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> {
86 item_name: ast::Ident,
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> dyn 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).
217 // FIXME(varkor): Separating out the parameters is messy.
218 let lifetimes: Vec<_> = generic_args.args.iter().filter_map(|arg| match arg {
219 GenericArg::Lifetime(lt) => Some(lt),
222 let types: Vec<_> = generic_args.args.iter().filter_map(|arg| match arg {
223 GenericArg::Type(ty) => Some(ty),
226 let lt_provided = lifetimes.len();
227 let ty_provided = types.len();
229 let decl_generics = tcx.generics_of(def_id);
230 let mut lt_accepted = 0;
231 let mut ty_params = ParamRange { required: 0, accepted: 0 };
232 for param in &decl_generics.params {
234 GenericParamDefKind::Lifetime => {
237 GenericParamDefKind::Type { has_default, .. } => {
238 ty_params.accepted += 1;
240 ty_params.required += 1;
245 if self_ty.is_some() {
246 ty_params.required -= 1;
247 ty_params.accepted -= 1;
250 if lt_accepted != lt_provided {
251 report_lifetime_number_error(tcx, span, lt_provided, lt_accepted);
254 // If a self-type was declared, one should be provided.
255 assert_eq!(decl_generics.has_self, self_ty.is_some());
257 // Check the number of type parameters supplied by the user.
258 if !infer_types || ty_provided > ty_params.required {
259 check_type_argument_count(tcx, span, ty_provided, ty_params);
262 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
263 let default_needs_object_self = |param: &ty::GenericParamDef| {
264 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
265 if is_object && has_default {
266 if tcx.at(span).type_of(param.def_id).has_self_ty() {
267 // There is no suitable inference default for a type parameter
268 // that references self, in an object type.
277 let own_self = self_ty.is_some() as usize;
278 let substs = Substs::for_item(tcx, def_id, |param, substs| {
280 GenericParamDefKind::Lifetime => {
281 let i = param.index as usize - own_self;
282 if let Some(lt) = lifetimes.get(i) {
283 self.ast_region_to_region(lt, Some(param)).into()
285 tcx.types.re_static.into()
288 GenericParamDefKind::Type { has_default, .. } => {
289 let i = param.index as usize;
291 // Handle Self first, so we can adjust the index to match the AST.
292 if let (0, Some(ty)) = (i, self_ty) {
296 let i = i - (lt_accepted + own_self);
298 // A provided type parameter.
299 self.ast_ty_to_ty(&types[i]).into()
300 } else if infer_types {
301 // No type parameters were provided, we can infer all.
302 if !default_needs_object_self(param) {
303 self.ty_infer_for_def(param, span).into()
305 self.ty_infer(span).into()
307 } else if has_default {
308 // No type parameter provided, but a default exists.
310 // If we are converting an object type, then the
311 // `Self` parameter is unknown. However, some of the
312 // other type parameters may reference `Self` in their
313 // defaults. This will lead to an ICE if we are not
315 if default_needs_object_self(param) {
316 struct_span_err!(tcx.sess, span, E0393,
317 "the type parameter `{}` must be explicitly \
321 format!("missing reference to `{}`", param.name))
322 .note(&format!("because of the default `Self` reference, \
323 type parameters must be specified on object \
328 // This is a default type parameter.
331 tcx.at(span).type_of(param.def_id)
332 .subst_spanned(tcx, substs, Some(span))
336 // We've already errored above about the mismatch.
343 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
345 item_name: binding.ident,
346 ty: self.ast_ty_to_ty(&binding.ty),
351 debug!("create_substs_for_ast_path(decl_generics={:?}, self_ty={:?}) -> {:?}",
352 decl_generics, self_ty, substs);
354 (substs, assoc_bindings)
357 /// Instantiates the path for the given trait reference, assuming that it's
358 /// bound to a valid trait type. Returns the def_id for the defining trait.
359 /// The type _cannot_ be a type other than a trait type.
361 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
362 /// are disallowed. Otherwise, they are pushed onto the vector given.
