1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Conversion from AST representation of types to the `ty.rs`
12 //! representation. The main routine here is `ast_ty_to_ty()`: each use
13 //! is parameterized by an instance of `AstConv`.
15 use smallvec::SmallVec;
16 use hir::{self, GenericArg, GenericArgs};
18 use hir::def_id::DefId;
20 use middle::resolve_lifetime as rl;
21 use namespace::Namespace;
22 use rustc::ty::subst::{Kind, Subst, Substs};
24 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
25 use rustc::ty::{GenericParamDef, GenericParamDefKind};
26 use rustc::ty::wf::object_region_bounds;
27 use rustc_data_structures::sync::Lrc;
28 use rustc_target::spec::abi;
29 use std::collections::BTreeSet;
31 use require_c_abi_if_variadic;
32 use util::common::ErrorReported;
33 use util::nodemap::FxHashMap;
34 use errors::{Applicability, FatalError, DiagnosticId};
40 use syntax::feature_gate::{GateIssue, emit_feature_err};
41 use syntax_pos::{DUMMY_SP, Span, MultiSpan};
43 pub trait AstConv<'gcx, 'tcx> {
44 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
46 /// Returns the set of bounds in scope for the type parameter with
48 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
49 -> Lrc<ty::GenericPredicates<'tcx>>;
51 /// What lifetime should we use when a lifetime is omitted (and not elided)?
52 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
53 -> Option<ty::Region<'tcx>>;
55 /// What type should we use when a type is omitted?
56 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
58 /// Same as ty_infer, but with a known type parameter definition.
59 fn ty_infer_for_def(&self,
60 _def: &ty::GenericParamDef,
61 span: Span) -> Ty<'tcx> {
65 /// Projecting an associated type from a (potentially)
66 /// higher-ranked trait reference is more complicated, because of
67 /// the possibility of late-bound regions appearing in the
68 /// associated type binding. This is not legal in function
69 /// signatures for that reason. In a function body, we can always
70 /// handle it because we can use inference variables to remove the
71 /// late-bound regions.
72 fn projected_ty_from_poly_trait_ref(&self,
75 poly_trait_ref: ty::PolyTraitRef<'tcx>)
78 /// Normalize an associated type coming from the user.
79 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
81 /// Invoked when we encounter an error from some prior pass
82 /// (e.g. resolve) that is translated into a ty-error. This is
83 /// used to help suppress derived errors typeck might otherwise
85 fn set_tainted_by_errors(&self);
87 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
90 struct ConvertedBinding<'tcx> {
91 item_name: ast::Ident,
97 enum GenericArgPosition {
99 Value, // e.g. functions
103 /// Dummy type used for the `Self` of a `TraitRef` created for converting
104 /// a trait object, and which gets removed in `ExistentialTraitRef`.
105 /// This type must not appear anywhere in other converted types.
106 const TRAIT_OBJECT_DUMMY_SELF: ty::TyKind<'static> = ty::Infer(ty::FreshTy(0));
108 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
109 pub fn ast_region_to_region(&self,
110 lifetime: &hir::Lifetime,
111 def: Option<&ty::GenericParamDef>)
114 let tcx = self.tcx();
115 let lifetime_name = |def_id| {
116 tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap()).as_interned_str()
119 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
120 let r = match tcx.named_region(hir_id) {
121 Some(rl::Region::Static) => {
125 Some(rl::Region::LateBound(debruijn, id, _)) => {
126 let name = lifetime_name(id);
127 tcx.mk_region(ty::ReLateBound(debruijn,
128 ty::BrNamed(id, name)))
131 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
132 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
135 Some(rl::Region::EarlyBound(index, id, _)) => {
136 let name = lifetime_name(id);
137 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
144 Some(rl::Region::Free(scope, id)) => {
145 let name = lifetime_name(id);
146 tcx.mk_region(ty::ReFree(ty::FreeRegion {
148 bound_region: ty::BrNamed(id, name)
151 // (*) -- not late-bound, won't change
155 self.re_infer(lifetime.span, def)
157 // This indicates an illegal lifetime
158 // elision. `resolve_lifetime` should have
159 // reported an error in this case -- but if
160 // not, let's error out.
161 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
163 // Supply some dummy value. We don't have an
164 // `re_error`, annoyingly, so use `'static`.
170 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
177 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
178 /// returns an appropriate set of substitutions for this particular reference to `I`.
179 pub fn ast_path_substs_for_ty(&self,
182 item_segment: &hir::PathSegment)
183 -> &'tcx Substs<'tcx>
185 let (substs, assoc_bindings) = item_segment.with_generic_args(|generic_args| {
186 self.create_substs_for_ast_path(
190 item_segment.infer_types,
195 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
200 /// Report error if there is an explicit type parameter when using `impl Trait`.
204 seg: &hir::PathSegment,
205 generics: &ty::Generics,
207 let explicit = !seg.infer_types;
208 let impl_trait = generics.params.iter().any(|param| match param.kind {
209 ty::GenericParamDefKind::Type {
210 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
215 if explicit && impl_trait {
216 let mut err = struct_span_err! {
220 "cannot provide explicit type parameters when `impl Trait` is \
221 used in argument position."
230 /// Check that the correct number of generic arguments have been provided.
231 /// Used specifically for function calls.
