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 let mut reported_late_bound_region_err = None;
294 if !infer_lifetimes {
295 if let Some(span_late) = def.has_late_bound_regions {
296 let msg = "cannot specify lifetime arguments explicitly \
297 if late bound lifetime parameters are present";
298 let note = "the late bound lifetime parameter is introduced here";
299 let span = args.args[0].span();
300 if position == GenericArgPosition::Value
301 && arg_counts.lifetimes != param_counts.lifetimes {
302 let mut err = tcx.sess.struct_span_err(span, msg);
303 err.span_note(span_late, note);
305 reported_late_bound_region_err = Some(true);
307 let mut multispan = MultiSpan::from_span(span);
308 multispan.push_span_label(span_late, note.to_string());
309 tcx.lint_hir(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
310 args.args[0].id(), multispan, msg);
311 reported_late_bound_region_err = Some(false);
316 let check_kind_count = |kind, required, permitted, provided, offset| {
318 "check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}",
325 // We enforce the following: `required` <= `provided` <= `permitted`.
326 // For kinds without defaults (i.e., lifetimes), `required == permitted`.
327 // For other kinds (i.e., types), `permitted` may be greater than `required`.
328 if required <= provided && provided <= permitted {
329 return (reported_late_bound_region_err.unwrap_or(false), None);
332 // Unfortunately lifetime and type parameter mismatches are typically styled
333 // differently in diagnostics, which means we have a few cases to consider here.
334 let (bound, quantifier) = if required != permitted {
335 if provided < required {
336 (required, "at least ")
337 } else { // provided > permitted
338 (permitted, "at most ")
344 let mut potential_assoc_types: Option<Vec<Span>> = None;
345 let (spans, label) = if required == permitted && provided > permitted {
346 // In the case when the user has provided too many arguments,
347 // we want to point to the unexpected arguments.
348 let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
350 .map(|arg| arg.span())
352 potential_assoc_types = Some(spans.clone());
353 (spans, format!( "unexpected {} argument", kind))
355 (vec![span], format!(
356 "expected {}{} {} argument{}",
360 if bound != 1 { "s" } else { "" },
364 let mut err = tcx.sess.struct_span_err_with_code(
367 "wrong number of {} arguments: expected {}{}, found {}",
373 DiagnosticId::Error("E0107".into())
376 err.span_label(span, label.as_str());
380 (provided > required, // `suppress_error`
381 potential_assoc_types)
384 if reported_late_bound_region_err.is_none()
385 && (!infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes) {
388 param_counts.lifetimes,
389 param_counts.lifetimes,
390 arg_counts.lifetimes,
394 // FIXME(const_generics:defaults)
395 if !infer_consts || arg_counts.consts > param_counts.consts {
401 arg_counts.lifetimes + arg_counts.types,
404 // Note that type errors are currently be emitted *after* const errors.
406 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
409 param_counts.types - defaults.types - has_self as usize,
410 param_counts.types - has_self as usize,
412 arg_counts.lifetimes,
415 (reported_late_bound_region_err.unwrap_or(false), None)
419 /// Creates the relevant generic argument substitutions
420 /// corresponding to a set of generic parameters. This is a
421 /// rather complex function. Let us try to explain the role
422 /// of each of its parameters:
424 /// To start, we are given the `def_id` of the thing we are
425 /// creating the substitutions for, and a partial set of
426 /// substitutions `parent_substs`. In general, the substitutions
427 /// for an item begin with substitutions for all the "parents" of
428 /// that item -- e.g., for a method it might include the
429 /// parameters from the impl.
431 /// Therefore, the method begins by walking down these parents,
432 /// starting with the outermost parent and proceed inwards until
433 /// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
434 /// first to see if the parent's substitutions are listed in there. If so,
435 /// we can append those and move on. Otherwise, it invokes the
436 /// three callback functions:
438 /// - `args_for_def_id`: given the `DefId` `P`, supplies back the
439 /// generic arguments that were given to that parent from within
440 /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
441 /// might refer to the trait `Foo`, and the arguments might be
442 /// `[T]`. The boolean value indicates whether to infer values
443 /// for arguments whose values were not explicitly provided.
444 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
445 /// instantiate a `Kind`.
446 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
447 /// creates a suitable inference variable.
448 pub fn create_substs_for_generic_args<'a, 'b>(
449 tcx: TyCtxt<'a, 'gcx, 'tcx>,
451 parent_substs: &[Kind<'tcx>],
453 self_ty: Option<Ty<'tcx>>,
454 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
455 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
456 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
457 ) -> SubstsRef<'tcx> {
458 // Collect the segments of the path; we need to substitute arguments
459 // for parameters throughout the entire path (wherever there are
460 // generic parameters).
461 let mut parent_defs = tcx.generics_of(def_id);
462 let count = parent_defs.count();
463 let mut stack = vec![(def_id, parent_defs)];
464 while let Some(def_id) = parent_defs.parent {
465 parent_defs = tcx.generics_of(def_id);
466 stack.push((def_id, parent_defs));
469 // We manually build up the substitution, rather than using convenience
470 // methods in `subst.rs`, so that we can iterate over the arguments and
471 // parameters in lock-step linearly, instead of trying to match each pair.
472 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
474 // Iterate over each segment of the path.
475 while let Some((def_id, defs)) = stack.pop() {
476 let mut params = defs.params.iter().peekable();
478 // If we have already computed substitutions for parents, we can use those directly.
479 while let Some(¶m) = params.peek() {
480 if let Some(&kind) = parent_substs.get(param.index as usize) {
488 // `Self` is handled first, unless it's been handled in `parent_substs`.
490 if let Some(¶m) = params.peek() {
491 if param.index == 0 {
492 if let GenericParamDefKind::Type { .. } = param.kind {
493 substs.push(self_ty.map(|ty| ty.into())
494 .unwrap_or_else(|| inferred_kind(None, param, true)));
501 // Check whether this segment takes generic arguments and the user has provided any.
502 let (generic_args, infer_types) = args_for_def_id(def_id);
504 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
508 // We're going to iterate through the generic arguments that the user
509 // provided, matching them with the generic parameters we expect.
510 // Mismatches can occur as a result of elided lifetimes, or for malformed
511 // input. We try to handle both sensibly.