363 pub fn instantiate_mono_trait_ref(&self,
364 trait_ref: &hir::TraitRef,
366 -> ty::TraitRef<'tcx>
368 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
370 let trait_def_id = self.trait_def_id(trait_ref);
371 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
374 trait_ref.path.segments.last().unwrap())
377 /// Get the DefId of the given trait ref. It _must_ actually be a trait.
378 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
379 let path = &trait_ref.path;
381 Def::Trait(trait_def_id) => trait_def_id,
382 Def::TraitAlias(alias_def_id) => alias_def_id,
390 /// The given `trait_ref` must actually be trait.
391 pub(super) fn instantiate_poly_trait_ref_inner(&self,
392 trait_ref: &hir::TraitRef,
394 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>,
396 -> ty::PolyTraitRef<'tcx>
398 let trait_def_id = self.trait_def_id(trait_ref);
400 debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
402 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
404 let (substs, assoc_bindings) =
405 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
408 trait_ref.path.segments.last().unwrap());
409 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
411 let mut dup_bindings = FxHashMap::default();
412 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
413 // specify type to assert that error was already reported in Err case:
414 let predicate: Result<_, ErrorReported> =
415 self.ast_type_binding_to_poly_projection_predicate(
416 trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
417 predicate.ok() // ok to ignore Err() because ErrorReported (see above)
420 debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
421 trait_ref, poly_projections, poly_trait_ref);
425 pub fn instantiate_poly_trait_ref(&self,
426 poly_trait_ref: &hir::PolyTraitRef,
428 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
429 -> ty::PolyTraitRef<'tcx>
431 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
432 poly_projections, false)
435 fn ast_path_to_mono_trait_ref(&self,
439 trait_segment: &hir::PathSegment)
440 -> ty::TraitRef<'tcx>
442 let (substs, assoc_bindings) =
443 self.create_substs_for_ast_trait_ref(span,
447 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
448 ty::TraitRef::new(trait_def_id, substs)
451 fn create_substs_for_ast_trait_ref(&self,
455 trait_segment: &hir::PathSegment)
456 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
458 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
461 let trait_def = self.tcx().trait_def(trait_def_id);
463 if !self.tcx().features().unboxed_closures &&
464 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
465 != trait_def.paren_sugar {
466 // For now, require that parenthetical notation be used only with `Fn()` etc.
467 let msg = if trait_def.paren_sugar {
468 "the precise format of `Fn`-family traits' type parameters is subject to change. \
469 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
471 "parenthetical notation is only stable when used with `Fn`-family traits"
473 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
474 span, GateIssue::Language, msg);
477 trait_segment.with_generic_args(|generic_args| {
478 self.create_substs_for_ast_path(span,
481 trait_segment.infer_types,
486 fn trait_defines_associated_type_named(&self,
488 assoc_name: ast::Ident)
491 self.tcx().associated_items(trait_def_id).any(|item| {
492 item.kind == ty::AssociatedKind::Type &&
493 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
497 fn ast_type_binding_to_poly_projection_predicate(
500 trait_ref: ty::PolyTraitRef<'tcx>,
501 binding: &ConvertedBinding<'tcx>,
503 dup_bindings: &mut FxHashMap<DefId, Span>)
504 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
506 let tcx = self.tcx();
509 // Given something like `U : SomeTrait<T=X>`, we want to produce a
510 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
511 // subtle in the event that `T` is defined in a supertrait of
512 // `SomeTrait`, because in that case we need to upcast.
514 // That is, consider this case:
517 // trait SubTrait : SuperTrait<int> { }
518 // trait SuperTrait<A> { type T; }
520 // ... B : SubTrait<T=foo> ...
523 // We want to produce `<B as SuperTrait<int>>::T == foo`.
525 // Find any late-bound regions declared in `ty` that are not
526 // declared in the trait-ref. These are not wellformed.
