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_target::spec::abi;
28 use std::collections::BTreeSet;
30 use require_c_abi_if_variadic;
31 use util::common::ErrorReported;
32 use util::nodemap::FxHashMap;
33 use errors::{FatalError, DiagnosticId};
39 use syntax::feature_gate::{GateIssue, emit_feature_err};
40 use syntax_pos::{Span, MultiSpan};
42 pub trait AstConv<'gcx, 'tcx> {
43 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
45 /// Returns the set of bounds in scope for the type parameter with
47 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
48 -> ty::GenericPredicates<'tcx>;
50 /// What lifetime should we use when a lifetime is omitted (and not elided)?
51 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
52 -> Option<ty::Region<'tcx>>;
54 /// What type should we use when a type is omitted?
55 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
57 /// Same as ty_infer, but with a known type parameter definition.
58 fn ty_infer_for_def(&self,
59 _def: &ty::GenericParamDef,
60 span: Span) -> Ty<'tcx> {
64 /// Projecting an associated type from a (potentially)
65 /// higher-ranked trait reference is more complicated, because of
66 /// the possibility of late-bound regions appearing in the
67 /// associated type binding. This is not legal in function
68 /// signatures for that reason. In a function body, we can always
69 /// handle it because we can use inference variables to remove the
70 /// late-bound regions.
71 fn projected_ty_from_poly_trait_ref(&self,
74 poly_trait_ref: ty::PolyTraitRef<'tcx>)
77 /// Normalize an associated type coming from the user.
78 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
80 /// Invoked when we encounter an error from some prior pass
81 /// (e.g. resolve) that is translated into a ty-error. This is
82 /// used to help suppress derived errors typeck might otherwise
84 fn set_tainted_by_errors(&self);
86 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
89 struct ConvertedBinding<'tcx> {
90 item_name: ast::Ident,
96 enum GenericArgPosition {
98 Value, // e.g. functions
102 /// Dummy type used for the `Self` of a `TraitRef` created for converting
103 /// a trait object, and which gets removed in `ExistentialTraitRef`.
104 /// This type must not appear anywhere in other converted types.
105 const TRAIT_OBJECT_DUMMY_SELF: ty::TyKind<'static> = ty::Infer(ty::FreshTy(0));
107 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
108 pub fn ast_region_to_region(&self,
109 lifetime: &hir::Lifetime,
110 def: Option<&ty::GenericParamDef>)
113 let tcx = self.tcx();
114 let lifetime_name = |def_id| {
115 tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap()).as_interned_str()
118 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
119 let r = match tcx.named_region(hir_id) {
120 Some(rl::Region::Static) => {
124 Some(rl::Region::LateBound(debruijn, id, _)) => {
125 let name = lifetime_name(id);
126 tcx.mk_region(ty::ReLateBound(debruijn,
127 ty::BrNamed(id, name)))
130 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
131 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
134 Some(rl::Region::EarlyBound(index, id, _)) => {
135 let name = lifetime_name(id);
136 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
143 Some(rl::Region::Free(scope, id)) => {
144 let name = lifetime_name(id);
145 tcx.mk_region(ty::ReFree(ty::FreeRegion {
147 bound_region: ty::BrNamed(id, name)
150 // (*) -- not late-bound, won't change
154 self.re_infer(lifetime.span, def)
156 // This indicates an illegal lifetime
157 // elision. `resolve_lifetime` should have
158 // reported an error in this case -- but if
159 // not, let's error out.
160 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
162 // Supply some dummy value. We don't have an
163 // `re_error`, annoyingly, so use `'static`.
169 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
176 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
177 /// returns an appropriate set of substitutions for this particular reference to `I`.
178 pub fn ast_path_substs_for_ty(&self,
181 item_segment: &hir::PathSegment)
182 -> &'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 ")
342 let label = if required == permitted && provided > permitted {
343 let diff = provided - permitted;
345 // In the case when the user has provided too many arguments,
346 // we want to point to the first unexpected argument.
347 let first_superfluous_arg: &GenericArg = &args.args[offset + permitted];
348 span = first_superfluous_arg.span();
351 "{}unexpected {} argument{}",
352 if diff != 1 { format!("{} ", diff) } else { String::new() },
354 if diff != 1 { "s" } else { "" },
358 "expected {}{} {} argument{}",
362 if bound != 1 { "s" } else { "" },
366 tcx.sess.struct_span_err_with_code(
369 "wrong number of {} arguments: expected {}{}, found {}",
375 DiagnosticId::Error("E0107".into())
376 ).span_label(span, label).emit();
378 provided > required // `suppress_error`
381 if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes {
384 param_counts.lifetimes,
385 param_counts.lifetimes,
386 arg_counts.lifetimes,
391 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
394 param_counts.types - defaults.types - has_self as usize,
395 param_counts.types - has_self as usize,
397 arg_counts.lifetimes,
404 /// Creates the relevant generic argument substitutions
405 /// corresponding to a set of generic parameters. This is a
406 /// rather complex little function. Let me try to explain the
407 /// role of each of its parameters:
409 /// To start, we are given the `def_id` of the thing we are
410 /// creating the substitutions for, and a partial set of
411 /// substitutions `parent_substs`. In general, the substitutions
412 /// for an item begin with substitutions for all the "parents" of
413 /// that item -- so e.g. for a method it might include the
414 /// parameters from the impl.
