1 //! Conversion from AST representation of types to the `ty.rs` representation.
2 //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
3 //! instance of `AstConv`.
5 use errors::{Applicability, DiagnosticId};
6 use crate::hir::{self, GenericArg, GenericArgs, ExprKind};
7 use crate::hir::def::{CtorOf, Res, DefKind};
8 use crate::hir::def_id::DefId;
9 use crate::hir::HirVec;
11 use crate::middle::resolve_lifetime as rl;
12 use crate::namespace::Namespace;
13 use rustc::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
15 use rustc::ty::{self, DefIdTree, Ty, TyCtxt, ToPredicate, TypeFoldable};
16 use rustc::ty::{GenericParamDef, GenericParamDefKind};
17 use rustc::ty::subst::{Kind, Subst, InternalSubsts, SubstsRef};
18 use rustc::ty::wf::object_region_bounds;
19 use rustc::mir::interpret::ConstValue;
20 use rustc_data_structures::sync::Lrc;
21 use rustc_target::spec::abi;
22 use crate::require_c_abi_if_c_variadic;
23 use smallvec::SmallVec;
25 use syntax::feature_gate::{GateIssue, emit_feature_err};
27 use syntax::util::lev_distance::find_best_match_for_name;
28 use syntax::symbol::sym;
29 use syntax_pos::{DUMMY_SP, Span, MultiSpan};
30 use crate::util::common::ErrorReported;
31 use crate::util::nodemap::FxHashMap;
33 use std::collections::BTreeSet;
37 use super::{check_type_alias_enum_variants_enabled};
38 use rustc_data_structures::fx::FxHashSet;
41 pub struct PathSeg(pub DefId, pub usize);
43 pub trait AstConv<'gcx, 'tcx> {
44 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
46 /// Returns the set of bounds in scope for the type parameter with
48 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
49 -> Lrc<ty::GenericPredicates<'tcx>>;
51 /// What lifetime should we use when a lifetime is omitted (and not elided)?
52 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
53 -> Option<ty::Region<'tcx>>;
55 /// What type should we use when a type is omitted?
56 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
58 /// Same as ty_infer, but with a known type parameter definition.
59 fn ty_infer_for_def(&self,
60 _def: &ty::GenericParamDef,
61 span: Span) -> Ty<'tcx> {
65 /// Projecting an associated type from a (potentially)
66 /// higher-ranked trait reference is more complicated, because of
67 /// the possibility of late-bound regions appearing in the
68 /// associated type binding. This is not legal in function
69 /// signatures for that reason. In a function body, we can always
70 /// handle it because we can use inference variables to remove the
71 /// late-bound regions.
72 fn projected_ty_from_poly_trait_ref(&self,
75 poly_trait_ref: ty::PolyTraitRef<'tcx>)
78 /// Normalize an associated type coming from the user.
79 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
81 /// Invoked when we encounter an error from some prior pass
82 /// (e.g., resolve) that is translated into a ty-error. This is
83 /// used to help suppress derived errors typeck might otherwise
85 fn set_tainted_by_errors(&self);
87 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
90 struct ConvertedBinding<'tcx> {
91 item_name: ast::Ident,
97 enum GenericArgPosition {
99 Value, // e.g., functions
103 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
104 pub fn ast_region_to_region(&self,
105 lifetime: &hir::Lifetime,
106 def: Option<&ty::GenericParamDef>)
109 let tcx = self.tcx();
110 let lifetime_name = |def_id| {
111 tcx.hir().name_by_hir_id(tcx.hir().as_local_hir_id(def_id).unwrap()).as_interned_str()
114 let r = match tcx.named_region(lifetime.hir_id) {
115 Some(rl::Region::Static) => {
116 tcx.lifetimes.re_static
119 Some(rl::Region::LateBound(debruijn, id, _)) => {
120 let name = lifetime_name(id);
121 tcx.mk_region(ty::ReLateBound(debruijn,
122 ty::BrNamed(id, name)))
125 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
126 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
129 Some(rl::Region::EarlyBound(index, id, _)) => {
130 let name = lifetime_name(id);
131 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
138 Some(rl::Region::Free(scope, id)) => {
139 let name = lifetime_name(id);
140 tcx.mk_region(ty::ReFree(ty::FreeRegion {
142 bound_region: ty::BrNamed(id, name)
145 // (*) -- not late-bound, won't change
149 self.re_infer(lifetime.span, def)
151 // This indicates an illegal lifetime
152 // elision. `resolve_lifetime` should have
153 // reported an error in this case -- but if
154 // not, let's error out.
155 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
157 // Supply some dummy value. We don't have an
158 // `re_error`, annoyingly, so use `'static`.
159 tcx.lifetimes.re_static
164 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
171 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
172 /// returns an appropriate set of substitutions for this particular reference to `I`.
173 pub fn ast_path_substs_for_ty(&self,
176 item_segment: &hir::PathSegment)
179 let (substs, assoc_bindings, _) = item_segment.with_generic_args(|generic_args| {
180 self.create_substs_for_ast_path(
184 item_segment.infer_types,
189 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
194 /// Report error if there is an explicit type parameter when using `impl Trait`.
196 tcx: TyCtxt<'_, '_, '_>,
198 seg: &hir::PathSegment,
199 generics: &ty::Generics,
201 let explicit = !seg.infer_types;
202 let impl_trait = generics.params.iter().any(|param| match param.kind {
203 ty::GenericParamDefKind::Type {
204 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
209 if explicit && impl_trait {
210 let mut err = struct_span_err! {
214 "cannot provide explicit type parameters when `impl Trait` is \
215 used in argument position."
224 /// Checks that the correct number of generic arguments have been provided.
225 /// Used specifically for function calls.
226 pub fn check_generic_arg_count_for_call(
227 tcx: TyCtxt<'_, '_, '_>,
230 seg: &hir::PathSegment,
231 is_method_call: bool,
233 let empty_args = P(hir::GenericArgs {
234 args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
236 let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
237 Self::check_generic_arg_count(
241 if let Some(ref args) = seg.args {
247 GenericArgPosition::MethodCall
249 GenericArgPosition::Value
251 def.parent.is_none() && def.has_self, // `has_self`
252 seg.infer_types || suppress_mismatch, // `infer_types`
256 /// Checks that the correct number of generic arguments have been provided.
257 /// This is used both for datatypes and function calls.
258 fn check_generic_arg_count(
259 tcx: TyCtxt<'_, '_, '_>,
262 args: &hir::GenericArgs,
263 position: GenericArgPosition,
266 ) -> (bool, Option<Vec<Span>>) {
267 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
268 // that lifetimes will proceed types. So it suffices to check the number of each generic
269 // arguments in order to validate them with respect to the generic parameters.