512 match (args.peek(), params.peek()) {
513 (Some(&arg), Some(¶m)) => {
514 match (arg, ¶m.kind) {
515 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
516 | (GenericArg::Type(_), GenericParamDefKind::Type { .. })
517 | (GenericArg::Const(_), GenericParamDefKind::Const) => {
518 substs.push(provided_kind(param, arg));
522 (GenericArg::Type(_), GenericParamDefKind::Lifetime)
523 | (GenericArg::Const(_), GenericParamDefKind::Lifetime) => {
524 // We expected a lifetime argument, but got a type or const
525 // argument. That means we're inferring the lifetimes.
526 substs.push(inferred_kind(None, param, infer_types));
530 // We expected one kind of parameter, but the user provided
531 // another. This is an error, but we need to handle it
532 // gracefully so we can report sensible errors.
533 // In this case, we're simply going to infer this argument.
539 // We should never be able to reach this point with well-formed input.
540 // Getting to this point means the user supplied more arguments than
541 // there are parameters.
544 (None, Some(¶m)) => {
545 // If there are fewer arguments than parameters, it means
546 // we're inferring the remaining arguments.
547 substs.push(inferred_kind(Some(&substs), param, infer_types));
551 (None, None) => break,
556 tcx.intern_substs(&substs)
559 /// Given the type/lifetime/const arguments provided to some path (along with
560 /// an implicit `Self`, if this is a trait reference) returns the complete
561 /// set of substitutions. This may involve applying defaulted type parameters.
563 /// Note that the type listing given here is *exactly* what the user provided.
564 fn create_substs_for_ast_path(&self,
567 generic_args: &hir::GenericArgs,
569 self_ty: Option<Ty<'tcx>>)
570 -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>)
572 // If the type is parameterized by this region, then replace this
573 // region with the current anon region binding (in other words,
574 // whatever & would get replaced with).
575 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
577 def_id, self_ty, generic_args);
579 let tcx = self.tcx();
580 let generic_params = tcx.generics_of(def_id);
582 // If a self-type was declared, one should be provided.
583 assert_eq!(generic_params.has_self, self_ty.is_some());
585 let has_self = generic_params.has_self;
586 let (_, potential_assoc_types) = Self::check_generic_arg_count(
591 GenericArgPosition::Type,
596 let is_object = self_ty.map_or(false, |ty| {
597 ty == self.tcx().types.trait_object_dummy_self
599 let default_needs_object_self = |param: &ty::GenericParamDef| {
600 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
601 if is_object && has_default {
602 if tcx.at(span).type_of(param.def_id).has_self_ty() {
603 // There is no suitable inference default for a type parameter
604 // that references self, in an object type.
613 let substs = Self::create_substs_for_generic_args(
619 // Provide the generic args, and whether types should be inferred.
620 |_| (Some(generic_args), infer_types),
621 // Provide substitutions for parameters for which (valid) arguments have been provided.
623 match (¶m.kind, arg) {
624 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
625 self.ast_region_to_region(<, Some(param)).into()
627 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
628 self.ast_ty_to_ty(&ty).into()
630 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
631 self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
636 // Provide substitutions for parameters for which arguments are inferred.
637 |substs, param, infer_types| {
639 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
640 GenericParamDefKind::Type { has_default, .. } => {
641 if !infer_types && has_default {
642 // No type parameter provided, but a default exists.
644 // If we are converting an object type, then the
645 // `Self` parameter is unknown. However, some of the
646 // other type parameters may reference `Self` in their
647 // defaults. This will lead to an ICE if we are not
649 if default_needs_object_self(param) {
650 struct_span_err!(tcx.sess, span, E0393,
651 "the type parameter `{}` must be explicitly specified",
654 .span_label(span, format!(
655 "missing reference to `{}`", param.name))
657 "because of the default `Self` reference, type parameters \
658 must be specified on object types"))
662 // This is a default type parameter.
665 tcx.at(span).type_of(param.def_id)
666 .subst_spanned(tcx, substs.unwrap(), Some(span))
669 } else if infer_types {
670 // No type parameters were provided, we can infer all.
671 if !default_needs_object_self(param) {
672 self.ty_infer_for_def(param, span).into()
674 self.ty_infer(span).into()
677 // We've already errored above about the mismatch.
681 GenericParamDefKind::Const => {
682 // FIXME(const_generics:defaults)
683 // We've already errored above about the mismatch.
684 tcx.consts.err.into()
690 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
692 item_name: binding.ident,
693 ty: self.ast_ty_to_ty(&binding.ty),
698 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
699 generic_params, self_ty, substs);
701 (substs, assoc_bindings, potential_assoc_types)
704 /// Instantiates the path for the given trait reference, assuming that it's
705 /// bound to a valid trait type. Returns the def-ID for the defining trait.
706 /// The type _cannot_ be a type other than a trait type.
708 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
709 /// are disallowed. Otherwise, they are pushed onto the vector given.
710 pub fn instantiate_mono_trait_ref(&self,
711 trait_ref: &hir::TraitRef,
713 -> ty::TraitRef<'tcx>
715 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
717 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
718 trait_ref.trait_def_id(),
720 trait_ref.path.segments.last().unwrap())
723 /// The given trait-ref must actually be a trait.
724 pub(super) fn instantiate_poly_trait_ref_inner(&self,
725 trait_ref: &hir::TraitRef,
727 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
729 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
731 let trait_def_id = trait_ref.trait_def_id();
733 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
735 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
737 let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
741 trait_ref.path.segments.last().unwrap(),
743 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
745 let mut dup_bindings = FxHashMap::default();
746 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
747 // specify type to assert that error was already reported in Err case:
748 let predicate: Result<_, ErrorReported> =
749 self.ast_type_binding_to_poly_projection_predicate(
750 trait_ref.hir_ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
751 // okay to ignore Err because of ErrorReported (see above)
752 Some((predicate.ok()?, binding.span))
755 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
756 trait_ref, poly_projections, poly_trait_ref);
757 (poly_trait_ref, potential_assoc_types)
760 pub fn instantiate_poly_trait_ref(&self,
761 poly_trait_ref: &hir::PolyTraitRef,
763 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
764 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
766 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
767 poly_projections, false)
770 fn ast_path_to_mono_trait_ref(&self,
774 trait_segment: &hir::PathSegment)
775 -> ty::TraitRef<'tcx>
777 let (substs, assoc_bindings, _) =
778 self.create_substs_for_ast_trait_ref(span,
782 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
783 ty::TraitRef::new(trait_def_id, substs)
786 fn create_substs_for_ast_trait_ref(
791 trait_segment: &hir::PathSegment,
792 ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>) {
793 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
796 let trait_def = self.tcx().trait_def(trait_def_id);
798 if !self.tcx().features().unboxed_closures &&
799 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
800 != trait_def.paren_sugar {
801 // For now, require that parenthetical notation be used only with `Fn()` etc.