416 /// Therefore, the method begins by walking down these parents,
417 /// starting with the outermost parent and proceed inwards until
418 /// it reaches `def_id`. For each parent P, it will check `parent_substs`
419 /// first to see if the parent's substitutions are listed in there. If so,
420 /// we can append those and move on. Otherwise, it invokes the
421 /// three callback functions:
423 /// - `args_for_def_id`: given the def-id P, supplies back the
424 /// generic arguments that were given to that parent from within
425 /// the path; so e.g. if you have `<T as Foo>::Bar`, the def-id
426 /// might refer to the trait `Foo`, and the arguments might be
427 /// `[T]`. The boolean value indicates whether to infer values
428 /// for arguments whose values were not explicitly provided.
429 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
430 /// instantiate a `Kind`
431 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
432 /// creates a suitable inference variable.
433 pub fn create_substs_for_generic_args<'a, 'b>(
434 tcx: TyCtxt<'a, 'gcx, 'tcx>,
436 parent_substs: &[Kind<'tcx>],
438 self_ty: Option<Ty<'tcx>>,
439 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
440 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
441 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
442 ) -> &'tcx Substs<'tcx> {
443 // Collect the segments of the path: we need to substitute arguments
444 // for parameters throughout the entire path (wherever there are
445 // generic parameters).
446 let mut parent_defs = tcx.generics_of(def_id);
447 let count = parent_defs.count();
448 let mut stack = vec![(def_id, parent_defs)];
449 while let Some(def_id) = parent_defs.parent {
450 parent_defs = tcx.generics_of(def_id);
451 stack.push((def_id, parent_defs));
454 // We manually build up the substitution, rather than using convenience
455 // methods in subst.rs so that we can iterate over the arguments and
456 // parameters in lock-step linearly, rather than trying to match each pair.
457 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
459 // Iterate over each segment of the path.
460 while let Some((def_id, defs)) = stack.pop() {
461 let mut params = defs.params.iter().peekable();
463 // If we have already computed substitutions for parents, we can use those directly.
464 while let Some(¶m) = params.peek() {
465 if let Some(&kind) = parent_substs.get(param.index as usize) {
473 // (Unless it's been handled in `parent_substs`) `Self` is handled first.
475 if let Some(¶m) = params.peek() {
476 if param.index == 0 {
477 if let GenericParamDefKind::Type { .. } = param.kind {
478 substs.push(self_ty.map(|ty| ty.into())
479 .unwrap_or_else(|| inferred_kind(None, param, true)));
486 // Check whether this segment takes generic arguments and the user has provided any.
487 let (generic_args, infer_types) = args_for_def_id(def_id);
489 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
493 // We're going to iterate through the generic arguments that the user
494 // provided, matching them with the generic parameters we expect.
495 // Mismatches can occur as a result of elided lifetimes, or for malformed
496 // input. We try to handle both sensibly.
497 match (args.peek(), params.peek()) {
498 (Some(&arg), Some(¶m)) => {
499 match (arg, ¶m.kind) {
500 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
501 | (GenericArg::Type(_), GenericParamDefKind::Type { .. }) => {
502 substs.push(provided_kind(param, arg));
506 (GenericArg::Lifetime(_), GenericParamDefKind::Type { .. }) => {
507 // We expected a type argument, but got a lifetime
508 // argument. This is an error, but we need to handle it
509 // gracefully so we can report sensible errors. In this
510 // case, we're simply going to infer this argument.
513 (GenericArg::Type(_), GenericParamDefKind::Lifetime) => {
514 // We expected a lifetime argument, but got a type
515 // argument. That means we're inferring the lifetimes.
516 substs.push(inferred_kind(None, param, infer_types));
522 // We should never be able to reach this point with well-formed input.
523 // Getting to this point means the user supplied more arguments than
524 // there are parameters.
527 (None, Some(¶m)) => {
528 // If there are fewer arguments than parameters, it means
529 // we're inferring the remaining arguments.
