1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Conversion from AST representation of types to the `ty.rs`
12 //! representation. The main routine here is `ast_ty_to_ty()`: each use
13 //! is parameterized by an instance of `AstConv`.
15 use smallvec::SmallVec;
16 use hir::{self, GenericArg, GenericArgs};
18 use hir::def_id::DefId;
20 use middle::resolve_lifetime as rl;
21 use namespace::Namespace;
22 use rustc::ty::subst::{Kind, Subst, Substs};
24 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
25 use rustc::ty::{GenericParamDef, GenericParamDefKind};
26 use rustc::ty::wf::object_region_bounds;
27 use rustc_data_structures::sync::Lrc;
28 use rustc_target::spec::abi;
29 use std::collections::BTreeSet;
31 use require_c_abi_if_variadic;
32 use util::common::ErrorReported;
33 use util::nodemap::FxHashMap;
34 use errors::{Applicability, FatalError, DiagnosticId};
39 use syntax::feature_gate::{GateIssue, emit_feature_err};
41 use syntax::util::lev_distance::find_best_match_for_name;
42 use syntax_pos::{DUMMY_SP, Span, MultiSpan};
44 pub trait AstConv<'gcx, 'tcx> {
45 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
47 /// Returns the set of bounds in scope for the type parameter with
49 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
50 -> Lrc<ty::GenericPredicates<'tcx>>;
52 /// What lifetime should we use when a lifetime is omitted (and not elided)?
53 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
54 -> Option<ty::Region<'tcx>>;
56 /// What type should we use when a type is omitted?
57 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
59 /// Same as ty_infer, but with a known type parameter definition.
60 fn ty_infer_for_def(&self,
61 _def: &ty::GenericParamDef,
62 span: Span) -> Ty<'tcx> {
66 /// Projecting an associated type from a (potentially)
67 /// higher-ranked trait reference is more complicated, because of
68 /// the possibility of late-bound regions appearing in the
69 /// associated type binding. This is not legal in function
70 /// signatures for that reason. In a function body, we can always
71 /// handle it because we can use inference variables to remove the
72 /// late-bound regions.
73 fn projected_ty_from_poly_trait_ref(&self,
76 poly_trait_ref: ty::PolyTraitRef<'tcx>)
79 /// Normalize an associated type coming from the user.
80 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
82 /// Invoked when we encounter an error from some prior pass
83 /// (e.g. resolve) that is translated into a ty-error. This is
84 /// used to help suppress derived errors typeck might otherwise
86 fn set_tainted_by_errors(&self);
88 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
91 struct ConvertedBinding<'tcx> {
92 item_name: ast::Ident,
98 enum GenericArgPosition {
100 Value, // e.g. functions
104 /// Dummy type used for the `Self` of a `TraitRef` created for converting
105 /// a trait object, and which gets removed in `ExistentialTraitRef`.
106 /// This type must not appear anywhere in other converted types.
107 const TRAIT_OBJECT_DUMMY_SELF: ty::TyKind<'static> = ty::Infer(ty::FreshTy(0));
109 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
110 pub fn ast_region_to_region(&self,
111 lifetime: &hir::Lifetime,
112 def: Option<&ty::GenericParamDef>)
115 let tcx = self.tcx();
116 let lifetime_name = |def_id| {
117 tcx.hir().name(tcx.hir().as_local_node_id(def_id).unwrap()).as_interned_str()
120 let hir_id = tcx.hir().node_to_hir_id(lifetime.id);
121 let r = match tcx.named_region(hir_id) {
122 Some(rl::Region::Static) => {
126 Some(rl::Region::LateBound(debruijn, id, _)) => {
127 let name = lifetime_name(id);
128 tcx.mk_region(ty::ReLateBound(debruijn,
129 ty::BrNamed(id, name)))
132 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
133 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
136 Some(rl::Region::EarlyBound(index, id, _)) => {
137 let name = lifetime_name(id);
138 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
145 Some(rl::Region::Free(scope, id)) => {
146 let name = lifetime_name(id);
147 tcx.mk_region(ty::ReFree(ty::FreeRegion {
149 bound_region: ty::BrNamed(id, name)
152 // (*) -- not late-bound, won't change
156 self.re_infer(lifetime.span, def)
158 // This indicates an illegal lifetime
159 // elision. `resolve_lifetime` should have
160 // reported an error in this case -- but if
161 // not, let's error out.
162 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
164 // Supply some dummy value. We don't have an
165 // `re_error`, annoyingly, so use `'static`.
171 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
178 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
179 /// returns an appropriate set of substitutions for this particular reference to `I`.
180 pub fn ast_path_substs_for_ty(&self,
183 item_segment: &hir::PathSegment)
184 -> &'tcx Substs<'tcx>
186 let (substs, assoc_bindings, _) = item_segment.with_generic_args(|generic_args| {
187 self.create_substs_for_ast_path(
191 item_segment.infer_types,
196 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
201 /// Report error if there is an explicit type parameter when using `impl Trait`.
205 seg: &hir::PathSegment,
206 generics: &ty::Generics,
208 let explicit = !seg.infer_types;
209 let impl_trait = generics.params.iter().any(|param| match param.kind {
210 ty::GenericParamDefKind::Type {
211 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
216 if explicit && impl_trait {
217 let mut err = struct_span_err! {
221 "cannot provide explicit type parameters when `impl Trait` is \
222 used in argument position."
231 /// Check that the correct number of generic arguments have been provided.
232 /// Used specifically for function calls.