530 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
531 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
532 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
533 let late_bound_in_ty =
534 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
535 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
536 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
537 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
538 let br_name = match *br {
539 ty::BrNamed(_, name) => name,
543 "anonymous bound region {:?} in binding but not trait ref",
547 struct_span_err!(tcx.sess,
550 "binding for associated type `{}` references lifetime `{}`, \
551 which does not appear in the trait input types",
552 binding.item_name, br_name)
557 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
559 // Simple case: X is defined in the current trait.
562 // Otherwise, we have to walk through the supertraits to find
564 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
565 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
567 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
568 binding.item_name, binding.span)
571 let (assoc_ident, def_scope) =
572 tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
573 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
574 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
575 }).expect("missing associated type");
577 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
578 let msg = format!("associated type `{}` is private", binding.item_name);
579 tcx.sess.span_err(binding.span, &msg);
581 tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
584 dup_bindings.entry(assoc_ty.def_id)
585 .and_modify(|prev_span| {
586 let mut err = self.tcx().struct_span_lint_node(
587 ::rustc::lint::builtin::DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
590 &format!("associated type binding `{}` specified more than once",
593 err.span_label(binding.span, "used more than once");
594 err.span_label(*prev_span, format!("first use of `{}`", binding.item_name));
597 .or_insert(binding.span);
600 Ok(candidate.map_bound(|trait_ref| {
601 ty::ProjectionPredicate {
602 projection_ty: ty::ProjectionTy::from_ref_and_name(
612 fn ast_path_to_ty(&self,
615 item_segment: &hir::PathSegment)
618 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
621 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
625 /// Transform a PolyTraitRef into a PolyExistentialTraitRef by
626 /// removing the dummy Self type (TRAIT_OBJECT_DUMMY_SELF).
627 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
628 -> ty::ExistentialTraitRef<'tcx> {
629 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
630 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
633 fn conv_object_ty_poly_trait_ref(&self,
635 trait_bounds: &[hir::PolyTraitRef],
636 lifetime: &hir::Lifetime)
639 let tcx = self.tcx();
641 if trait_bounds.is_empty() {
642 span_err!(tcx.sess, span, E0224,
643 "at least one non-builtin trait is required for an object type");
644 return tcx.types.err;
647 let mut projection_bounds = vec![];
648 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
649 let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
651 &mut projection_bounds);
653 for trait_bound in trait_bounds[1..].iter() {
654 // Sanity check for non-principal trait bounds
655 self.instantiate_poly_trait_ref(trait_bound,
660 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
662 if !trait_bounds.is_empty() {
663 let b = &trait_bounds[0];
664 let span = b.trait_ref.path.span;
665 struct_span_err!(self.tcx().sess, span, E0225,
666 "only auto traits can be used as additional traits in a trait object")
667 .span_label(span, "non-auto additional trait")
671 // Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
672 let existential_principal = principal.map_bound(|trait_ref| {
673 self.trait_ref_to_existential(trait_ref)
675 let existential_projections = projection_bounds.iter().map(|bound| {
676 bound.map_bound(|b| {
677 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
678 ty::ExistentialProjection {
680 item_def_id: b.projection_ty.item_def_id,
681 substs: trait_ref.substs,
686 // check that there are no gross object safety violations,
687 // most importantly, that the supertraits don't contain Self,
689 let object_safety_violations =
690 tcx.astconv_object_safety_violations(principal.def_id());
691 if !object_safety_violations.is_empty() {
692 tcx.report_object_safety_error(
693 span, principal.def_id(), object_safety_violations)
695 return tcx.types.err;
698 let mut associated_types = FxHashSet::default();
699 for tr in traits::supertraits(tcx, principal) {
700 associated_types.extend(tcx.associated_items(tr.def_id())
701 .filter(|item| item.kind == ty::AssociatedKind::Type)
702 .map(|item| item.def_id));
705 for projection_bound in &projection_bounds {
706 associated_types.remove(&projection_bound.projection_def_id());
709 for item_def_id in associated_types {
710 let assoc_item = tcx.associated_item(item_def_id);
711 let trait_def_id = assoc_item.container.id();
712 struct_span_err!(tcx.sess, span, E0191,
713 "the value of the associated type `{}` (from the trait `{}`) must be specified",
715 tcx.item_path_str(trait_def_id))
716 .span_label(span, format!(
717 "missing associated type `{}` value", assoc_item.ident))
721 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
725 // skip_binder is okay, because the predicates are re-bound.