531 GenericParamDefKind::Lifetime | GenericParamDefKind::Type { .. } => {
532 let kind = inferred_kind(Some(&substs), param, infer_types);
539 (None, None) => break,
544 tcx.intern_substs(&substs)
547 /// Given the type/region arguments provided to some path (along with
548 /// an implicit Self, if this is a trait reference) returns the complete
549 /// set of substitutions. This may involve applying defaulted type parameters.
551 /// Note that the type listing given here is *exactly* what the user provided.
552 fn create_substs_for_ast_path(&self,
555 generic_args: &hir::GenericArgs,
557 self_ty: Option<Ty<'tcx>>)
558 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
560 // If the type is parameterized by this region, then replace this
561 // region with the current anon region binding (in other words,
562 // whatever & would get replaced with).
563 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
565 def_id, self_ty, generic_args);
567 let tcx = self.tcx();
568 let generic_params = tcx.generics_of(def_id);
570 // If a self-type was declared, one should be provided.
571 assert_eq!(generic_params.has_self, self_ty.is_some());
573 let has_self = generic_params.has_self;
574 Self::check_generic_arg_count(
579 GenericArgPosition::Type,
584 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
585 let default_needs_object_self = |param: &ty::GenericParamDef| {
586 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
587 if is_object && has_default {
588 if tcx.at(span).type_of(param.def_id).has_self_ty() {
589 // There is no suitable inference default for a type parameter
590 // that references self, in an object type.
599 let substs = Self::create_substs_for_generic_args(
605 // Provide the generic args, and whether types should be inferred.
606 |_| (Some(generic_args), infer_types),
607 // Provide substitutions for parameters for which (valid) arguments have been provided.
609 match (¶m.kind, arg) {
610 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
611 self.ast_region_to_region(<, Some(param)).into()
613 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
614 self.ast_ty_to_ty(&ty).into()
619 // Provide substitutions for parameters for which arguments are inferred.
620 |substs, param, infer_types| {
622 GenericParamDefKind::Lifetime => tcx.types.re_static.into(),
623 GenericParamDefKind::Type { has_default, .. } => {
624 if !infer_types && has_default {
625 // No type parameter provided, but a default exists.
627 // If we are converting an object type, then the
628 // `Self` parameter is unknown. However, some of the
629 // other type parameters may reference `Self` in their
630 // defaults. This will lead to an ICE if we are not
632 if default_needs_object_self(param) {
633 struct_span_err!(tcx.sess, span, E0393,
634 "the type parameter `{}` must be explicitly \
638 format!("missing reference to `{}`", param.name))
639 .note(&format!("because of the default `Self` reference, \
640 type parameters must be specified on object \
645 // This is a default type parameter.
648 tcx.at(span).type_of(param.def_id)
649 .subst_spanned(tcx, substs.unwrap(), Some(span))
652 } else if infer_types {
653 // No type parameters were provided, we can infer all.
654 if !default_needs_object_self(param) {
655 self.ty_infer_for_def(param, span).into()
657 self.ty_infer(span).into()
660 // We've already errored above about the mismatch.
668 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
670 item_name: binding.ident,
671 ty: self.ast_ty_to_ty(&binding.ty),
676 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
677 generic_params, self_ty, substs);
679 (substs, assoc_bindings)
682 /// Instantiates the path for the given trait reference, assuming that it's
683 /// bound to a valid trait type. Returns the def_id for the defining trait.
684 /// The type _cannot_ be a type other than a trait type.
686 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
687 /// are disallowed. Otherwise, they are pushed onto the vector given.
688 pub fn instantiate_mono_trait_ref(&self,
689 trait_ref: &hir::TraitRef,
691 -> ty::TraitRef<'tcx>
693 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
695 let trait_def_id = self.trait_def_id(trait_ref);
696 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
699 trait_ref.path.segments.last().unwrap())
702 /// Get the DefId of the given trait ref. It _must_ actually be a trait.
703 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
704 let path = &trait_ref.path;
706 Def::Trait(trait_def_id) => trait_def_id,
707 Def::TraitAlias(alias_def_id) => alias_def_id,
715 /// The given `trait_ref` must actually be trait.
