tables.fru_field_types().iter() {
585 let hir_id = hir::HirId { owner: common_hir_owner, local_id };
586 let ftys = self.resolve(ftys, &hir_id);
587 self.tables.fru_field_types_mut().insert(hir_id, ftys);
591 fn resolve<T>(&mut self, x: &T, span: &dyn Locatable) -> T
593 T: TypeFoldable<'tcx>,
595 let mut resolver = Resolver::new(self.fcx, span, self.body);
596 let x = x.fold_with(&mut resolver);
597 if cfg!(debug_assertions) && x.needs_infer() {
598 span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x);
601 // We may have introduced e.g. `ty::Error`, if inference failed, make sure
602 // to mark the `TypeckTables` as tainted in that case, so that downstream
603 // users of the tables don't produce extra errors, or worse, ICEs.
604 if resolver.replaced_with_error {
605 // FIXME(eddyb) keep track of `ErrorReported` from where the error was emitted.
606 self.tables.tainted_by_errors = Some(ErrorReported);
614 fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
617 impl Locatable for Span {
618 fn to_span(&self, _: TyCtxt<'_>) -> Span {
623 impl Locatable for hir::HirId {
624 fn to_span(&self, tcx: TyCtxt<'_>) -> Span {
625 tcx.hir().span(*self)
629 /// The Resolver. This is the type folding engine that detects
630 /// unresolved types and so forth.
631 struct Resolver<'cx, 'tcx> {
633 infcx: &'cx InferCtxt<'cx, 'tcx>,
634 span: &'cx dyn Locatable,
635 body: &'tcx hir::Body<'tcx>,
637 /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`.
638 replaced_with_error: bool,
641 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
643 fcx: &'cx FnCtxt<'cx, 'tcx>,
644 span: &'cx dyn Locatable,
645 body: &'tcx hir::Body<'tcx>,
646 ) -> Resolver<'cx, 'tcx> {
647 Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false }
650 fn report_error(&self, t: Ty<'tcx>) {
651 if !self.tcx.sess.has_errors() {
653 .need_type_info_err(Some(self.body.id()), self.span.to_span(self.tcx), t, E0282)
659 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
660 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
664 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
665 match self.infcx.fully_resolve(&t) {
666 Ok(t) => self.infcx.tcx.erase_regions(&t),
668 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t);
669 self.report_error(t);
670 self.replaced_with_error = true;
676 fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
677 debug_assert!(!r.is_late_bound(), "Should not be resolving bound region.");
678 self.tcx.lifetimes.re_erased
681 fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
682 match self.infcx.fully_resolve(&ct) {
683 Ok(ct) => self.infcx.tcx.erase_regions(&ct),
685 debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct);
686 // FIXME: we'd like to use `self.report_error`, but it doesn't yet
687 // accept a &'tcx ty::Const.
688 self.replaced_with_error = true;
689 self.tcx().mk_const(ty::Const { val: ty::ConstKind::Error, ty: ct.ty })
695 ///////////////////////////////////////////////////////////////////////////
696 // During type check, we store promises with the result of trait
697 // lookup rather than the actual results (because the results are not
698 // necessarily available immediately). These routines unwind the
699 // promises. It is expected that we will have already reported any
700 // errors that may be encountered, so if the promises store an error,
701 // a dummy result is returned.