233 pub fn check_generic_arg_count_for_call(
237 seg: &hir::PathSegment,
238 is_method_call: bool,
240 let empty_args = P(hir::GenericArgs {
241 args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
243 let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
244 Self::check_generic_arg_count(
248 if let Some(ref args) = seg.args {
254 GenericArgPosition::MethodCall
256 GenericArgPosition::Value
258 def.parent.is_none() && def.has_self, // `has_self`
259 seg.infer_types || suppress_mismatch, // `infer_types`
263 /// Check that the correct number of generic arguments have been provided.
264 /// This is used both for datatypes and function calls.
265 fn check_generic_arg_count(
269 args: &hir::GenericArgs,
270 position: GenericArgPosition,
273 ) -> (bool, Option<Vec<Span>>) {
274 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
275 // that lifetimes will proceed types. So it suffices to check the number of each generic
276 // arguments in order to validate them with respect to the generic parameters.
277 let param_counts = def.own_counts();
278 let arg_counts = args.own_counts();
279 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
281 let mut defaults: ty::GenericParamCount = Default::default();
282 for param in &def.params {
284 GenericParamDefKind::Lifetime => {}
285 GenericParamDefKind::Type { has_default, .. } => {
286 defaults.types += has_default as usize
291 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
292 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
295 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
296 if !infer_lifetimes {
297 if let Some(span_late) = def.has_late_bound_regions {
298 let msg = "cannot specify lifetime arguments explicitly \
299 if late bound lifetime parameters are present";
300 let note = "the late bound lifetime parameter is introduced here";
301 let span = args.args[0].span();
302 if position == GenericArgPosition::Value
303 && arg_counts.lifetimes != param_counts.lifetimes {
304 let mut err = tcx.sess.struct_span_err(span, msg);
305 err.span_note(span_late, note);
309 let mut multispan = MultiSpan::from_span(span);
310 multispan.push_span_label(span_late, note.to_string());
311 tcx.lint_node(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
312 args.args[0].id(), multispan, msg);
313 return (false, None);
318 let check_kind_count = |kind,
323 // We enforce the following: `required` <= `provided` <= `permitted`.
324 // For kinds without defaults (i.e. lifetimes), `required == permitted`.
325 // For other kinds (i.e. types), `permitted` may be greater than `required`.
326 if required <= provided && provided <= permitted {
327 return (false, None);
330 // Unfortunately lifetime and type parameter mismatches are typically styled
331 // differently in diagnostics, which means we have a few cases to consider here.
332 let (bound, quantifier) = if required != permitted {
333 if provided < required {
334 (required, "at least ")
335 } else { // provided > permitted
336 (permitted, "at most ")
342 let mut potential_assoc_types: Option<Vec<Span>> = None;
343 let (spans, label) = if required == permitted && provided > permitted {
344 // In the case when the user has provided too many arguments,
345 // we want to point to the unexpected arguments.
346 let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
348 .map(|arg| arg.span())
350 potential_assoc_types = Some(spans.clone());
351 (spans, format!( "unexpected {} argument", kind))
353 (vec![span], format!(
354 "expected {}{} {} argument{}",
358 if bound != 1 { "s" } else { "" },
362 let mut err = tcx.sess.struct_span_err_with_code(
365 "wrong number of {} arguments: expected {}{}, found {}",
371 DiagnosticId::Error("E0107".into())
374 err.span_label(span, label.as_str());
378 (provided > required, // `suppress_error`
379 potential_assoc_types)
382 if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes {
385 param_counts.lifetimes,
386 param_counts.lifetimes,
387 arg_counts.lifetimes,
392 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
395 param_counts.types - defaults.types - has_self as usize,
396 param_counts.types - has_self as usize,
398 arg_counts.lifetimes,
405 /// Creates the relevant generic argument substitutions
406 /// corresponding to a set of generic parameters. This is a
407 /// rather complex little function. Let me try to explain the
408 /// role of each of its parameters:
410 /// To start, we are given the `def_id` of the thing we are
411 /// creating the substitutions for, and a partial set of
412 /// substitutions `parent_substs`. In general, the substitutions
413 /// for an item begin with substitutions for all the "parents" of
414 /// that item -- so e.g. for a method it might include the
415 /// parameters from the impl.
417 /// Therefore, the method begins by walking down these parents,
418 /// starting with the outermost parent and proceed inwards until
419 /// it reaches `def_id`. For each parent P, it will check `parent_substs`
420 /// first to see if the parent's substitutions are listed in there. If so,
421 /// we can append those and move on. Otherwise, it invokes the
422 /// three callback functions:
424 /// - `args_for_def_id`: given the def-id P, supplies back the
425 /// generic arguments that were given to that parent from within
426 /// the path; so e.g. if you have `<T as Foo>::Bar`, the def-id
427 /// might refer to the trait `Foo`, and the arguments might be
428 /// `[T]`. The boolean value indicates whether to infer values
429 /// for arguments whose values were not explicitly provided.
430 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
431 /// instantiate a `Kind`
432 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
433 /// creates a suitable inference variable.
434 pub fn create_substs_for_generic_args<'a, 'b>(
435 tcx: TyCtxt<'a, 'gcx, 'tcx>,
437 parent_substs: &[Kind<'tcx>],
439 self_ty: Option<Ty<'tcx>>,
440 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
441 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
442 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
443 ) -> &'tcx Substs<'tcx> {
444 // Collect the segments of the path: we need to substitute arguments
445 // for parameters throughout the entire path (wherever there are
446 // generic parameters).
447 let mut parent_defs = tcx.generics_of(def_id);
448 let count = parent_defs.count();
449 let mut stack = vec![(def_id, parent_defs)];
450 while let Some(def_id) = parent_defs.parent {
451 parent_defs = tcx.generics_of(def_id);
452 stack.push((def_id, parent_defs));
455 // We manually build up the substitution, rather than using convenience
456 // methods in `subst.rs` so that we can iterate over the arguments and
457 // parameters in lock-step linearly, rather than trying to match each pair.