716 pub(super) fn instantiate_poly_trait_ref_inner(&self,
717 trait_ref: &hir::TraitRef,
719 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
721 -> ty::PolyTraitRef<'tcx>
723 let trait_def_id = self.trait_def_id(trait_ref);
725 debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
727 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
729 let (substs, assoc_bindings) =
730 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
733 trait_ref.path.segments.last().unwrap());
734 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
736 let mut dup_bindings = FxHashMap::default();
737 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
738 // specify type to assert that error was already reported in Err case:
739 let predicate: Result<_, ErrorReported> =
740 self.ast_type_binding_to_poly_projection_predicate(
741 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
742 // ok to ignore Err() because ErrorReported (see above)
743 Some((predicate.ok()?, binding.span))
746 debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
747 trait_ref, poly_projections, poly_trait_ref);
751 pub fn instantiate_poly_trait_ref(&self,
752 poly_trait_ref: &hir::PolyTraitRef,
754 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
755 -> ty::PolyTraitRef<'tcx>
757 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
758 poly_projections, false)
761 fn ast_path_to_mono_trait_ref(&self,
765 trait_segment: &hir::PathSegment)
766 -> ty::TraitRef<'tcx>
768 let (substs, assoc_bindings) =
769 self.create_substs_for_ast_trait_ref(span,
773 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
774 ty::TraitRef::new(trait_def_id, substs)
777 fn create_substs_for_ast_trait_ref(&self,
781 trait_segment: &hir::PathSegment)
782 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
784 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
787 let trait_def = self.tcx().trait_def(trait_def_id);
789 if !self.tcx().features().unboxed_closures &&
790 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
791 != trait_def.paren_sugar {
792 // For now, require that parenthetical notation be used only with `Fn()` etc.
793 let msg = if trait_def.paren_sugar {
794 "the precise format of `Fn`-family traits' type parameters is subject to change. \
795 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
797 "parenthetical notation is only stable when used with `Fn`-family traits"
799 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
800 span, GateIssue::Language, msg);
803 trait_segment.with_generic_args(|generic_args| {
804 self.create_substs_for_ast_path(span,
807 trait_segment.infer_types,
812 fn trait_defines_associated_type_named(&self,
814 assoc_name: ast::Ident)
817 self.tcx().associated_items(trait_def_id).any(|item| {
818 item.kind == ty::AssociatedKind::Type &&
819 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
823 fn ast_type_binding_to_poly_projection_predicate(
826 trait_ref: ty::PolyTraitRef<'tcx>,
827 binding: &ConvertedBinding<'tcx>,
829 dup_bindings: &mut FxHashMap<DefId, Span>)
830 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
832 let tcx = self.tcx();
835 // Given something like `U : SomeTrait<T=X>`, we want to produce a
836 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
837 // subtle in the event that `T` is defined in a supertrait of
838 // `SomeTrait`, because in that case we need to upcast.
840 // That is, consider this case:
843 // trait SubTrait : SuperTrait<int> { }
844 // trait SuperTrait<A> { type T; }
846 // ... B : SubTrait<T=foo> ...
849 // We want to produce `<B as SuperTrait<int>>::T == foo`.
851 // Find any late-bound regions declared in `ty` that are not
852 // declared in the trait-ref. These are not wellformed.
856 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
857 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
858 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
859 let late_bound_in_ty =
860 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
861 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
862 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
863 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
864 let br_name = match *br {
865 ty::BrNamed(_, name) => name,
869 "anonymous bound region {:?} in binding but not trait ref",
873 struct_span_err!(tcx.sess,
876 "binding for associated type `{}` references lifetime `{}`, \
877 which does not appear in the trait input types",
878 binding.item_name, br_name)
883 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
885 // Simple case: X is defined in the current trait.
888 // Otherwise, we have to walk through the supertraits to find
890 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
891 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
893 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
894 binding.item_name, binding.span)
897 let (assoc_ident, def_scope) =
898 tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
899 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
900 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
901 }).expect("missing associated type");
903 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
904 let msg = format!("associated type `{}` is private", binding.item_name);
905 tcx.sess.span_err(binding.span, &msg);
907 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
910 dup_bindings.entry(assoc_ty.def_id)
911 .and_modify(|prev_span| {
912 let mut err = self.tcx().struct_span_lint_node(
913 ::rustc::lint::builtin::DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
916 &format!("associated type binding `{}` specified more than once",
919 err.span_label(binding.span, "used more than once");
920 err.span_label(*prev_span, format!("first use of `{}`", 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![];
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);
979 for trait_bound in trait_bounds[1..].iter() {
980 // Sanity check for non-principal trait bounds
981 self.instantiate_poly_trait_ref(trait_bound,
986 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
988 if !trait_bounds.is_empty() {
989 let b = &trait_bounds[0];
990 let span = b.trait_ref.path.span;
991 struct_span_err!(self.tcx().sess, span, E0225,