802 let msg = if trait_def.paren_sugar {
803 "the precise format of `Fn`-family traits' type parameters is subject to change. \
804 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
806 "parenthetical notation is only stable when used with `Fn`-family traits"
808 emit_feature_err(&self.tcx().sess.parse_sess, sym::unboxed_closures,
809 span, GateIssue::Language, msg);
812 trait_segment.with_generic_args(|generic_args| {
813 self.create_substs_for_ast_path(span,
816 trait_segment.infer_types,
821 fn trait_defines_associated_type_named(&self,
823 assoc_name: ast::Ident)
826 self.tcx().associated_items(trait_def_id).any(|item| {
827 item.kind == ty::AssociatedKind::Type &&
828 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
832 fn ast_type_binding_to_poly_projection_predicate(
834 hir_ref_id: hir::HirId,
835 trait_ref: ty::PolyTraitRef<'tcx>,
836 binding: &ConvertedBinding<'tcx>,
838 dup_bindings: &mut FxHashMap<DefId, Span>)
839 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
841 let tcx = self.tcx();
844 // Given something like `U: SomeTrait<T = X>`, we want to produce a
845 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
846 // subtle in the event that `T` is defined in a supertrait of
847 // `SomeTrait`, because in that case we need to upcast.
849 // That is, consider this case:
852 // trait SubTrait: SuperTrait<int> { }
853 // trait SuperTrait<A> { type T; }
855 // ... B : SubTrait<T=foo> ...
858 // We want to produce `<B as SuperTrait<int>>::T == foo`.
860 // Find any late-bound regions declared in `ty` that are not
861 // declared in the trait-ref. These are not wellformed.
865 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
866 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
867 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
868 let late_bound_in_ty =
869 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
870 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
871 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
872 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
873 let br_name = match *br {
874 ty::BrNamed(_, name) => name,
878 "anonymous bound region {:?} in binding but not trait ref",
882 struct_span_err!(tcx.sess,
885 "binding for associated type `{}` references lifetime `{}`, \
886 which does not appear in the trait input types",
887 binding.item_name, br_name)
892 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
894 // Simple case: X is defined in the current trait.
897 // Otherwise, we have to walk through the supertraits to find
899 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
900 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
902 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
903 binding.item_name, binding.span)
906 let (assoc_ident, def_scope) =
907 tcx.adjust_ident(binding.item_name, candidate.def_id(), hir_ref_id);
908 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
909 i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
910 }).expect("missing associated type");
912 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
913 let msg = format!("associated type `{}` is private", binding.item_name);
914 tcx.sess.span_err(binding.span, &msg);
916 tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
919 dup_bindings.entry(assoc_ty.def_id)
920 .and_modify(|prev_span| {
921 struct_span_err!(self.tcx().sess, binding.span, E0719,
922 "the value of the associated type `{}` (from the trait `{}`) \
923 is already specified",
925 tcx.def_path_str(assoc_ty.container.id()))
926 .span_label(binding.span, "re-bound here")
927 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
930 .or_insert(binding.span);
933 Ok(candidate.map_bound(|trait_ref| {
934 ty::ProjectionPredicate {
935 projection_ty: ty::ProjectionTy::from_ref_and_name(
945 fn ast_path_to_ty(&self,
948 item_segment: &hir::PathSegment)
951 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
954 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
958 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
959 /// removing the dummy `Self` type (`trait_object_dummy_self`).
960 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
961 -> ty::ExistentialTraitRef<'tcx> {
962 if trait_ref.self_ty() != self.tcx().types.trait_object_dummy_self {
963 bug!("trait_ref_to_existential called on {:?} with non-dummy Self", trait_ref);
965 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
968 fn conv_object_ty_poly_trait_ref(&self,
970 trait_bounds: &[hir::PolyTraitRef],
971 lifetime: &hir::Lifetime)
974 let tcx = self.tcx();
976 let mut projection_bounds = Vec::new();
977 let mut potential_assoc_types = Vec::new();
978 let dummy_self = self.tcx().types.trait_object_dummy_self;
979 // FIXME: we want to avoid collecting into a `Vec` here, but simply cloning the iterator is
980 // not straightforward due to the borrow checker.
981 let bound_trait_refs: Vec<_> = trait_bounds
985 let (trait_ref, cur_potential_assoc_types) = self.instantiate_poly_trait_ref(
988 &mut projection_bounds
990 potential_assoc_types.extend(cur_potential_assoc_types.into_iter().flatten());
991 (trait_ref, trait_bound.span)
995 // Expand trait aliases recursively and check that only one regular (non-auto) trait
996 // is used and no 'maybe' bounds are used.
997 let expanded_traits = traits::expand_trait_aliases(tcx, bound_trait_refs.clone());
998 let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
999 expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
1000 if regular_traits.len() > 1 {
1001 let first_trait = ®ular_traits[0];
1002 let additional_trait = ®ular_traits[1];
1003 let mut err = struct_span_err!(tcx.sess, additional_trait.bottom().1, E0225,
1004 "only auto traits can be used as additional traits in a trait object"
1006 additional_trait.label_with_exp_info(&mut err,
1007 "additional non-auto trait", "additional use");
1008 first_trait.label_with_exp_info(&mut err,
1009 "first non-auto trait", "first use");
1013 if regular_traits.is_empty() && auto_traits.is_empty() {
1014 span_err!(tcx.sess, span, E0224,
1015 "at least one non-builtin trait is required for an object type");
1016 return tcx.types.err;
1019 // Check that there are no gross object safety violations;
1020 // most importantly, that the supertraits don't contain `Self`,
1022 for item in ®ular_traits {
1023 let object_safety_violations =
1024 tcx.global_tcx().astconv_object_safety_violations(item.trait_ref().def_id());
1025 if !object_safety_violations.is_empty() {
1026 tcx.report_object_safety_error(
1028 item.trait_ref().def_id(),
1029 object_safety_violations
1031 .map(|mut err| err.emit());
1032 return tcx.types.err;
1036 // Use a `BTreeSet` to keep output in a more consistent order.