458 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
460 // Iterate over each segment of the path.
461 while let Some((def_id, defs)) = stack.pop() {
462 let mut params = defs.params.iter().peekable();
464 // If we have already computed substitutions for parents, we can use those directly.
465 while let Some(¶m) = params.peek() {
466 if let Some(&kind) = parent_substs.get(param.index as usize) {
474 // `Self` is handled first, unless it's been handled in `parent_substs`.
476 if let Some(¶m) = params.peek() {
477 if param.index == 0 {
478 if let GenericParamDefKind::Type { .. } = param.kind {
479 substs.push(self_ty.map(|ty| ty.into())
480 .unwrap_or_else(|| inferred_kind(None, param, true)));
487 // Check whether this segment takes generic arguments and the user has provided any.
488 let (generic_args, infer_types) = args_for_def_id(def_id);
490 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
494 // We're going to iterate through the generic arguments that the user
495 // provided, matching them with the generic parameters we expect.
496 // Mismatches can occur as a result of elided lifetimes, or for malformed
497 // input. We try to handle both sensibly.
498 match (args.peek(), params.peek()) {
499 (Some(&arg), Some(¶m)) => {
500 match (arg, ¶m.kind) {
501 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
502 | (GenericArg::Type(_), GenericParamDefKind::Type { .. }) => {
503 substs.push(provided_kind(param, arg));
507 (GenericArg::Lifetime(_), GenericParamDefKind::Type { .. }) => {
508 // We expected a type argument, but got a lifetime
509 // argument. This is an error, but we need to handle it
510 // gracefully so we can report sensible errors. In this
511 // case, we're simply going to infer this argument.
514 (GenericArg::Type(_), GenericParamDefKind::Lifetime) => {
515 // We expected a lifetime argument, but got a type
516 // argument. That means we're inferring the lifetimes.
517 substs.push(inferred_kind(None, param, infer_types));
523 // We should never be able to reach this point with well-formed input.
524 // Getting to this point means the user supplied more arguments than
525 // there are parameters.
528 (None, Some(¶m)) => {
529 // If there are fewer arguments than parameters, it means
530 // we're inferring the remaining arguments.
532 GenericParamDefKind::Lifetime | GenericParamDefKind::Type { .. } => {
533 let kind = inferred_kind(Some(&substs), param, infer_types);
540 (None, None) => break,
545 tcx.intern_substs(&substs)
548 /// Given the type/region arguments provided to some path (along with
549 /// an implicit `Self`, if this is a trait reference) returns the complete
550 /// set of substitutions. This may involve applying defaulted type parameters.
552 /// Note that the type listing given here is *exactly* what the user provided.
553 fn create_substs_for_ast_path(&self,
556 generic_args: &hir::GenericArgs,
558 self_ty: Option<Ty<'tcx>>)
559 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>)
561 // If the type is parameterized by this region, then replace this
562 // region with the current anon region binding (in other words,
563 // whatever & would get replaced with).
564 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
566 def_id, self_ty, generic_args);
568 let tcx = self.tcx();
569 let generic_params = tcx.generics_of(def_id);
571 // If a self-type was declared, one should be provided.
572 assert_eq!(generic_params.has_self, self_ty.is_some());
574 let has_self = generic_params.has_self;
575 let (_, potential_assoc_types) = Self::check_generic_arg_count(
580 GenericArgPosition::Type,
585 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
586 let default_needs_object_self = |param: &ty::GenericParamDef| {
587 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
588 if is_object && has_default {
589 if tcx.at(span).type_of(param.def_id).has_self_ty() {
590 // There is no suitable inference default for a type parameter
591 // that references self, in an object type.
600 let substs = Self::create_substs_for_generic_args(
606 // Provide the generic args, and whether types should be inferred.
607 |_| (Some(generic_args), infer_types),
608 // Provide substitutions for parameters for which (valid) arguments have been provided.
610 match (¶m.kind, arg) {
611 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
612 self.ast_region_to_region(<, Some(param)).into()
614 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
615 self.ast_ty_to_ty(&ty).into()
620 // Provide substitutions for parameters for which arguments are inferred.
621 |substs, param, infer_types| {
623 GenericParamDefKind::Lifetime => tcx.types.re_static.into(),
624 GenericParamDefKind::Type { has_default, .. } => {
625 if !infer_types && has_default {
626 // No type parameter provided, but a default exists.
628 // If we are converting an object type, then the
629 // `Self` parameter is unknown. However, some of the
630 // other type parameters may reference `Self` in their
631 // defaults. This will lead to an ICE if we are not
633 if default_needs_object_self(param) {
634 struct_span_err!(tcx.sess, span, E0393,
635 "the type parameter `{}` must be explicitly \
639 format!("missing reference to `{}`", param.name))
640 .note(&format!("because of the default `Self` reference, \
641 type parameters must be specified on object \
646 // This is a default type parameter.
649 tcx.at(span).type_of(param.def_id)
650 .subst_spanned(tcx, substs.unwrap(), Some(span))
653 } else if infer_types {
654 // No type parameters were provided, we can infer all.
655 if !default_needs_object_self(param) {
656 self.ty_infer_for_def(param, span).into()
658 self.ty_infer(span).into()
661 // We've already errored above about the mismatch.
669 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
671 item_name: binding.ident,
672 ty: self.ast_ty_to_ty(&binding.ty),
677 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
678 generic_params, self_ty, substs);
680 (substs, assoc_bindings, potential_assoc_types)
683 /// Instantiates the path for the given trait reference, assuming that it's
684 /// bound to a valid trait type. Returns the def_id for the defining trait.
685 /// The type _cannot_ be a type other than a trait type.
687 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
688 /// are disallowed. Otherwise, they are pushed onto the vector given.