992 "only auto traits can be used as additional traits in a trait object")
993 .span_label(span, "non-auto additional trait")
997 // Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
998 let existential_principal = principal.map_bound(|trait_ref| {
999 self.trait_ref_to_existential(trait_ref)
1001 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1002 bound.map_bound(|b| {
1003 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1004 ty::ExistentialProjection {
1006 item_def_id: b.projection_ty.item_def_id,
1007 substs: trait_ref.substs,
1012 // check that there are no gross object safety violations,
1013 // most importantly, that the supertraits don't contain Self,
1015 let object_safety_violations =
1016 tcx.astconv_object_safety_violations(principal.def_id());
1017 if !object_safety_violations.is_empty() {
1018 tcx.report_object_safety_error(
1019 span, principal.def_id(), object_safety_violations)
1021 return tcx.types.err;
1024 // use a btreeset to keep output in a more consistent order
1025 let mut associated_types = BTreeSet::default();
1027 for tr in traits::supertraits(tcx, principal) {
1028 associated_types.extend(tcx.associated_items(tr.def_id())
1029 .filter(|item| item.kind == ty::AssociatedKind::Type)
1030 .map(|item| item.def_id));
1033 for (projection_bound, _) in &projection_bounds {
1034 associated_types.remove(&projection_bound.projection_def_id());
1037 for item_def_id in associated_types {
1038 let assoc_item = tcx.associated_item(item_def_id);
1039 let trait_def_id = assoc_item.container.id();
1040 struct_span_err!(tcx.sess, span, E0191, "the value of the associated type `{}` \
1041 (from the trait `{}`) must be specified",
1043 tcx.item_path_str(trait_def_id))
1044 .span_label(span, format!("missing associated type `{}` value",
1049 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
1051 auto_traits.dedup();
1053 // skip_binder is okay, because the predicates are re-bound.
1055 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
1056 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
1057 .chain(existential_projections
1058 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1059 .collect::<SmallVec<[_; 8]>>();
1060 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1061 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1063 // Explicitly specified region bound. Use that.
1064 let region_bound = if !lifetime.is_elided() {
1065 self.ast_region_to_region(lifetime, None)
1067 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1068 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
1069 if tcx.named_region(hir_id).is_some() {
1070 self.ast_region_to_region(lifetime, None)
1072 self.re_infer(span, None).unwrap_or_else(|| {
1073 span_err!(tcx.sess, span, E0228,
1074 "the lifetime bound for this object type cannot be deduced \
1075 from context; please supply an explicit bound");
1082 debug!("region_bound: {:?}", region_bound);
1084 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1085 debug!("trait_object_type: {:?}", ty);
1089 fn report_ambiguous_associated_type(&self,
1094 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
1095 .span_label(span, "ambiguous associated type")
1096 .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
1097 type_str, trait_str, name))
1102 // Search for a bound on a type parameter which includes the associated item
1103 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1104 // This function will fail if there are no suitable bounds or there is
1106 fn find_bound_for_assoc_item(&self,
1107 ty_param_def_id: DefId,
1108 assoc_name: ast::Ident,
1110 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1112 let tcx = self.tcx();
1114 let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
1115 .predicates.into_iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref()).collect();
1117 // Check that there is exactly one way to find an associated type with the
1119 let suitable_bounds = traits::transitive_bounds(tcx, &bounds)
1120 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1122 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
1123 let param_name = tcx.hir.ty_param_name(param_node_id);
1124 self.one_bound_for_assoc_type(suitable_bounds,
1125 ¶m_name.as_str(),
1131 // Checks that bounds contains exactly one element and reports appropriate
1132 // errors otherwise.
1133 fn one_bound_for_assoc_type<I>(&self,
1135 ty_param_name: &str,
1136 assoc_name: ast::Ident,
1138 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1139 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1141 let bound = match bounds.next() {
1142 Some(bound) => bound,
1144 struct_span_err!(self.tcx().sess, span, E0220,
1145 "associated type `{}` not found for `{}`",
1148 .span_label(span, format!("associated type `{}` not found", assoc_name))
1150 return Err(ErrorReported);
1154 if let Some(bound2) = bounds.next() {
1155 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1156 let mut err = struct_span_err!(
1157 self.tcx().sess, span, E0221,
1158 "ambiguous associated type `{}` in bounds of `{}`",
1161 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1163 for bound in bounds {
1164 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1165 item.kind == ty::AssociatedKind::Type &&
1166 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1168 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
1170 if let Some(span) = bound_span {
1171 err.span_label(span, format!("ambiguous `{}` from `{}`",
1175 span_note!(&mut err, span,
1176 "associated type `{}` could derive from `{}`",
1187 // Create a type from a path to an associated type.
1188 // For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
1189 // and item_segment is the path segment for D. We return a type and a def for
1191 // Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
1192 // parameter or Self.
1193 pub fn associated_path_def_to_ty(&self,
1194 ref_id: ast::NodeId,
1198 item_segment: &hir::PathSegment)
1201 let tcx = self.tcx();
1202 let assoc_name = item_segment.ident;
1204 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
1206 self.prohibit_generics(slice::from_ref(item_segment));
1208 // Find the type of the associated item, and the trait where the associated
1209 // item is declared.
