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 rustc_data_structures::accumulate_vec::AccumulateVec;
16 use hir::{self, GenericArg};
18 use hir::def_id::DefId;
19 use middle::resolve_lifetime as rl;
20 use namespace::Namespace;
21 use rustc::ty::subst::{Subst, Substs};
23 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
24 use rustc::ty::GenericParamDefKind;
25 use rustc::ty::wf::object_region_bounds;
26 use rustc_target::spec::abi;
28 use require_c_abi_if_variadic;
29 use util::common::ErrorReported;
30 use util::nodemap::{FxHashSet, FxHashMap};
31 use errors::FatalError;
35 use syntax::feature_gate::{GateIssue, emit_feature_err};
38 pub trait AstConv<'gcx, 'tcx> {
39 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
41 /// Returns the set of bounds in scope for the type parameter with
43 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
44 -> ty::GenericPredicates<'tcx>;
46 /// What lifetime should we use when a lifetime is omitted (and not elided)?
47 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
48 -> Option<ty::Region<'tcx>>;
50 /// What type should we use when a type is omitted?
51 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
53 /// Same as ty_infer, but with a known type parameter definition.
54 fn ty_infer_for_def(&self,
55 _def: &ty::GenericParamDef,
56 span: Span) -> Ty<'tcx> {
60 /// Projecting an associated type from a (potentially)
61 /// higher-ranked trait reference is more complicated, because of
62 /// the possibility of late-bound regions appearing in the
63 /// associated type binding. This is not legal in function
64 /// signatures for that reason. In a function body, we can always
65 /// handle it because we can use inference variables to remove the
66 /// late-bound regions.
67 fn projected_ty_from_poly_trait_ref(&self,
70 poly_trait_ref: ty::PolyTraitRef<'tcx>)
73 /// Normalize an associated type coming from the user.
74 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
76 /// Invoked when we encounter an error from some prior pass
77 /// (e.g. resolve) that is translated into a ty-error. This is
78 /// used to help suppress derived errors typeck might otherwise
80 fn set_tainted_by_errors(&self);
82 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
85 struct ConvertedBinding<'tcx> {
96 /// Dummy type used for the `Self` of a `TraitRef` created for converting
97 /// a trait object, and which gets removed in `ExistentialTraitRef`.
98 /// This type must not appear anywhere in other converted types.
99 const TRAIT_OBJECT_DUMMY_SELF: ty::TypeVariants<'static> = ty::TyInfer(ty::FreshTy(0));
101 impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
102 pub fn ast_region_to_region(&self,
103 lifetime: &hir::Lifetime,
104 def: Option<&ty::GenericParamDef>)
107 let tcx = self.tcx();
108 let lifetime_name = |def_id| {
109 tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap()).as_interned_str()
112 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
113 let r = match tcx.named_region(hir_id) {
114 Some(rl::Region::Static) => {
118 Some(rl::Region::LateBound(debruijn, id, _)) => {
119 let name = lifetime_name(id);
120 tcx.mk_region(ty::ReLateBound(debruijn,
121 ty::BrNamed(id, name)))
124 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
125 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
128 Some(rl::Region::EarlyBound(index, id, _)) => {
129 let name = lifetime_name(id);
130 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
137 Some(rl::Region::Free(scope, id)) => {
138 let name = lifetime_name(id);
139 tcx.mk_region(ty::ReFree(ty::FreeRegion {
141 bound_region: ty::BrNamed(id, name)
144 // (*) -- not late-bound, won't change
148 self.re_infer(lifetime.span, def)
150 // This indicates an illegal lifetime
151 // elision. `resolve_lifetime` should have
152 // reported an error in this case -- but if
153 // not, let's error out.
154 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
156 // Supply some dummy value. We don't have an
157 // `re_error`, annoyingly, so use `'static`.
163 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
170 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
171 /// returns an appropriate set of substitutions for this particular reference to `I`.
172 pub fn ast_path_substs_for_ty(&self,
175 item_segment: &hir::PathSegment)
176 -> &'tcx Substs<'tcx>
179 let (substs, assoc_bindings) =
180 item_segment.with_generic_args(|generic_args| {
181 self.create_substs_for_ast_path(
185 item_segment.infer_types,
189 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
194 /// Given the type/region arguments provided to some path (along with
195 /// an implicit Self, if this is a trait reference) returns the complete
196 /// set of substitutions. This may involve applying defaulted type parameters.
198 /// Note that the type listing given here is *exactly* what the user provided.