232 pub fn check_generic_arg_count_for_call(
236 seg: &hir::PathSegment,
237 is_method_call: bool,
239 let empty_args = P(hir::GenericArgs {
240 args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
242 let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
243 Self::check_generic_arg_count(
247 if let Some(ref args) = seg.args {
253 GenericArgPosition::MethodCall
255 GenericArgPosition::Value
257 def.parent.is_none() && def.has_self, // `has_self`
258 seg.infer_types || suppress_mismatch, // `infer_types`
262 /// Check that the correct number of generic arguments have been provided.
263 /// This is used both for datatypes and function calls.
264 fn check_generic_arg_count(
268 args: &hir::GenericArgs,
269 position: GenericArgPosition,
273 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
274 // that lifetimes will proceed types. So it suffices to check the number of each generic
275 // arguments in order to validate them with respect to the generic parameters.
276 let param_counts = def.own_counts();
277 let arg_counts = args.own_counts();
278 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
280 let mut defaults: ty::GenericParamCount = Default::default();
281 for param in &def.params {
283 GenericParamDefKind::Lifetime => {}
284 GenericParamDefKind::Type { has_default, .. } => {
285 defaults.types += has_default as usize
290 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
291 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
294 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
295 if !infer_lifetimes {
296 if let Some(span_late) = def.has_late_bound_regions {
297 let msg = "cannot specify lifetime arguments explicitly \
298 if late bound lifetime parameters are present";
299 let note = "the late bound lifetime parameter is introduced here";
300 let span = args.args[0].span();
301 if position == GenericArgPosition::Value
302 && arg_counts.lifetimes != param_counts.lifetimes {
303 let mut err = tcx.sess.struct_span_err(span, msg);
304 err.span_note(span_late, note);
308 let mut multispan = MultiSpan::from_span(span);
309 multispan.push_span_label(span_late, note.to_string());
310 tcx.lint_node(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
311 args.args[0].id(), multispan, msg);
317 let check_kind_count = |kind,
322 // We enforce the following: `required` <= `provided` <= `permitted`.
323 // For kinds without defaults (i.e. lifetimes), `required == permitted`.
324 // For other kinds (i.e. types), `permitted` may be greater than `required`.
325 if required <= provided && provided <= permitted {
329 // Unfortunately lifetime and type parameter mismatches are typically styled
330 // differently in diagnostics, which means we have a few cases to consider here.
331 let (bound, quantifier) = if required != permitted {
332 if provided < required {
333 (required, "at least ")
334 } else { // provided > permitted
335 (permitted, "at most ")
341 let (spans, label) = if required == permitted && provided > permitted {
342 // In the case when the user has provided too many arguments,
343 // we want to point to the unexpected arguments.
345 args.args[offset+permitted .. offset+provided]
347 .map(|arg| arg.span())
350 "unexpected {} argument",
355 (vec![span], format!(
356 "expected {}{} {} argument{}",
360 if bound != 1 { "s" } else { "" },
364 let mut err = tcx.sess.struct_span_err_with_code(
367 "wrong number of {} arguments: expected {}{}, found {}",
373 DiagnosticId::Error("E0107".into())
376 err.span_label(span, label.as_str());
380 provided > required // `suppress_error`
383 if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes {
386 param_counts.lifetimes,
387 param_counts.lifetimes,
388 arg_counts.lifetimes,
393 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
396 param_counts.types - defaults.types - has_self as usize,
397 param_counts.types - has_self as usize,
399 arg_counts.lifetimes,
406 /// Creates the relevant generic argument substitutions
407 /// corresponding to a set of generic parameters. This is a
408 /// rather complex little function. Let me try to explain the
409 /// role of each of its parameters:
411 /// To start, we are given the `def_id` of the thing we are
412 /// creating the substitutions for, and a partial set of
413 /// substitutions `parent_substs`. In general, the substitutions
414 /// for an item begin with substitutions for all the "parents" of
415 /// that item -- so e.g. for a method it might include the
416 /// parameters from the impl.
418 /// Therefore, the method begins by walking down these parents,
419 /// starting with the outermost parent and proceed inwards until
420 /// it reaches `def_id`. For each parent P, it will check `parent_substs`
421 /// first to see if the parent's substitutions are listed in there. If so,
422 /// we can append those and move on. Otherwise, it invokes the
423 /// three callback functions:
425 /// - `args_for_def_id`: given the def-id P, supplies back the
426 /// generic arguments that were given to that parent from within
427 /// the path; so e.g. if you have `<T as Foo>::Bar`, the def-id
428 /// might refer to the trait `Foo`, and the arguments might be
429 /// `[T]`. The boolean value indicates whether to infer values
430 /// for arguments whose values were not explicitly provided.
431 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
432 /// instantiate a `Kind`
433 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
434 /// creates a suitable inference variable.
435 pub fn create_substs_for_generic_args<'a, 'b>(
436 tcx: TyCtxt<'a, 'gcx, 'tcx>,
438 parent_substs: &[Kind<'tcx>],
440 self_ty: Option<Ty<'tcx>>,
441 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
442 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
443 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
444 ) -> &'tcx Substs<'tcx> {
445 // Collect the segments of the path: we need to substitute arguments
446 // for parameters throughout the entire path (wherever there are
447 // generic parameters).