727 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
728 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
729 .chain(existential_projections
730 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
731 .collect::<AccumulateVec<[_; 8]>>();
732 v.sort_by(|a, b| a.stable_cmp(tcx, b));
733 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
736 // Explicitly specified region bound. Use that.
737 let region_bound = if !lifetime.is_elided() {
738 self.ast_region_to_region(lifetime, None)
740 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
741 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
742 if tcx.named_region(hir_id).is_some() {
743 self.ast_region_to_region(lifetime, None)
745 self.re_infer(span, None).unwrap_or_else(|| {
746 span_err!(tcx.sess, span, E0228,
747 "the lifetime bound for this object type cannot be deduced \
748 from context; please supply an explicit bound");
755 debug!("region_bound: {:?}", region_bound);
757 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
758 debug!("trait_object_type: {:?}", ty);
762 fn report_ambiguous_associated_type(&self,
767 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
768 .span_label(span, "ambiguous associated type")
769 .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
770 type_str, trait_str, name))
775 // Search for a bound on a type parameter which includes the associated item
776 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
777 // This function will fail if there are no suitable bounds or there is
779 fn find_bound_for_assoc_item(&self,
780 ty_param_def_id: DefId,
781 assoc_name: ast::Ident,
783 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
785 let tcx = self.tcx();
787 let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
788 .predicates.into_iter().filter_map(|p| p.to_opt_poly_trait_ref()).collect();
790 // Check that there is exactly one way to find an associated type with the
792 let suitable_bounds =
793 traits::transitive_bounds(tcx, &bounds)
794 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
796 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
797 let param_name = tcx.hir.ty_param_name(param_node_id);
798 self.one_bound_for_assoc_type(suitable_bounds,
799 ¶m_name.as_str(),
805 // Checks that bounds contains exactly one element and reports appropriate
807 fn one_bound_for_assoc_type<I>(&self,
810 assoc_name: ast::Ident,
812 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
813 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
815 let bound = match bounds.next() {
816 Some(bound) => bound,
818 struct_span_err!(self.tcx().sess, span, E0220,
819 "associated type `{}` not found for `{}`",
822 .span_label(span, format!("associated type `{}` not found", assoc_name))
824 return Err(ErrorReported);
828 if let Some(bound2) = bounds.next() {
829 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
830 let mut err = struct_span_err!(
831 self.tcx().sess, span, E0221,
832 "ambiguous associated type `{}` in bounds of `{}`",
835 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
837 for bound in bounds {
838 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
839 item.kind == ty::AssociatedKind::Type &&
840 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
842 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
844 if let Some(span) = bound_span {
845 err.span_label(span, format!("ambiguous `{}` from `{}`",
849 span_note!(&mut err, span,
850 "associated type `{}` could derive from `{}`",
861 // Create a type from a path to an associated type.
862 // For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
863 // and item_segment is the path segment for D. We return a type and a def for
865 // Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
866 // parameter or Self.
867 pub fn associated_path_def_to_ty(&self,
872 item_segment: &hir::PathSegment)
875 let tcx = self.tcx();
876 let assoc_name = item_segment.ident;
878 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
880 self.prohibit_generics(slice::from_ref(item_segment));
882 // Find the type of the associated item, and the trait where the associated
884 let bound = match (&ty.sty, ty_path_def) {
885 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
886 // `Self` in an impl of a trait - we have a concrete self type and a
888 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
889 Some(trait_ref) => trait_ref,
891 // A cycle error occurred, most likely.
892 return (tcx.types.err, Def::Err);
897 traits::supertraits(tcx, ty::Binder::bind(trait_ref))
898 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
900 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
902 Err(ErrorReported) => return (tcx.types.err, Def::Err),
905 (&ty::TyParam(_), Def::SelfTy(Some(param_did), None)) |
906 (&ty::TyParam(_), Def::TyParam(param_did)) => {
907 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
909 Err(ErrorReported) => return (tcx.types.err, Def::Err),
913 // Don't print TyErr to the user.