199 fn create_substs_for_ast_path(&self,
202 generic_args: &hir::GenericArgs,
204 self_ty: Option<Ty<'tcx>>)
205 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
207 let tcx = self.tcx();
209 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
211 def_id, self_ty, generic_args);
213 // If the type is parameterized by this region, then replace this
214 // region with the current anon region binding (in other words,
215 // whatever & would get replaced with).
216 let mut lt_provided = 0;
217 let mut ty_provided = 0;
218 for arg in &generic_args.args {
220 GenericArg::Lifetime(_) => lt_provided += 1,
221 GenericArg::Type(_) => ty_provided += 1,
225 let decl_generics = tcx.generics_of(def_id);
226 let mut lt_accepted = 0;
227 let mut ty_params = ParamRange { required: 0, accepted: 0 };
228 for param in &decl_generics.params {
230 GenericParamDefKind::Lifetime => {
233 GenericParamDefKind::Type { has_default, .. } => {
234 ty_params.accepted += 1;
236 ty_params.required += 1;
241 if self_ty.is_some() {
242 ty_params.required -= 1;
243 ty_params.accepted -= 1;
246 if lt_accepted != lt_provided {
247 report_lifetime_number_error(tcx, span, lt_provided, lt_accepted);
250 // If a self-type was declared, one should be provided.
251 assert_eq!(decl_generics.has_self, self_ty.is_some());
253 // Check the number of type parameters supplied by the user.
254 if !infer_types || ty_provided > ty_params.required {
255 check_type_argument_count(tcx, span, ty_provided, ty_params);
258 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
259 let default_needs_object_self = |param: &ty::GenericParamDef| {
260 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
261 if is_object && has_default {
262 if tcx.at(span).type_of(param.def_id).has_self_ty() {
263 // There is no suitable inference default for a type parameter
264 // that references self, in an object type.
273 let own_self = self_ty.is_some() as usize;
274 // FIXME(varkor): Separating out the parameters is messy.
275 let lifetimes: Vec<_> = generic_args.args.iter().filter_map(|arg| match arg {
276 GenericArg::Lifetime(lt) => Some(lt),
279 let types: Vec<_> = generic_args.args.iter().filter_map(|arg| match arg {
280 GenericArg::Type(ty) => Some(ty),
283 let substs = Substs::for_item(tcx, def_id, |param, substs| {
285 GenericParamDefKind::Lifetime => {
286 let i = param.index as usize - own_self;
287 if let Some(lt) = lifetimes.get(i) {
288 self.ast_region_to_region(lt, Some(param)).into()
290 tcx.types.re_static.into()
293 GenericParamDefKind::Type { has_default, .. } => {
294 let i = param.index as usize;
296 // Handle Self first, so we can adjust the index to match the AST.
297 if let (0, Some(ty)) = (i, self_ty) {
301 let i = i - (lt_accepted + own_self);
303 // A provided type parameter.
304 self.ast_ty_to_ty(&types[i]).into()
305 } else if infer_types {
306 // No type parameters were provided, we can infer all.
307 if !default_needs_object_self(param) {
308 self.ty_infer_for_def(param, span).into()
310 self.ty_infer(span).into()
312 } else if has_default {
313 // No type parameter provided, but a default exists.
315 // If we are converting an object type, then the
316 // `Self` parameter is unknown. However, some of the
317 // other type parameters may reference `Self` in their
318 // defaults. This will lead to an ICE if we are not
320 if default_needs_object_self(param) {
321 struct_span_err!(tcx.sess, span, E0393,
322 "the type parameter `{}` must be explicitly \
326 format!("missing reference to `{}`", param.name))
327 .note(&format!("because of the default `Self` reference, \
328 type parameters must be specified on object \
333 // This is a default type parameter.
336 tcx.at(span).type_of(param.def_id)
337 .subst_spanned(tcx, substs, Some(span))
341 // We've already errored above about the mismatch.
348 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
350 item_name: binding.name,
351 ty: self.ast_ty_to_ty(&binding.ty),
356 debug!("create_substs_for_ast_path(decl_generics={:?}, self_ty={:?}) -> {:?}",
357 decl_generics, self_ty, substs);
359 (substs, assoc_bindings)
362 /// Instantiates the path for the given trait reference, assuming that it's
363 /// bound to a valid trait type. Returns the def_id for the defining trait.
364 /// The type _cannot_ be a type other than a trait type.
366 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
367 /// are disallowed. Otherwise, they are pushed onto the vector given.
368 pub fn instantiate_mono_trait_ref(&self,
369 trait_ref: &hir::TraitRef,
371 -> ty::TraitRef<'tcx>
373 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
375 let trait_def_id = self.trait_def_id(trait_ref);
376 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
379 trait_ref.path.segments.last().unwrap())
382 /// Get the DefId of the given trait ref. It _must_ actually be a trait.