448 let mut parent_defs = tcx.generics_of(def_id);
449 let count = parent_defs.count();
450 let mut stack = vec![(def_id, parent_defs)];
451 while let Some(def_id) = parent_defs.parent {
452 parent_defs = tcx.generics_of(def_id);
453 stack.push((def_id, parent_defs));
456 // We manually build up the substitution, rather than using convenience
457 // methods in `subst.rs` so that we can iterate over the arguments and
458 // parameters in lock-step linearly, rather than trying to match each pair.
459 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
461 // Iterate over each segment of the path.
462 while let Some((def_id, defs)) = stack.pop() {
463 let mut params = defs.params.iter().peekable();
465 // If we have already computed substitutions for parents, we can use those directly.
466 while let Some(¶m) = params.peek() {
467 if let Some(&kind) = parent_substs.get(param.index as usize) {
475 // `Self` is handled first, unless it's been handled in `parent_substs`.
477 if let Some(¶m) = params.peek() {
478 if param.index == 0 {
479 if let GenericParamDefKind::Type { .. } = param.kind {
480 substs.push(self_ty.map(|ty| ty.into())
481 .unwrap_or_else(|| inferred_kind(None, param, true)));
488 // Check whether this segment takes generic arguments and the user has provided any.
489 let (generic_args, infer_types) = args_for_def_id(def_id);
491 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
495 // We're going to iterate through the generic arguments that the user
496 // provided, matching them with the generic parameters we expect.
497 // Mismatches can occur as a result of elided lifetimes, or for malformed
498 // input. We try to handle both sensibly.
499 match (args.peek(), params.peek()) {
500 (Some(&arg), Some(¶m)) => {
501 match (arg, ¶m.kind) {
502 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
503 | (GenericArg::Type(_), GenericParamDefKind::Type { .. }) => {
504 substs.push(provided_kind(param, arg));
508 (GenericArg::Lifetime(_), GenericParamDefKind::Type { .. }) => {
509 // We expected a type argument, but got a lifetime
510 // argument. This is an error, but we need to handle it
511 // gracefully so we can report sensible errors. In this
512 // case, we're simply going to infer this argument.
515 (GenericArg::Type(_), GenericParamDefKind::Lifetime) => {
516 // We expected a lifetime argument, but got a type
517 // argument. That means we're inferring the lifetimes.
518 substs.push(inferred_kind(None, param, infer_types));
524 // We should never be able to reach this point with well-formed input.
525 // Getting to this point means the user supplied more arguments than
526 // there are parameters.
529 (None, Some(¶m)) => {
530 // If there are fewer arguments than parameters, it means
531 // we're inferring the remaining arguments.
533 GenericParamDefKind::Lifetime | GenericParamDefKind::Type { .. } => {
534 let kind = inferred_kind(Some(&substs), param, infer_types);
541 (None, None) => break,
546 tcx.intern_substs(&substs)
549 /// Given the type/region arguments provided to some path (along with
550 /// an implicit `Self`, if this is a trait reference) returns the complete
551 /// set of substitutions. This may involve applying defaulted type parameters.
553 /// Note that the type listing given here is *exactly* what the user provided.
554 fn create_substs_for_ast_path(&self,
557 generic_args: &hir::GenericArgs,
559 self_ty: Option<Ty<'tcx>>)
560 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
562 // If the type is parameterized by this region, then replace this
563 // region with the current anon region binding (in other words,
564 // whatever & would get replaced with).
565 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
567 def_id, self_ty, generic_args);
569 let tcx = self.tcx();
570 let generic_params = tcx.generics_of(def_id);
572 // If a self-type was declared, one should be provided.
573 assert_eq!(generic_params.has_self, self_ty.is_some());
575 let has_self = generic_params.has_self;
576 Self::check_generic_arg_count(
581 GenericArgPosition::Type,
586 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
587 let default_needs_object_self = |param: &ty::GenericParamDef| {
588 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
589 if is_object && has_default {
590 if tcx.at(span).type_of(param.def_id).has_self_ty() {
591 // There is no suitable inference default for a type parameter
592 // that references self, in an object type.
601 let substs = Self::create_substs_for_generic_args(
607 // Provide the generic args, and whether types should be inferred.
608 |_| (Some(generic_args), infer_types),
609 // Provide substitutions for parameters for which (valid) arguments have been provided.
611 match (¶m.kind, arg) {
612 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
613 self.ast_region_to_region(<, Some(param)).into()
615 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
616 self.ast_ty_to_ty(&ty).into()
621 // Provide substitutions for parameters for which arguments are inferred.
622 |substs, param, infer_types| {
624 GenericParamDefKind::Lifetime => tcx.types.re_static.into(),
625 GenericParamDefKind::Type { has_default, .. } => {
626 if !infer_types && has_default {
627 // No type parameter provided, but a default exists.
629 // If we are converting an object type, then the
630 // `Self` parameter is unknown. However, some of the
631 // other type parameters may reference `Self` in their
632 // defaults. This will lead to an ICE if we are not
634 if default_needs_object_self(param) {
635 struct_span_err!(tcx.sess, span, E0393,
636 "the type parameter `{}` must be explicitly \
640 format!("missing reference to `{}`", param.name))
641 .note(&format!("because of the default `Self` reference, \
642 type parameters must be specified on object \
647 // This is a default type parameter.
650 tcx.at(span).type_of(param.def_id)
651 .subst_spanned(tcx, substs.unwrap(), Some(span))
654 } else if infer_types {
655 // No type parameters were provided, we can infer all.