1037 let mut associated_types = BTreeSet::default();
1039 let regular_traits_refs = bound_trait_refs
1041 .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()))
1042 .map(|(trait_ref, _)| trait_ref);
1043 for trait_ref in traits::elaborate_trait_refs(tcx, regular_traits_refs) {
1044 debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", trait_ref);
1046 ty::Predicate::Trait(pred) => {
1048 .extend(tcx.associated_items(pred.def_id())
1049 .filter(|item| item.kind == ty::AssociatedKind::Type)
1050 .map(|item| item.def_id));
1052 ty::Predicate::Projection(pred) => {
1053 // A `Self` within the original bound will be substituted with a
1054 // `trait_object_dummy_self`, so check for that.
1055 let references_self =
1056 pred.skip_binder().ty.walk().any(|t| t == dummy_self);
1058 // If the projection output contains `Self`, force the user to
1059 // elaborate it explicitly to avoid a lot of complexity.
1061 // The "classicaly useful" case is the following:
1063 // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
1068 // Here, the user could theoretically write `dyn MyTrait<Output = X>`,
1069 // but actually supporting that would "expand" to an infinitely-long type
1070 // `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`.
1072 // Instead, we force the user to write `dyn MyTrait<MyOutput = X, Output = X>`,
1073 // which is uglier but works. See the discussion in #56288 for alternatives.
1074 if !references_self {
1075 // Include projections defined on supertraits.
1076 projection_bounds.push((pred, DUMMY_SP))
1083 for (projection_bound, _) in &projection_bounds {
1084 associated_types.remove(&projection_bound.projection_def_id());
1087 if !associated_types.is_empty() {
1088 let names = associated_types.iter().map(|item_def_id| {
1089 let assoc_item = tcx.associated_item(*item_def_id);
1090 let trait_def_id = assoc_item.container.id();
1092 "`{}` (from the trait `{}`)",
1094 tcx.def_path_str(trait_def_id),
1096 }).collect::<Vec<_>>().join(", ");
1097 let mut err = struct_span_err!(
1101 "the value of the associated type{} {} must be specified",
1102 if associated_types.len() == 1 { "" } else { "s" },
1105 let (suggest, potential_assoc_types_spans) =
1106 if potential_assoc_types.len() == associated_types.len() {
1107 // Only suggest when the amount of missing associated types equals the number of
1108 // extra type arguments present, as that gives us a relatively high confidence
1109 // that the user forgot to give the associtated type's name. The canonical
1110 // example would be trying to use `Iterator<isize>` instead of
1111 // `Iterator<Item = isize>`.
1112 (true, potential_assoc_types)
1116 let mut suggestions = Vec::new();
1117 for (i, item_def_id) in associated_types.iter().enumerate() {
1118 let assoc_item = tcx.associated_item(*item_def_id);
1121 format!("associated type `{}` must be specified", assoc_item.ident),
1123 if item_def_id.is_local() {
1125 tcx.def_span(*item_def_id),
1126 format!("`{}` defined here", assoc_item.ident),
1130 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
1131 potential_assoc_types_spans[i],
1134 potential_assoc_types_spans[i],
1135 format!("{} = {}", assoc_item.ident, snippet),
1140 if !suggestions.is_empty() {
1141 let msg = format!("if you meant to specify the associated {}, write",
1142 if suggestions.len() == 1 { "type" } else { "types" });
1143 err.multipart_suggestion(
1146 Applicability::MaybeIncorrect,
1152 // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
1153 // `dyn Trait + Send`.
1154 auto_traits.sort_by_key(|i| i.trait_ref().def_id());
1155 auto_traits.dedup_by_key(|i| i.trait_ref().def_id());
1156 debug!("regular_traits: {:?}", regular_traits);
1157 debug!("auto_traits: {:?}", auto_traits);
1159 // Erase the `dummy_self` (`trait_object_dummy_self`) used above.
1160 let existential_trait_refs = regular_traits.iter().map(|i| {
1161 i.trait_ref().map_bound(|trait_ref| self.trait_ref_to_existential(trait_ref))
1163 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1164 bound.map_bound(|b| {
1165 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1166 ty::ExistentialProjection {
1168 item_def_id: b.projection_ty.item_def_id,
1169 substs: trait_ref.substs,
1174 // Calling `skip_binder` is okay because the predicates are re-bound.
1175 let regular_trait_predicates = existential_trait_refs.map(
1176 |trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder()));
1177 let auto_trait_predicates = auto_traits.into_iter().map(
1178 |trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()));
1180 regular_trait_predicates
1181 .chain(auto_trait_predicates)
1182 .chain(existential_projections
1183 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1184 .collect::<SmallVec<[_; 8]>>();
1185 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1187 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1189 // Use explicitly-specified region bound.
1190 let region_bound = if !lifetime.is_elided() {
1191 self.ast_region_to_region(lifetime, None)
1193 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1194 if tcx.named_region(lifetime.hir_id).is_some() {
1195 self.ast_region_to_region(lifetime, None)
1197 self.re_infer(span, None).unwrap_or_else(|| {
1198 span_err!(tcx.sess, span, E0228,
1199 "the lifetime bound for this object type cannot be deduced \
1200 from context; please supply an explicit bound");
1201 tcx.lifetimes.re_static
1206 debug!("region_bound: {:?}", region_bound);
1208 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1209 debug!("trait_object_type: {:?}", ty);
1213 fn report_ambiguous_associated_type(
1220 let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
1221 if let (Some(_), Ok(snippet)) = (
1222 self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
1223 self.tcx().sess.source_map().span_to_snippet(span),
1225 err.span_suggestion(
1227 "you are looking for the module in `std`, not the primitive type",
1228 format!("std::{}", snippet),
1229 Applicability::MachineApplicable,
1232 err.span_suggestion(
1234 "use fully-qualified syntax",
1235 format!("<{} as {}>::{}", type_str, trait_str, name),
1236 Applicability::HasPlaceholders
1242 // Search for a bound on a type parameter which includes the associated item
1243 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
1244 // This function will fail if there are no suitable bounds or there is
1246 fn find_bound_for_assoc_item(&self,
1247 ty_param_def_id: DefId,
1248 assoc_name: ast::Ident,
1250 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1252 let tcx = self.tcx();
1254 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1255 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1257 // Check that there is exactly one way to find an associated type with the
1259 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1260 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1262 let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
1263 let param_name = tcx.hir().ty_param_name(param_hir_id);
1264 self.one_bound_for_assoc_type(suitable_bounds,
1265 ¶m_name.as_str(),
1270 // Checks that `bounds` contains exactly one element and reports appropriate
1271 // errors otherwise.