383 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
384 let path = &trait_ref.path;
386 Def::Trait(trait_def_id) => trait_def_id,
387 Def::TraitAlias(alias_def_id) => alias_def_id,
395 /// The given `trait_ref` must actually be trait.
396 pub(super) fn instantiate_poly_trait_ref_inner(&self,
397 trait_ref: &hir::TraitRef,
399 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>,
401 -> ty::PolyTraitRef<'tcx>
403 let trait_def_id = self.trait_def_id(trait_ref);
405 debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
407 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
409 let (substs, assoc_bindings) =
410 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
413 trait_ref.path.segments.last().unwrap());
414 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
416 let mut dup_bindings = FxHashMap::default();
417 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
418 // specify type to assert that error was already reported in Err case:
419 let predicate: Result<_, ErrorReported> =
420 self.ast_type_binding_to_poly_projection_predicate(
421 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
422 predicate.ok() // ok to ignore Err() because ErrorReported (see above)
425 debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
426 trait_ref, poly_projections, poly_trait_ref);
430 pub fn instantiate_poly_trait_ref(&self,
431 poly_trait_ref: &hir::PolyTraitRef,
433 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
434 -> ty::PolyTraitRef<'tcx>
436 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
437 poly_projections, false)
440 fn ast_path_to_mono_trait_ref(&self,
444 trait_segment: &hir::PathSegment)
445 -> ty::TraitRef<'tcx>
447 let (substs, assoc_bindings) =
448 self.create_substs_for_ast_trait_ref(span,
452 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
453 ty::TraitRef::new(trait_def_id, substs)
456 fn create_substs_for_ast_trait_ref(&self,
460 trait_segment: &hir::PathSegment)
461 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
463 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
466 let trait_def = self.tcx().trait_def(trait_def_id);
468 if !self.tcx().features().unboxed_closures &&
469 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
470 != trait_def.paren_sugar {
471 // For now, require that parenthetical notation be used only with `Fn()` etc.
472 let msg = if trait_def.paren_sugar {
473 "the precise format of `Fn`-family traits' type parameters is subject to change. \
474 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
476 "parenthetical notation is only stable when used with `Fn`-family traits"
478 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
479 span, GateIssue::Language, msg);
482 trait_segment.with_generic_args(|generic_args| {
483 self.create_substs_for_ast_path(span,
486 trait_segment.infer_types,
491 fn trait_defines_associated_type_named(&self,
493 assoc_name: ast::Name)
496 self.tcx().associated_items(trait_def_id).any(|item| {
497 item.kind == ty::AssociatedKind::Type &&
498 self.tcx().hygienic_eq(assoc_name, item.name, trait_def_id)
502 fn ast_type_binding_to_poly_projection_predicate(
505 trait_ref: ty::PolyTraitRef<'tcx>,
506 binding: &ConvertedBinding<'tcx>,
508 dup_bindings: &mut FxHashMap<DefId, Span>)
509 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
511 let tcx = self.tcx();
514 // Given something like `U : SomeTrait<T=X>`, we want to produce a
515 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
516 // subtle in the event that `T` is defined in a supertrait of
517 // `SomeTrait`, because in that case we need to upcast.
519 // That is, consider this case:
522 // trait SubTrait : SuperTrait<int> { }
523 // trait SuperTrait<A> { type T; }
525 // ... B : SubTrait<T=foo> ...
528 // We want to produce `<B as SuperTrait<int>>::T == foo`.
530 // Find any late-bound regions declared in `ty` that are not
531 // declared in the trait-ref. These are not wellformed.
535 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
536 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
537 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
538 let late_bound_in_ty =
539 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
540 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
541 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
542 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
543 let br_name = match *br {
544 ty::BrNamed(_, name) => name,
548 "anonymous bound region {:?} in binding but not trait ref",
552 struct_span_err!(tcx.sess,
555 "binding for associated type `{}` references lifetime `{}`, \
556 which does not appear in the trait input types",
557 binding.item_name, br_name)
562 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
564 // Simple case: X is defined in the current trait.