270 let param_counts = def.own_counts();
271 let arg_counts = args.own_counts();
272 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
273 let infer_consts = position != GenericArgPosition::Type && arg_counts.consts == 0;
275 let mut defaults: ty::GenericParamCount = Default::default();
276 for param in &def.params {
278 GenericParamDefKind::Lifetime => {}
279 GenericParamDefKind::Type { has_default, .. } => {
280 defaults.types += has_default as usize
282 GenericParamDefKind::Const => {
283 // FIXME(const_generics:defaults)
288 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
289 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
292 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
293 if !infer_lifetimes {
294 if let Some(span_late) = def.has_late_bound_regions {
295 let msg = "cannot specify lifetime arguments explicitly \
296 if late bound lifetime parameters are present";
297 let note = "the late bound lifetime parameter is introduced here";
298 let span = args.args[0].span();
299 if position == GenericArgPosition::Value
300 && arg_counts.lifetimes != param_counts.lifetimes {
301 let mut err = tcx.sess.struct_span_err(span, msg);
302 err.span_note(span_late, note);
306 let mut multispan = MultiSpan::from_span(span);
307 multispan.push_span_label(span_late, note.to_string());
308 tcx.lint_hir(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
309 args.args[0].id(), multispan, msg);
310 return (false, None);
315 let check_kind_count = |kind, required, permitted, provided, offset| {
317 "check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}",
324 // We enforce the following: `required` <= `provided` <= `permitted`.
325 // For kinds without defaults (i.e., lifetimes), `required == permitted`.
326 // For other kinds (i.e., types), `permitted` may be greater than `required`.
327 if required <= provided && provided <= permitted {
328 return (false, None);
331 // Unfortunately lifetime and type parameter mismatches are typically styled
332 // differently in diagnostics, which means we have a few cases to consider here.
333 let (bound, quantifier) = if required != permitted {
334 if provided < required {
335 (required, "at least ")
336 } else { // provided > permitted
337 (permitted, "at most ")
343 let mut potential_assoc_types: Option<Vec<Span>> = None;
344 let (spans, label) = if required == permitted && provided > permitted {
345 // In the case when the user has provided too many arguments,
346 // we want to point to the unexpected arguments.
347 let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
349 .map(|arg| arg.span())
351 potential_assoc_types = Some(spans.clone());
352 (spans, format!( "unexpected {} argument", kind))
354 (vec![span], format!(
355 "expected {}{} {} argument{}",
359 if bound != 1 { "s" } else { "" },
363 let mut err = tcx.sess.struct_span_err_with_code(
366 "wrong number of {} arguments: expected {}{}, found {}",
372 DiagnosticId::Error("E0107".into())
375 err.span_label(span, label.as_str());
379 (provided > required, // `suppress_error`
380 potential_assoc_types)
383 if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes {
386 param_counts.lifetimes,
387 param_counts.lifetimes,
388 arg_counts.lifetimes,
392 // FIXME(const_generics:defaults)
393 if !infer_consts || arg_counts.consts > param_counts.consts {
399 arg_counts.lifetimes + arg_counts.types,
402 // Note that type errors are currently be emitted *after* const errors.
404 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
407 param_counts.types - defaults.types - has_self as usize,
408 param_counts.types - has_self as usize,
410 arg_counts.lifetimes,
417 /// Creates the relevant generic argument substitutions
418 /// corresponding to a set of generic parameters. This is a
419 /// rather complex function. Let us try to explain the role
420 /// of each of its parameters:
422 /// To start, we are given the `def_id` of the thing we are
423 /// creating the substitutions for, and a partial set of
424 /// substitutions `parent_substs`. In general, the substitutions
425 /// for an item begin with substitutions for all the "parents" of
426 /// that item -- e.g., for a method it might include the
427 /// parameters from the impl.
429 /// Therefore, the method begins by walking down these parents,
430 /// starting with the outermost parent and proceed inwards until
431 /// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
432 /// first to see if the parent's substitutions are listed in there. If so,
433 /// we can append those and move on. Otherwise, it invokes the
434 /// three callback functions:
436 /// - `args_for_def_id`: given the `DefId` `P`, supplies back the
437 /// generic arguments that were given to that parent from within
438 /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
439 /// might refer to the trait `Foo`, and the arguments might be
440 /// `[T]`. The boolean value indicates whether to infer values
441 /// for arguments whose values were not explicitly provided.
442 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
443 /// instantiate a `Kind`.
444 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
445 /// creates a suitable inference variable.
446 pub fn create_substs_for_generic_args<'a, 'b>(
447 tcx: TyCtxt<'a, 'gcx, 'tcx>,
449 parent_substs: &[Kind<'tcx>],
451 self_ty: Option<Ty<'tcx>>,
452 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
453 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
454 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
455 ) -> SubstsRef<'tcx> {
456 // Collect the segments of the path; we need to substitute arguments
457 // for parameters throughout the entire path (wherever there are
458 // generic parameters).
459 let mut parent_defs = tcx.generics_of(def_id);
460 let count = parent_defs.count();
461 let mut stack = vec![(def_id, parent_defs)];
462 while let Some(def_id) = parent_defs.parent {
463 parent_defs = tcx.generics_of(def_id);
464 stack.push((def_id, parent_defs));
467 // We manually build up the substitution, rather than using convenience
468 // methods in `subst.rs`, so that we can iterate over the arguments and
469 // parameters in lock-step linearly, instead of trying to match each pair.
470 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
472 // Iterate over each segment of the path.
473 while let Some((def_id, defs)) = stack.pop() {
474 let mut params = defs.params.iter().peekable();
476 // If we have already computed substitutions for parents, we can use those directly.
477 while let Some(¶m) = params.peek() {
478 if let Some(&kind) = parent_substs.get(param.index as usize) {
486 // `Self` is handled first, unless it's been handled in `parent_substs`.
488 if let Some(¶m) = params.peek() {
489 if param.index == 0 {
490 if let GenericParamDefKind::Type { .. } = param.kind {
491 substs.push(self_ty.map(|ty| ty.into())
492 .unwrap_or_else(|| inferred_kind(None, param, true)));
499 // Check whether this segment takes generic arguments and the user has provided any.
500 let (generic_args, infer_types) = args_for_def_id(def_id);
502 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
506 // We're going to iterate through the generic arguments that the user
507 // provided, matching them with the generic parameters we expect.
508 // Mismatches can occur as a result of elided lifetimes, or for malformed
509 // input. We try to handle both sensibly.
510 match (args.peek(), params.peek()) {
511 (Some(&arg), Some(¶m)) => {
512 match (arg, ¶m.kind) {
513 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
514 | (GenericArg::Type(_), GenericParamDefKind::Type { .. })
515 | (GenericArg::Const(_), GenericParamDefKind::Const) => {
516 substs.push(provided_kind(param, arg));
520 (GenericArg::Type(_), GenericParamDefKind::Lifetime)
521 | (GenericArg::Const(_), GenericParamDefKind::Lifetime) => {
522 // We expected a lifetime argument, but got a type or const
523 // argument. That means we're inferring the lifetimes.
524 substs.push(inferred_kind(None, param, infer_types));
528 // We expected one kind of parameter, but the user provided
529 // another. This is an error, but we need to handle it
530 // gracefully so we can report sensible errors.
531 // In this case, we're simply going to infer this argument.
537 // We should never be able to reach this point with well-formed input.