1272 fn one_bound_for_assoc_type<I>(&self,
1274 ty_param_name: &str,
1275 assoc_name: ast::Ident,
1277 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1278 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1280 let bound = match bounds.next() {
1281 Some(bound) => bound,
1283 struct_span_err!(self.tcx().sess, span, E0220,
1284 "associated type `{}` not found for `{}`",
1287 .span_label(span, format!("associated type `{}` not found", assoc_name))
1289 return Err(ErrorReported);
1293 if let Some(bound2) = bounds.next() {
1294 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1295 let mut err = struct_span_err!(
1296 self.tcx().sess, span, E0221,
1297 "ambiguous associated type `{}` in bounds of `{}`",
1300 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1302 for bound in bounds {
1303 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1304 item.kind == ty::AssociatedKind::Type &&
1305 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1307 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
1309 if let Some(span) = bound_span {
1310 err.span_label(span, format!("ambiguous `{}` from `{}`",
1314 span_note!(&mut err, span,
1315 "associated type `{}` could derive from `{}`",
1326 // Create a type from a path to an associated type.
1327 // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
1328 // and item_segment is the path segment for `D`. We return a type and a def for
1330 // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
1331 // parameter or `Self`.
1332 pub fn associated_path_to_ty(
1334 hir_ref_id: hir::HirId,
1338 assoc_segment: &hir::PathSegment,
1339 permit_variants: bool,
1340 ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
1341 let tcx = self.tcx();
1342 let assoc_ident = assoc_segment.ident;
1344 debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
1346 self.prohibit_generics(slice::from_ref(assoc_segment));
1348 // Check if we have an enum variant.
1349 let mut variant_resolution = None;
1350 if let ty::Adt(adt_def, _) = qself_ty.sty {
1351 if adt_def.is_enum() {
1352 let variant_def = adt_def.variants.iter().find(|vd| {
1353 tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did)
1355 if let Some(variant_def) = variant_def {
1356 if permit_variants {
1357 check_type_alias_enum_variants_enabled(tcx, span);
1358 tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
1359 return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
1361 variant_resolution = Some(variant_def.def_id);
1367 // Find the type of the associated item, and the trait where the associated
1368 // item is declared.
1369 let bound = match (&qself_ty.sty, qself_res) {
1370 (_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
1371 // `Self` in an impl of a trait -- we have a concrete self type and a
1373 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1374 Some(trait_ref) => trait_ref,
1376 // A cycle error occurred, most likely.
1377 return Err(ErrorReported);
1381 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1382 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_ident));
1384 self.one_bound_for_assoc_type(candidates, "Self", assoc_ident, span)?
1386 (&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
1387 (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
1388 self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
1391 if variant_resolution.is_some() {
1392 // Variant in type position
1393 let msg = format!("expected type, found variant `{}`", assoc_ident);
1394 tcx.sess.span_err(span, &msg);
1395 } else if qself_ty.is_enum() {
1396 let mut err = tcx.sess.struct_span_err(
1398 &format!("no variant `{}` in enum `{}`", assoc_ident, qself_ty),
1401 let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
1402 if let Some(suggested_name) = find_best_match_for_name(
1403 adt_def.variants.iter().map(|variant| &variant.ident.name),
1404 &assoc_ident.as_str(),
1407 err.span_suggestion(
1409 "there is a variant with a similar name",
1410 suggested_name.to_string(),
1411 Applicability::MaybeIncorrect,
1414 err.span_label(span, format!("variant not found in `{}`", qself_ty));
1417 if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
1418 let sp = tcx.sess.source_map().def_span(sp);
1419 err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
1423 } else if !qself_ty.references_error() {
1424 // Don't print `TyErr` to the user.