567 // Otherwise, we have to walk through the supertraits to find
569 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
570 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
572 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
573 binding.item_name, binding.span)
576 let (assoc_ident, def_scope) =
577 tcx.adjust_ident(binding.item_name.to_ident(), candidate.def_id(), ref_id);
578 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
579 i.kind == ty::AssociatedKind::Type && i.name.to_ident() == assoc_ident
580 }).expect("missing associated type");
582 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
583 let msg = format!("associated type `{}` is private", binding.item_name);
584 tcx.sess.span_err(binding.span, &msg);
586 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
589 dup_bindings.entry(assoc_ty.def_id)
590 .and_modify(|prev_span| {
591 let mut err = self.tcx().struct_span_lint_node(
592 ::rustc::lint::builtin::DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
595 &format!("associated type binding `{}` specified more than once",
598 err.span_label(binding.span, "used more than once");
599 err.span_label(*prev_span, format!("first use of `{}`", binding.item_name));
602 .or_insert(binding.span);
605 Ok(candidate.map_bound(|trait_ref| {
606 ty::ProjectionPredicate {
607 projection_ty: ty::ProjectionTy::from_ref_and_name(
617 fn ast_path_to_ty(&self,
620 item_segment: &hir::PathSegment)
623 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
626 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
630 /// Transform a PolyTraitRef into a PolyExistentialTraitRef by
631 /// removing the dummy Self type (TRAIT_OBJECT_DUMMY_SELF).
632 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
633 -> ty::ExistentialTraitRef<'tcx> {
634 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
635 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
638 fn conv_object_ty_poly_trait_ref(&self,
640 trait_bounds: &[hir::PolyTraitRef],
641 lifetime: &hir::Lifetime)
644 let tcx = self.tcx();
646 if trait_bounds.is_empty() {
647 span_err!(tcx.sess, span, E0224,
648 "at least one non-builtin trait is required for an object type");
649 return tcx.types.err;
652 let mut projection_bounds = vec![];
653 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
654 let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
656 &mut projection_bounds);
658 for trait_bound in trait_bounds[1..].iter() {
659 // Sanity check for non-principal trait bounds
660 self.instantiate_poly_trait_ref(trait_bound,
665 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
667 if !trait_bounds.is_empty() {
668 let b = &trait_bounds[0];
669 let span = b.trait_ref.path.span;
670 struct_span_err!(self.tcx().sess, span, E0225,
671 "only auto traits can be used as additional traits in a trait object")
672 .span_label(span, "non-auto additional trait")
676 // Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
677 let existential_principal = principal.map_bound(|trait_ref| {
678 self.trait_ref_to_existential(trait_ref)
680 let existential_projections = projection_bounds.iter().map(|bound| {
681 bound.map_bound(|b| {
682 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
683 ty::ExistentialProjection {
685 item_def_id: b.projection_ty.item_def_id,
686 substs: trait_ref.substs,
691 // check that there are no gross object safety violations,
692 // most importantly, that the supertraits don't contain Self,
694 let object_safety_violations =
695 tcx.astconv_object_safety_violations(principal.def_id());
696 if !object_safety_violations.is_empty() {
697 tcx.report_object_safety_error(
698 span, principal.def_id(), object_safety_violations)
700 return tcx.types.err;
703 let mut associated_types = FxHashSet::default();
704 for tr in traits::supertraits(tcx, principal) {
705 associated_types.extend(tcx.associated_items(tr.def_id())
706 .filter(|item| item.kind == ty::AssociatedKind::Type)
707 .map(|item| item.def_id));
710 for projection_bound in &projection_bounds {
711 associated_types.remove(&projection_bound.projection_def_id());
714 for item_def_id in associated_types {
715 let assoc_item = tcx.associated_item(item_def_id);
716 let trait_def_id = assoc_item.container.id();
717 struct_span_err!(tcx.sess, span, E0191,
718 "the value of the associated type `{}` (from the trait `{}`) must be specified",
720 tcx.item_path_str(trait_def_id))
721 .span_label(span, format!(
722 "missing associated type `{}` value", assoc_item.name))
726 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
730 // skip_binder is okay, because the predicates are re-bound.
732 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
733 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
734 .chain(existential_projections
735 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
736 .collect::<AccumulateVec<[_; 8]>>();
737 v.sort_by(|a, b| a.stable_cmp(tcx, b));
738 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
741 // Explicitly specified region bound. Use that.