689 pub fn instantiate_mono_trait_ref(&self,
690 trait_ref: &hir::TraitRef,
692 -> ty::TraitRef<'tcx>
694 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
696 let trait_def_id = self.trait_def_id(trait_ref);
697 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
700 trait_ref.path.segments.last().unwrap())
703 /// Get the `DefId` of the given trait ref. It _must_ actually be a trait.
704 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
705 let path = &trait_ref.path;
707 Def::Trait(trait_def_id) => trait_def_id,
708 Def::TraitAlias(alias_def_id) => alias_def_id,
716 /// The given trait ref must actually be a trait.
717 pub(super) fn instantiate_poly_trait_ref_inner(&self,
718 trait_ref: &hir::TraitRef,
720 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
722 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
724 let trait_def_id = self.trait_def_id(trait_ref);
726 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
728 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
730 let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
734 trait_ref.path.segments.last().unwrap(),
736 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
738 let mut dup_bindings = FxHashMap::default();
739 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
740 // specify type to assert that error was already reported in Err case:
741 let predicate: Result<_, ErrorReported> =
742 self.ast_type_binding_to_poly_projection_predicate(
743 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
744 // okay to ignore Err because of ErrorReported (see above)
745 Some((predicate.ok()?, binding.span))
748 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
749 trait_ref, poly_projections, poly_trait_ref);
750 (poly_trait_ref, potential_assoc_types)
753 pub fn instantiate_poly_trait_ref(&self,
754 poly_trait_ref: &hir::PolyTraitRef,
756 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
757 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
759 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
760 poly_projections, false)
763 fn ast_path_to_mono_trait_ref(&self,
767 trait_segment: &hir::PathSegment)
768 -> ty::TraitRef<'tcx>
770 let (substs, assoc_bindings, _) =
771 self.create_substs_for_ast_trait_ref(span,
775 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
776 ty::TraitRef::new(trait_def_id, substs)
779 fn create_substs_for_ast_trait_ref(
784 trait_segment: &hir::PathSegment,
785 ) -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>) {
786 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
789 let trait_def = self.tcx().trait_def(trait_def_id);
791 if !self.tcx().features().unboxed_closures &&
792 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
793 != trait_def.paren_sugar {
794 // For now, require that parenthetical notation be used only with `Fn()` etc.
795 let msg = if trait_def.paren_sugar {
796 "the precise format of `Fn`-family traits' type parameters is subject to change. \
797 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
799 "parenthetical notation is only stable when used with `Fn`-family traits"
801 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
802 span, GateIssue::Language, msg);
805 trait_segment.with_generic_args(|generic_args| {
806 self.create_substs_for_ast_path(span,
809 trait_segment.infer_types,
814 fn trait_defines_associated_type_named(&self,
816 assoc_name: ast::Ident)
819 self.tcx().associated_items(trait_def_id).any(|item| {
820 item.kind == ty::AssociatedKind::Type &&
821 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
825 fn ast_type_binding_to_poly_projection_predicate(
828 trait_ref: ty::PolyTraitRef<'tcx>,
829 binding: &ConvertedBinding<'tcx>,
831 dup_bindings: &mut FxHashMap<DefId, Span>)
832 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
834 let tcx = self.tcx();
837 // Given something like `U: SomeTrait<T = X>`, we want to produce a
838 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
839 // subtle in the event that `T` is defined in a supertrait of
840 // `SomeTrait`, because in that case we need to upcast.
842 // That is, consider this case:
845 // trait SubTrait: SuperTrait<int> { }
846 // trait SuperTrait<A> { type T; }
848 // ... B : SubTrait<T=foo> ...
851 // We want to produce `<B as SuperTrait<int>>::T == foo`.
853 // Find any late-bound regions declared in `ty` that are not
854 // declared in the trait-ref. These are not wellformed.
858 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
859 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
860 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
861 let late_bound_in_ty =
862 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
863 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
864 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
865 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
866 let br_name = match *br {
867 ty::BrNamed(_, name) => name,
871 "anonymous bound region {:?} in binding but not trait ref",
875 struct_span_err!(tcx.sess,
878 "binding for associated type `{}` references lifetime `{}`, \
879 which does not appear in the trait input types",
880 binding.item_name, br_name)
885 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
887 // Simple case: X is defined in the current trait.
890 // Otherwise, we have to walk through the supertraits to find
892 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
893 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
895 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
896 binding.item_name, binding.span)
899 let (assoc_ident, def_scope) =
900 tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
901 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
902 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
903 }).expect("missing associated type");
905 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
906 let msg = format!("associated type `{}` is private", binding.item_name);
907 tcx.sess.span_err(binding.span, &msg);
909 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
912 dup_bindings.entry(assoc_ty.def_id)
913 .and_modify(|prev_span| {
914 struct_span_err!(self.tcx().sess, binding.span, E0719,
915 "the value of the associated type `{}` (from the trait `{}`) \
916 is already specified",
918 tcx.item_path_str(assoc_ty.container.id()))
919 .span_label(binding.span, "re-bound here")
920 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
923 .or_insert(binding.span);
926 Ok(candidate.map_bound(|trait_ref| {
927 ty::ProjectionPredicate {
928 projection_ty: ty::ProjectionTy::from_ref_and_name(
938 fn ast_path_to_ty(&self,
941 item_segment: &hir::PathSegment)
944 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
947 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
951 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
952 /// removing the dummy `Self` type (`TRAIT_OBJECT_DUMMY_SELF`).
