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` representation.
12 //! The main routine here is `ast_ty_to_ty()`; each use is is parameterized by
13 //! an instance of `AstConv`.
15 use errors::{Applicability, FatalError, DiagnosticId};
16 use hir::{self, GenericArg, GenericArgs};
18 use hir::def_id::DefId;
21 use middle::resolve_lifetime as rl;
22 use namespace::Namespace;
23 use rustc::traits::{self, TraitRefExpansionInfoDignosticBuilder};
24 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
25 use rustc::ty::{GenericParamDef, GenericParamDefKind};
26 use rustc::ty::subst::{Kind, Subst, Substs};
27 use rustc::ty::wf::object_region_bounds;
28 use rustc_data_structures::sync::Lrc;
29 use rustc_target::spec::abi;
30 use require_c_abi_if_variadic;
31 use smallvec::SmallVec;
33 use syntax::feature_gate::{GateIssue, emit_feature_err};
35 use syntax::util::lev_distance::find_best_match_for_name;
36 use syntax_pos::{DUMMY_SP, Span, MultiSpan};
37 use util::common::ErrorReported;
38 use util::nodemap::FxHashMap;
40 use std::collections::BTreeSet;
45 pub trait AstConv<'gcx, 'tcx> {
46 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
48 /// Returns the set of bounds in scope for the type parameter with
50 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
51 -> Lrc<ty::GenericPredicates<'tcx>>;
53 /// What lifetime should we use when a lifetime is omitted (and not elided)?
54 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
55 -> Option<ty::Region<'tcx>>;
57 /// What type should we use when a type is omitted?
58 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
60 /// Same as ty_infer, but with a known type parameter definition.
61 fn ty_infer_for_def(&self,
62 _def: &ty::GenericParamDef,
63 span: Span) -> Ty<'tcx> {
67 /// Projecting an associated type from a (potentially)
68 /// higher-ranked trait reference is more complicated, because of
69 /// the possibility of late-bound regions appearing in the
70 /// associated type binding. This is not legal in function
71 /// signatures for that reason. In a function body, we can always
72 /// handle it because we can use inference variables to remove the
73 /// late-bound regions.
74 fn projected_ty_from_poly_trait_ref(&self,
77 poly_trait_ref: ty::PolyTraitRef<'tcx>)
80 /// Normalize an associated type coming from the user.
81 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
83 /// Invoked when we encounter an error from some prior pass
84 /// (e.g., resolve) that is translated into a ty-error. This is
85 /// used to help suppress derived errors typeck might otherwise
87 fn set_tainted_by_errors(&self);
89 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
92 struct ConvertedBinding<'tcx> {
93 item_name: ast::Ident,
99 enum GenericArgPosition {
101 Value, // e.g., functions
105 /// Dummy type used for the `Self` of a `TraitRef` created for converting
106 /// a trait object, and which gets removed in `ExistentialTraitRef`.
107 /// This type must not appear anywhere in other converted types.
108 const TRAIT_OBJECT_DUMMY_SELF: ty::TyKind<'static> = ty::Infer(ty::FreshTy(0));
110 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
111 pub fn ast_region_to_region(&self,
112 lifetime: &hir::Lifetime,
113 def: Option<&ty::GenericParamDef>)
116 let tcx = self.tcx();
117 let lifetime_name = |def_id| {
118 tcx.hir().name(tcx.hir().as_local_node_id(def_id).unwrap()).as_interned_str()
121 let hir_id = tcx.hir().node_to_hir_id(lifetime.id);
122 let r = match tcx.named_region(hir_id) {
123 Some(rl::Region::Static) => {
127 Some(rl::Region::LateBound(debruijn, id, _)) => {
128 let name = lifetime_name(id);
129 tcx.mk_region(ty::ReLateBound(debruijn,
130 ty::BrNamed(id, name)))
133 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
134 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
137 Some(rl::Region::EarlyBound(index, id, _)) => {
138 let name = lifetime_name(id);
139 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
146 Some(rl::Region::Free(scope, id)) => {
147 let name = lifetime_name(id);
148 tcx.mk_region(ty::ReFree(ty::FreeRegion {
150 bound_region: ty::BrNamed(id, name)
153 // (*) -- not late-bound, won't change
157 self.re_infer(lifetime.span, def)
159 // This indicates an illegal lifetime
160 // elision. `resolve_lifetime` should have
161 // reported an error in this case -- but if
162 // not, let's error out.
163 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
165 // Supply some dummy value. We don't have an
166 // `re_error`, annoyingly, so use `'static`.
172 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
179 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
180 /// returns an appropriate set of substitutions for this particular reference to `I`.