742 let region_bound = if !lifetime.is_elided() {
743 self.ast_region_to_region(lifetime, None)
745 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
746 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
747 if tcx.named_region(hir_id).is_some() {
748 self.ast_region_to_region(lifetime, None)
750 self.re_infer(span, None).unwrap_or_else(|| {
751 span_err!(tcx.sess, span, E0228,
752 "the lifetime bound for this object type cannot be deduced \
753 from context; please supply an explicit bound");
760 debug!("region_bound: {:?}", region_bound);
762 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
763 debug!("trait_object_type: {:?}", ty);
767 fn report_ambiguous_associated_type(&self,
772 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
773 .span_label(span, "ambiguous associated type")
774 .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
775 type_str, trait_str, name))
780 // Search for a bound on a type parameter which includes the associated item
781 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
782 // This function will fail if there are no suitable bounds or there is
784 fn find_bound_for_assoc_item(&self,
785 ty_param_def_id: DefId,
786 assoc_name: ast::Name,
788 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
790 let tcx = self.tcx();
792 let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
793 .predicates.into_iter().filter_map(|p| p.to_opt_poly_trait_ref()).collect();
795 // Check that there is exactly one way to find an associated type with the
797 let suitable_bounds =
798 traits::transitive_bounds(tcx, &bounds)
799 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
801 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
802 let param_name = tcx.hir.ty_param_name(param_node_id);
803 self.one_bound_for_assoc_type(suitable_bounds,
804 ¶m_name.as_str(),
810 // Checks that bounds contains exactly one element and reports appropriate
812 fn one_bound_for_assoc_type<I>(&self,
815 assoc_name: ast::Name,
817 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
818 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
820 let bound = match bounds.next() {
821 Some(bound) => bound,
823 struct_span_err!(self.tcx().sess, span, E0220,
824 "associated type `{}` not found for `{}`",
827 .span_label(span, format!("associated type `{}` not found", assoc_name))
829 return Err(ErrorReported);
833 if let Some(bound2) = bounds.next() {
834 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
835 let mut err = struct_span_err!(
836 self.tcx().sess, span, E0221,
837 "ambiguous associated type `{}` in bounds of `{}`",
840 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
842 for bound in bounds {
843 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
844 item.kind == ty::AssociatedKind::Type &&
845 self.tcx().hygienic_eq(assoc_name, item.name, bound.def_id())
847 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
849 if let Some(span) = bound_span {
850 err.span_label(span, format!("ambiguous `{}` from `{}`",
854 span_note!(&mut err, span,
855 "associated type `{}` could derive from `{}`",
866 // Create a type from a path to an associated type.
867 // For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
868 // and item_segment is the path segment for D. We return a type and a def for
870 // Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
871 // parameter or Self.
872 pub fn associated_path_def_to_ty(&self,
877 item_segment: &hir::PathSegment)
880 let tcx = self.tcx();
881 let assoc_name = item_segment.name;
883 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
885 self.prohibit_generics(slice::from_ref(item_segment));
887 // Find the type of the associated item, and the trait where the associated
889 let bound = match (&ty.sty, ty_path_def) {
890 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
891 // `Self` in an impl of a trait - we have a concrete self type and a
893 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
894 Some(trait_ref) => trait_ref,
896 // A cycle error occurred, most likely.
897 return (tcx.types.err, Def::Err);
902 traits::supertraits(tcx, ty::Binder::bind(trait_ref))
903 .filter(|r| self.trait_defines_associated_type_named(r.def_id(),
906 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
908 Err(ErrorReported) => return (tcx.types.err, Def::Err),
911 (&ty::TyParam(_), Def::SelfTy(Some(param_did), None)) |
912 (&ty::TyParam(_), Def::TyParam(param_did)) => {
913 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
915 Err(ErrorReported) => return (tcx.types.err, Def::Err),
919 // Don't print TyErr to the user.