656 if !default_needs_object_self(param) {
657 self.ty_infer_for_def(param, span).into()
659 self.ty_infer(span).into()
662 // We've already errored above about the mismatch.
670 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
672 item_name: binding.ident,
673 ty: self.ast_ty_to_ty(&binding.ty),
678 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
679 generic_params, self_ty, substs);
681 (substs, assoc_bindings)
684 /// Instantiates the path for the given trait reference, assuming that it's
685 /// bound to a valid trait type. Returns the def_id for the defining trait.
686 /// The type _cannot_ be a type other than a trait type.
688 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
689 /// are disallowed. Otherwise, they are pushed onto the vector given.
690 pub fn instantiate_mono_trait_ref(&self,
691 trait_ref: &hir::TraitRef,
693 -> ty::TraitRef<'tcx>
695 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
697 let trait_def_id = self.trait_def_id(trait_ref);
698 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
701 trait_ref.path.segments.last().unwrap())
704 /// Get the `DefId` of the given trait ref. It _must_ actually be a trait.
705 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
706 let path = &trait_ref.path;
708 Def::Trait(trait_def_id) => trait_def_id,
709 Def::TraitAlias(alias_def_id) => alias_def_id,
717 /// The given trait ref must actually be a trait.
718 pub(super) fn instantiate_poly_trait_ref_inner(&self,
719 trait_ref: &hir::TraitRef,
721 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
723 -> ty::PolyTraitRef<'tcx>
725 let trait_def_id = self.trait_def_id(trait_ref);
727 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
729 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
731 let (substs, assoc_bindings) =
732 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
735 trait_ref.path.segments.last().unwrap());
736 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
738 let mut dup_bindings = FxHashMap::default();
739 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
740 // specify type to assert that error was already reported in Err case:
741 let predicate: Result<_, ErrorReported> =
742 self.ast_type_binding_to_poly_projection_predicate(
743 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
744 // okay to ignore Err because of ErrorReported (see above)
745 Some((predicate.ok()?, binding.span))
748 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
749 trait_ref, poly_projections, poly_trait_ref);
753 pub fn instantiate_poly_trait_ref(&self,
754 poly_trait_ref: &hir::PolyTraitRef,
756 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
757 -> ty::PolyTraitRef<'tcx>
759 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
760 poly_projections, false)
763 fn ast_path_to_mono_trait_ref(&self,
767 trait_segment: &hir::PathSegment)
768 -> ty::TraitRef<'tcx>
770 let (substs, assoc_bindings) =
771 self.create_substs_for_ast_trait_ref(span,
775 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
776 ty::TraitRef::new(trait_def_id, substs)
779 fn create_substs_for_ast_trait_ref(&self,
783 trait_segment: &hir::PathSegment)
784 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
786 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
789 let trait_def = self.tcx().trait_def(trait_def_id);
791 if !self.tcx().features().unboxed_closures &&
792 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
793 != trait_def.paren_sugar {
794 // For now, require that parenthetical notation be used only with `Fn()` etc.
795 let msg = if trait_def.paren_sugar {
796 "the precise format of `Fn`-family traits' type parameters is subject to change. \
797 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
799 "parenthetical notation is only stable when used with `Fn`-family traits"
801 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
802 span, GateIssue::Language, msg);
805 trait_segment.with_generic_args(|generic_args| {
806 self.create_substs_for_ast_path(span,
809 trait_segment.infer_types,
814 fn trait_defines_associated_type_named(&self,
816 assoc_name: ast::Ident)
819 self.tcx().associated_items(trait_def_id).any(|item| {
820 item.kind == ty::AssociatedKind::Type &&
821 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
825 fn ast_type_binding_to_poly_projection_predicate(
828 trait_ref: ty::PolyTraitRef<'tcx>,
829 binding: &ConvertedBinding<'tcx>,
831 dup_bindings: &mut FxHashMap<DefId, Span>)
832 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
834 let tcx = self.tcx();
837 // Given something like `U: SomeTrait<T = X>`, we want to produce a
838 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
839 // subtle in the event that `T` is defined in a supertrait of
840 // `SomeTrait`, because in that case we need to upcast.
842 // That is, consider this case:
845 // trait SubTrait: SuperTrait<int> { }
846 // trait SuperTrait<A> { type T; }
848 // ... B : SubTrait<T=foo> ...
851 // We want to produce `<B as SuperTrait<int>>::T == foo`.
853 // Find any late-bound regions declared in `ty` that are not
854 // declared in the trait-ref. These are not wellformed.
858 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
859 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
860 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
861 let late_bound_in_ty =
862 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
863 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
864 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
865 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
866 let br_name = match *br {
867 ty::BrNamed(_, name) => name,
871 "anonymous bound region {:?} in binding but not trait ref",
875 struct_span_err!(tcx.sess,
878 "binding for associated type `{}` references lifetime `{}`, \
879 which does not appear in the trait input types",
880 binding.item_name, br_name)
885 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
887 // Simple case: X is defined in the current trait.