914 if !ty.references_error() {
915 self.report_ambiguous_associated_type(span,
918 &assoc_name.as_str());
920 return (tcx.types.err, Def::Err);
924 let trait_did = bound.def_id();
925 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
926 let item = tcx.associated_items(trait_did).find(|i| {
927 Namespace::from(i.kind) == Namespace::Type &&
928 i.ident.modern() == assoc_ident
930 .expect("missing associated type");
932 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
933 let ty = self.normalize_ty(span, ty);
935 let def = Def::AssociatedTy(item.def_id);
936 if !item.vis.is_accessible_from(def_scope, tcx) {
937 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
938 tcx.sess.span_err(span, &msg);
940 tcx.check_stability(item.def_id, Some(ref_id), span);
945 fn qpath_to_ty(&self,
947 opt_self_ty: Option<Ty<'tcx>>,
949 trait_segment: &hir::PathSegment,
950 item_segment: &hir::PathSegment)
953 let tcx = self.tcx();
954 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
956 self.prohibit_generics(slice::from_ref(item_segment));
958 let self_ty = if let Some(ty) = opt_self_ty {
961 let path_str = tcx.item_path_str(trait_def_id);
962 self.report_ambiguous_associated_type(span,
965 &item_segment.ident.as_str());
966 return tcx.types.err;
969 debug!("qpath_to_ty: self_type={:?}", self_ty);
971 let trait_ref = self.ast_path_to_mono_trait_ref(span,
976 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
978 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
981 pub fn prohibit_generics(&self, segments: &[hir::PathSegment]) {
982 for segment in segments {
983 segment.with_generic_args(|generic_args| {
984 let (mut err_for_lt, mut err_for_ty) = (false, false);
985 for arg in &generic_args.args {
986 let (mut span_err, span, kind) = match arg {
987 hir::GenericArg::Lifetime(lt) => {
988 if err_for_lt { continue }
990 (struct_span_err!(self.tcx().sess, lt.span, E0110,
991 "lifetime parameters are not allowed on \
996 hir::GenericArg::Type(ty) => {
997 if err_for_ty { continue }
999 (struct_span_err!(self.tcx().sess, ty.span, E0109,
1000 "type parameters are not allowed on this type"),
1005 span_err.span_label(span, format!("{} parameter not allowed", kind))
1007 if err_for_lt && err_for_ty {
1011 for binding in &generic_args.bindings {
1012 self.prohibit_projection(binding.span);
1019 pub fn prohibit_projection(&self, span: Span) {
1020 let mut err = struct_span_err!(self.tcx().sess, span, E0229,
1021 "associated type bindings are not allowed here");
1022 err.span_label(span, "associated type not allowed here").emit();
1025 // Check a type Path and convert it to a Ty.
1026 pub fn def_to_ty(&self,
1027 opt_self_ty: Option<Ty<'tcx>>,
1029 permit_variants: bool)
1031 let tcx = self.tcx();
1033 debug!("base_def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
1034 path.def, opt_self_ty, path.segments);
1036 let span = path.span;
1038 Def::Existential(did) => {
1039 // check for desugared impl trait
1040 if let Some(node_id) = tcx.hir.as_local_node_id(did) {
1041 if let hir::map::NodeItem(item) = tcx.hir.get(node_id) {
1042 if let hir::ItemKind::Existential(ref exist_ty) = item.node {
1043 if exist_ty.impl_trait_fn.is_some() {
1044 let lifetimes = &path.segments[0].args.as_ref().unwrap().args;
1045 return self.impl_trait_ty_to_ty(did, lifetimes);
1050 let item_segment = path.segments.split_last().unwrap();
1051 self.prohibit_generics(item_segment.1);
1052 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1055 tcx.mk_anon(did, substs),
1058 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
1059 Def::Union(did) | Def::TyForeign(did) => {
1060 assert_eq!(opt_self_ty, None);
1061 self.prohibit_generics(path.segments.split_last().unwrap().1);
1062 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1064 Def::Variant(did) if permit_variants => {
1065 // Convert "variant type" as if it were a real type.