920 if !ty.references_error() {
921 self.report_ambiguous_associated_type(span,
924 &assoc_name.as_str());
926 return (tcx.types.err, Def::Err);
930 let trait_did = bound.def_id();
931 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name.to_ident(), trait_did, ref_id);
932 let item = tcx.associated_items(trait_did).find(|i| {
933 Namespace::from(i.kind) == Namespace::Type &&
934 i.name.to_ident() == assoc_ident
936 .expect("missing associated type");
938 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
939 let ty = self.normalize_ty(span, ty);
941 let def = Def::AssociatedTy(item.def_id);
942 if !item.vis.is_accessible_from(def_scope, tcx) {
943 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
944 tcx.sess.span_err(span, &msg);
946 tcx.check_stability(item.def_id, Some(ref_id), span);
951 fn qpath_to_ty(&self,
953 opt_self_ty: Option<Ty<'tcx>>,
955 trait_segment: &hir::PathSegment,
956 item_segment: &hir::PathSegment)
959 let tcx = self.tcx();
960 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
962 self.prohibit_generics(slice::from_ref(item_segment));
964 let self_ty = if let Some(ty) = opt_self_ty {
967 let path_str = tcx.item_path_str(trait_def_id);
968 self.report_ambiguous_associated_type(span,
971 &item_segment.name.as_str());
972 return tcx.types.err;
975 debug!("qpath_to_ty: self_type={:?}", self_ty);
977 let trait_ref = self.ast_path_to_mono_trait_ref(span,
982 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
984 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
987 pub fn prohibit_generics(&self, segments: &[hir::PathSegment]) {
988 for segment in segments {
989 segment.with_generic_args(|generic_args| {
990 let (mut err_for_lt, mut err_for_ty) = (false, false);
991 for arg in &generic_args.args {
992 let (mut span_err, span, kind) = match arg {
993 hir::GenericArg::Lifetime(lt) => {
994 if err_for_lt { continue }
996 (struct_span_err!(self.tcx().sess, lt.span, E0110,
997 "lifetime parameters are not allowed on \
1002 hir::GenericArg::Type(ty) => {
1003 if err_for_ty { continue }
1005 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1006 "type parameters are not allowed on this type"),
1011 span_err.span_label(span, format!("{} parameter not allowed", kind))
1013 if err_for_lt && err_for_ty {
1017 for binding in &generic_args.bindings {
1018 self.prohibit_projection(binding.span);
1025 pub fn prohibit_projection(&self, span: Span) {
1026 let mut err = struct_span_err!(self.tcx().sess, span, E0229,
1027 "associated type bindings are not allowed here");
1028 err.span_label(span, "associated type not allowed here").emit();
1031 // Check a type Path and convert it to a Ty.
1032 pub fn def_to_ty(&self,
1033 opt_self_ty: Option<Ty<'tcx>>,
1035 permit_variants: bool)
1037 let tcx = self.tcx();
1039 debug!("base_def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1040 path.def, opt_self_ty, path.segments);
1042 let span = path.span;
1044 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1045 Def::Union(did) | Def::TyForeign(did) => {
1046 assert_eq!(opt_self_ty, None);
1047 self.prohibit_generics(path.segments.split_last().unwrap().1);
1048 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1050 Def::Variant(did) if permit_variants => {
1051 // Convert "variant type" as if it were a real type.
1052 // The resulting `Ty` is type of the variant's enum for now.
1053 assert_eq!(opt_self_ty, None);
1054 self.prohibit_generics(path.segments.split_last().unwrap().1);
1055 self.ast_path_to_ty(span,
1056 tcx.parent_def_id(did).unwrap(),
1057 path.segments.last().unwrap())
1059 Def::TyParam(did) => {
1060 assert_eq!(opt_self_ty, None);
1061 self.prohibit_generics(&path.segments);
1063 let node_id = tcx.hir.as_local_node_id(did).unwrap();
1064 let item_id = tcx.hir.get_parent_node(node_id);
1065 let item_def_id = tcx.hir.local_def_id(item_id);
1066 let generics = tcx.generics_of(item_def_id);
1067 let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
1068 tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
1070 Def::SelfTy(_, Some(def_id)) => {
1071 // Self in impl (we know the concrete type).
1073 assert_eq!(opt_self_ty, None);
1074 self.prohibit_generics(&path.segments);
1076 tcx.at(span).type_of(def_id)
1078 Def::SelfTy(Some(_), None) => {
1080 assert_eq!(opt_self_ty, None);
1081 self.prohibit_generics(&path.segments);
1084 Def::AssociatedTy(def_id) => {
1085 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1086 self.qpath_to_ty(span,
1089 &path.segments[path.segments.len()-2],
1090 path.segments.last().unwrap())
1092 Def::PrimTy(prim_ty) => {
1093 assert_eq!(opt_self_ty, None);
1094 self.prohibit_generics(&path.segments);
1096 hir::TyBool => tcx.types.bool,
1097 hir::TyChar => tcx.types.char,
1098 hir::TyInt(it) => tcx.mk_mach_int(it),
1099 hir::TyUint(uit) => tcx.mk_mach_uint(uit),
1100 hir::TyFloat(ft) => tcx.mk_mach_float(ft),
1101 hir::TyStr => tcx.mk_str()
1105 self.set_tainted_by_errors();
1106 return self.tcx().types.err;
1108 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1112 /// Parses the programmer's textual representation of a type into our
1113 /// internal notion of a type.