953 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
954 -> ty::ExistentialTraitRef<'tcx> {
955 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
956 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
959 fn conv_object_ty_poly_trait_ref(&self,
961 trait_bounds: &[hir::PolyTraitRef],
962 lifetime: &hir::Lifetime)
965 let tcx = self.tcx();
967 if trait_bounds.is_empty() {
968 span_err!(tcx.sess, span, E0224,
969 "at least one non-builtin trait is required for an object type");
970 return tcx.types.err;
973 let mut projection_bounds = Vec::new();
974 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
975 let (principal, potential_assoc_types) = self.instantiate_poly_trait_ref(
978 &mut projection_bounds,
980 debug!("principal: {:?}", principal);
982 for trait_bound in trait_bounds[1..].iter() {
983 // sanity check for non-principal trait bounds
984 self.instantiate_poly_trait_ref(trait_bound,
989 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
991 if !trait_bounds.is_empty() {
992 let b = &trait_bounds[0];
993 let span = b.trait_ref.path.span;
994 struct_span_err!(self.tcx().sess, span, E0225,
995 "only auto traits can be used as additional traits in a trait object")
996 .span_label(span, "non-auto additional trait")
1000 // Check that there are no gross object safety violations;
1001 // most importantly, that the supertraits don't contain `Self`,
1003 let object_safety_violations =
1004 tcx.global_tcx().astconv_object_safety_violations(principal.def_id());
1005 if !object_safety_violations.is_empty() {
1006 tcx.report_object_safety_error(
1007 span, principal.def_id(), object_safety_violations)
1009 return tcx.types.err;
1012 // Use a `BTreeSet` to keep output in a more consistent order.
1013 let mut associated_types = BTreeSet::default();
1015 for tr in traits::elaborate_trait_ref(tcx, principal) {
1017 ty::Predicate::Trait(pred) => {
1018 associated_types.extend(tcx.associated_items(pred.def_id())
1019 .filter(|item| item.kind == ty::AssociatedKind::Type)
1020 .map(|item| item.def_id));
1022 ty::Predicate::Projection(pred) => {
1023 // Include projections defined on supertraits.
1024 projection_bounds.push((pred, DUMMY_SP))
1030 for (projection_bound, _) in &projection_bounds {
1031 associated_types.remove(&projection_bound.projection_def_id());
1034 if !associated_types.is_empty() {
1035 let names = associated_types.iter().map(|item_def_id| {
1036 let assoc_item = tcx.associated_item(*item_def_id);
1037 let trait_def_id = assoc_item.container.id();
1039 "`{}` (from the trait `{}`)",
1041 tcx.item_path_str(trait_def_id),
1043 }).collect::<Vec<_>>().join(", ");
1044 let mut err = struct_span_err!(
1048 "the value of the associated type{} {} must be specified",
1049 if associated_types.len() == 1 { "" } else { "s" },
1052 let mut suggest = false;
1053 let mut potential_assoc_types_spans = vec![];
1054 if let Some(potential_assoc_types) = potential_assoc_types {
1055 if potential_assoc_types.len() == associated_types.len() {
1056 // Only suggest when the amount of missing associated types is equals to the
1057 // extra type arguments present, as that gives us a relatively high confidence
1058 // that the user forgot to give the associtated type's name. The canonical
1059 // example would be trying to use `Iterator<isize>` instead of
1060 // `Iterator<Item=isize>`.
1062 potential_assoc_types_spans = potential_assoc_types;
1065 let mut suggestions = vec![];
1066 for (i, item_def_id) in associated_types.iter().enumerate() {
1067 let assoc_item = tcx.associated_item(*item_def_id);
1070 format!("associated type `{}` must be specified", assoc_item.ident),
1072 if item_def_id.is_local() {
1074 tcx.def_span(*item_def_id),
1075 format!("`{}` defined here", assoc_item.ident),
1079 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
1080 potential_assoc_types_spans[i],
1083 potential_assoc_types_spans[i],
1084 format!("{} = {}", assoc_item.ident, snippet),
1089 if !suggestions.is_empty() {
1090 let msg = if suggestions.len() == 1 {
1091 "if you meant to specify the associated type, write"
1093 "if you meant to specify the associated types, write"
1095 err.multipart_suggestion_with_applicability(
1098 Applicability::MaybeIncorrect,
1104 // Erase the `dummy_self` (`TRAIT_OBJECT_DUMMY_SELF`) used above.
1105 let existential_principal = principal.map_bound(|trait_ref| {
1106 self.trait_ref_to_existential(trait_ref)
1108 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1109 bound.map_bound(|b| {
1110 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1111 ty::ExistentialProjection {
1113 item_def_id: b.projection_ty.item_def_id,
1114 substs: trait_ref.substs,
1119 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
1121 auto_traits.dedup();
1123 // Calling `skip_binder` is okay, because the predicates are re-bound.
1125 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
1126 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
1127 .chain(existential_projections
1128 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1129 .collect::<SmallVec<[_; 8]>>();
1130 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1131 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1133 // Use explicitly-specified region bound.
1134 let region_bound = if !lifetime.is_elided() {
1135 self.ast_region_to_region(lifetime, None)
1137 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1138 let hir_id = tcx.hir().node_to_hir_id(lifetime.id);
1139 if tcx.named_region(hir_id).is_some() {
1140 self.ast_region_to_region(lifetime, None)
1142 self.re_infer(span, None).unwrap_or_else(|| {
1143 span_err!(tcx.sess, span, E0228,
1144 "the lifetime bound for this object type cannot be deduced \
1145 from context; please supply an explicit bound");
1152 debug!("region_bound: {:?}", region_bound);
1154 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1155 debug!("trait_object_type: {:?}", ty);
1159 fn report_ambiguous_associated_type(&self,
1164 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
1165 .span_suggestion_with_applicability(
1167 "use fully-qualified syntax",
1168 format!("<{} as {}>::{}", type_str, trait_str, name),
1169 Applicability::HasPlaceholders
1173 // Search for a bound on a type parameter which includes the associated item
1174 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1175 // This function will fail if there are no suitable bounds or there is
1177 fn find_bound_for_assoc_item(&self,
1178 ty_param_def_id: DefId,
1179 assoc_name: ast::Ident,
1181 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1183 let tcx = self.tcx();
1185 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1186 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1188 // Check that there is exactly one way to find an associated type with the
1190 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1191 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1193 let param_node_id = tcx.hir().as_local_node_id(ty_param_def_id).unwrap();
1194 let param_name = tcx.hir().ty_param_name(param_node_id);
1195 self.one_bound_for_assoc_type(suitable_bounds,
1196 ¶m_name.as_str(),
1201 // Checks that `bounds` contains exactly one element and reports appropriate
1202 // errors otherwise.