1425 self.report_ambiguous_associated_type(
1427 &qself_ty.to_string(),
1429 &assoc_ident.as_str(),
1432 return Err(ErrorReported);
1436 let trait_did = bound.def_id();
1437 let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_ident, trait_did, hir_ref_id);
1438 let item = tcx.associated_items(trait_did).find(|i| {
1439 Namespace::from(i.kind) == Namespace::Type &&
1440 i.ident.modern() == assoc_ident
1441 }).expect("missing associated type");
1443 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1444 let ty = self.normalize_ty(span, ty);
1446 let kind = DefKind::AssociatedTy;
1447 if !item.vis.is_accessible_from(def_scope, tcx) {
1448 let msg = format!("{} `{}` is private", kind.descr(), assoc_ident);
1449 tcx.sess.span_err(span, &msg);
1451 tcx.check_stability(item.def_id, Some(hir_ref_id), span);
1453 if let Some(variant_def_id) = variant_resolution {
1454 let mut err = tcx.struct_span_lint_hir(
1455 AMBIGUOUS_ASSOCIATED_ITEMS,
1458 "ambiguous associated item",
1461 let mut could_refer_to = |kind: DefKind, def_id, also| {
1462 let note_msg = format!("`{}` could{} refer to {} defined here",
1463 assoc_ident, also, kind.descr());
1464 err.span_note(tcx.def_span(def_id), ¬e_msg);
1466 could_refer_to(DefKind::Variant, variant_def_id, "");
1467 could_refer_to(kind, item.def_id, " also");
1469 err.span_suggestion(
1471 "use fully-qualified syntax",
1472 format!("<{} as {}>::{}", qself_ty, "Trait", assoc_ident),
1473 Applicability::HasPlaceholders,
1477 Ok((ty, kind, item.def_id))
1480 fn qpath_to_ty(&self,
1482 opt_self_ty: Option<Ty<'tcx>>,
1484 trait_segment: &hir::PathSegment,
1485 item_segment: &hir::PathSegment)
1488 let tcx = self.tcx();
1489 let trait_def_id = tcx.parent(item_def_id).unwrap();
1491 self.prohibit_generics(slice::from_ref(item_segment));
1493 let self_ty = if let Some(ty) = opt_self_ty {
1496 let path_str = tcx.def_path_str(trait_def_id);
1497 self.report_ambiguous_associated_type(
1501 &item_segment.ident.as_str(),
1503 return tcx.types.err;
1506 debug!("qpath_to_ty: self_type={:?}", self_ty);
1508 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1513 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1515 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1518 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(
1519 &self, segments: T) -> bool {
1520 let mut has_err = false;
1521 for segment in segments {
1522 segment.with_generic_args(|generic_args| {
1523 let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
1524 for arg in &generic_args.args {
1525 let (span, kind) = match arg {
1526 hir::GenericArg::Lifetime(lt) => {
1527 if err_for_lt { continue }
1530 (lt.span, "lifetime")
1532 hir::GenericArg::Type(ty) => {
1533 if err_for_ty { continue }
1538 hir::GenericArg::Const(ct) => {
1539 if err_for_ct { continue }
1544 let mut err = struct_span_err!(
1548 "{} arguments are not allowed for this type",
1551 err.span_label(span, format!("{} argument not allowed", kind));
1553 if err_for_lt && err_for_ty && err_for_ct {
1557 for binding in &generic_args.bindings {
1559 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1567 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_, '_, '_>, span: Span) {
1568 let mut err = struct_span_err!(tcx.sess, span, E0229,
1569 "associated type bindings are not allowed here");
1570 err.span_label(span, "associated type not allowed here").emit();
1573 // FIXME(eddyb, varkor) handle type paths here too, not just value ones.
1574 pub fn def_ids_for_value_path_segments(
1576 segments: &[hir::PathSegment],
1577 self_ty: Option<Ty<'tcx>>,
1581 // We need to extract the type parameters supplied by the user in
1582 // the path `path`. Due to the current setup, this is a bit of a
1583 // tricky-process; the problem is that resolve only tells us the
1584 // end-point of the path resolution, and not the intermediate steps.
1585 // Luckily, we can (at least for now) deduce the intermediate steps
1586 // just from the end-point.
1588 // There are basically five cases to consider:
1590 // 1. Reference to a constructor of a struct:
1592 // struct Foo<T>(...)
1594 // In this case, the parameters are declared in the type space.
1596 // 2. Reference to a constructor of an enum variant:
1598 // enum E<T> { Foo(...) }
1600 // In this case, the parameters are defined in the type space,
1601 // but may be specified either on the type or the variant.
1603 // 3. Reference to a fn item or a free constant:
1607 // In this case, the path will again always have the form
1608 // `a::b::foo::<T>` where only the final segment should have
1609 // type parameters. However, in this case, those parameters are
1610 // declared on a value, and hence are in the `FnSpace`.
1612 // 4. Reference to a method or an associated constant:
1614 // impl<A> SomeStruct<A> {
1618 // Here we can have a path like
1619 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
1620 // may appear in two places. The penultimate segment,
1621 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
1622 // final segment, `foo::<B>` contains parameters in fn space.
1624 // The first step then is to categorize the segments appropriately.
1626 let tcx = self.tcx();
1628 assert!(!segments.is_empty());
1629 let last = segments.len() - 1;
1631 let mut path_segs = vec![];
1634 // Case 1. Reference to a struct constructor.
1635 DefKind::Ctor(CtorOf::Struct, ..) => {
1636 // Everything but the final segment should have no
1637 // parameters at all.
1638 let generics = tcx.generics_of(def_id);
1639 // Variant and struct constructors use the
1640 // generics of their parent type definition.
1641 let generics_def_id = generics.parent.unwrap_or(def_id);
1642 path_segs.push(PathSeg(generics_def_id, last));
1645 // Case 2. Reference to a variant constructor.
1646 DefKind::Ctor(CtorOf::Variant, ..)
1647 | DefKind::Variant => {
1648 let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
1649 let (generics_def_id, index) = if let Some(adt_def) = adt_def {
1650 debug_assert!(adt_def.is_enum());
1652 } else if last >= 1 && segments[last - 1].args.is_some() {
1653 // Everything but the penultimate segment should have no
1654 // parameters at all.
1655 let mut def_id = def_id;
1657 // `DefKind::Ctor` -> `DefKind::Variant`
1658 if let DefKind::Ctor(..) = kind {
1659 def_id = tcx.parent(def_id).unwrap()
1662 // `DefKind::Variant` -> `DefKind::Enum`
1663 let enum_def_id = tcx.parent(def_id).unwrap();
1664 (enum_def_id, last - 1)
1666 // FIXME: lint here recommending `Enum::<...>::Variant` form
1667 // instead of `Enum::Variant::<...>` form.
1669 // Everything but the final segment should have no
1670 // parameters at all.
1671 let generics = tcx.generics_of(def_id);
1672 // Variant and struct constructors use the
1673 // generics of their parent type definition.
1674 (generics.parent.unwrap_or(def_id), last)
1676 path_segs.push(PathSeg(generics_def_id, index));
1679 // Case 3. Reference to a top-level value.
1682 | DefKind::ConstParam
1683 | DefKind::Static => {
1684 path_segs.push(PathSeg(def_id, last));
1687 // Case 4. Reference to a method or associated const.
1689 | DefKind::AssociatedConst => {
1690 if segments.len() >= 2 {
1691 let generics = tcx.generics_of(def_id);
1692 path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
1694 path_segs.push(PathSeg(def_id, last));
1697 kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
1700 debug!("path_segs = {:?}", path_segs);
1705 // Check a type `Path` and convert it to a `Ty`.
1706 pub fn res_to_ty(&self,
1707 opt_self_ty: Option<Ty<'tcx>>,
1709 permit_variants: bool)
1711 let tcx = self.tcx();
1713 debug!("res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
1714 path.res, opt_self_ty, path.segments);
1716 let span = path.span;
1718 Res::Def(DefKind::Existential, did) => {
1719 // Check for desugared impl trait.