1114 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1115 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
1118 let tcx = self.tcx();
1120 let result_ty = match ast_ty.node {
1121 hir::TySlice(ref ty) => {
1122 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1124 hir::TyPtr(ref mt) => {
1125 tcx.mk_ptr(ty::TypeAndMut {
1126 ty: self.ast_ty_to_ty(&mt.ty),
1130 hir::TyRptr(ref region, ref mt) => {
1131 let r = self.ast_region_to_region(region, None);
1132 debug!("TyRef r={:?}", r);
1133 let t = self.ast_ty_to_ty(&mt.ty);
1134 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1139 hir::TyTup(ref fields) => {
1140 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1142 hir::TyBareFn(ref bf) => {
1143 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1144 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1146 hir::TyTraitObject(ref bounds, ref lifetime) => {
1147 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1149 hir::TyImplTraitExistential(_, def_id, ref lifetimes) => {
1150 self.impl_trait_ty_to_ty(def_id, lifetimes)
1152 hir::TyPath(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1153 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1154 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1155 self.ast_ty_to_ty(qself)
1157 self.def_to_ty(opt_self_ty, path, false)
1159 hir::TyPath(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1160 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1161 let ty = self.ast_ty_to_ty(qself);
1163 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
1168 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1170 hir::TyArray(ref ty, ref length) => {
1171 let length_def_id = tcx.hir.local_def_id(length.id);
1172 let substs = Substs::identity_for_item(tcx, length_def_id);
1173 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1174 let array_ty = tcx.mk_ty(ty::TyArray(self.ast_ty_to_ty(&ty), length));
1175 self.normalize_ty(ast_ty.span, array_ty)
1177 hir::TyTypeof(ref _e) => {
1178 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1179 "`typeof` is a reserved keyword but unimplemented")
1180 .span_label(ast_ty.span, "reserved keyword")
1186 // TyInfer also appears as the type of arguments or return
1187 // values in a ExprClosure, or as
1188 // the type of local variables. Both of these cases are
1189 // handled specially and will not descend into this routine.
1190 self.ty_infer(ast_ty.span)
1197 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1201 pub fn impl_trait_ty_to_ty(
1204 lifetimes: &[hir::Lifetime],
1206 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1207 let tcx = self.tcx();
1209 let generics = tcx.generics_of(def_id);
1211 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1212 let substs = Substs::for_item(tcx, def_id, |param, _| {
1213 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1214 // Our own parameters are the resolved lifetimes.
1216 GenericParamDefKind::Lifetime => {
1217 self.ast_region_to_region(&lifetimes[i], None).into()
1222 // Replace all parent lifetimes with 'static.
1224 GenericParamDefKind::Lifetime => {
1225 tcx.types.re_static.into()
1227 _ => tcx.mk_param_from_def(param)
1231 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1233 let ty = tcx.mk_anon(def_id, substs);
1234 debug!("impl_trait_ty_to_ty: {}", ty);
1238 pub fn ty_of_arg(&self,
1240 expected_ty: Option<Ty<'tcx>>)
1244 hir::TyInfer if expected_ty.is_some() => {
1245 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1246 expected_ty.unwrap()
1248 _ => self.ast_ty_to_ty(ty),
1252 pub fn ty_of_fn(&self,
1253 unsafety: hir::Unsafety,
1256 -> ty::PolyFnSig<'tcx> {
1259 let tcx = self.tcx();
1260 let input_tys: Vec<Ty> =
1261 decl.inputs.iter().map(|a| self.ty_of_arg(a, None)).collect();
1263 let output_ty = match decl.output {
1264 hir::Return(ref output) => self.ast_ty_to_ty(output),
1265 hir::DefaultReturn(..) => tcx.mk_nil(),
1268 debug!("ty_of_fn: output_ty={:?}", output_ty);
1270 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1271 input_tys.into_iter(),
1278 // Find any late-bound regions declared in return type that do
1279 // not appear in the arguments. These are not wellformed.
1282 // for<'a> fn() -> &'a str <-- 'a is bad
1283 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1284 let inputs = bare_fn_ty.inputs();
1285 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1286 &inputs.map_bound(|i| i.to_owned()));
1287 let output = bare_fn_ty.output();
1288 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1289 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1290 let lifetime_name = match *br {
1291 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1292 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => format!("an anonymous lifetime"),
1294 let mut err = struct_span_err!(tcx.sess,
1297 "return type references {} \
1298 which is not constrained by the fn input types",
1300 if let ty::BrAnon(_) = *br {
1301 // The only way for an anonymous lifetime to wind up
1302 // in the return type but **also** be unconstrained is
1303 // if it only appears in "associated types" in the
1304 // input. See #47511 for an example. In this case,
1305 // though we can easily give a hint that ought to be
1307 err.note("lifetimes appearing in an associated type \
1308 are not considered constrained");
1316 /// Given the bounds on an object, determines what single region bound (if any) we can
1317 /// use to summarize this type. The basic idea is that we will use the bound the user
1318 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1319 /// for region bounds. It may be that we can derive no bound at all, in which case
1320 /// we return `None`.