1203 fn one_bound_for_assoc_type<I>(&self,
1205 ty_param_name: &str,
1206 assoc_name: ast::Ident,
1208 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1209 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1211 let bound = match bounds.next() {
1212 Some(bound) => bound,
1214 struct_span_err!(self.tcx().sess, span, E0220,
1215 "associated type `{}` not found for `{}`",
1218 .span_label(span, format!("associated type `{}` not found", assoc_name))
1220 return Err(ErrorReported);
1224 if let Some(bound2) = bounds.next() {
1225 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1226 let mut err = struct_span_err!(
1227 self.tcx().sess, span, E0221,
1228 "ambiguous associated type `{}` in bounds of `{}`",
1231 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1233 for bound in bounds {
1234 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1235 item.kind == ty::AssociatedKind::Type &&
1236 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1238 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
1240 if let Some(span) = bound_span {
1241 err.span_label(span, format!("ambiguous `{}` from `{}`",
1245 span_note!(&mut err, span,
1246 "associated type `{}` could derive from `{}`",
1257 // Create a type from a path to an associated type.
1258 // For a path `A::B::C::D`, `ty` and `ty_path_def` are the type and def for `A::B::C`
1259 // and item_segment is the path segment for `D`. We return a type and a def for
1261 // Will fail except for `T::A` and `Self::A`; i.e., if `ty`/`ty_path_def` are not a type
1262 // parameter or `Self`.
1263 pub fn associated_path_def_to_ty(&self,
1264 ref_id: ast::NodeId,
1268 item_segment: &hir::PathSegment)
1271 let tcx = self.tcx();
1272 let assoc_name = item_segment.ident;
1274 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
1276 self.prohibit_generics(slice::from_ref(item_segment));
1278 // Find the type of the associated item, and the trait where the associated
1279 // item is declared.
1280 let bound = match (&ty.sty, ty_path_def) {
1281 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
1282 // `Self` in an impl of a trait - we have a concrete `self` type and a
1284 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1285 Some(trait_ref) => trait_ref,
1287 // A cycle error occurred, most likely.
1288 return (tcx.types.err, Def::Err);
1292 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1293 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
1295 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
1297 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1300 (&ty::Param(_), Def::SelfTy(Some(param_did), None)) |
1301 (&ty::Param(_), Def::TyParam(param_did)) => {
1302 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
1304 Err(ErrorReported) => return (tcx.types.err, Def::Err),
1307 (&ty::Adt(adt_def, _substs), Def::Enum(_did)) => {
1308 let ty_str = ty.to_string();
1309 // Incorrect enum variant
1310 let mut err = tcx.sess.struct_span_err(
1312 &format!("no variant `{}` on enum `{}`", &assoc_name.as_str(), ty_str),
1314 // Check if it was a typo
1315 let input = adt_def.variants.iter().map(|variant| &variant.name);
1316 if let Some(suggested_name) = find_best_match_for_name(
1318 &assoc_name.as_str(),
1321 err.span_suggestion_with_applicability(
1324 format!("{}::{}", ty_str, suggested_name.to_string()),
1325 Applicability::MaybeIncorrect,
1328 err.span_label(span, "unknown variant");
1331 return (tcx.types.err, Def::Err);
1334 // Don't print TyErr to the user.
1335 if !ty.references_error() {
1336 self.report_ambiguous_associated_type(span,
1339 &assoc_name.as_str());
1341 return (tcx.types.err, Def::Err);
1345 let trait_did = bound.def_id();
1346 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
1347 let item = tcx.associated_items(trait_did).find(|i| {
1348 Namespace::from(i.kind) == Namespace::Type &&
1349 i.ident.modern() == assoc_ident
1351 .expect("missing associated type");
1353 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1354 let ty = self.normalize_ty(span, ty);
1356 let def = Def::AssociatedTy(item.def_id);
1357 if !item.vis.is_accessible_from(def_scope, tcx) {
1358 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
1359 tcx.sess.span_err(span, &msg);
1361 tcx.check_stability(item.def_id, Some(ref_id), span);
1366 fn qpath_to_ty(&self,
1368 opt_self_ty: Option<Ty<'tcx>>,
1370 trait_segment: &hir::PathSegment,
1371 item_segment: &hir::PathSegment)
1374 let tcx = self.tcx();
1375 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
1377 self.prohibit_generics(slice::from_ref(item_segment));
1379 let self_ty = if let Some(ty) = opt_self_ty {
1382 let path_str = tcx.item_path_str(trait_def_id);
1383 self.report_ambiguous_associated_type(span,
1386 &item_segment.ident.as_str());
1387 return tcx.types.err;
1390 debug!("qpath_to_ty: self_type={:?}", self_ty);
1392 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1397 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1399 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1402 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(&self, segments: T) {
1403 for segment in segments {
1404 segment.with_generic_args(|generic_args| {
1405 let (mut err_for_lt, mut err_for_ty) = (false, false);
1406 for arg in &generic_args.args {
1407 let (mut span_err, span, kind) = match arg {
1408 hir::GenericArg::Lifetime(lt) => {
1409 if err_for_lt { continue }
1411 (struct_span_err!(self.tcx().sess, lt.span, E0110,
1412 "lifetime parameters are not allowed on this type"),
1416 hir::GenericArg::Type(ty) => {
1417 if err_for_ty { continue }
1419 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1420 "type parameters are not allowed on this type"),
1425 span_err.span_label(span, format!("{} parameter not allowed", kind))
1427 if err_for_lt && err_for_ty {
1431 for binding in &generic_args.bindings {
1432 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1439 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt, span: Span) {
1440 let mut err = struct_span_err!(tcx.sess, span, E0229,
1441 "associated type bindings are not allowed here");
1442 err.span_label(span, "associated type not allowed here").emit();
1445 // Check a type `Path` and convert it to a `Ty`.