181 pub fn ast_path_substs_for_ty(&self,
184 item_segment: &hir::PathSegment)
185 -> &'tcx Substs<'tcx>
187 let (substs, assoc_bindings, _) = item_segment.with_generic_args(|generic_args| {
188 self.create_substs_for_ast_path(
192 item_segment.infer_types,
197 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
202 /// Report error if there is an explicit type parameter when using `impl Trait`.
206 seg: &hir::PathSegment,
207 generics: &ty::Generics,
209 let explicit = !seg.infer_types;
210 let impl_trait = generics.params.iter().any(|param| match param.kind {
211 ty::GenericParamDefKind::Type {
212 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
217 if explicit && impl_trait {
218 let mut err = struct_span_err! {
222 "cannot provide explicit type parameters when `impl Trait` is \
223 used in argument position."
232 /// Check that the correct number of generic arguments have been provided.
233 /// Used specifically for function calls.
234 pub fn check_generic_arg_count_for_call(
238 seg: &hir::PathSegment,
239 is_method_call: bool,
241 let empty_args = P(hir::GenericArgs {
242 args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
244 let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
245 Self::check_generic_arg_count(
249 if let Some(ref args) = seg.args {
255 GenericArgPosition::MethodCall
257 GenericArgPosition::Value
259 def.parent.is_none() && def.has_self, // `has_self`
260 seg.infer_types || suppress_mismatch, // `infer_types`
264 /// Check that the correct number of generic arguments have been provided.
265 /// This is used both for datatypes and function calls.
266 fn check_generic_arg_count(
270 args: &hir::GenericArgs,
271 position: GenericArgPosition,
274 ) -> (bool, Option<Vec<Span>>) {
275 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
276 // that lifetimes will proceed types. So it suffices to check the number of each generic
277 // arguments in order to validate them with respect to the generic parameters.
278 let param_counts = def.own_counts();
279 let arg_counts = args.own_counts();
280 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
282 let mut defaults: ty::GenericParamCount = Default::default();
283 for param in &def.params {
285 GenericParamDefKind::Lifetime => {}
286 GenericParamDefKind::Type { has_default, .. } => {
287 defaults.types += has_default as usize
292 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
293 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
296 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
297 if !infer_lifetimes {
298 if let Some(span_late) = def.has_late_bound_regions {
299 let msg = "cannot specify lifetime arguments explicitly \
300 if late bound lifetime parameters are present";
301 let note = "the late bound lifetime parameter is introduced here";
302 let span = args.args[0].span();
303 if position == GenericArgPosition::Value
304 && arg_counts.lifetimes != param_counts.lifetimes {
305 let mut err = tcx.sess.struct_span_err(span, msg);
306 err.span_note(span_late, note);
310 let mut multispan = MultiSpan::from_span(span);
311 multispan.push_span_label(span_late, note.to_string());
312 tcx.lint_node(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
313 args.args[0].id(), multispan, msg);
314 return (false, None);
319 let check_kind_count = |kind,
324 // We enforce the following: `required` <= `provided` <= `permitted`.
325 // For kinds without defaults (i.e., lifetimes), `required == permitted`.
326 // For other kinds (i.e., types), `permitted` may be greater than `required`.
327 if required <= provided && provided <= permitted {
328 return (false, None);
331 // Unfortunately lifetime and type parameter mismatches are typically styled
332 // differently in diagnostics, which means we have a few cases to consider here.
333 let (bound, quantifier) = if required != permitted {
334 if provided < required {
335 (required, "at least ")
336 } else { // provided > permitted
337 (permitted, "at most ")
343 let mut potential_assoc_types: Option<Vec<Span>> = None;
344 let (spans, label) = if required == permitted && provided > permitted {
345 // In the case when the user has provided too many arguments,
346 // we want to point to the unexpected arguments.
