1 // ignore-tidy-filelength FIXME(#67418) Split up this file.
2 //! Conversion from AST representation of types to the `ty.rs` representation.
3 //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
4 //! instance of `AstConv`.
6 // ignore-tidy-filelength
8 use crate::collect::PlaceholderHirTyCollector;
10 use crate::middle::lang_items::SizedTraitLangItem;
11 use crate::middle::resolve_lifetime as rl;
12 use crate::require_c_abi_if_c_variadic;
13 use crate::util::common::ErrorReported;
14 use rustc::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
15 use rustc::session::{parse::feature_err, Session};
16 use rustc::ty::subst::{self, InternalSubsts, Subst, SubstsRef};
17 use rustc::ty::{self, Const, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness};
18 use rustc::ty::{GenericParamDef, GenericParamDefKind};
20 use rustc_ast::util::lev_distance::find_best_match_for_name;
21 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
22 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId};
24 use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
25 use rustc_hir::def_id::DefId;
26 use rustc_hir::intravisit::Visitor;
28 use rustc_hir::{Constness, ExprKind, GenericArg, GenericArgs};
29 use rustc_infer::traits;
30 use rustc_infer::traits::astconv_object_safety_violations;
31 use rustc_infer::traits::error_reporting::report_object_safety_error;
32 use rustc_infer::traits::wf::object_region_bounds;
33 use rustc_span::symbol::sym;
34 use rustc_span::{MultiSpan, Span, DUMMY_SP};
35 use rustc_target::spec::abi;
36 use smallvec::SmallVec;
38 use std::collections::BTreeSet;
42 use rustc::mir::interpret::LitToConstInput;
45 pub struct PathSeg(pub DefId, pub usize);
47 pub trait AstConv<'tcx> {
48 fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
50 fn item_def_id(&self) -> Option<DefId>;
52 fn default_constness_for_trait_bounds(&self) -> Constness;
54 /// Returns predicates in scope of the form `X: Foo`, where `X` is
55 /// a type parameter `X` with the given id `def_id`. This is a
56 /// subset of the full set of predicates.
58 /// This is used for one specific purpose: resolving "short-hand"
59 /// associated type references like `T::Item`. In principle, we
60 /// would do that by first getting the full set of predicates in
61 /// scope and then filtering down to find those that apply to `T`,
62 /// but this can lead to cycle errors. The problem is that we have
63 /// to do this resolution *in order to create the predicates in
64 /// the first place*. Hence, we have this "special pass".
65 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx>;
67 /// Returns the lifetime to use when a lifetime is omitted (and not elided).
68 fn re_infer(&self, param: Option<&ty::GenericParamDef>, span: Span)
69 -> Option<ty::Region<'tcx>>;
71 /// Returns the type to use when a type is omitted.
72 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;
74 /// Returns `true` if `_` is allowed in type signatures in the current context.
75 fn allow_ty_infer(&self) -> bool;
77 /// Returns the const to use when a const is omitted.
81 param: Option<&ty::GenericParamDef>,
83 ) -> &'tcx Const<'tcx>;
85 /// Projecting an associated type from a (potentially)
86 /// higher-ranked trait reference is more complicated, because of
87 /// the possibility of late-bound regions appearing in the
88 /// associated type binding. This is not legal in function
89 /// signatures for that reason. In a function body, we can always
90 /// handle it because we can use inference variables to remove the
91 /// late-bound regions.
92 fn projected_ty_from_poly_trait_ref(
96 item_segment: &hir::PathSegment<'_>,
97 poly_trait_ref: ty::PolyTraitRef<'tcx>,
100 /// Normalize an associated type coming from the user.
101 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
103 /// Invoked when we encounter an error from some prior pass
104 /// (e.g., resolve) that is translated into a ty-error. This is
105 /// used to help suppress derived errors typeck might otherwise
107 fn set_tainted_by_errors(&self);
109 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
112 pub enum SizedByDefault {
117 struct ConvertedBinding<'a, 'tcx> {
118 item_name: ast::Ident,
119 kind: ConvertedBindingKind<'a, 'tcx>,
123 enum ConvertedBindingKind<'a, 'tcx> {
125 Constraint(&'a [hir::GenericBound<'a>]),
129 enum GenericArgPosition {
131 Value, // e.g., functions
135 /// A marker denoting that the generic arguments that were
136 /// provided did not match the respective generic parameters.
137 pub struct GenericArgCountMismatch {
138 /// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`).
139 pub reported: Option<ErrorReported>,
140 /// A list of spans of arguments provided that were not valid.
141 pub invalid_args: Vec<Span>,
144 impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
145 pub fn ast_region_to_region(
147 lifetime: &hir::Lifetime,
148 def: Option<&ty::GenericParamDef>,
149 ) -> ty::Region<'tcx> {
150 let tcx = self.tcx();
151 let lifetime_name = |def_id| tcx.hir().name(tcx.hir().as_local_hir_id(def_id).unwrap());
153 let r = match tcx.named_region(lifetime.hir_id) {
154 Some(rl::Region::Static) => tcx.lifetimes.re_static,
156 Some(rl::Region::LateBound(debruijn, id, _)) => {
157 let name = lifetime_name(id);
158 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrNamed(id, name)))
161 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
162 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
165 Some(rl::Region::EarlyBound(index, id, _)) => {
166 let name = lifetime_name(id);
167 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion { def_id: id, index, name }))
170 Some(rl::Region::Free(scope, id)) => {
171 let name = lifetime_name(id);
172 tcx.mk_region(ty::ReFree(ty::FreeRegion {
174 bound_region: ty::BrNamed(id, name),
177 // (*) -- not late-bound, won't change
181 self.re_infer(def, lifetime.span).unwrap_or_else(|| {
182 // This indicates an illegal lifetime
183 // elision. `resolve_lifetime` should have
184 // reported an error in this case -- but if
185 // not, let's error out.