538 // Getting to this point means the user supplied more arguments than
539 // there are parameters.
542 (None, Some(¶m)) => {
543 // If there are fewer arguments than parameters, it means
544 // we're inferring the remaining arguments.
545 substs.push(inferred_kind(Some(&substs), param, infer_types));
549 (None, None) => break,
554 tcx.intern_substs(&substs)
557 /// Given the type/lifetime/const arguments provided to some path (along with
558 /// an implicit `Self`, if this is a trait reference) returns the complete
559 /// set of substitutions. This may involve applying defaulted type parameters.
561 /// Note that the type listing given here is *exactly* what the user provided.
562 fn create_substs_for_ast_path(&self,
565 generic_args: &hir::GenericArgs,
567 self_ty: Option<Ty<'tcx>>)
568 -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>)
570 // If the type is parameterized by this region, then replace this
571 // region with the current anon region binding (in other words,
572 // whatever & would get replaced with).
573 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
575 def_id, self_ty, generic_args);
577 let tcx = self.tcx();
578 let generic_params = tcx.generics_of(def_id);
580 // If a self-type was declared, one should be provided.
581 assert_eq!(generic_params.has_self, self_ty.is_some());
583 let has_self = generic_params.has_self;
584 let (_, potential_assoc_types) = Self::check_generic_arg_count(
589 GenericArgPosition::Type,
594 let is_object = self_ty.map_or(false, |ty| {
595 ty == self.tcx().types.trait_object_dummy_self
597 let default_needs_object_self = |param: &ty::GenericParamDef| {
598 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
599 if is_object && has_default {
600 if tcx.at(span).type_of(param.def_id).has_self_ty() {
601 // There is no suitable inference default for a type parameter
602 // that references self, in an object type.
611 let substs = Self::create_substs_for_generic_args(
617 // Provide the generic args, and whether types should be inferred.
618 |_| (Some(generic_args), infer_types),
619 // Provide substitutions for parameters for which (valid) arguments have been provided.
621 match (¶m.kind, arg) {
622 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
623 self.ast_region_to_region(<, Some(param)).into()
625 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
626 self.ast_ty_to_ty(&ty).into()
628 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
629 self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
634 // Provide substitutions for parameters for which arguments are inferred.
635 |substs, param, infer_types| {
637 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
638 GenericParamDefKind::Type { has_default, .. } => {
639 if !infer_types && has_default {
640 // No type parameter provided, but a default exists.
642 // If we are converting an object type, then the
643 // `Self` parameter is unknown. However, some of the
644 // other type parameters may reference `Self` in their
645 // defaults. This will lead to an ICE if we are not
647 if default_needs_object_self(param) {
648 struct_span_err!(tcx.sess, span, E0393,
649 "the type parameter `{}` must be explicitly \
653 format!("missing reference to `{}`", param.name))
654 .note(&format!("because of the default `Self` reference, \
655 type parameters must be specified on object \
660 // This is a default type parameter.
663 tcx.at(span).type_of(param.def_id)
664 .subst_spanned(tcx, substs.unwrap(), Some(span))
667 } else if infer_types {
668 // No type parameters were provided, we can infer all.
669 if !default_needs_object_self(param) {
670 self.ty_infer_for_def(param, span).into()
672 self.ty_infer(span).into()
675 // We've already errored above about the mismatch.
679 GenericParamDefKind::Const => {
680 // FIXME(const_generics:defaults)
681 // We've already errored above about the mismatch.
682 tcx.consts.err.into()
688 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
690 item_name: binding.ident,
691 ty: self.ast_ty_to_ty(&binding.ty),
696 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
697 generic_params, self_ty, substs);
699 (substs, assoc_bindings, potential_assoc_types)
702 /// Instantiates the path for the given trait reference, assuming that it's
703 /// bound to a valid trait type. Returns the def_id for the defining trait.
704 /// The type _cannot_ be a type other than a trait type.
706 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
707 /// are disallowed. Otherwise, they are pushed onto the vector given.
708 pub fn instantiate_mono_trait_ref(&self,
709 trait_ref: &hir::TraitRef,
711 -> ty::TraitRef<'tcx>
713 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
715 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
716 trait_ref.trait_def_id(),
718 trait_ref.path.segments.last().unwrap())
721 /// The given trait-ref must actually be a trait.
722 pub(super) fn instantiate_poly_trait_ref_inner(&self,
723 trait_ref: &hir::TraitRef,
725 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
727 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
729 let trait_def_id = trait_ref.trait_def_id();
731 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
733 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
735 let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
739 trait_ref.path.segments.last().unwrap(),
741 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
743 let mut dup_bindings = FxHashMap::default();
744 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
745 // specify type to assert that error was already reported in Err case:
746 let predicate: Result<_, ErrorReported> =
747 self.ast_type_binding_to_poly_projection_predicate(
748 trait_ref.hir_ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
749 // okay to ignore Err because of ErrorReported (see above)
750 Some((predicate.ok()?, binding.span))
753 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
754 trait_ref, poly_projections, poly_trait_ref);
755 (poly_trait_ref, potential_assoc_types)
758 pub fn instantiate_poly_trait_ref(&self,
759 poly_trait_ref: &hir::PolyTraitRef,
761 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
762 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
764 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
765 poly_projections, false)
768 fn ast_path_to_mono_trait_ref(&self,
772 trait_segment: &hir::PathSegment)
773 -> ty::TraitRef<'tcx>
775 let (substs, assoc_bindings, _) =
776 self.create_substs_for_ast_trait_ref(span,
780 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
781 ty::TraitRef::new(trait_def_id, substs)
784 fn create_substs_for_ast_trait_ref(
789 trait_segment: &hir::PathSegment,
790 ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>) {
791 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
794 let trait_def = self.tcx().trait_def(trait_def_id);
796 if !self.tcx().features().unboxed_closures &&
797 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
798 != trait_def.paren_sugar {
799 // For now, require that parenthetical notation be used only with `Fn()` etc.
800 let msg = if trait_def.paren_sugar {
801 "the precise format of `Fn`-family traits' type parameters is subject to change. \
802 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
804 "parenthetical notation is only stable when used with `Fn`-family traits"
806 emit_feature_err(&self.tcx().sess.parse_sess, sym::unboxed_closures,
807 span, GateIssue::Language, msg);
810 trait_segment.with_generic_args(|generic_args| {
811 self.create_substs_for_ast_path(span,
814 trait_segment.infer_types,
819 fn trait_defines_associated_type_named(&self,
821 assoc_name: ast::Ident)
824 self.tcx().associated_items(trait_def_id).any(|item| {
825 item.kind == ty::AssociatedKind::Type &&
826 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
830 fn ast_type_binding_to_poly_projection_predicate(
832 hir_ref_id: hir::HirId,
833 trait_ref: ty::PolyTraitRef<'tcx>,
834 binding: &ConvertedBinding<'tcx>,
836 dup_bindings: &mut FxHashMap<DefId, Span>)
837 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
839 let tcx = self.tcx();
842 // Given something like `U: SomeTrait<T = X>`, we want to produce a
843 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
844 // subtle in the event that `T` is defined in a supertrait of
845 // `SomeTrait`, because in that case we need to upcast.