347 let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
349 .map(|arg| arg.span())
351 potential_assoc_types = Some(spans.clone());
352 (spans, format!( "unexpected {} argument", kind))
354 (vec![span], format!(
355 "expected {}{} {} argument{}",
359 if bound != 1 { "s" } else { "" },
363 let mut err = tcx.sess.struct_span_err_with_code(
366 "wrong number of {} arguments: expected {}{}, found {}",
372 DiagnosticId::Error("E0107".into())
375 err.span_label(span, label.as_str());
379 (provided > required, // `suppress_error`
380 potential_assoc_types)
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 -- 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, instead of 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>>, Option<Vec<Span>>)
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 let (_, potential_assoc_types) = 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, potential_assoc_types)
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>, Option<Vec<Span>>)
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, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
735 trait_ref.path.segments.last().unwrap(),
737 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
739 let mut dup_bindings = FxHashMap::default();
740 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
741 // specify type to assert that error was already reported in Err case:
742 let predicate: Result<_, ErrorReported> =
743 self.ast_type_binding_to_poly_projection_predicate(
744 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
745 // okay to ignore Err because of ErrorReported (see above)
746 Some((predicate.ok()?, binding.span))
749 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
750 trait_ref, poly_projections, poly_trait_ref);
751 (poly_trait_ref, potential_assoc_types)
754 pub fn instantiate_poly_trait_ref(&self,
755 poly_trait_ref: &hir::PolyTraitRef,
757 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
758 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
760 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
761 poly_projections, false)
764 fn ast_path_to_mono_trait_ref(&self,
768 trait_segment: &hir::PathSegment)
769 -> ty::TraitRef<'tcx>
771 let (substs, assoc_bindings, _) =
772 self.create_substs_for_ast_trait_ref(span,
776 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
777 ty::TraitRef::new(trait_def_id, substs)
780 fn create_substs_for_ast_trait_ref(
785 trait_segment: &hir::PathSegment,
786 ) -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>) {
787 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
790 let trait_def = self.tcx().trait_def(trait_def_id);
792 if !self.tcx().features().unboxed_closures &&
793 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
794 != trait_def.paren_sugar {
795 // For now, require that parenthetical notation be used only with `Fn()` etc.
796 let msg = if trait_def.paren_sugar {
797 "the precise format of `Fn`-family traits' type parameters is subject to change. \
798 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
800 "parenthetical notation is only stable when used with `Fn`-family traits"
802 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
803 span, GateIssue::Language, msg);
806 trait_segment.with_generic_args(|generic_args| {
807 self.create_substs_for_ast_path(span,
810 trait_segment.infer_types,
815 fn trait_defines_associated_type_named(&self,
817 assoc_name: ast::Ident)
820 self.tcx().associated_items(trait_def_id).any(|item| {
821 item.kind == ty::AssociatedKind::Type &&
822 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
826 fn ast_type_binding_to_poly_projection_predicate(
829 trait_ref: ty::PolyTraitRef<'tcx>,
830 binding: &ConvertedBinding<'tcx>,
832 dup_bindings: &mut FxHashMap<DefId, Span>)
833 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
835 let tcx = self.tcx();
838 // Given something like `U: SomeTrait<T = X>`, we want to produce a
839 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
840 // subtle in the event that `T` is defined in a supertrait of
841 // `SomeTrait`, because in that case we need to upcast.
843 // That is, consider this case:
846 // trait SubTrait: SuperTrait<int> { }
847 // trait SuperTrait<A> { type T; }
849 // ... B : SubTrait<T=foo> ...
852 // We want to produce `<B as SuperTrait<int>>::T == foo`.
854 // Find any late-bound regions declared in `ty` that are not
855 // declared in the trait-ref. These are not wellformed.
859 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
860 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
861 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
862 let late_bound_in_ty =
863 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
864 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
865 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
866 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
867 let br_name = match *br {
868 ty::BrNamed(_, name) => name,
872 "anonymous bound region {:?} in binding but not trait ref",
876 struct_span_err!(tcx.sess,
879 "binding for associated type `{}` references lifetime `{}`, \
880 which does not appear in the trait input types",
881 binding.item_name, br_name)
886 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
888 // Simple case: X is defined in the current trait.
891 // Otherwise, we have to walk through the supertraits to find
893 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
894 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
896 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
897 binding.item_name, binding.span)
900 let (assoc_ident, def_scope) =
901 tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
902 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
903 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
904 }).expect("missing associated type");
906 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
907 let msg = format!("associated type `{}` is private", binding.item_name);
908 tcx.sess.span_err(binding.span, &msg);
910 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
913 dup_bindings.entry(assoc_ty.def_id)
914 .and_modify(|prev_span| {
915 struct_span_err!(self.tcx().sess, binding.span, E0719,
916 "the value of the associated type `{}` (from the trait `{}`) \
917 is already specified",
919 tcx.item_path_str(assoc_ty.container.id()))
920 .span_label(binding.span, "re-bound here")
921 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
924 .or_insert(binding.span);
927 Ok(candidate.map_bound(|trait_ref| {
928 ty::ProjectionPredicate {
929 projection_ty: ty::ProjectionTy::from_ref_and_name(
939 fn ast_path_to_ty(&self,
942 item_segment: &hir::PathSegment)
945 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
948 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
952 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
953 /// removing the dummy `Self` type (`TRAIT_OBJECT_DUMMY_SELF`).