1210 let bound = match (&ty.sty, ty_path_def) {
1211 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
1212 // `Self` in an impl of a trait - we have a concrete self type and a
1214 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1215 Some(trait_ref) => trait_ref,
1217 // A cycle error occurred, most likely.
1218 return (tcx.types.err, Def::Err);
1222 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1223 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
1225 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
1227 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1230 (&ty::Param(_), Def::SelfTy(Some(param_did), None)) |
1231 (&ty::Param(_), Def::TyParam(param_did)) => {
1232 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
1234 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1238 // Don't print TyErr to the user.
1239 if !ty.references_error() {
1240 self.report_ambiguous_associated_type(span,
1243 &assoc_name.as_str());
1245 return (tcx.types.err, Def::Err);
1249 let trait_did = bound.def_id();
1250 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
1251 let item = tcx.associated_items(trait_did).find(|i| {
1252 Namespace::from(i.kind) == Namespace::Type &&
1253 i.ident.modern() == assoc_ident
1255 .expect("missing associated type");
1257 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1258 let ty = self.normalize_ty(span, ty);
1260 let def = Def::AssociatedTy(item.def_id);
1261 if !item.vis.is_accessible_from(def_scope, tcx) {
1262 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
1263 tcx.sess.span_err(span, &msg);
1265 tcx.check_stability(item.def_id, Some(ref_id), span);
1270 fn qpath_to_ty(&self,
1272 opt_self_ty: Option<Ty<'tcx>>,
1274 trait_segment: &hir::PathSegment,
1275 item_segment: &hir::PathSegment)
1278 let tcx = self.tcx();
1279 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
1281 self.prohibit_generics(slice::from_ref(item_segment));
1283 let self_ty = if let Some(ty) = opt_self_ty {
1286 let path_str = tcx.item_path_str(trait_def_id);
1287 self.report_ambiguous_associated_type(span,
1290 &item_segment.ident.as_str());
1291 return tcx.types.err;
1294 debug!("qpath_to_ty: self_type={:?}", self_ty);
1296 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1301 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1303 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1306 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(&self, segments: T) {
1307 for segment in segments {
1308 segment.with_generic_args(|generic_args| {
1309 let (mut err_for_lt, mut err_for_ty) = (false, false);
1310 for arg in &generic_args.args {
1311 let (mut span_err, span, kind) = match arg {
1312 hir::GenericArg::Lifetime(lt) => {
1313 if err_for_lt { continue }
1315 (struct_span_err!(self.tcx().sess, lt.span, E0110,
1316 "lifetime parameters are not allowed on this type"),
1320 hir::GenericArg::Type(ty) => {
1321 if err_for_ty { continue }
1323 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1324 "type parameters are not allowed on this type"),
1329 span_err.span_label(span, format!("{} parameter not allowed", kind))
1331 if err_for_lt && err_for_ty {
1335 for binding in &generic_args.bindings {
1336 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1343 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt, span: Span) {
1344 let mut err = struct_span_err!(tcx.sess, span, E0229,
1345 "associated type bindings are not allowed here");
1346 err.span_label(span, "associated type not allowed here").emit();
1349 // Check a type Path and convert it to a Ty.
1350 pub fn def_to_ty(&self,
1351 opt_self_ty: Option<Ty<'tcx>>,
1353 permit_variants: bool)
1355 let tcx = self.tcx();
1357 debug!("def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1358 path.def, opt_self_ty, path.segments);
1360 let span = path.span;
1362 Def::Existential(did) => {
1363 // check for desugared impl trait
1364 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1365 let item_segment = path.segments.split_last().unwrap();
1366 self.prohibit_generics(item_segment.1);
1367 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1370 tcx.mk_opaque(did, substs),
1373 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1374 Def::Union(did) | Def::ForeignTy(did) => {
1375 assert_eq!(opt_self_ty, None);
1376 self.prohibit_generics(path.segments.split_last().unwrap().1);
1377 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1379 Def::Variant(did) if permit_variants => {
1380 // Convert "variant type" as if it were a real type.
1381 // The resulting `Ty` is type of the variant's enum for now.
1382 assert_eq!(opt_self_ty, None);
1383 self.prohibit_generics(path.segments.split_last().unwrap().1);
1384 self.ast_path_to_ty(span,
1385 tcx.parent_def_id(did).unwrap(),
1386 path.segments.last().unwrap())
1388 Def::TyParam(did) => {
1389 assert_eq!(opt_self_ty, None);
1390 self.prohibit_generics(&path.segments);
1392 let node_id = tcx.hir.as_local_node_id(did).unwrap();
1393 let item_id = tcx.hir.get_parent_node(node_id);
1394 let item_def_id = tcx.hir.local_def_id(item_id);
1395 let generics = tcx.generics_of(item_def_id);
1396 let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
1397 tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
1399 Def::SelfTy(_, Some(def_id)) => {
1400 // Self in impl (we know the concrete type).