847 // That is, consider this case:
850 // trait SubTrait: SuperTrait<int> { }
851 // trait SuperTrait<A> { type T; }
853 // ... B : SubTrait<T=foo> ...
856 // We want to produce `<B as SuperTrait<int>>::T == foo`.
858 // Find any late-bound regions declared in `ty` that are not
859 // declared in the trait-ref. These are not wellformed.
863 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
864 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
865 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
866 let late_bound_in_ty =
867 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
868 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
869 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
870 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
871 let br_name = match *br {
872 ty::BrNamed(_, name) => name,
876 "anonymous bound region {:?} in binding but not trait ref",
880 struct_span_err!(tcx.sess,
883 "binding for associated type `{}` references lifetime `{}`, \
884 which does not appear in the trait input types",
885 binding.item_name, br_name)
890 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
892 // Simple case: X is defined in the current trait.
895 // Otherwise, we have to walk through the supertraits to find
897 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
898 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
900 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
901 binding.item_name, binding.span)
904 let (assoc_ident, def_scope) =
905 tcx.adjust_ident(binding.item_name, candidate.def_id(), hir_ref_id);
906 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
907 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
908 }).expect("missing associated type");
910 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
911 let msg = format!("associated type `{}` is private", binding.item_name);
912 tcx.sess.span_err(binding.span, &msg);
914 tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
917 dup_bindings.entry(assoc_ty.def_id)
918 .and_modify(|prev_span| {
919 struct_span_err!(self.tcx().sess, binding.span, E0719,
920 "the value of the associated type `{}` (from the trait `{}`) \
921 is already specified",
923 tcx.def_path_str(assoc_ty.container.id()))
924 .span_label(binding.span, "re-bound here")
925 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
928 .or_insert(binding.span);
931 Ok(candidate.map_bound(|trait_ref| {
932 ty::ProjectionPredicate {
933 projection_ty: ty::ProjectionTy::from_ref_and_name(
943 fn ast_path_to_ty(&self,
946 item_segment: &hir::PathSegment)
949 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
952 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
956 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
957 /// removing the dummy `Self` type (`trait_object_dummy_self`).
958 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
959 -> ty::ExistentialTraitRef<'tcx> {
960 if trait_ref.self_ty() != self.tcx().types.trait_object_dummy_self {
961 bug!("trait_ref_to_existential called on {:?} with non-dummy Self", trait_ref);
963 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
966 fn conv_object_ty_poly_trait_ref(&self,
968 trait_bounds: &[hir::PolyTraitRef],
969 lifetime: &hir::Lifetime)
972 let tcx = self.tcx();
974 if trait_bounds.is_empty() {
975 span_err!(tcx.sess, span, E0224,
976 "at least one non-builtin trait is required for an object type");
977 return tcx.types.err;
980 let mut projection_bounds = Vec::new();
981 let dummy_self = self.tcx().types.trait_object_dummy_self;
982 let (principal, potential_assoc_types) = self.instantiate_poly_trait_ref(
985 &mut projection_bounds,
987 debug!("principal: {:?}", principal);
989 for trait_bound in trait_bounds[1..].iter() {
990 // sanity check for non-principal trait bounds
991 self.instantiate_poly_trait_ref(trait_bound,
996 let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
998 if !trait_bounds.is_empty() {
999 let b = &trait_bounds[0];
1000 let span = b.trait_ref.path.span;
1001 struct_span_err!(self.tcx().sess, span, E0225,
1002 "only auto traits can be used as additional traits in a trait object")
1003 .span_label(span, "non-auto additional trait")
1007 // Check that there are no gross object safety violations;
1008 // most importantly, that the supertraits don't contain `Self`,
1010 let object_safety_violations =
1011 tcx.global_tcx().astconv_object_safety_violations(principal.def_id());
1012 if !object_safety_violations.is_empty() {
1013 tcx.report_object_safety_error(span, principal.def_id(), object_safety_violations)
1014 .map(|mut err| err.emit());
1015 return tcx.types.err;
1018 // Use a `BTreeSet` to keep output in a more consistent order.
1019 let mut associated_types = BTreeSet::default();
1021 for tr in traits::elaborate_trait_ref(tcx, principal) {
1022 debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", tr);
1024 ty::Predicate::Trait(pred) => {
1025 associated_types.extend(tcx.associated_items(pred.def_id())
1026 .filter(|item| item.kind == ty::AssociatedKind::Type)
1027 .map(|item| item.def_id));
1029 ty::Predicate::Projection(pred) => {
1030 // A `Self` within the original bound will be substituted with a
1031 // `trait_object_dummy_self`, so check for that.
1032 let references_self =
1033 pred.skip_binder().ty.walk().any(|t| t == dummy_self);
1035 // If the projection output contains `Self`, force the user to
1036 // elaborate it explicitly to avoid a bunch of complexity.
1038 // The "classicaly useful" case is the following:
1040 // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
1045 // Here, the user could theoretically write `dyn MyTrait<Output=X>`,
1046 // but actually supporting that would "expand" to an infinitely-long type
1047 // `fix $ τ → dyn MyTrait<MyOutput=X, Output=<τ as MyTrait>::MyOutput`.
1049 // Instead, we force the user to write `dyn MyTrait<MyOutput=X, Output=X>`,
1050 // which is uglier but works. See the discussion in #56288 for alternatives.
1051 if !references_self {
1052 // Include projections defined on supertraits,
1053 projection_bounds.push((pred, DUMMY_SP))
1060 for (projection_bound, _) in &projection_bounds {
1061 associated_types.remove(&projection_bound.projection_def_id());
1064 if !associated_types.is_empty() {
1065 let names = associated_types.iter().map(|item_def_id| {
1066 let assoc_item = tcx.associated_item(*item_def_id);
1067 let trait_def_id = assoc_item.container.id();
1069 "`{}` (from the trait `{}`)",
1071 tcx.def_path_str(trait_def_id),
1073 }).collect::<Vec<_>>().join(", ");
1074 let mut err = struct_span_err!(
1078 "the value of the associated type{} {} must be specified",
1079 if associated_types.len() == 1 { "" } else { "s" },
1082 let mut suggest = false;
1083 let mut potential_assoc_types_spans = vec![];
1084 if let Some(potential_assoc_types) = potential_assoc_types {
1085 if potential_assoc_types.len() == associated_types.len() {
1086 // Only suggest when the amount of missing associated types is equals to the
1087 // extra type arguments present, as that gives us a relatively high confidence
1088 // that the user forgot to give the associtated type's name. The canonical
1089 // example would be trying to use `Iterator<isize>` instead of
1090 // `Iterator<Item=isize>`.