954 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
955 -> ty::ExistentialTraitRef<'tcx> {
956 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
957 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
960 fn conv_object_ty_poly_trait_ref(&self,
962 trait_bounds: &[hir::PolyTraitRef],
963 lifetime: &hir::Lifetime)
966 let tcx = self.tcx();
968 if trait_bounds.is_empty() {
969 span_err!(tcx.sess, span, E0224,
970 "at least one non-builtin trait is required for an object type");
971 return tcx.types.err;
974 let mut projection_bounds = Vec::new();
975 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
976 let (principal, potential_assoc_types) = self.instantiate_poly_trait_ref(
979 &mut projection_bounds,
981 debug!("principal: {:?}", principal);
983 for trait_bound in trait_bounds[1..].iter() {
984 // sanity check for non-principal trait bounds
985 self.instantiate_poly_trait_ref(trait_bound,
990 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
992 if !trait_bounds.is_empty() {
993 let b = &trait_bounds[0];
994 let span = b.trait_ref.path.span;
995 struct_span_err!(self.tcx().sess, span, E0225,
996 "only auto traits can be used as additional traits in a trait object")
997 .span_label(span, "non-auto additional trait")
1001 // Check that there are no gross object safety violations;
1002 // most importantly, that the supertraits don't contain `Self`,
1004 let object_safety_violations =
1005 tcx.global_tcx().astconv_object_safety_violations(principal.def_id());
1006 if !object_safety_violations.is_empty() {
1007 tcx.report_object_safety_error(
1008 span, principal.def_id(), object_safety_violations)
1010 return tcx.types.err;
1013 // Use a `BTreeSet` to keep output in a more consistent order.
1014 let mut associated_types = BTreeSet::default();
1016 for tr in traits::elaborate_trait_ref(tcx, principal) {
1018 ty::Predicate::Trait(pred) => {
1019 associated_types.extend(tcx.associated_items(pred.def_id())
1020 .filter(|item| item.kind == ty::AssociatedKind::Type)
1021 .map(|item| item.def_id));
1023 ty::Predicate::Projection(pred) => {
1024 // Include projections defined on supertraits.
1025 projection_bounds.push((pred, DUMMY_SP))
1031 for (projection_bound, _) in &projection_bounds {
1032 associated_types.remove(&projection_bound.projection_def_id());
1035 if !associated_types.is_empty() {
1036 let names = associated_types.iter().map(|item_def_id| {
1037 let assoc_item = tcx.associated_item(*item_def_id);
1038 let trait_def_id = assoc_item.container.id();
1040 "`{}` (from the trait `{}`)",
1042 tcx.item_path_str(trait_def_id),
1044 }).collect::<Vec<_>>().join(", ");
1045 let mut err = struct_span_err!(
1049 "the value of the associated type{} {} must be specified",
1050 if associated_types.len() == 1 { "" } else { "s" },
1053 let mut suggest = false;
1054 let mut potential_assoc_types_spans = vec![];
1055 if let Some(potential_assoc_types) = potential_assoc_types {
1056 if potential_assoc_types.len() == associated_types.len() {
1057 // Only suggest when the amount of missing associated types is equals to the
1058 // extra type arguments present, as that gives us a relatively high confidence
1059 // that the user forgot to give the associtated type's name. The canonical
1060 // example would be trying to use `Iterator<isize>` instead of
1061 // `Iterator<Item=isize>`.
1063 potential_assoc_types_spans = potential_assoc_types;
1066 let mut suggestions = vec![];
1067 for (i, item_def_id) in associated_types.iter().enumerate() {
1068 let assoc_item = tcx.associated_item(*item_def_id);
1071 format!("associated type `{}` must be specified", assoc_item.ident),
1073 if item_def_id.is_local() {
1075 tcx.def_span(*item_def_id),
1076 format!("`{}` defined here", assoc_item.ident),
1080 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
1081 potential_assoc_types_spans[i],
1084 potential_assoc_types_spans[i],
1085 format!("{} = {}", assoc_item.ident, snippet),
1090 if !suggestions.is_empty() {
1091 let msg = format!("if you meant to specify the associated {}, write",
1092 if suggestions.len() == 1 { "type" } else { "types" });
1093 err.multipart_suggestion_with_applicability(
1096 Applicability::MaybeIncorrect,
1102 // Erase the `dummy_self` (`TRAIT_OBJECT_DUMMY_SELF`) used above.
1103 let existential_principal = principal.map_bound(|trait_ref| {
1104 self.trait_ref_to_existential(trait_ref)
1106 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1107 bound.map_bound(|b| {
1108 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1109 ty::ExistentialProjection {
1111 item_def_id: b.projection_ty.item_def_id,
1112 substs: trait_ref.substs,
1117 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
1119 auto_traits.dedup();
1121 // Calling `skip_binder` is okay, because the predicates are re-bound.