1402 assert_eq!(opt_self_ty, None);
1403 self.prohibit_generics(&path.segments);
1405 tcx.at(span).type_of(def_id)
1407 Def::SelfTy(Some(_), None) => {
1409 assert_eq!(opt_self_ty, None);
1410 self.prohibit_generics(&path.segments);
1413 Def::AssociatedTy(def_id) => {
1414 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1415 self.qpath_to_ty(span,
1418 &path.segments[path.segments.len()-2],
1419 path.segments.last().unwrap())
1421 Def::PrimTy(prim_ty) => {
1422 assert_eq!(opt_self_ty, None);
1423 self.prohibit_generics(&path.segments);
1425 hir::Bool => tcx.types.bool,
1426 hir::Char => tcx.types.char,
1427 hir::Int(it) => tcx.mk_mach_int(it),
1428 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1429 hir::Float(ft) => tcx.mk_mach_float(ft),
1430 hir::Str => tcx.mk_str()
1434 self.set_tainted_by_errors();
1435 return self.tcx().types.err;
1437 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1441 /// Parses the programmer's textual representation of a type into our
1442 /// internal notion of a type.
1443 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1444 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
1447 let tcx = self.tcx();
1449 let result_ty = match ast_ty.node {
1450 hir::TyKind::Slice(ref ty) => {
1451 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1453 hir::TyKind::Ptr(ref mt) => {
1454 tcx.mk_ptr(ty::TypeAndMut {
1455 ty: self.ast_ty_to_ty(&mt.ty),
1459 hir::TyKind::Rptr(ref region, ref mt) => {
1460 let r = self.ast_region_to_region(region, None);
1461 debug!("Ref r={:?}", r);
1462 let t = self.ast_ty_to_ty(&mt.ty);
1463 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1465 hir::TyKind::Never => {
1468 hir::TyKind::Tup(ref fields) => {
1469 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1471 hir::TyKind::BareFn(ref bf) => {
1472 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1473 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1475 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1476 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1478 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1479 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1480 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1481 self.ast_ty_to_ty(qself)
1483 self.def_to_ty(opt_self_ty, path, false)
1485 hir::TyKind::Def(item_id, ref lifetimes) => {
1486 let did = tcx.hir.local_def_id(item_id.id);
1487 self.impl_trait_ty_to_ty(did, lifetimes)
1489 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1490 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1491 let ty = self.ast_ty_to_ty(qself);
1493 let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1498 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1500 hir::TyKind::Array(ref ty, ref length) => {
1501 let length_def_id = tcx.hir.local_def_id(length.id);
1502 let substs = Substs::identity_for_item(tcx, length_def_id);
1503 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1504 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1505 self.normalize_ty(ast_ty.span, array_ty)
1507 hir::TyKind::Typeof(ref _e) => {
1508 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1509 "`typeof` is a reserved keyword but unimplemented")
1510 .span_label(ast_ty.span, "reserved keyword")
1515 hir::TyKind::Infer => {
1516 // Infer also appears as the type of arguments or return
1517 // values in a ExprKind::Closure, or as
1518 // the type of local variables. Both of these cases are
1519 // handled specially and will not descend into this routine.
1520 self.ty_infer(ast_ty.span)
1522 hir::TyKind::Err => {
1527 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1531 pub fn impl_trait_ty_to_ty(
1534 lifetimes: &[hir::GenericArg],
1536 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1537 let tcx = self.tcx();
1539 let generics = tcx.generics_of(def_id);
1541 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1542 let substs = Substs::for_item(tcx, def_id, |param, _| {
1543 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1544 // Our own parameters are the resolved lifetimes.
1546 GenericParamDefKind::Lifetime => {
1547 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1548 self.ast_region_to_region(lifetime, None).into()
1556 // Replace all parent lifetimes with 'static.