1066 // The resulting `Ty` is type of the variant's enum for now.
1067 assert_eq!(opt_self_ty, None);
1068 self.prohibit_generics(path.segments.split_last().unwrap().1);
1069 self.ast_path_to_ty(span,
1070 tcx.parent_def_id(did).unwrap(),
1071 path.segments.last().unwrap())
1073 Def::TyParam(did) => {
1074 assert_eq!(opt_self_ty, None);
1075 self.prohibit_generics(&path.segments);
1077 let node_id = tcx.hir.as_local_node_id(did).unwrap();
1078 let item_id = tcx.hir.get_parent_node(node_id);
1079 let item_def_id = tcx.hir.local_def_id(item_id);
1080 let generics = tcx.generics_of(item_def_id);
1081 let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
1082 tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
1084 Def::SelfTy(_, Some(def_id)) => {
1085 // Self in impl (we know the concrete type).
1087 assert_eq!(opt_self_ty, None);
1088 self.prohibit_generics(&path.segments);
1090 tcx.at(span).type_of(def_id)
1092 Def::SelfTy(Some(_), None) => {
1094 assert_eq!(opt_self_ty, None);
1095 self.prohibit_generics(&path.segments);
1098 Def::AssociatedTy(def_id) => {
1099 self.prohibit_generics(&path.segments[..path.segments.len()-2]);
1100 self.qpath_to_ty(span,
1103 &path.segments[path.segments.len()-2],
1104 path.segments.last().unwrap())
1106 Def::PrimTy(prim_ty) => {
1107 assert_eq!(opt_self_ty, None);
1108 self.prohibit_generics(&path.segments);
1110 hir::TyBool => tcx.types.bool,
1111 hir::TyChar => tcx.types.char,
1112 hir::TyInt(it) => tcx.mk_mach_int(it),
1113 hir::TyUint(uit) => tcx.mk_mach_uint(uit),
1114 hir::TyFloat(ft) => tcx.mk_mach_float(ft),
1115 hir::TyStr => tcx.mk_str()
1119 self.set_tainted_by_errors();
1120 return self.tcx().types.err;
1122 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1126 /// Parses the programmer's textual representation of a type into our
1127 /// internal notion of a type.
1128 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1129 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
1132 let tcx = self.tcx();
1134 let result_ty = match ast_ty.node {
1135 hir::TyKind::Slice(ref ty) => {
1136 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1138 hir::TyKind::Ptr(ref mt) => {
1139 tcx.mk_ptr(ty::TypeAndMut {
1140 ty: self.ast_ty_to_ty(&mt.ty),
1144 hir::TyKind::Rptr(ref region, ref mt) => {
1145 let r = self.ast_region_to_region(region, None);
1146 debug!("TyRef r={:?}", r);
1147 let t = self.ast_ty_to_ty(&mt.ty);
1148 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1150 hir::TyKind::Never => {
1153 hir::TyKind::Tup(ref fields) => {
1154 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1156 hir::TyKind::BareFn(ref bf) => {
1157 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1158 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1160 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1161 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1163 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1164 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1165 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1166 self.ast_ty_to_ty(qself)
1168 self.def_to_ty(opt_self_ty, path, false)
1170 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1171 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1172 let ty = self.ast_ty_to_ty(qself);
1174 let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1179 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1181 hir::TyKind::Array(ref ty, ref length) => {
1182 let length_def_id = tcx.hir.local_def_id(length.id);
1183 let substs = Substs::identity_for_item(tcx, length_def_id);
1184 let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
1185 let array_ty = tcx.mk_ty(ty::TyArray(self.ast_ty_to_ty(&ty), length));
1186 self.normalize_ty(ast_ty.span, array_ty)
1188 hir::TyKind::Typeof(ref _e) => {
1189 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1190 "`typeof` is a reserved keyword but unimplemented")
1191 .span_label(ast_ty.span, "reserved keyword")
1196 hir::TyKind::Infer => {
1197 // TyInfer also appears as the type of arguments or return
1198 // values in a ExprKind::Closure, or as
1199 // the type of local variables. Both of these cases are
1200 // handled specially and will not descend into this routine.