1123 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
1124 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
1125 .chain(existential_projections
1126 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1127 .collect::<SmallVec<[_; 8]>>();
1128 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1129 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1131 // Use explicitly-specified region bound.
1132 let region_bound = if !lifetime.is_elided() {
1133 self.ast_region_to_region(lifetime, None)
1135 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1136 let hir_id = tcx.hir().node_to_hir_id(lifetime.id);
1137 if tcx.named_region(hir_id).is_some() {
1138 self.ast_region_to_region(lifetime, None)
1140 self.re_infer(span, None).unwrap_or_else(|| {
1141 span_err!(tcx.sess, span, E0228,
1142 "the lifetime bound for this object type cannot be deduced \
1143 from context; please supply an explicit bound");
1150 debug!("region_bound: {:?}", region_bound);
1152 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1153 debug!("trait_object_type: {:?}", ty);
1157 fn report_ambiguous_associated_type(&self,
1162 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
1163 .span_suggestion_with_applicability(
1165 "use fully-qualified syntax",
1166 format!("<{} as {}>::{}", type_str, trait_str, name),
1167 Applicability::HasPlaceholders
1171 // Search for a bound on a type parameter which includes the associated item
1172 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1173 // This function will fail if there are no suitable bounds or there is
1175 fn find_bound_for_assoc_item(&self,
1176 ty_param_def_id: DefId,
1177 assoc_name: ast::Ident,
1179 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1181 let tcx = self.tcx();
1183 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1184 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1186 // Check that there is exactly one way to find an associated type with the
1188 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1189 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1191 let param_node_id = tcx.hir().as_local_node_id(ty_param_def_id).unwrap();
1192 let param_name = tcx.hir().ty_param_name(param_node_id);
1193 self.one_bound_for_assoc_type(suitable_bounds,
1194 ¶m_name.as_str(),
1199 // Checks that `bounds` contains exactly one element and reports appropriate
1200 // errors otherwise.
1201 fn one_bound_for_assoc_type<I>(&self,
1203 ty_param_name: &str,
1204 assoc_name: ast::Ident,
1206 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1207 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1209 let bound = match bounds.next() {
1210 Some(bound) => bound,
1212 struct_span_err!(self.tcx().sess, span, E0220,
1213 "associated type `{}` not found for `{}`",
1216 .span_label(span, format!("associated type `{}` not found", assoc_name))
1218 return Err(ErrorReported);
1222 if let Some(bound2) = bounds.next() {
1223 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1224 let mut err = struct_span_err!(
1225 self.tcx().sess, span, E0221,
1226 "ambiguous associated type `{}` in bounds of `{}`",
1229 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1231 for bound in bounds {
1232 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1233 item.kind == ty::AssociatedKind::Type &&
1234 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1236 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
1238 if let Some(span) = bound_span {
1239 err.span_label(span, format!("ambiguous `{}` from `{}`",
1243 span_note!(&mut err, span,
1244 "associated type `{}` could derive from `{}`",
1255 // Create a type from a path to an associated type.
1256 // For a path `A::B::C::D`, `ty` and `ty_path_def` are the type and def for `A::B::C`
1257 // and item_segment is the path segment for `D`. We return a type and a def for
1259 // Will fail except for `T::A` and `Self::A`; i.e., if `ty`/`ty_path_def` are not a type
1260 // parameter or `Self`.
1261 pub fn associated_path_def_to_ty(&self,
1262 ref_id: ast::NodeId,
1266 item_segment: &hir::PathSegment)
1269 let tcx = self.tcx();
1270 let assoc_name = item_segment.ident;
1272 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
1274 self.prohibit_generics(slice::from_ref(item_segment));
1276 // Find the type of the associated item, and the trait where the associated
1277 // item is declared.
1278 let bound = match (&ty.sty, ty_path_def) {
1279 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
1280 // `Self` in an impl of a trait - we have a concrete `self` type and a
1282 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1283 Some(trait_ref) => trait_ref,
1285 // A cycle error occurred, most likely.
1286 return (tcx.types.err, Def::Err);
1290 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1291 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
1293 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
1295 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1298 (&ty::Param(_), Def::SelfTy(Some(param_did), None)) |
1299 (&ty::Param(_), Def::TyParam(param_did)) => {
1300 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
1302 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1305 (&ty::Adt(adt_def, _substs), Def::Enum(_did)) => {
1306 let ty_str = ty.to_string();
1307 // Incorrect enum variant
1308 let mut err = tcx.sess.struct_span_err(
1310 &format!("no variant `{}` on enum `{}`", &assoc_name.as_str(), ty_str),
1312 // Check if it was a typo
1313 let input = adt_def.variants.iter().map(|variant| &variant.name);
1314 if let Some(suggested_name) = find_best_match_for_name(
1316 &assoc_name.as_str(),
1319 err.span_suggestion_with_applicability(
1322 format!("{}::{}", ty_str, suggested_name.to_string()),
1323 Applicability::MaybeIncorrect,
1326 err.span_label(span, "unknown variant");
1329 return (tcx.types.err, Def::Err);
1332 // Don't print TyErr to the user.