1321 fn compute_object_lifetime_bound(&self,
1323 existential_predicates: ty::Binder<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>)
1324 -> Option<ty::Region<'tcx>> // if None, use the default
1326 let tcx = self.tcx();
1328 debug!("compute_opt_region_bound(existential_predicates={:?})",
1329 existential_predicates);
1331 // No explicit region bound specified. Therefore, examine trait
1332 // bounds and see if we can derive region bounds from those.
1333 let derived_region_bounds =
1334 object_region_bounds(tcx, existential_predicates);
1336 // If there are no derived region bounds, then report back that we
1337 // can find no region bound. The caller will use the default.
1338 if derived_region_bounds.is_empty() {
1342 // If any of the derived region bounds are 'static, that is always
1344 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1345 return Some(tcx.types.re_static);
1348 // Determine whether there is exactly one unique region in the set
1349 // of derived region bounds. If so, use that. Otherwise, report an
1351 let r = derived_region_bounds[0];
1352 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1353 span_err!(tcx.sess, span, E0227,
1354 "ambiguous lifetime bound, explicit lifetime bound required");
1360 /// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
1361 /// remaining general trait bounds.
1362 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1363 trait_bounds: &'b [hir::PolyTraitRef])
1364 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1366 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1367 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1368 match bound.trait_ref.path.def {
1369 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1376 let auto_traits = auto_traits.into_iter().map(|tr| {
1377 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1382 }).collect::<Vec<_>>();
1384 (auto_traits, trait_bounds)
1387 fn check_type_argument_count(tcx: TyCtxt,
1390 ty_params: ParamRange)
1392 let (required, accepted) = (ty_params.required, ty_params.accepted);
1393 if supplied < required {
1394 let expected = if required < accepted {
1399 let arguments_plural = if required == 1 { "" } else { "s" };
1401 struct_span_err!(tcx.sess, span, E0243,
1402 "wrong number of type arguments: {} {}, found {}",
1403 expected, required, supplied)
1405 format!("{} {} type argument{}",
1410 } else if supplied > accepted {
1411 let expected = if required < accepted {
1412 format!("expected at most {}", accepted)
1414 format!("expected {}", accepted)
1416 let arguments_plural = if accepted == 1 { "" } else { "s" };
1418 struct_span_err!(tcx.sess, span, E0244,
1419 "wrong number of type arguments: {}, found {}",
1423 format!("{} type argument{}",
1424 if accepted == 0 { "expected no" } else { &expected },
1431 fn report_lifetime_number_error(tcx: TyCtxt, span: Span, number: usize, expected: usize) {
1432 let label = if number < expected {
1434 format!("expected {} lifetime parameter", expected)
1436 format!("expected {} lifetime parameters", expected)
1439 let additional = number - expected;
1440 if additional == 1 {
1441 "unexpected lifetime parameter".to_string()
1443 format!("{} unexpected lifetime parameters", additional)
1446 struct_span_err!(tcx.sess, span, E0107,
1447 "wrong number of lifetime parameters: expected {}, found {}",
1449 .span_label(span, label)
1453 // A helper struct for conveniently grouping a set of bounds which we pass to
1454 // and return from functions in multiple places.
1455 #[derive(PartialEq, Eq, Clone, Debug)]
1456 pub struct Bounds<'tcx> {
1457 pub region_bounds: Vec<ty::Region<'tcx>>,
1458 pub implicitly_sized: bool,
1459 pub trait_bounds: Vec<ty::PolyTraitRef<'tcx>>,
1460 pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
1463 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1464 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1465 -> Vec<ty::Predicate<'tcx>>
1467 let mut vec = Vec::new();
1469 // If it could be sized, and is, add the sized predicate
1470 if self.implicitly_sized {
1471 if let Some(sized) = tcx.lang_items().sized_trait() {
1472 let trait_ref = ty::TraitRef {
1474 substs: tcx.mk_substs_trait(param_ty, &[])
1476 vec.push(trait_ref.to_predicate());
1480 for ®ion_bound in &self.region_bounds {
1481 // account for the binder being introduced below; no need to shift `param_ty`
1482 // because, at present at least, it can only refer to early-bound regions
1483 let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
1485 ty::Binder::dummy(ty::OutlivesPredicate(param_ty, region_bound)).to_predicate());
1488 for bound_trait_ref in &self.trait_bounds {
1489 vec.push(bound_trait_ref.to_predicate());
1492 for projection in &self.projection_bounds {
1493 vec.push(projection.to_predicate());