1446 pub fn def_to_ty(&self,
1447 opt_self_ty: Option<Ty<'tcx>>,
1449 permit_variants: bool)
1451 let tcx = self.tcx();
1453 debug!("def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1454 path.def, opt_self_ty, path.segments);
1456 let span = path.span;
1458 Def::Existential(did) => {
1459 // Check for desugared impl trait.
1460 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1461 let item_segment = path.segments.split_last().unwrap();
1462 self.prohibit_generics(item_segment.1);
1463 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1466 tcx.mk_opaque(did, substs),
1469 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1470 Def::Union(did) | Def::ForeignTy(did) => {
1471 assert_eq!(opt_self_ty, None);
1472 self.prohibit_generics(path.segments.split_last().unwrap().1);
1473 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1475 Def::Variant(did) if permit_variants => {
1476 // Convert "variant type" as if it were a real type.
1477 // The resulting `Ty` is type of the variant's enum for now.
1478 assert_eq!(opt_self_ty, None);
1479 self.prohibit_generics(path.segments.split_last().unwrap().1);
1480 self.ast_path_to_ty(span,
1481 tcx.parent_def_id(did).unwrap(),
1482 path.segments.last().unwrap())
1484 Def::TyParam(did) => {
1485 assert_eq!(opt_self_ty, None);
1486 self.prohibit_generics(&path.segments);
1488 let node_id = tcx.hir().as_local_node_id(did).unwrap();
1489 let item_id = tcx.hir().get_parent_node(node_id);
1490 let item_def_id = tcx.hir().local_def_id(item_id);
1491 let generics = tcx.generics_of(item_def_id);
1492 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(node_id)];
1493 tcx.mk_ty_param(index, tcx.hir().name(node_id).as_interned_str())
1495 Def::SelfTy(_, Some(def_id)) => {
1496 // `Self` in impl (we know the concrete type)
1498 assert_eq!(opt_self_ty, None);
1499 self.prohibit_generics(&path.segments);
1501 tcx.at(span).type_of(def_id)
1503 Def::SelfTy(Some(_), None) => {
1505 assert_eq!(opt_self_ty, None);
1506 self.prohibit_generics(&path.segments);
1509 Def::AssociatedTy(def_id) => {
1510 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1511 self.qpath_to_ty(span,
1514 &path.segments[path.segments.len()-2],
1515 path.segments.last().unwrap())
1517 Def::PrimTy(prim_ty) => {
1518 assert_eq!(opt_self_ty, None);
1519 self.prohibit_generics(&path.segments);
1521 hir::Bool => tcx.types.bool,
1522 hir::Char => tcx.types.char,
1523 hir::Int(it) => tcx.mk_mach_int(it),
1524 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1525 hir::Float(ft) => tcx.mk_mach_float(ft),
1526 hir::Str => tcx.mk_str()
1530 self.set_tainted_by_errors();
1531 return self.tcx().types.err;
1533 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1537 /// Parses the programmer's textual representation of a type into our
1538 /// internal notion of a type.
1539 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1540 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1541 ast_ty.id, ast_ty, ast_ty.node);
1543 let tcx = self.tcx();
1545 let result_ty = match ast_ty.node {
1546 hir::TyKind::Slice(ref ty) => {
1547 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1549 hir::TyKind::Ptr(ref mt) => {
1550 tcx.mk_ptr(ty::TypeAndMut {
1551 ty: self.ast_ty_to_ty(&mt.ty),
1555 hir::TyKind::Rptr(ref region, ref mt) => {
1556 let r = self.ast_region_to_region(region, None);
1557 debug!("Ref r={:?}", r);
1558 let t = self.ast_ty_to_ty(&mt.ty);
1559 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1561 hir::TyKind::Never => {
1564 hir::TyKind::Tup(ref fields) => {
1565 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1567 hir::TyKind::BareFn(ref bf) => {
1568 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1569 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1571 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1572 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1574 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1575 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1576 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1577 self.ast_ty_to_ty(qself)
1579 self.def_to_ty(opt_self_ty, path, false)
1581 hir::TyKind::Def(item_id, ref lifetimes) => {
1582 let did = tcx.hir().local_def_id(item_id.id);
1583 self.impl_trait_ty_to_ty(did, lifetimes)
1585 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1586 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1587 let ty = self.ast_ty_to_ty(qself);
1589 let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1594 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1596 hir::TyKind::Array(ref ty, ref length) => {
1597 let length_def_id = tcx.hir().local_def_id(length.id);
1598 let substs = Substs::identity_for_item(tcx, length_def_id);
1599 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1600 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1601 self.normalize_ty(ast_ty.span, array_ty)
1603 hir::TyKind::Typeof(ref _e) => {
1604 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1605 "`typeof` is a reserved keyword but unimplemented")
1606 .span_label(ast_ty.span, "reserved keyword")
1611 hir::TyKind::Infer => {
1612 // Infer also appears as the type of arguments or return
1613 // values in a ExprKind::Closure, or as
1614 // the type of local variables. Both of these cases are
1615 // handled specially and will not descend into this routine.