1333 if !ty.references_error() {
1334 self.report_ambiguous_associated_type(span,
1337 &assoc_name.as_str());
1339 return (tcx.types.err, Def::Err);
1343 let trait_did = bound.def_id();
1344 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
1345 let item = tcx.associated_items(trait_did).find(|i| {
1346 Namespace::from(i.kind) == Namespace::Type &&
1347 i.ident.modern() == assoc_ident
1349 .expect("missing associated type");
1351 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1352 let ty = self.normalize_ty(span, ty);
1354 let def = Def::AssociatedTy(item.def_id);
1355 if !item.vis.is_accessible_from(def_scope, tcx) {
1356 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
1357 tcx.sess.span_err(span, &msg);
1359 tcx.check_stability(item.def_id, Some(ref_id), span);
1364 fn qpath_to_ty(&self,
1366 opt_self_ty: Option<Ty<'tcx>>,
1368 trait_segment: &hir::PathSegment,
1369 item_segment: &hir::PathSegment)
1372 let tcx = self.tcx();
1373 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
1375 self.prohibit_generics(slice::from_ref(item_segment));
1377 let self_ty = if let Some(ty) = opt_self_ty {
1380 let path_str = tcx.item_path_str(trait_def_id);
1381 self.report_ambiguous_associated_type(span,
1384 &item_segment.ident.as_str());
1385 return tcx.types.err;
1388 debug!("qpath_to_ty: self_type={:?}", self_ty);
1390 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1395 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1397 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1400 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(&self, segments: T) {
1401 for segment in segments {
1402 segment.with_generic_args(|generic_args| {
1403 let (mut err_for_lt, mut err_for_ty) = (false, false);
1404 for arg in &generic_args.args {
1405 let (mut span_err, span, kind) = match arg {
1406 hir::GenericArg::Lifetime(lt) => {
1407 if err_for_lt { continue }
1409 (struct_span_err!(self.tcx().sess, lt.span, E0110,
1410 "lifetime parameters are not allowed on this type"),
1414 hir::GenericArg::Type(ty) => {
1415 if err_for_ty { continue }
1417 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1418 "type parameters are not allowed on this type"),
1423 span_err.span_label(span, format!("{} parameter not allowed", kind))
1425 if err_for_lt && err_for_ty {
1429 for binding in &generic_args.bindings {
1430 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1437 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt, span: Span) {
1438 let mut err = struct_span_err!(tcx.sess, span, E0229,
1439 "associated type bindings are not allowed here");
1440 err.span_label(span, "associated type not allowed here").emit();
1443 // Check a type `Path` and convert it to a `Ty`.
1444 pub fn def_to_ty(&self,
1445 opt_self_ty: Option<Ty<'tcx>>,
1447 permit_variants: bool)
1449 let tcx = self.tcx();
1451 debug!("def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1452 path.def, opt_self_ty, path.segments);
1454 let span = path.span;
1456 Def::Existential(did) => {
1457 // Check for desugared impl trait.
1458 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1459 let item_segment = path.segments.split_last().unwrap();
1460 self.prohibit_generics(item_segment.1);
1461 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1464 tcx.mk_opaque(did, substs),
1467 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1468 Def::Union(did) | Def::ForeignTy(did) => {
1469 assert_eq!(opt_self_ty, None);
1470 self.prohibit_generics(path.segments.split_last().unwrap().1);
1471 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1473 Def::Variant(did) if permit_variants => {
1474 // Convert "variant type" as if it were a real type.
1475 // The resulting `Ty` is type of the variant's enum for now.