890 // Otherwise, we have to walk through the supertraits to find
892 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
893 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
895 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
896 binding.item_name, binding.span)
899 let (assoc_ident, def_scope) =
900 tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
901 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
902 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
903 }).expect("missing associated type");
905 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
906 let msg = format!("associated type `{}` is private", binding.item_name);
907 tcx.sess.span_err(binding.span, &msg);
909 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
912 dup_bindings.entry(assoc_ty.def_id)
913 .and_modify(|prev_span| {
914 struct_span_err!(self.tcx().sess, binding.span, E0719,
915 "the value of the associated type `{}` (from the trait `{}`) \
916 is already specified",
918 tcx.item_path_str(assoc_ty.container.id()))
919 .span_label(binding.span, "re-bound here")
920 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
923 .or_insert(binding.span);
926 Ok(candidate.map_bound(|trait_ref| {
927 ty::ProjectionPredicate {
928 projection_ty: ty::ProjectionTy::from_ref_and_name(
938 fn ast_path_to_ty(&self,
941 item_segment: &hir::PathSegment)
944 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
947 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
951 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
952 /// removing the dummy `Self` type (`TRAIT_OBJECT_DUMMY_SELF`).
953 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
954 -> ty::ExistentialTraitRef<'tcx> {
955 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
956 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
959 fn conv_object_ty_poly_trait_ref(&self,
961 trait_bounds: &[hir::PolyTraitRef],
962 lifetime: &hir::Lifetime)
965 let tcx = self.tcx();
967 if trait_bounds.is_empty() {
968 span_err!(tcx.sess, span, E0224,
969 "at least one non-builtin trait is required for an object type");
970 return tcx.types.err;
973 let mut projection_bounds = Vec::new();
974 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
975 let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
977 &mut projection_bounds);
978 debug!("principal: {:?}", principal);
980 for trait_bound in trait_bounds[1..].iter() {
981 // sanity check for non-principal trait bounds
982 self.instantiate_poly_trait_ref(trait_bound,
987 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
989 if !trait_bounds.is_empty() {
990 let b = &trait_bounds[0];
991 let span = b.trait_ref.path.span;
992 struct_span_err!(self.tcx().sess, span, E0225,
993 "only auto traits can be used as additional traits in a trait object")
994 .span_label(span, "non-auto additional trait")
998 // Check that there are no gross object safety violations;
999 // most importantly, that the supertraits don't contain `Self`,
1001 let object_safety_violations =
1002 tcx.global_tcx().astconv_object_safety_violations(principal.def_id());
1003 if !object_safety_violations.is_empty() {
1004 tcx.report_object_safety_error(
1005 span, principal.def_id(), object_safety_violations)
1007 return tcx.types.err;
1010 // Use a `BTreeSet` to keep output in a more consistent order.
1011 let mut associated_types = BTreeSet::default();
1013 for tr in traits::elaborate_trait_ref(tcx, principal) {
1015 ty::Predicate::Trait(pred) => {
1016 associated_types.extend(tcx.associated_items(pred.def_id())
1017 .filter(|item| item.kind == ty::AssociatedKind::Type)
1018 .map(|item| item.def_id));
1020 ty::Predicate::Projection(pred) => {
1021 // Include projections defined on supertraits.
1022 projection_bounds.push((pred, DUMMY_SP))
1028 for (projection_bound, _) in &projection_bounds {
1029 associated_types.remove(&projection_bound.projection_def_id());
1032 for item_def_id in associated_types {
1033 let assoc_item = tcx.associated_item(item_def_id);
1034 let trait_def_id = assoc_item.container.id();
1035 let mut err = struct_span_err!(
1039 "the value of the associated type `{}` (from the trait `{}`) must be specified",
1041 tcx.item_path_str(trait_def_id),
1043 err.span_label(span, format!("missing associated type `{}` value", assoc_item.ident));
1047 // Erase the `dummy_self` (`TRAIT_OBJECT_DUMMY_SELF`) used above.
1048 let existential_principal = principal.map_bound(|trait_ref| {
1049 self.trait_ref_to_existential(trait_ref)
1051 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1052 bound.map_bound(|b| {
1053 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1054 ty::ExistentialProjection {
1056 item_def_id: b.projection_ty.item_def_id,
1057 substs: trait_ref.substs,
1062 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
1064 auto_traits.dedup();
1066 // Calling `skip_binder` is okay, because the predicates are re-bound.
1068 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
1069 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
1070 .chain(existential_projections
1071 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1072 .collect::<SmallVec<[_; 8]>>();
1073 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1074 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1076 // Use explicitly-specified region bound.
1077 let region_bound = if !lifetime.is_elided() {
1078 self.ast_region_to_region(lifetime, None)
1080 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1081 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
1082 if tcx.named_region(hir_id).is_some() {
1083 self.ast_region_to_region(lifetime, None)
1085 self.re_infer(span, None).unwrap_or_else(|| {
1086 span_err!(tcx.sess, span, E0228,
1087 "the lifetime bound for this object type cannot be deduced \
1088 from context; please supply an explicit bound");
1095 debug!("region_bound: {:?}", region_bound);
1097 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1098 debug!("trait_object_type: {:?}", ty);
1102 fn report_ambiguous_associated_type(&self,
1107 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
1108 .span_suggestion_with_applicability(
1110 "use fully-qualified syntax",
1111 format!("<{} as {}>::{}", type_str, trait_str, name),
1112 Applicability::HasPlaceholders
1116 // Search for a bound on a type parameter which includes the associated item
1117 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1118 // This function will fail if there are no suitable bounds or there is
1120 fn find_bound_for_assoc_item(&self,
1121 ty_param_def_id: DefId,
1122 assoc_name: ast::Ident,
1124 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1126 let tcx = self.tcx();
1128 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1129 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1131 // Check that there is exactly one way to find an associated type with the
1133 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1134 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1136 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
1137 let param_name = tcx.hir.ty_param_name(param_node_id);
1138 self.one_bound_for_assoc_type(suitable_bounds,
1139 ¶m_name.as_str(),
1144 // Checks that `bounds` contains exactly one element and reports appropriate
1145 // errors otherwise.