1720 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1721 let item_segment = path.segments.split_last().unwrap();
1722 self.prohibit_generics(item_segment.1);
1723 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1726 tcx.mk_opaque(did, substs),
1729 Res::Def(DefKind::Enum, did)
1730 | Res::Def(DefKind::TyAlias, did)
1731 | Res::Def(DefKind::Struct, did)
1732 | Res::Def(DefKind::Union, did)
1733 | Res::Def(DefKind::ForeignTy, did) => {
1734 assert_eq!(opt_self_ty, None);
1735 self.prohibit_generics(path.segments.split_last().unwrap().1);
1736 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1738 Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
1739 // Convert "variant type" as if it were a real type.
1740 // The resulting `Ty` is type of the variant's enum for now.
1741 assert_eq!(opt_self_ty, None);
1744 self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
1745 let generic_segs: FxHashSet<_> =
1746 path_segs.iter().map(|PathSeg(_, index)| index).collect();
1747 self.prohibit_generics(path.segments.iter().enumerate().filter_map(|(index, seg)| {
1748 if !generic_segs.contains(&index) {
1755 let PathSeg(def_id, index) = path_segs.last().unwrap();
1756 self.ast_path_to_ty(span, *def_id, &path.segments[*index])
1758 Res::Def(DefKind::TyParam, did) => {
1759 assert_eq!(opt_self_ty, None);
1760 self.prohibit_generics(&path.segments);
1762 let hir_id = tcx.hir().as_local_hir_id(did).unwrap();
1763 let item_id = tcx.hir().get_parent_node_by_hir_id(hir_id);
1764 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1765 let generics = tcx.generics_of(item_def_id);
1766 let index = generics.param_def_id_to_index[
1767 &tcx.hir().local_def_id_from_hir_id(hir_id)];
1768 tcx.mk_ty_param(index, tcx.hir().name_by_hir_id(hir_id).as_interned_str())
1770 Res::SelfTy(_, Some(def_id)) => {
1771 // `Self` in impl (we know the concrete type).
1772 assert_eq!(opt_self_ty, None);
1773 self.prohibit_generics(&path.segments);
1774 // Try to evaluate any array length constants
1775 self.normalize_ty(span, tcx.at(span).type_of(def_id))
1777 Res::SelfTy(Some(_), None) => {
1779 assert_eq!(opt_self_ty, None);
1780 self.prohibit_generics(&path.segments);
1783 Res::Def(DefKind::AssociatedTy, def_id) => {
1784 debug_assert!(path.segments.len() >= 2);
1785 self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
1786 self.qpath_to_ty(span,
1789 &path.segments[path.segments.len() - 2],
1790 path.segments.last().unwrap())
1792 Res::PrimTy(prim_ty) => {
1793 assert_eq!(opt_self_ty, None);
1794 self.prohibit_generics(&path.segments);
1796 hir::Bool => tcx.types.bool,
1797 hir::Char => tcx.types.char,
1798 hir::Int(it) => tcx.mk_mach_int(it),
1799 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1800 hir::Float(ft) => tcx.mk_mach_float(ft),
1801 hir::Str => tcx.mk_str()
1805 self.set_tainted_by_errors();
1806 return self.tcx().types.err;
1808 _ => span_bug!(span, "unexpected resolution: {:?}", path.res)
1812 /// Parses the programmer's textual representation of a type into our
1813 /// internal notion of a type.
1814 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1815 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1816 ast_ty.hir_id, ast_ty, ast_ty.node);
1818 let tcx = self.tcx();
1820 let result_ty = match ast_ty.node {
1821 hir::TyKind::Slice(ref ty) => {
1822 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1824 hir::TyKind::Ptr(ref mt) => {
1825 tcx.mk_ptr(ty::TypeAndMut {
1826 ty: self.ast_ty_to_ty(&mt.ty),
1830 hir::TyKind::Rptr(ref region, ref mt) => {
1831 let r = self.ast_region_to_region(region, None);
1832 debug!("Ref r={:?}", r);
1833 let t = self.ast_ty_to_ty(&mt.ty);
1834 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1836 hir::TyKind::Never => {
1839 hir::TyKind::Tup(ref fields) => {
1840 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1842 hir::TyKind::BareFn(ref bf) => {
1843 require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1844 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1846 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1847 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1849 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1850 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1851 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1852 self.ast_ty_to_ty(qself)
1854 self.res_to_ty(opt_self_ty, path, false)
1856 hir::TyKind::Def(item_id, ref lifetimes) => {
1857 let did = tcx.hir().local_def_id_from_hir_id(item_id.id);
1858 self.impl_trait_ty_to_ty(did, lifetimes)
1860 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1861 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1862 let ty = self.ast_ty_to_ty(qself);
1864 let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1869 self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
1870 .map(|(ty, _, _)| ty).unwrap_or(tcx.types.err)
1872 hir::TyKind::Array(ref ty, ref length) => {
1873 let length = self.ast_const_to_const(length, tcx.types.usize);
1874 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1875 self.normalize_ty(ast_ty.span, array_ty)
1877 hir::TyKind::Typeof(ref _e) => {
1878 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1879 "`typeof` is a reserved keyword but unimplemented")
1880 .span_label(ast_ty.span, "reserved keyword")
1885 hir::TyKind::Infer => {
1886 // Infer also appears as the type of arguments or return
1887 // values in a ExprKind::Closure, or as
1888 // the type of local variables. Both of these cases are
1889 // handled specially and will not descend into this routine.