1476 assert_eq!(opt_self_ty, None);
1477 self.prohibit_generics(path.segments.split_last().unwrap().1);
1478 self.ast_path_to_ty(span,
1479 tcx.parent_def_id(did).unwrap(),
1480 path.segments.last().unwrap())
1482 Def::TyParam(did) => {
1483 assert_eq!(opt_self_ty, None);
1484 self.prohibit_generics(&path.segments);
1486 let node_id = tcx.hir().as_local_node_id(did).unwrap();
1487 let item_id = tcx.hir().get_parent_node(node_id);
1488 let item_def_id = tcx.hir().local_def_id(item_id);
1489 let generics = tcx.generics_of(item_def_id);
1490 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(node_id)];
1491 tcx.mk_ty_param(index, tcx.hir().name(node_id).as_interned_str())
1493 Def::SelfTy(_, Some(def_id)) => {
1494 // `Self` in impl (we know the concrete type)
1496 assert_eq!(opt_self_ty, None);
1497 self.prohibit_generics(&path.segments);
1499 tcx.at(span).type_of(def_id)
1501 Def::SelfTy(Some(_), None) => {
1503 assert_eq!(opt_self_ty, None);
1504 self.prohibit_generics(&path.segments);
1507 Def::AssociatedTy(def_id) => {
1508 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1509 self.qpath_to_ty(span,
1512 &path.segments[path.segments.len()-2],
1513 path.segments.last().unwrap())
1515 Def::PrimTy(prim_ty) => {
1516 assert_eq!(opt_self_ty, None);
1517 self.prohibit_generics(&path.segments);
1519 hir::Bool => tcx.types.bool,
1520 hir::Char => tcx.types.char,
1521 hir::Int(it) => tcx.mk_mach_int(it),
1522 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1523 hir::Float(ft) => tcx.mk_mach_float(ft),
1524 hir::Str => tcx.mk_str()
1528 self.set_tainted_by_errors();
1529 return self.tcx().types.err;
1531 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1535 /// Parses the programmer's textual representation of a type into our
1536 /// internal notion of a type.
1537 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1538 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1539 ast_ty.id, ast_ty, ast_ty.node);
1541 let tcx = self.tcx();
1543 let result_ty = match ast_ty.node {
1544 hir::TyKind::Slice(ref ty) => {
1545 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1547 hir::TyKind::Ptr(ref mt) => {
1548 tcx.mk_ptr(ty::TypeAndMut {
1549 ty: self.ast_ty_to_ty(&mt.ty),
1553 hir::TyKind::Rptr(ref region, ref mt) => {
1554 let r = self.ast_region_to_region(region, None);
1555 debug!("Ref r={:?}", r);
1556 let t = self.ast_ty_to_ty(&mt.ty);
1557 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1559 hir::TyKind::Never => {
1562 hir::TyKind::Tup(ref fields) => {
1563 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1565 hir::TyKind::BareFn(ref bf) => {
1566 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1567 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1569 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1570 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1572 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1573 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1574 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1575 self.ast_ty_to_ty(qself)
1577 self.def_to_ty(opt_self_ty, path, false)
1579 hir::TyKind::Def(item_id, ref lifetimes) => {
1580 let did = tcx.hir().local_def_id(item_id.id);
1581 self.impl_trait_ty_to_ty(did, lifetimes)
1583 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1584 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1585 let ty = self.ast_ty_to_ty(qself);
1587 let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1592 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1594 hir::TyKind::Array(ref ty, ref length) => {
1595 let length_def_id = tcx.hir().local_def_id(length.id);
1596 let substs = Substs::identity_for_item(tcx, length_def_id);
1597 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1598 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1599 self.normalize_ty(ast_ty.span, array_ty)
1601 hir::TyKind::Typeof(ref _e) => {
1602 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1603 "`typeof` is a reserved keyword but unimplemented")
1604 .span_label(ast_ty.span, "reserved keyword")
1609 hir::TyKind::Infer => {
1610 // Infer also appears as the type of arguments or return
1611 // values in a ExprKind::Closure, or as
1612 // the type of local variables. Both of these cases are
1613 // handled specially and will not descend into this routine.
1614 self.ty_infer(ast_ty.span)
1616 hir::TyKind::Err => {
1621 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1625 pub fn impl_trait_ty_to_ty(
1628 lifetimes: &[hir::GenericArg],
1630 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1631 let tcx = self.tcx();
1633 let generics = tcx.generics_of(def_id);
1635 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1636 let substs = Substs::for_item(tcx, def_id, |param, _| {
1637 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1638 // Our own parameters are the resolved lifetimes.
1640 GenericParamDefKind::Lifetime => {
1641 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1642 self.ast_region_to_region(lifetime, None).into()
1650 // Replace all parent lifetimes with 'static.