1146 fn one_bound_for_assoc_type<I>(&self,
1148 ty_param_name: &str,
1149 assoc_name: ast::Ident,
1151 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1152 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1154 let bound = match bounds.next() {
1155 Some(bound) => bound,
1157 struct_span_err!(self.tcx().sess, span, E0220,
1158 "associated type `{}` not found for `{}`",
1161 .span_label(span, format!("associated type `{}` not found", assoc_name))
1163 return Err(ErrorReported);
1167 if let Some(bound2) = bounds.next() {
1168 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1169 let mut err = struct_span_err!(
1170 self.tcx().sess, span, E0221,
1171 "ambiguous associated type `{}` in bounds of `{}`",
1174 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1176 for bound in bounds {
1177 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1178 item.kind == ty::AssociatedKind::Type &&
1179 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1181 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
1183 if let Some(span) = bound_span {
1184 err.span_label(span, format!("ambiguous `{}` from `{}`",
1188 span_note!(&mut err, span,
1189 "associated type `{}` could derive from `{}`",
1200 // Create a type from a path to an associated type.
1201 // For a path `A::B::C::D`, `ty` and `ty_path_def` are the type and def for `A::B::C`
1202 // and item_segment is the path segment for `D`. We return a type and a def for
1204 // Will fail except for `T::A` and `Self::A`; i.e., if `ty`/`ty_path_def` are not a type
1205 // parameter or `Self`.
1206 pub fn associated_path_def_to_ty(&self,
1207 ref_id: ast::NodeId,
1211 item_segment: &hir::PathSegment)
1214 let tcx = self.tcx();
1215 let assoc_name = item_segment.ident;
1217 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
1219 self.prohibit_generics(slice::from_ref(item_segment));
1221 // Find the type of the associated item, and the trait where the associated
1222 // item is declared.
1223 let bound = match (&ty.sty, ty_path_def) {
1224 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
1225 // `Self` in an impl of a trait - we have a concrete `self` type and a
1227 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1228 Some(trait_ref) => trait_ref,
1230 // A cycle error occurred, most likely.
1231 return (tcx.types.err, Def::Err);
1235 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1236 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
1238 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
1240 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1243 (&ty::Param(_), Def::SelfTy(Some(param_did), None)) |
1244 (&ty::Param(_), Def::TyParam(param_did)) => {
1245 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
1247 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1251 // Don't print TyErr to the user.
1252 if !ty.references_error() {
1253 self.report_ambiguous_associated_type(span,
1256 &assoc_name.as_str());
1258 return (tcx.types.err, Def::Err);
1262 let trait_did = bound.def_id();
1263 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
1264 let item = tcx.associated_items(trait_did).find(|i| {
1265 Namespace::from(i.kind) == Namespace::Type &&
1266 i.ident.modern() == assoc_ident
1268 .expect("missing associated type");
1270 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1271 let ty = self.normalize_ty(span, ty);
1273 let def = Def::AssociatedTy(item.def_id);
1274 if !item.vis.is_accessible_from(def_scope, tcx) {
1275 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
1276 tcx.sess.span_err(span, &msg);
1278 tcx.check_stability(item.def_id, Some(ref_id), span);
1283 fn qpath_to_ty(&self,
1285 opt_self_ty: Option<Ty<'tcx>>,
1287 trait_segment: &hir::PathSegment,
1288 item_segment: &hir::PathSegment)
1291 let tcx = self.tcx();
1292 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
1294 self.prohibit_generics(slice::from_ref(item_segment));
1296 let self_ty = if let Some(ty) = opt_self_ty {
1299 let path_str = tcx.item_path_str(trait_def_id);
1300 self.report_ambiguous_associated_type(span,
1303 &item_segment.ident.as_str());
1304 return tcx.types.err;
1307 debug!("qpath_to_ty: self_type={:?}", self_ty);
1309 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1314 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1316 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1319 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(&self, segments: T) {
1320 for segment in segments {
1321 segment.with_generic_args(|generic_args| {
1322 let (mut err_for_lt, mut err_for_ty) = (false, false);
1323 for arg in &generic_args.args {
1324 let (mut span_err, span, kind) = match arg {
1325 hir::GenericArg::Lifetime(lt) => {
1326 if err_for_lt { continue }
1328 (struct_span_err!(self.tcx().sess, lt.span, E0110,
1329 "lifetime parameters are not allowed on this type"),
1333 hir::GenericArg::Type(ty) => {
1334 if err_for_ty { continue }
1336 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1337 "type parameters are not allowed on this type"),
1342 span_err.span_label(span, format!("{} parameter not allowed", kind))
1344 if err_for_lt && err_for_ty {
1348 for binding in &generic_args.bindings {
1349 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1356 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt, span: Span) {
1357 let mut err = struct_span_err!(tcx.sess, span, E0229,
1358 "associated type bindings are not allowed here");
1359 err.span_label(span, "associated type not allowed here").emit();
1362 // Check a type `Path` and convert it to a `Ty`.