1092 potential_assoc_types_spans = potential_assoc_types;
1095 let mut suggestions = vec![];
1096 for (i, item_def_id) in associated_types.iter().enumerate() {
1097 let assoc_item = tcx.associated_item(*item_def_id);
1100 format!("associated type `{}` must be specified", assoc_item.ident),
1102 if item_def_id.is_local() {
1104 tcx.def_span(*item_def_id),
1105 format!("`{}` defined here", assoc_item.ident),
1109 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
1110 potential_assoc_types_spans[i],
1113 potential_assoc_types_spans[i],
1114 format!("{} = {}", assoc_item.ident, snippet),
1119 if !suggestions.is_empty() {
1120 let msg = format!("if you meant to specify the associated {}, write",
1121 if suggestions.len() == 1 { "type" } else { "types" });
1122 err.multipart_suggestion(
1125 Applicability::MaybeIncorrect,
1131 // Erase the `dummy_self` (`trait_object_dummy_self`) used above.
1132 let existential_principal = principal.map_bound(|trait_ref| {
1133 self.trait_ref_to_existential(trait_ref)
1135 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1136 bound.map_bound(|b| {
1137 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1138 ty::ExistentialProjection {
1140 item_def_id: b.projection_ty.item_def_id,
1141 substs: trait_ref.substs,
1146 // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
1148 auto_traits.dedup();
1150 // Calling `skip_binder` is okay, because the predicates are re-bound.
1151 let principal = if tcx.trait_is_auto(existential_principal.def_id()) {
1152 ty::ExistentialPredicate::AutoTrait(existential_principal.def_id())
1154 ty::ExistentialPredicate::Trait(*existential_principal.skip_binder())
1157 iter::once(principal)
1158 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
1159 .chain(existential_projections
1160 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1161 .collect::<SmallVec<[_; 8]>>();
1162 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1164 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1166 // Use explicitly-specified region bound.
1167 let region_bound = if !lifetime.is_elided() {
1168 self.ast_region_to_region(lifetime, None)
1170 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1171 if tcx.named_region(lifetime.hir_id).is_some() {
1172 self.ast_region_to_region(lifetime, None)
1174 self.re_infer(span, None).unwrap_or_else(|| {
1175 span_err!(tcx.sess, span, E0228,
1176 "the lifetime bound for this object type cannot be deduced \
1177 from context; please supply an explicit bound");
1178 tcx.lifetimes.re_static
1184 debug!("region_bound: {:?}", region_bound);
1186 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1187 debug!("trait_object_type: {:?}", ty);
1191 fn report_ambiguous_associated_type(
1198 let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
1199 if let (Some(_), Ok(snippet)) = (
1200 self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
1201 self.tcx().sess.source_map().span_to_snippet(span),
1203 err.span_suggestion(
1205 "you are looking for the module in `std`, not the primitive type",
1206 format!("std::{}", snippet),
1207 Applicability::MachineApplicable,
1210 err.span_suggestion(
1212 "use fully-qualified syntax",
1213 format!("<{} as {}>::{}", type_str, trait_str, name),
1214 Applicability::HasPlaceholders
1220 // Search for a bound on a type parameter which includes the associated item
1221 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1222 // This function will fail if there are no suitable bounds or there is
1224 fn find_bound_for_assoc_item(&self,
1225 ty_param_def_id: DefId,
1226 assoc_name: ast::Ident,
1228 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1230 let tcx = self.tcx();
1232 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1233 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1235 // Check that there is exactly one way to find an associated type with the
1237 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1238 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1240 let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
1241 let param_name = tcx.hir().ty_param_name(param_hir_id);
1242 self.one_bound_for_assoc_type(suitable_bounds,
1243 ¶m_name.as_str(),
1248 // Checks that `bounds` contains exactly one element and reports appropriate
1249 // errors otherwise.
1250 fn one_bound_for_assoc_type<I>(&self,
1252 ty_param_name: &str,
1253 assoc_name: ast::Ident,
1255 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1256 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1258 let bound = match bounds.next() {
1259 Some(bound) => bound,
1261 struct_span_err!(self.tcx().sess, span, E0220,
1262 "associated type `{}` not found for `{}`",
1265 .span_label(span, format!("associated type `{}` not found", assoc_name))
1267 return Err(ErrorReported);
1271 if let Some(bound2) = bounds.next() {
1272 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1273 let mut err = struct_span_err!(
1274 self.tcx().sess, span, E0221,
1275 "ambiguous associated type `{}` in bounds of `{}`",
1278 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1280 for bound in bounds {
1281 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1282 item.kind == ty::AssociatedKind::Type &&
1283 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1285 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
1287 if let Some(span) = bound_span {
1288 err.span_label(span, format!("ambiguous `{}` from `{}`",
1292 span_note!(&mut err, span,
1293 "associated type `{}` could derive from `{}`",
1304 // Create a type from a path to an associated type.
1305 // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
1306 // and item_segment is the path segment for `D`. We return a type and a def for
1308 // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
1309 // parameter or `Self`.
1310 pub fn associated_path_to_ty(
1312 hir_ref_id: hir::HirId,
1316 assoc_segment: &hir::PathSegment,
1317 permit_variants: bool,
1318 ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
1319 let tcx = self.tcx();
1320 let assoc_ident = assoc_segment.ident;
1322 debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
1324 self.prohibit_generics(slice::from_ref(assoc_segment));
1326 // Check if we have an enum variant.
1327 let mut variant_resolution = None;
1328 if let ty::Adt(adt_def, _) = qself_ty.sty {
1329 if adt_def.is_enum() {
1330 let variant_def = adt_def.variants.iter().find(|vd| {
1331 tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did)
1333 if let Some(variant_def) = variant_def {
1334 if permit_variants {
1335 check_type_alias_enum_variants_enabled(tcx, span);
1336 tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
1337 return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
1339 variant_resolution = Some(variant_def.def_id);
1345 // Find the type of the associated item, and the trait where the associated
1346 // item is declared.
1347 let bound = match (&qself_ty.sty, qself_res) {
1348 (_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
1349 // `Self` in an impl of a trait -- we have a concrete self type and a
1351 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1352 Some(trait_ref) => trait_ref,
1354 // A cycle error occurred, most likely.
1355 return Err(ErrorReported);
1359 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1360 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_ident));
1362 self.one_bound_for_assoc_type(candidates, "Self", assoc_ident, span)?
1364 (&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
1365 (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
1366 self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
1369 if variant_resolution.is_some() {
1370 // Variant in type position
1371 let msg = format!("expected type, found variant `{}`", assoc_ident);
1372 tcx.sess.span_err(span, &msg);
1373 } else if qself_ty.is_enum() {
1374 let mut err = tcx.sess.struct_span_err(
1376 &format!("no variant `{}` in enum `{}`", assoc_ident, qself_ty),
1379 let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
1380 if let Some(suggested_name) = find_best_match_for_name(
1381 adt_def.variants.iter().map(|variant| &variant.ident.name),
1382 &assoc_ident.as_str(),
1385 err.span_suggestion(
1387 "there is a variant with a similar name",
1388 suggested_name.to_string(),
1389 Applicability::MaybeIncorrect,
1392 err.span_label(span, format!("variant not found in `{}`", qself_ty));
1395 if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
1396 let sp = tcx.sess.source_map().def_span(sp);
1397 err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
1401 } else if !qself_ty.references_error() {
1402 // Don't print `TyErr` to the user.