1652 GenericParamDefKind::Lifetime => {
1653 tcx.types.re_static.into()
1655 _ => tcx.mk_param_from_def(param)
1659 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1661 let ty = tcx.mk_opaque(def_id, substs);
1662 debug!("impl_trait_ty_to_ty: {}", ty);
1666 pub fn ty_of_arg(&self,
1668 expected_ty: Option<Ty<'tcx>>)
1672 hir::TyKind::Infer if expected_ty.is_some() => {
1673 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1674 expected_ty.unwrap()
1676 _ => self.ast_ty_to_ty(ty),
1680 pub fn ty_of_fn(&self,
1681 unsafety: hir::Unsafety,
1684 -> ty::PolyFnSig<'tcx> {
1687 let tcx = self.tcx();
1689 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
1691 let output_ty = match decl.output {
1692 hir::Return(ref output) => self.ast_ty_to_ty(output),
1693 hir::DefaultReturn(..) => tcx.mk_unit(),
1696 debug!("ty_of_fn: output_ty={:?}", output_ty);
1698 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1706 // Find any late-bound regions declared in return type that do
1707 // not appear in the arguments. These are not well-formed.
1710 // for<'a> fn() -> &'a str <-- 'a is bad
1711 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1712 let inputs = bare_fn_ty.inputs();
1713 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1714 &inputs.map_bound(|i| i.to_owned()));
1715 let output = bare_fn_ty.output();
1716 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1717 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1718 let lifetime_name = match *br {
1719 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1720 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
1722 let mut err = struct_span_err!(tcx.sess,
1725 "return type references {} \
1726 which is not constrained by the fn input types",
1728 if let ty::BrAnon(_) = *br {
1729 // The only way for an anonymous lifetime to wind up
1730 // in the return type but **also** be unconstrained is
1731 // if it only appears in "associated types" in the
1732 // input. See #47511 for an example. In this case,
1733 // though we can easily give a hint that ought to be
1735 err.note("lifetimes appearing in an associated type \
1736 are not considered constrained");
1744 /// Given the bounds on an object, determines what single region bound (if any) we can
1745 /// use to summarize this type. The basic idea is that we will use the bound the user
1746 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1747 /// for region bounds. It may be that we can derive no bound at all, in which case
1748 /// we return `None`.
1749 fn compute_object_lifetime_bound(&self,
1751 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
1752 -> Option<ty::Region<'tcx>> // if None, use the default
1754 let tcx = self.tcx();
1756 debug!("compute_opt_region_bound(existential_predicates={:?})",
1757 existential_predicates);
1759 // No explicit region bound specified. Therefore, examine trait
1760 // bounds and see if we can derive region bounds from those.
1761 let derived_region_bounds =
1762 object_region_bounds(tcx, existential_predicates);
1764 // If there are no derived region bounds, then report back that we
1765 // can find no region bound. The caller will use the default.
1766 if derived_region_bounds.is_empty() {
1770 // If any of the derived region bounds are 'static, that is always
1772 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1773 return Some(tcx.types.re_static);
1776 // Determine whether there is exactly one unique region in the set
1777 // of derived region bounds. If so, use that. Otherwise, report an
1779 let r = derived_region_bounds[0];
1780 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1781 span_err!(tcx.sess, span, E0227,
1782 "ambiguous lifetime bound, explicit lifetime bound required");
1788 /// Divides a list of general trait bounds into two groups: auto traits (e.g., Sync and Send) and
1789 /// the remaining general trait bounds.
1790 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1791 trait_bounds: &'b [hir::PolyTraitRef])
1792 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1794 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1795 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1796 match bound.trait_ref.path.def {
1797 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1804 let auto_traits = auto_traits.into_iter().map(|tr| {
1805 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1810 }).collect::<Vec<_>>();
1812 (auto_traits, trait_bounds)
1815 // A helper struct for conveniently grouping a set of bounds which we pass to
1816 // and return from functions in multiple places.
1817 #[derive(PartialEq, Eq, Clone, Debug)]
1818 pub struct Bounds<'tcx> {
1819 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
1820 pub implicitly_sized: Option<Span>,
1821 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
1822 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
1825 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1826 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1827 -> Vec<(ty::Predicate<'tcx>, Span)>
1829 // If it could be sized, and is, add the sized predicate.
1830 let sized_predicate = self.implicitly_sized.and_then(|span| {
1831 tcx.lang_items().sized_trait().map(|sized| {
1832 let trait_ref = ty::TraitRef {
1834 substs: tcx.mk_substs_trait(param_ty, &[])
1836 (trait_ref.to_predicate(), span)
1840 sized_predicate.into_iter().chain(
1841 self.region_bounds.iter().map(|&(region_bound, span)| {
1842 // Account for the binder being introduced below; no need to shift `param_ty`
1843 // because, at present at least, it can only refer to early-bound regions.
1844 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
1845 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
1846 (ty::Binder::dummy(outlives).to_predicate(), span)
1848 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
1849 (bound_trait_ref.to_predicate(), span)
1852 self.projection_bounds.iter().map(|&(projection, span)| {
1853 (projection.to_predicate(), span)