1616 self.ty_infer(ast_ty.span)
1618 hir::TyKind::Err => {
1623 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1627 pub fn impl_trait_ty_to_ty(
1630 lifetimes: &[hir::GenericArg],
1632 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1633 let tcx = self.tcx();
1635 let generics = tcx.generics_of(def_id);
1637 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1638 let substs = Substs::for_item(tcx, def_id, |param, _| {
1639 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1640 // Our own parameters are the resolved lifetimes.
1642 GenericParamDefKind::Lifetime => {
1643 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1644 self.ast_region_to_region(lifetime, None).into()
1652 // Replace all parent lifetimes with 'static.
1654 GenericParamDefKind::Lifetime => {
1655 tcx.types.re_static.into()
1657 _ => tcx.mk_param_from_def(param)
1661 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1663 let ty = tcx.mk_opaque(def_id, substs);
1664 debug!("impl_trait_ty_to_ty: {}", ty);
1668 pub fn ty_of_arg(&self,
1670 expected_ty: Option<Ty<'tcx>>)
1674 hir::TyKind::Infer if expected_ty.is_some() => {
1675 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1676 expected_ty.unwrap()
1678 _ => self.ast_ty_to_ty(ty),
1682 pub fn ty_of_fn(&self,
1683 unsafety: hir::Unsafety,
1686 -> ty::PolyFnSig<'tcx> {
1689 let tcx = self.tcx();
1691 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
1693 let output_ty = match decl.output {
1694 hir::Return(ref output) => self.ast_ty_to_ty(output),
1695 hir::DefaultReturn(..) => tcx.mk_unit(),
1698 debug!("ty_of_fn: output_ty={:?}", output_ty);
1700 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1708 // Find any late-bound regions declared in return type that do
1709 // not appear in the arguments. These are not well-formed.
1712 // for<'a> fn() -> &'a str <-- 'a is bad
1713 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1714 let inputs = bare_fn_ty.inputs();
1715 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1716 &inputs.map_bound(|i| i.to_owned()));
1717 let output = bare_fn_ty.output();
1718 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1719 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1720 let lifetime_name = match *br {
1721 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1722 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
1724 let mut err = struct_span_err!(tcx.sess,
1727 "return type references {} \
1728 which is not constrained by the fn input types",
1730 if let ty::BrAnon(_) = *br {
1731 // The only way for an anonymous lifetime to wind up
1732 // in the return type but **also** be unconstrained is
1733 // if it only appears in "associated types" in the
1734 // input. See #47511 for an example. In this case,
1735 // though we can easily give a hint that ought to be
1737 err.note("lifetimes appearing in an associated type \
1738 are not considered constrained");
1746 /// Given the bounds on an object, determines what single region bound (if any) we can
1747 /// use to summarize this type. The basic idea is that we will use the bound the user
1748 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1749 /// for region bounds. It may be that we can derive no bound at all, in which case
1750 /// we return `None`.
1751 fn compute_object_lifetime_bound(&self,
1753 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
1754 -> Option<ty::Region<'tcx>> // if None, use the default
1756 let tcx = self.tcx();
1758 debug!("compute_opt_region_bound(existential_predicates={:?})",
1759 existential_predicates);
1761 // No explicit region bound specified. Therefore, examine trait
1762 // bounds and see if we can derive region bounds from those.
1763 let derived_region_bounds =
1764 object_region_bounds(tcx, existential_predicates);
1766 // If there are no derived region bounds, then report back that we
1767 // can find no region bound. The caller will use the default.
1768 if derived_region_bounds.is_empty() {
1772 // If any of the derived region bounds are 'static, that is always
1774 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1775 return Some(tcx.types.re_static);
1778 // Determine whether there is exactly one unique region in the set
1779 // of derived region bounds. If so, use that. Otherwise, report an
1781 let r = derived_region_bounds[0];
1782 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1783 span_err!(tcx.sess, span, E0227,
1784 "ambiguous lifetime bound, explicit lifetime bound required");
1790 /// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
1791 /// remaining general trait bounds.
1792 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1793 trait_bounds: &'b [hir::PolyTraitRef])
1794 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1796 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1797 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1798 match bound.trait_ref.path.def {
1799 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1806 let auto_traits = auto_traits.into_iter().map(|tr| {
1807 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1812 }).collect::<Vec<_>>();
1814 (auto_traits, trait_bounds)
1817 // A helper struct for conveniently grouping a set of bounds which we pass to
1818 // and return from functions in multiple places.
1819 #[derive(PartialEq, Eq, Clone, Debug)]
1820 pub struct Bounds<'tcx> {
1821 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
1822 pub implicitly_sized: Option<Span>,
1823 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
1824 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
1827 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1828 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1829 -> Vec<(ty::Predicate<'tcx>, Span)>
1831 // If it could be sized, and is, add the sized predicate
1832 let sized_predicate = self.implicitly_sized.and_then(|span| {
1833 tcx.lang_items().sized_trait().map(|sized| {
1834 let trait_ref = ty::TraitRef {
1836 substs: tcx.mk_substs_trait(param_ty, &[])
1838 (trait_ref.to_predicate(), span)
1842 sized_predicate.into_iter().chain(
1843 self.region_bounds.iter().map(|&(region_bound, span)| {
1844 // account for the binder being introduced below; no need to shift `param_ty`
1845 // because, at present at least, it can only refer to early-bound regions
1846 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
1847 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
1848 (ty::Binder::dummy(outlives).to_predicate(), span)
1850 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
1851 (bound_trait_ref.to_predicate(), span)
1854 self.projection_bounds.iter().map(|&(projection, span)| {
1855 (projection.to_predicate(), span)