1558 GenericParamDefKind::Lifetime => {
1559 tcx.types.re_static.into()
1561 _ => tcx.mk_param_from_def(param)
1565 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1567 let ty = tcx.mk_opaque(def_id, substs);
1568 debug!("impl_trait_ty_to_ty: {}", ty);
1572 pub fn ty_of_arg(&self,
1574 expected_ty: Option<Ty<'tcx>>)
1578 hir::TyKind::Infer if expected_ty.is_some() => {
1579 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1580 expected_ty.unwrap()
1582 _ => self.ast_ty_to_ty(ty),
1586 pub fn ty_of_fn(&self,
1587 unsafety: hir::Unsafety,
1590 -> ty::PolyFnSig<'tcx> {
1593 let tcx = self.tcx();
1594 let input_tys: Vec<Ty> =
1595 decl.inputs.iter().map(|a| self.ty_of_arg(a, None)).collect();
1597 let output_ty = match decl.output {
1598 hir::Return(ref output) => self.ast_ty_to_ty(output),
1599 hir::DefaultReturn(..) => tcx.mk_unit(),
1602 debug!("ty_of_fn: output_ty={:?}", output_ty);
1604 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1605 input_tys.into_iter(),
1612 // Find any late-bound regions declared in return type that do
1613 // not appear in the arguments. These are not well-formed.
1616 // for<'a> fn() -> &'a str <-- 'a is bad
1617 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1618 let inputs = bare_fn_ty.inputs();
1619 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1620 &inputs.map_bound(|i| i.to_owned()));
1621 let output = bare_fn_ty.output();
1622 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1623 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1624 let lifetime_name = match *br {
1625 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1626 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
1628 let mut err = struct_span_err!(tcx.sess,
1631 "return type references {} \
1632 which is not constrained by the fn input types",
1634 if let ty::BrAnon(_) = *br {
1635 // The only way for an anonymous lifetime to wind up
1636 // in the return type but **also** be unconstrained is
1637 // if it only appears in "associated types" in the
1638 // input. See #47511 for an example. In this case,
1639 // though we can easily give a hint that ought to be
1641 err.note("lifetimes appearing in an associated type \
1642 are not considered constrained");
1650 /// Given the bounds on an object, determines what single region bound (if any) we can
1651 /// use to summarize this type. The basic idea is that we will use the bound the user
1652 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1653 /// for region bounds. It may be that we can derive no bound at all, in which case
1654 /// we return `None`.
1655 fn compute_object_lifetime_bound(&self,
1657 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
1658 -> Option<ty::Region<'tcx>> // if None, use the default
1660 let tcx = self.tcx();
1662 debug!("compute_opt_region_bound(existential_predicates={:?})",
1663 existential_predicates);
1665 // No explicit region bound specified. Therefore, examine trait
1666 // bounds and see if we can derive region bounds from those.
1667 let derived_region_bounds =
1668 object_region_bounds(tcx, existential_predicates);
1670 // If there are no derived region bounds, then report back that we
1671 // can find no region bound. The caller will use the default.
1672 if derived_region_bounds.is_empty() {
1676 // If any of the derived region bounds are 'static, that is always
1678 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1679 return Some(tcx.types.re_static);
1682 // Determine whether there is exactly one unique region in the set
1683 // of derived region bounds. If so, use that. Otherwise, report an
1685 let r = derived_region_bounds[0];
1686 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1687 span_err!(tcx.sess, span, E0227,
1688 "ambiguous lifetime bound, explicit lifetime bound required");
1694 /// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
1695 /// remaining general trait bounds.
1696 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1697 trait_bounds: &'b [hir::PolyTraitRef])
1698 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1700 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1701 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1702 match bound.trait_ref.path.def {
1703 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1710 let auto_traits = auto_traits.into_iter().map(|tr| {
1711 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1716 }).collect::<Vec<_>>();
1718 (auto_traits, trait_bounds)
1721 // A helper struct for conveniently grouping a set of bounds which we pass to
1722 // and return from functions in multiple places.
1723 #[derive(PartialEq, Eq, Clone, Debug)]
1724 pub struct Bounds<'tcx> {
1725 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
1726 pub implicitly_sized: Option<Span>,
1727 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
1728 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
1731 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1732 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1733 -> Vec<(ty::Predicate<'tcx>, Span)>
1735 // If it could be sized, and is, add the sized predicate
1736 let sized_predicate = self.implicitly_sized.and_then(|span| {
1737 tcx.lang_items().sized_trait().map(|sized| {
1738 let trait_ref = ty::TraitRef {
1740 substs: tcx.mk_substs_trait(param_ty, &[])
1742 (trait_ref.to_predicate(), span)
1746 sized_predicate.into_iter().chain(
1747 self.region_bounds.iter().map(|&(region_bound, span)| {
1748 // account for the binder being introduced below; no need to shift `param_ty`
1749 // because, at present at least, it can only refer to early-bound regions
1750 let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
1751 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
1752 (ty::Binder::dummy(outlives).to_predicate(), span)
1754 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
1755 (bound_trait_ref.to_predicate(), span)
1758 self.projection_bounds.iter().map(|&(projection, span)| {
1759 (projection.to_predicate(), span)