1403 self.report_ambiguous_associated_type(
1405 &qself_ty.to_string(),
1407 &assoc_ident.as_str(),
1410 return Err(ErrorReported);
1414 let trait_did = bound.def_id();
1415 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_ident, trait_did, hir_ref_id);
1416 let item = tcx.associated_items(trait_did).find(|i| {
1417 Namespace::from(i.kind) == Namespace::Type &&
1418 i.ident.modern() == assoc_ident
1419 }).expect("missing associated type");
1421 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1422 let ty = self.normalize_ty(span, ty);
1424 let kind = DefKind::AssociatedTy;
1425 if !item.vis.is_accessible_from(def_scope, tcx) {
1426 let msg = format!("{} `{}` is private", kind.descr(), assoc_ident);
1427 tcx.sess.span_err(span, &msg);
1429 tcx.check_stability(item.def_id, Some(hir_ref_id), span);
1431 if let Some(variant_def_id) = variant_resolution {
1432 let mut err = tcx.struct_span_lint_hir(
1433 AMBIGUOUS_ASSOCIATED_ITEMS,
1436 "ambiguous associated item",
1439 let mut could_refer_to = |kind: DefKind, def_id, also| {
1440 let note_msg = format!("`{}` could{} refer to {} defined here",
1441 assoc_ident, also, kind.descr());
1442 err.span_note(tcx.def_span(def_id), ¬e_msg);
1444 could_refer_to(DefKind::Variant, variant_def_id, "");
1445 could_refer_to(kind, item.def_id, " also");
1447 err.span_suggestion(
1449 "use fully-qualified syntax",
1450 format!("<{} as {}>::{}", qself_ty, "Trait", assoc_ident),
1451 Applicability::HasPlaceholders,
1455 Ok((ty, kind, item.def_id))
1458 fn qpath_to_ty(&self,
1460 opt_self_ty: Option<Ty<'tcx>>,
1462 trait_segment: &hir::PathSegment,
1463 item_segment: &hir::PathSegment)
1466 let tcx = self.tcx();
1467 let trait_def_id = tcx.parent(item_def_id).unwrap();
1469 self.prohibit_generics(slice::from_ref(item_segment));
1471 let self_ty = if let Some(ty) = opt_self_ty {
1474 let path_str = tcx.def_path_str(trait_def_id);
1475 self.report_ambiguous_associated_type(
1479 &item_segment.ident.as_str(),
1481 return tcx.types.err;
1484 debug!("qpath_to_ty: self_type={:?}", self_ty);
1486 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1491 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1493 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1496 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(
1497 &self, segments: T) -> bool {
1498 let mut has_err = false;
1499 for segment in segments {
1500 segment.with_generic_args(|generic_args| {
1501 let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
1502 for arg in &generic_args.args {
1503 let (span, kind) = match arg {
1504 hir::GenericArg::Lifetime(lt) => {
1505 if err_for_lt { continue }
1508 (lt.span, "lifetime")
1510 hir::GenericArg::Type(ty) => {
1511 if err_for_ty { continue }
1516 hir::GenericArg::Const(ct) => {
1517 if err_for_ct { continue }
1522 let mut err = struct_span_err!(
1526 "{} arguments are not allowed for this type",
1529 err.span_label(span, format!("{} argument not allowed", kind));
1531 if err_for_lt && err_for_ty && err_for_ct {
1535 for binding in &generic_args.bindings {
1537 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1545 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_, '_, '_>, span: Span) {
1546 let mut err = struct_span_err!(tcx.sess, span, E0229,
1547 "associated type bindings are not allowed here");
1548 err.span_label(span, "associated type not allowed here").emit();
1551 // FIXME(eddyb, varkor) handle type paths here too, not just value ones.
1552 pub fn def_ids_for_value_path_segments(
1554 segments: &[hir::PathSegment],
1555 self_ty: Option<Ty<'tcx>>,
1559 // We need to extract the type parameters supplied by the user in
1560 // the path `path`. Due to the current setup, this is a bit of a
1561 // tricky-process; the problem is that resolve only tells us the
1562 // end-point of the path resolution, and not the intermediate steps.
1563 // Luckily, we can (at least for now) deduce the intermediate steps
1564 // just from the end-point.
1566 // There are basically five cases to consider:
1568 // 1. Reference to a constructor of a struct:
1570 // struct Foo<T>(...)
1572 // In this case, the parameters are declared in the type space.
1574 // 2. Reference to a constructor of an enum variant:
1576 // enum E<T> { Foo(...) }
1578 // In this case, the parameters are defined in the type space,
1579 // but may be specified either on the type or the variant.
1581 // 3. Reference to a fn item or a free constant:
1585 // In this case, the path will again always have the form
1586 // `a::b::foo::<T>` where only the final segment should have
1587 // type parameters. However, in this case, those parameters are
1588 // declared on a value, and hence are in the `FnSpace`.
1590 // 4. Reference to a method or an associated constant:
1592 // impl<A> SomeStruct<A> {
1596 // Here we can have a path like
1597 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
1598 // may appear in two places. The penultimate segment,
1599 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
1600 // final segment, `foo::<B>` contains parameters in fn space.
1602 // The first step then is to categorize the segments appropriately.
1604 let tcx = self.tcx();
1606 assert!(!segments.is_empty());
1607 let last = segments.len() - 1;
1609 let mut path_segs = vec![];
1612 // Case 1. Reference to a struct constructor.
1613 DefKind::Ctor(CtorOf::Struct, ..) => {
1614 // Everything but the final segment should have no
1615 // parameters at all.
1616 let generics = tcx.generics_of(def_id);
1617 // Variant and struct constructors use the
1618 // generics of their parent type definition.
1619 let generics_def_id = generics.parent.unwrap_or(def_id);
1620 path_segs.push(PathSeg(generics_def_id, last));
1623 // Case 2. Reference to a variant constructor.
1624 DefKind::Ctor(CtorOf::Variant, ..)
1625 | DefKind::Variant => {
1626 let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
1627 let (generics_def_id, index) = if let Some(adt_def) = adt_def {
1628 debug_assert!(adt_def.is_enum());
1630 } else if last >= 1 && segments[last - 1].args.is_some() {
1631 // Everything but the penultimate segment should have no
1632 // parameters at all.
1633 let mut def_id = def_id;
1635 // `DefKind::Ctor` -> `DefKind::Variant`
1636 if let DefKind::Ctor(..) = kind {
1637 def_id = tcx.parent(def_id).unwrap()
1640 // `DefKind::Variant` -> `DefKind::Enum`
1641 let enum_def_id = tcx.parent(def_id).unwrap();
1642 (enum_def_id, last - 1)
1644 // FIXME: lint here recommending `Enum::<...>::Variant` form
1645 // instead of `Enum::Variant::<...>` form.
1647 // Everything but the final segment should have no
1648 // parameters at all.
1649 let generics = tcx.generics_of(def_id);
1650 // Variant and struct constructors use the
1651 // generics of their parent type definition.