1363 pub fn def_to_ty(&self,
1364 opt_self_ty: Option<Ty<'tcx>>,
1366 permit_variants: bool)
1368 let tcx = self.tcx();
1370 debug!("def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1371 path.def, opt_self_ty, path.segments);
1373 let span = path.span;
1375 Def::Existential(did) => {
1376 // Check for desugared impl trait.
1377 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1378 let item_segment = path.segments.split_last().unwrap();
1379 self.prohibit_generics(item_segment.1);
1380 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1383 tcx.mk_opaque(did, substs),
1386 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1387 Def::Union(did) | Def::ForeignTy(did) => {
1388 assert_eq!(opt_self_ty, None);
1389 self.prohibit_generics(path.segments.split_last().unwrap().1);
1390 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1392 Def::Variant(did) if permit_variants => {
1393 // Convert "variant type" as if it were a real type.
1394 // The resulting `Ty` is type of the variant's enum for now.
1395 assert_eq!(opt_self_ty, None);
1396 self.prohibit_generics(path.segments.split_last().unwrap().1);
1397 self.ast_path_to_ty(span,
1398 tcx.parent_def_id(did).unwrap(),
1399 path.segments.last().unwrap())
1401 Def::TyParam(did) => {
1402 assert_eq!(opt_self_ty, None);
1403 self.prohibit_generics(&path.segments);
1405 let node_id = tcx.hir.as_local_node_id(did).unwrap();
1406 let item_id = tcx.hir.get_parent_node(node_id);
1407 let item_def_id = tcx.hir.local_def_id(item_id);
1408 let generics = tcx.generics_of(item_def_id);
1409 let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
1410 tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
1412 Def::SelfTy(_, Some(def_id)) => {
1413 // `Self` in impl (we know the concrete type)
1415 assert_eq!(opt_self_ty, None);
1416 self.prohibit_generics(&path.segments);
1418 tcx.at(span).type_of(def_id)
1420 Def::SelfTy(Some(_), None) => {
1422 assert_eq!(opt_self_ty, None);
1423 self.prohibit_generics(&path.segments);
1426 Def::AssociatedTy(def_id) => {
1427 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1428 self.qpath_to_ty(span,
1431 &path.segments[path.segments.len()-2],
1432 path.segments.last().unwrap())
1434 Def::PrimTy(prim_ty) => {
1435 assert_eq!(opt_self_ty, None);
1436 self.prohibit_generics(&path.segments);
1438 hir::Bool => tcx.types.bool,
1439 hir::Char => tcx.types.char,
1440 hir::Int(it) => tcx.mk_mach_int(it),
1441 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1442 hir::Float(ft) => tcx.mk_mach_float(ft),
1443 hir::Str => tcx.mk_str()
1447 self.set_tainted_by_errors();
1448 return self.tcx().types.err;
1450 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1454 /// Parses the programmer's textual representation of a type into our
1455 /// internal notion of a type.
1456 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1457 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1458 ast_ty.id, ast_ty, ast_ty.node);
1460 let tcx = self.tcx();
1462 let result_ty = match ast_ty.node {
1463 hir::TyKind::Slice(ref ty) => {
1464 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1466 hir::TyKind::Ptr(ref mt) => {
1467 tcx.mk_ptr(ty::TypeAndMut {
1468 ty: self.ast_ty_to_ty(&mt.ty),
1472 hir::TyKind::Rptr(ref region, ref mt) => {
1473 let r = self.ast_region_to_region(region, None);
1474 debug!("Ref r={:?}", r);
1475 let t = self.ast_ty_to_ty(&mt.ty);
1476 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1478 hir::TyKind::Never => {
1481 hir::TyKind::Tup(ref fields) => {
1482 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1484 hir::TyKind::BareFn(ref bf) => {
1485 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1486 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1488 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1489 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1491 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1492 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1493 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1494 self.ast_ty_to_ty(qself)
1496 self.def_to_ty(opt_self_ty, path, false)
1498 hir::TyKind::Def(item_id, ref lifetimes) => {
1499 let did = tcx.hir.local_def_id(item_id.id);
1500 self.impl_trait_ty_to_ty(did, lifetimes)
1502 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1503 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1504 let ty = self.ast_ty_to_ty(qself);
1506 let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1511 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1513 hir::TyKind::Array(ref ty, ref length) => {
1514 let length_def_id = tcx.hir.local_def_id(length.id);
1515 let substs = Substs::identity_for_item(tcx, length_def_id);
1516 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1517 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1518 self.normalize_ty(ast_ty.span, array_ty)
1520 hir::TyKind::Typeof(ref _e) => {
1521 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1522 "`typeof` is a reserved keyword but unimplemented")
1523 .span_label(ast_ty.span, "reserved keyword")
1528 hir::TyKind::Infer => {
1529 // Infer also appears as the type of arguments or return
1530 // values in a ExprKind::Closure, or as
1531 // the type of local variables. Both of these cases are
1532 // handled specially and will not descend into this routine.
1533 self.ty_infer(ast_ty.span)
1535 hir::TyKind::Err => {
1540 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1544 pub fn impl_trait_ty_to_ty(
1547 lifetimes: &[hir::GenericArg],
1549 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1550 let tcx = self.tcx();
1552 let generics = tcx.generics_of(def_id);
1554 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1555 let substs = Substs::for_item(tcx, def_id, |param, _| {
1556 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1557 // Our own parameters are the resolved lifetimes.