1890 self.ty_infer(ast_ty.span)
1892 hir::TyKind::Err => {
1895 hir::TyKind::CVarArgs(lt) => {
1896 let va_list_did = match tcx.lang_items().va_list() {
1898 None => span_bug!(ast_ty.span,
1899 "`va_list` lang item required for variadics"),
1901 let region = self.ast_region_to_region(<, None);
1902 tcx.type_of(va_list_did).subst(tcx, &[region.into()])
1906 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1910 pub fn ast_const_to_const(
1912 ast_const: &hir::AnonConst,
1914 ) -> &'tcx ty::Const<'tcx> {
1915 debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
1917 let tcx = self.tcx();
1918 let def_id = tcx.hir().local_def_id_from_hir_id(ast_const.hir_id);
1920 let mut const_ = ty::Const {
1921 val: ConstValue::Unevaluated(
1923 InternalSubsts::identity_for_item(tcx, def_id),
1928 let mut expr = &tcx.hir().body(ast_const.body).value;
1930 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
1931 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
1932 if let ExprKind::Block(block, _) = &expr.node {
1933 if block.stmts.is_empty() {
1934 if let Some(trailing) = &block.expr {
1940 if let ExprKind::Path(ref qpath) = expr.node {
1941 if let hir::QPath::Resolved(_, ref path) = qpath {
1942 if let Res::Def(DefKind::ConstParam, def_id) = path.res {
1943 let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
1944 let item_id = tcx.hir().get_parent_node(node_id);
1945 let item_def_id = tcx.hir().local_def_id(item_id);
1946 let generics = tcx.generics_of(item_def_id);
1947 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(node_id)];
1948 let name = tcx.hir().name(node_id).as_interned_str();
1949 const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
1954 tcx.mk_const(const_)
1957 pub fn impl_trait_ty_to_ty(
1960 lifetimes: &[hir::GenericArg],
1962 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1963 let tcx = self.tcx();
1965 let generics = tcx.generics_of(def_id);
1967 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1968 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
1969 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1970 // Our own parameters are the resolved lifetimes.
1972 GenericParamDefKind::Lifetime => {
1973 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1974 self.ast_region_to_region(lifetime, None).into()
1982 // Replace all parent lifetimes with 'static.
1984 GenericParamDefKind::Lifetime => {
1985 tcx.lifetimes.re_static.into()
1987 _ => tcx.mk_param_from_def(param)
1991 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1993 let ty = tcx.mk_opaque(def_id, substs);
1994 debug!("impl_trait_ty_to_ty: {}", ty);
1998 pub fn ty_of_arg(&self,
2000 expected_ty: Option<Ty<'tcx>>)
2004 hir::TyKind::Infer if expected_ty.is_some() => {
2005 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
2006 expected_ty.unwrap()
2008 _ => self.ast_ty_to_ty(ty),
2012 pub fn ty_of_fn(&self,
2013 unsafety: hir::Unsafety,
2016 -> ty::PolyFnSig<'tcx> {
2019 let tcx = self.tcx();
2021 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
2023 let output_ty = match decl.output {
2024 hir::Return(ref output) => self.ast_ty_to_ty(output),
2025 hir::DefaultReturn(..) => tcx.mk_unit(),
2028 debug!("ty_of_fn: output_ty={:?}", output_ty);
2030 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
2038 // Find any late-bound regions declared in return type that do
2039 // not appear in the arguments. These are not well-formed.
2042 // for<'a> fn() -> &'a str <-- 'a is bad
2043 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
2044 let inputs = bare_fn_ty.inputs();
2045 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
2046 &inputs.map_bound(|i| i.to_owned()));
2047 let output = bare_fn_ty.output();
2048 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
2049 for br in late_bound_in_ret.difference(&late_bound_in_args) {
2050 let lifetime_name = match *br {
2051 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
2052 ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
2054 let mut err = struct_span_err!(tcx.sess,
2057 "return type references {} \
2058 which is not constrained by the fn input types",
2060 if let ty::BrAnon(_) = *br {
2061 // The only way for an anonymous lifetime to wind up
2062 // in the return type but **also** be unconstrained is
2063 // if it only appears in "associated types" in the
2064 // input. See #47511 for an example. In this case,
2065 // though we can easily give a hint that ought to be
2067 err.note("lifetimes appearing in an associated type \
2068 are not considered constrained");
2076 /// Given the bounds on an object, determines what single region bound (if any) we can
2077 /// use to summarize this type. The basic idea is that we will use the bound the user
2078 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
2079 /// for region bounds. It may be that we can derive no bound at all, in which case
2080 /// we return `None`.
2081 fn compute_object_lifetime_bound(&self,
2083 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
2084 -> Option<ty::Region<'tcx>> // if None, use the default
2086 let tcx = self.tcx();
2088 debug!("compute_opt_region_bound(existential_predicates={:?})",
2089 existential_predicates);
2091 // No explicit region bound specified. Therefore, examine trait
2092 // bounds and see if we can derive region bounds from those.
2093 let derived_region_bounds =
2094 object_region_bounds(tcx, existential_predicates);
2096 // If there are no derived region bounds, then report back that we
2097 // can find no region bound. The caller will use the default.
2098 if derived_region_bounds.is_empty() {
2102 // If any of the derived region bounds are 'static, that is always
2104 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
2105 return Some(tcx.lifetimes.re_static);
2108 // Determine whether there is exactly one unique region in the set
2109 // of derived region bounds. If so, use that. Otherwise, report an
2111 let r = derived_region_bounds[0];
2112 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
2113 span_err!(tcx.sess, span, E0227,
2114 "ambiguous lifetime bound, explicit lifetime bound required");
2120 // A helper struct for conveniently grouping a set of bounds which we pass to
2121 // and return from functions in multiple places.
2122 #[derive(PartialEq, Eq, Clone, Debug)]
2123 pub struct Bounds<'tcx> {
2124 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
2125 pub implicitly_sized: Option<Span>,
2126 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
2127 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
2130 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
2131 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
2132 -> Vec<(ty::Predicate<'tcx>, Span)>
2134 // If it could be sized, and is, add the `Sized` predicate.
2135 let sized_predicate = self.implicitly_sized.and_then(|span| {
2136 tcx.lang_items().sized_trait().map(|sized| {
2137 let trait_ref = ty::TraitRef {
2139 substs: tcx.mk_substs_trait(param_ty, &[])
2141 (trait_ref.to_predicate(), span)
2145 sized_predicate.into_iter().chain(
2146 self.region_bounds.iter().map(|&(region_bound, span)| {
2147 // Account for the binder being introduced below; no need to shift `param_ty`
2148 // because, at present at least, it can only refer to early-bound regions.
2149 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
2150 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
2151 (ty::Binder::dummy(outlives).to_predicate(), span)
2153 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
2154 (bound_trait_ref.to_predicate(), span)
2157 self.projection_bounds.iter().map(|&(projection, span)| {
2158 (projection.to_predicate(), span)