1652 (generics.parent.unwrap_or(def_id), last)
1654 path_segs.push(PathSeg(generics_def_id, index));
1657 // Case 3. Reference to a top-level value.
1660 | DefKind::ConstParam
1661 | DefKind::Static => {
1662 path_segs.push(PathSeg(def_id, last));
1665 // Case 4. Reference to a method or associated const.
1667 | DefKind::AssociatedConst => {
1668 if segments.len() >= 2 {
1669 let generics = tcx.generics_of(def_id);
1670 path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
1672 path_segs.push(PathSeg(def_id, last));
1675 kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
1678 debug!("path_segs = {:?}", path_segs);
1683 // Check a type `Path` and convert it to a `Ty`.
1684 pub fn res_to_ty(&self,
1685 opt_self_ty: Option<Ty<'tcx>>,
1687 permit_variants: bool)
1689 let tcx = self.tcx();
1691 debug!("res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
1692 path.res, opt_self_ty, path.segments);
1694 let span = path.span;
1696 Res::Def(DefKind::Existential, did) => {
1697 // Check for desugared impl trait.
1698 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1699 let item_segment = path.segments.split_last().unwrap();
1700 self.prohibit_generics(item_segment.1);
1701 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1704 tcx.mk_opaque(did, substs),
1707 Res::Def(DefKind::Enum, did)
1708 | Res::Def(DefKind::TyAlias, did)
1709 | Res::Def(DefKind::Struct, did)
1710 | Res::Def(DefKind::Union, did)
1711 | Res::Def(DefKind::ForeignTy, did) => {
1712 assert_eq!(opt_self_ty, None);
1713 self.prohibit_generics(path.segments.split_last().unwrap().1);
1714 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1716 Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
1717 // Convert "variant type" as if it were a real type.
1718 // The resulting `Ty` is type of the variant's enum for now.
1719 assert_eq!(opt_self_ty, None);
1722 self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
1723 let generic_segs: FxHashSet<_> =
1724 path_segs.iter().map(|PathSeg(_, index)| index).collect();
1725 self.prohibit_generics(path.segments.iter().enumerate().filter_map(|(index, seg)| {
1726 if !generic_segs.contains(&index) {
1733 let PathSeg(def_id, index) = path_segs.last().unwrap();
1734 self.ast_path_to_ty(span, *def_id, &path.segments[*index])
1736 Res::Def(DefKind::TyParam, did) => {
1737 assert_eq!(opt_self_ty, None);
1738 self.prohibit_generics(&path.segments);
1740 let hir_id = tcx.hir().as_local_hir_id(did).unwrap();
1741 let item_id = tcx.hir().get_parent_node_by_hir_id(hir_id);
1742 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1743 let generics = tcx.generics_of(item_def_id);
1744 let index = generics.param_def_id_to_index[
1745 &tcx.hir().local_def_id_from_hir_id(hir_id)];
1746 tcx.mk_ty_param(index, tcx.hir().name_by_hir_id(hir_id).as_interned_str())
1748 Res::SelfTy(_, Some(def_id)) => {
1749 // `Self` in impl (we know the concrete type).
1750 assert_eq!(opt_self_ty, None);
1751 self.prohibit_generics(&path.segments);
1752 // Try to evaluate any array length constants
1753 self.normalize_ty(span, tcx.at(span).type_of(def_id))
1755 Res::SelfTy(Some(_), None) => {
1757 assert_eq!(opt_self_ty, None);
1758 self.prohibit_generics(&path.segments);
1761 Res::Def(DefKind::AssociatedTy, def_id) => {
1762 debug_assert!(path.segments.len() >= 2);
1763 self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
1764 self.qpath_to_ty(span,
1767 &path.segments[path.segments.len() - 2],
1768 path.segments.last().unwrap())
1770 Res::PrimTy(prim_ty) => {
1771 assert_eq!(opt_self_ty, None);
1772 self.prohibit_generics(&path.segments);
1774 hir::Bool => tcx.types.bool,
1775 hir::Char => tcx.types.char,
1776 hir::Int(it) => tcx.mk_mach_int(it),
1777 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1778 hir::Float(ft) => tcx.mk_mach_float(ft),
1779 hir::Str => tcx.mk_str()
1783 self.set_tainted_by_errors();
1784 return self.tcx().types.err;
1786 _ => span_bug!(span, "unexpected resolution: {:?}", path.res)
1790 /// Parses the programmer's textual representation of a type into our
1791 /// internal notion of a type.
1792 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1793 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1794 ast_ty.hir_id, ast_ty, ast_ty.node);
1796 let tcx = self.tcx();
1798 let result_ty = match ast_ty.node {
1799 hir::TyKind::Slice(ref ty) => {
1800 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1802 hir::TyKind::Ptr(ref mt) => {
1803 tcx.mk_ptr(ty::TypeAndMut {
1804 ty: self.ast_ty_to_ty(&mt.ty),
1808 hir::TyKind::Rptr(ref region, ref mt) => {
1809 let r = self.ast_region_to_region(region, None);
1810 debug!("Ref r={:?}", r);
1811 let t = self.ast_ty_to_ty(&mt.ty);
1812 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1814 hir::TyKind::Never => {
1817 hir::TyKind::Tup(ref fields) => {
1818 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1820 hir::TyKind::BareFn(ref bf) => {
1821 require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1822 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1824 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1825 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1827 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1828 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1829 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1830 self.ast_ty_to_ty(qself)
1832 self.res_to_ty(opt_self_ty, path, false)
1834 hir::TyKind::Def(item_id, ref lifetimes) => {
1835 let did = tcx.hir().local_def_id_from_hir_id(item_id.id);
1836 self.impl_trait_ty_to_ty(did, lifetimes)
1838 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1839 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1840 let ty = self.ast_ty_to_ty(qself);
1842 let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1847 self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
1848 .map(|(ty, _, _)| ty).unwrap_or(tcx.types.err)
1850 hir::TyKind::Array(ref ty, ref length) => {
1851 let length = self.ast_const_to_const(length, tcx.types.usize);
1852 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1853 self.normalize_ty(ast_ty.span, array_ty)
1855 hir::TyKind::Typeof(ref _e) => {
1856 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1857 "`typeof` is a reserved keyword but unimplemented")
1858 .span_label(ast_ty.span, "reserved keyword")
1863 hir::TyKind::Infer => {
1864 // Infer also appears as the type of arguments or return
1865 // values in a ExprKind::Closure, or as
1866 // the type of local variables. Both of these cases are
1867 // handled specially and will not descend into this routine.