1201 self.ty_infer(ast_ty.span)
1203 hir::TyKind::Err => {
1208 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1212 pub fn impl_trait_ty_to_ty(
1215 lifetimes: &[hir::GenericArg],
1217 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1218 let tcx = self.tcx();
1220 let generics = tcx.generics_of(def_id);
1222 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1223 let substs = Substs::for_item(tcx, def_id, |param, _| {
1224 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1225 // Our own parameters are the resolved lifetimes.
1227 GenericParamDefKind::Lifetime => {
1228 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1229 self.ast_region_to_region(lifetime, None).into()
1237 // Replace all parent lifetimes with 'static.
1239 GenericParamDefKind::Lifetime => {
1240 tcx.types.re_static.into()
1242 _ => tcx.mk_param_from_def(param)
1246 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1248 let ty = tcx.mk_anon(def_id, substs);
1249 debug!("impl_trait_ty_to_ty: {}", ty);
1253 pub fn ty_of_arg(&self,
1255 expected_ty: Option<Ty<'tcx>>)
1259 hir::TyKind::Infer if expected_ty.is_some() => {
1260 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1261 expected_ty.unwrap()
1263 _ => self.ast_ty_to_ty(ty),
1267 pub fn ty_of_fn(&self,
1268 unsafety: hir::Unsafety,
1271 -> ty::PolyFnSig<'tcx> {
1274 let tcx = self.tcx();
1275 let input_tys: Vec<Ty> =
1276 decl.inputs.iter().map(|a| self.ty_of_arg(a, None)).collect();
1278 let output_ty = match decl.output {
1279 hir::Return(ref output) => self.ast_ty_to_ty(output),
1280 hir::DefaultReturn(..) => tcx.mk_nil(),
1283 debug!("ty_of_fn: output_ty={:?}", output_ty);
1285 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
1286 input_tys.into_iter(),
1293 // Find any late-bound regions declared in return type that do
1294 // not appear in the arguments. These are not wellformed.
1297 // for<'a> fn() -> &'a str <-- 'a is bad
1298 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1299 let inputs = bare_fn_ty.inputs();
1300 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1301 &inputs.map_bound(|i| i.to_owned()));
1302 let output = bare_fn_ty.output();
1303 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1304 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1305 let lifetime_name = match *br {
1306 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
1307 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => format!("an anonymous lifetime"),
1309 let mut err = struct_span_err!(tcx.sess,
1312 "return type references {} \
1313 which is not constrained by the fn input types",
1315 if let ty::BrAnon(_) = *br {
1316 // The only way for an anonymous lifetime to wind up
1317 // in the return type but **also** be unconstrained is
1318 // if it only appears in "associated types" in the
1319 // input. See #47511 for an example. In this case,
1320 // though we can easily give a hint that ought to be
1322 err.note("lifetimes appearing in an associated type \
1323 are not considered constrained");
1331 /// Given the bounds on an object, determines what single region bound (if any) we can
1332 /// use to summarize this type. The basic idea is that we will use the bound the user
1333 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1334 /// for region bounds. It may be that we can derive no bound at all, in which case
1335 /// we return `None`.
1336 fn compute_object_lifetime_bound(&self,
1338 existential_predicates: ty::Binder<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>)
1339 -> Option<ty::Region<'tcx>> // if None, use the default
1341 let tcx = self.tcx();
1343 debug!("compute_opt_region_bound(existential_predicates={:?})",
1344 existential_predicates);
1346 // No explicit region bound specified. Therefore, examine trait
1347 // bounds and see if we can derive region bounds from those.