1559 GenericParamDefKind::Lifetime => {
1560 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1561 self.ast_region_to_region(lifetime, None).into()
1569 // Replace all parent lifetimes with 'static.
1571 GenericParamDefKind::Lifetime => {
1572 tcx.types.re_static.into()
1574 _ => tcx.mk_param_from_def(param)
1578 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1580 let ty = tcx.mk_opaque(def_id, substs);
1581 debug!("impl_trait_ty_to_ty: {}", ty);
1585 pub fn ty_of_arg(&self,
1587 expected_ty: Option<Ty<'tcx>>)
1591 hir::TyKind::Infer if expected_ty.is_some() => {
1592 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1593 expected_ty.unwrap()
1595 _ => self.ast_ty_to_ty(ty),
1599 pub fn ty_of_fn(&self,
1600 unsafety: hir::Unsafety,
1603 -> ty::PolyFnSig<'tcx> {
1606 let tcx = self.tcx();
1608 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
1610 let output_ty = match decl.output {
1611 hir::Return(ref output) => self.ast_ty_to_ty(output),
1612 hir::DefaultReturn(..) => tcx.mk_unit(),
1615 debug!("ty_of_fn: output_ty={:?}", output_ty);
1617 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1625 // Find any late-bound regions declared in return type that do
1626 // not appear in the arguments. These are not well-formed.
1629 // for<'a> fn() -> &'a str <-- 'a is bad
1630 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1631 let inputs = bare_fn_ty.inputs();
1632 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1633 &inputs.map_bound(|i| i.to_owned()));
1634 let output = bare_fn_ty.output();
1635 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1636 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1637 let lifetime_name = match *br {
1638 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1639 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
1641 let mut err = struct_span_err!(tcx.sess,
1644 "return type references {} \
1645 which is not constrained by the fn input types",
1647 if let ty::BrAnon(_) = *br {
1648 // The only way for an anonymous lifetime to wind up
1649 // in the return type but **also** be unconstrained is
1650 // if it only appears in "associated types" in the
1651 // input. See #47511 for an example. In this case,
1652 // though we can easily give a hint that ought to be
1654 err.note("lifetimes appearing in an associated type \
1655 are not considered constrained");
1663 /// Given the bounds on an object, determines what single region bound (if any) we can
1664 /// use to summarize this type. The basic idea is that we will use the bound the user
1665 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1666 /// for region bounds. It may be that we can derive no bound at all, in which case
1667 /// we return `None`.
1668 fn compute_object_lifetime_bound(&self,
1670 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
1671 -> Option<ty::Region<'tcx>> // if None, use the default
1673 let tcx = self.tcx();
1675 debug!("compute_opt_region_bound(existential_predicates={:?})",
1676 existential_predicates);
1678 // No explicit region bound specified. Therefore, examine trait
1679 // bounds and see if we can derive region bounds from those.
1680 let derived_region_bounds =
1681 object_region_bounds(tcx, existential_predicates);
1683 // If there are no derived region bounds, then report back that we
1684 // can find no region bound. The caller will use the default.
1685 if derived_region_bounds.is_empty() {
1689 // If any of the derived region bounds are 'static, that is always
1691 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1692 return Some(tcx.types.re_static);
1695 // Determine whether there is exactly one unique region in the set
1696 // of derived region bounds. If so, use that. Otherwise, report an
1698 let r = derived_region_bounds[0];
1699 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1700 span_err!(tcx.sess, span, E0227,
1701 "ambiguous lifetime bound, explicit lifetime bound required");
1707 /// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
1708 /// remaining general trait bounds.
1709 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1710 trait_bounds: &'b [hir::PolyTraitRef])
1711 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1713 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1714 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1715 match bound.trait_ref.path.def {
1716 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1723 let auto_traits = auto_traits.into_iter().map(|tr| {
1724 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1729 }).collect::<Vec<_>>();
1731 (auto_traits, trait_bounds)
1734 // A helper struct for conveniently grouping a set of bounds which we pass to
1735 // and return from functions in multiple places.
1736 #[derive(PartialEq, Eq, Clone, Debug)]
1737 pub struct Bounds<'tcx> {
1738 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
1739 pub implicitly_sized: Option<Span>,
1740 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
1741 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
1744 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1745 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1746 -> Vec<(ty::Predicate<'tcx>, Span)>
1748 // If it could be sized, and is, add the sized predicate
1749 let sized_predicate = self.implicitly_sized.and_then(|span| {
1750 tcx.lang_items().sized_trait().map(|sized| {
1751 let trait_ref = ty::TraitRef {
1753 substs: tcx.mk_substs_trait(param_ty, &[])
1755 (trait_ref.to_predicate(), span)
1759 sized_predicate.into_iter().chain(
1760 self.region_bounds.iter().map(|&(region_bound, span)| {
1761 // account for the binder being introduced below; no need to shift `param_ty`
1762 // because, at present at least, it can only refer to early-bound regions
1763 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
1764 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
1765 (ty::Binder::dummy(outlives).to_predicate(), span)
1767 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
1768 (bound_trait_ref.to_predicate(), span)
1771 self.projection_bounds.iter().map(|&(projection, span)| {
1772 (projection.to_predicate(), span)