1868 self.ty_infer(ast_ty.span)
1870 hir::TyKind::Err => {
1873 hir::TyKind::CVarArgs(lt) => {
1874 let va_list_did = match tcx.lang_items().va_list() {
1876 None => span_bug!(ast_ty.span,
1877 "`va_list` lang item required for variadics"),
1879 let region = self.ast_region_to_region(<, None);
1880 tcx.type_of(va_list_did).subst(tcx, &[region.into()])
1884 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1888 pub fn ast_const_to_const(
1890 ast_const: &hir::AnonConst,
1892 ) -> &'tcx ty::Const<'tcx> {
1893 debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
1895 let tcx = self.tcx();
1896 let def_id = tcx.hir().local_def_id_from_hir_id(ast_const.hir_id);
1898 let mut const_ = ty::Const {
1899 val: ConstValue::Unevaluated(
1901 InternalSubsts::identity_for_item(tcx, def_id),
1906 let mut expr = &tcx.hir().body(ast_const.body).value;
1908 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
1909 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
1910 if let ExprKind::Block(block, _) = &expr.node {
1911 if block.stmts.is_empty() {
1912 if let Some(trailing) = &block.expr {
1918 if let ExprKind::Path(ref qpath) = expr.node {
1919 if let hir::QPath::Resolved(_, ref path) = qpath {
1920 if let Res::Def(DefKind::ConstParam, def_id) = path.res {
1921 let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
1922 let item_id = tcx.hir().get_parent_node(node_id);
1923 let item_def_id = tcx.hir().local_def_id(item_id);
1924 let generics = tcx.generics_of(item_def_id);
1925 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(node_id)];
1926 let name = tcx.hir().name(node_id).as_interned_str();
1927 const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
1932 tcx.mk_const(const_)
1935 pub fn impl_trait_ty_to_ty(
1938 lifetimes: &[hir::GenericArg],
1940 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1941 let tcx = self.tcx();
1943 let generics = tcx.generics_of(def_id);
1945 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1946 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
1947 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1948 // Our own parameters are the resolved lifetimes.
1950 GenericParamDefKind::Lifetime => {
1951 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1952 self.ast_region_to_region(lifetime, None).into()
1960 // Replace all parent lifetimes with 'static.
1962 GenericParamDefKind::Lifetime => {
1963 tcx.lifetimes.re_static.into()
1965 _ => tcx.mk_param_from_def(param)
1969 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1971 let ty = tcx.mk_opaque(def_id, substs);
1972 debug!("impl_trait_ty_to_ty: {}", ty);
1976 pub fn ty_of_arg(&self,
1978 expected_ty: Option<Ty<'tcx>>)
1982 hir::TyKind::Infer if expected_ty.is_some() => {
1983 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1984 expected_ty.unwrap()
1986 _ => self.ast_ty_to_ty(ty),
1990 pub fn ty_of_fn(&self,
1991 unsafety: hir::Unsafety,
1994 -> ty::PolyFnSig<'tcx> {
1997 let tcx = self.tcx();
1999 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
2001 let output_ty = match decl.output {
2002 hir::Return(ref output) => self.ast_ty_to_ty(output),
2003 hir::DefaultReturn(..) => tcx.mk_unit(),
2006 debug!("ty_of_fn: output_ty={:?}", output_ty);
2008 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
2016 // Find any late-bound regions declared in return type that do
2017 // not appear in the arguments. These are not well-formed.
2020 // for<'a> fn() -> &'a str <-- 'a is bad
2021 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
2022 let inputs = bare_fn_ty.inputs();
2023 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
2024 &inputs.map_bound(|i| i.to_owned()));
2025 let output = bare_fn_ty.output();
2026 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
2027 for br in late_bound_in_ret.difference(&late_bound_in_args) {
2028 let lifetime_name = match *br {
2029 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
2030 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
2032 let mut err = struct_span_err!(tcx.sess,
2035 "return type references {} \
2036 which is not constrained by the fn input types",
2038 if let ty::BrAnon(_) = *br {
2039 // The only way for an anonymous lifetime to wind up
2040 // in the return type but **also** be unconstrained is
2041 // if it only appears in "associated types" in the
2042 // input. See #47511 for an example. In this case,
2043 // though we can easily give a hint that ought to be
2045 err.note("lifetimes appearing in an associated type \
2046 are not considered constrained");
2054 /// Given the bounds on an object, determines what single region bound (if any) we can
2055 /// use to summarize this type. The basic idea is that we will use the bound the user
2056 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
2057 /// for region bounds. It may be that we can derive no bound at all, in which case
2058 /// we return `None`.
2059 fn compute_object_lifetime_bound(&self,
2061 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
2062 -> Option<ty::Region<'tcx>> // if None, use the default
2064 let tcx = self.tcx();
2066 debug!("compute_opt_region_bound(existential_predicates={:?})",
2067 existential_predicates);
2069 // No explicit region bound specified. Therefore, examine trait
2070 // bounds and see if we can derive region bounds from those.
2071 let derived_region_bounds =
2072 object_region_bounds(tcx, existential_predicates);
2074 // If there are no derived region bounds, then report back that we
2075 // can find no region bound. The caller will use the default.
2076 if derived_region_bounds.is_empty() {
2080 // If any of the derived region bounds are 'static, that is always
2082 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
2083 return Some(tcx.lifetimes.re_static);
2086 // Determine whether there is exactly one unique region in the set
2087 // of derived region bounds. If so, use that. Otherwise, report an
2089 let r = derived_region_bounds[0];
2090 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
2091 span_err!(tcx.sess, span, E0227,
2092 "ambiguous lifetime bound, explicit lifetime bound required");
2098 /// Divides a list of general trait bounds into two groups: auto traits (e.g., Sync and Send) and
2099 /// the remaining general trait bounds.
2100 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
2101 trait_bounds: &'b [hir::PolyTraitRef])
2102 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
2104 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
2105 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
2106 match bound.trait_ref.path.res {
2107 Res::Def(DefKind::Trait, trait_did) if tcx.trait_is_auto(trait_did) => {
2114 let auto_traits = auto_traits.into_iter().map(|tr| {
2115 if let Res::Def(DefKind::Trait, trait_did) = tr.trait_ref.path.res {
2120 }).collect::<Vec<_>>();
2122 (auto_traits, trait_bounds)
2125 // A helper struct for conveniently grouping a set of bounds which we pass to
2126 // and return from functions in multiple places.
2127 #[derive(PartialEq, Eq, Clone, Debug)]
2128 pub struct Bounds<'tcx> {
2129 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
2130 pub implicitly_sized: Option<Span>,
2131 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
2132 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
2135 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
2136 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
2137 -> Vec<(ty::Predicate<'tcx>, Span)>
2139 // If it could be sized, and is, add the sized predicate.
2140 let sized_predicate = self.implicitly_sized.and_then(|span| {
2141 tcx.lang_items().sized_trait().map(|sized| {
2142 let trait_ref = ty::TraitRef {
2144 substs: tcx.mk_substs_trait(param_ty, &[])
2146 (trait_ref.to_predicate(), span)
2150 sized_predicate.into_iter().chain(
2151 self.region_bounds.iter().map(|&(region_bound, span)| {
2152 // Account for the binder being introduced below; no need to shift `param_ty`
2153 // because, at present at least, it can only refer to early-bound regions.
2154 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
2155 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
2156 (ty::Binder::dummy(outlives).to_predicate(), span)
2158 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
2159 (bound_trait_ref.to_predicate(), span)
2162 self.projection_bounds.iter().map(|&(projection, span)| {
2163 (projection.to_predicate(), span)