1348 let derived_region_bounds =
1349 object_region_bounds(tcx, existential_predicates);
1351 // If there are no derived region bounds, then report back that we
1352 // can find no region bound. The caller will use the default.
1353 if derived_region_bounds.is_empty() {
1357 // If any of the derived region bounds are 'static, that is always
1359 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1360 return Some(tcx.types.re_static);
1363 // Determine whether there is exactly one unique region in the set
1364 // of derived region bounds. If so, use that. Otherwise, report an
1366 let r = derived_region_bounds[0];
1367 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1368 span_err!(tcx.sess, span, E0227,
1369 "ambiguous lifetime bound, explicit lifetime bound required");
1375 /// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
1376 /// remaining general trait bounds.
1377 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1378 trait_bounds: &'b [hir::PolyTraitRef])
1379 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1381 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1382 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1383 match bound.trait_ref.path.def {
1384 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1391 let auto_traits = auto_traits.into_iter().map(|tr| {
1392 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1397 }).collect::<Vec<_>>();
1399 (auto_traits, trait_bounds)
1402 fn check_type_argument_count(tcx: TyCtxt,
1405 ty_params: ParamRange)
1407 let (required, accepted) = (ty_params.required, ty_params.accepted);
1408 if supplied < required {
1409 let expected = if required < accepted {
1414 let arguments_plural = if required == 1 { "" } else { "s" };
1416 struct_span_err!(tcx.sess, span, E0243,
1417 "wrong number of type arguments: {} {}, found {}",
1418 expected, required, supplied)
1420 format!("{} {} type argument{}",
1425 } else if supplied > accepted {
1426 let expected = if required < accepted {
1427 format!("expected at most {}", accepted)
1429 format!("expected {}", accepted)
1431 let arguments_plural = if accepted == 1 { "" } else { "s" };
1433 struct_span_err!(tcx.sess, span, E0244,
1434 "wrong number of type arguments: {}, found {}",
1438 format!("{} type argument{}",
1439 if accepted == 0 { "expected no" } else { &expected },
1446 fn report_lifetime_number_error(tcx: TyCtxt, span: Span, number: usize, expected: usize) {
1447 let label = if number < expected {
1449 format!("expected {} lifetime parameter", expected)
1451 format!("expected {} lifetime parameters", expected)
1454 let additional = number - expected;
1455 if additional == 1 {
1456 "unexpected lifetime parameter".to_string()
1458 format!("{} unexpected lifetime parameters", additional)
1461 struct_span_err!(tcx.sess, span, E0107,
1462 "wrong number of lifetime parameters: expected {}, found {}",
1464 .span_label(span, label)
1468 // A helper struct for conveniently grouping a set of bounds which we pass to
1469 // and return from functions in multiple places.
1470 #[derive(PartialEq, Eq, Clone, Debug)]
1471 pub struct Bounds<'tcx> {
1472 pub region_bounds: Vec<ty::Region<'tcx>>,
1473 pub implicitly_sized: bool,
1474 pub trait_bounds: Vec<ty::PolyTraitRef<'tcx>>,
1475 pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
1478 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1479 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1480 -> Vec<ty::Predicate<'tcx>>
1482 let mut vec = Vec::new();
1484 // If it could be sized, and is, add the sized predicate
1485 if self.implicitly_sized {
1486 if let Some(sized) = tcx.lang_items().sized_trait() {
1487 let trait_ref = ty::TraitRef {
1489 substs: tcx.mk_substs_trait(param_ty, &[])
1491 vec.push(trait_ref.to_predicate());
1495 for ®ion_bound in &self.region_bounds {
1496 // account for the binder being introduced below; no need to shift `param_ty`
1497 // because, at present at least, it can only refer to early-bound regions
1498 let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
1500 ty::Binder::dummy(ty::OutlivesPredicate(param_ty, region_bound)).to_predicate());
1503 for bound_trait_ref in &self.trait_bounds {
1504 vec.push(bound_trait_ref.to_predicate());
1507 for projection in &self.projection_bounds {
1508 vec.push(projection.to_predicate());