186 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
188 // Supply some dummy value. We don't have an
189 // `re_error`, annoyingly, so use `'static`.
190 tcx.lifetimes.re_static
195 debug!("ast_region_to_region(lifetime={:?}) yields {:?}", lifetime, r);
200 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
201 /// returns an appropriate set of substitutions for this particular reference to `I`.
202 pub fn ast_path_substs_for_ty(
206 item_segment: &hir::PathSegment<'_>,
207 ) -> SubstsRef<'tcx> {
208 let (substs, assoc_bindings, _) = self.create_substs_for_ast_path(
212 item_segment.generic_args(),
213 item_segment.infer_args,
217 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
222 /// Report error if there is an explicit type parameter when using `impl Trait`.
225 seg: &hir::PathSegment<'_>,
226 generics: &ty::Generics,
228 let explicit = !seg.infer_args;
229 let impl_trait = generics.params.iter().any(|param| match param.kind {
230 ty::GenericParamDefKind::Type {
231 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
237 if explicit && impl_trait {
242 .filter_map(|arg| match arg {
243 GenericArg::Type(_) => Some(arg.span()),
246 .collect::<Vec<_>>();
248 let mut err = struct_span_err! {
252 "cannot provide explicit generic arguments when `impl Trait` is \
253 used in argument position"
257 err.span_label(span, "explicit generic argument not allowed");
266 /// Checks that the correct number of generic arguments have been provided.
267 /// Used specifically for function calls.
268 pub fn check_generic_arg_count_for_call(
272 seg: &hir::PathSegment<'_>,
273 is_method_call: bool,
274 ) -> Result<(), GenericArgCountMismatch> {
275 let empty_args = hir::GenericArgs::none();
276 let suppress_mismatch = Self::check_impl_trait(tcx, seg, &def);
277 Self::check_generic_arg_count(
281 if let Some(ref args) = seg.args { args } else { &empty_args },
282 if is_method_call { GenericArgPosition::MethodCall } else { GenericArgPosition::Value },
283 def.parent.is_none() && def.has_self, // `has_self`
284 seg.infer_args || suppress_mismatch, // `infer_args`
288 /// Checks that the correct number of generic arguments have been provided.
289 /// This is used both for datatypes and function calls.
290 fn check_generic_arg_count(
294 args: &hir::GenericArgs<'_>,
295 position: GenericArgPosition,
298 ) -> Result<(), GenericArgCountMismatch> {
299 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
300 // that lifetimes will proceed types. So it suffices to check the number of each generic
301 // arguments in order to validate them with respect to the generic parameters.
302 let param_counts = def.own_counts();
303 let arg_counts = args.own_counts();
304 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
306 let mut defaults: ty::GenericParamCount = Default::default();
307 for param in &def.params {
309 GenericParamDefKind::Lifetime => {}
310 GenericParamDefKind::Type { has_default, .. } => {
311 defaults.types += has_default as usize
313 GenericParamDefKind::Const => {
314 // FIXME(const_generics:defaults)
319 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
320 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
323 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
324 let mut explicit_lifetimes = Ok(());
325 if !infer_lifetimes {
326 if let Some(span_late) = def.has_late_bound_regions {
327 let msg = "cannot specify lifetime arguments explicitly \
328 if late bound lifetime parameters are present";
329 let note = "the late bound lifetime parameter is introduced here";
330 let span = args.args[0].span();
331 if position == GenericArgPosition::Value
332 && arg_counts.lifetimes != param_counts.lifetimes
334 explicit_lifetimes = Err(true);
335 let mut err = tcx.sess.struct_span_err(span, msg);
336 err.span_note(span_late, note);
339 explicit_lifetimes = Err(false);
340 let mut multispan = MultiSpan::from_span(span);
341 multispan.push_span_label(span_late, note.to_string());
342 tcx.struct_span_lint_hir(
343 lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
346 |lint| lint.build(msg).emit(),
352 let check_kind_count =
353 |kind, required, permitted, provided, offset, unexpected_spans: &mut Vec<Span>| {
355 "check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}",
356 kind, required, permitted, provided, offset
358 // We enforce the following: `required` <= `provided` <= `permitted`.
359 // For kinds without defaults (e.g.., lifetimes), `required == permitted`.
360 // For other kinds (i.e., types), `permitted` may be greater than `required`.
361 if required <= provided && provided <= permitted {
365 // Unfortunately lifetime and type parameter mismatches are typically styled
366 // differently in diagnostics, which means we have a few cases to consider here.
367 let (bound, quantifier) = if required != permitted {
368 if provided < required {
369 (required, "at least ")
371 // provided > permitted
372 (permitted, "at most ")
378 let (spans, label) = if required == permitted && provided > permitted {
379 // In the case when the user has provided too many arguments,
380 // we want to point to the unexpected arguments.
381 let spans: Vec<Span> = args.args[offset + permitted..offset + provided]
383 .map(|arg| arg.span())
385 unexpected_spans.extend(spans.clone());
386 (spans, format!("unexpected {} argument", kind))
391 "expected {}{} {} argument{}",
400 let mut err = tcx.sess.struct_span_err_with_code(
403 "wrong number of {} arguments: expected {}{}, found {}",
404 kind, quantifier, bound, provided,
406 DiagnosticId::Error("E0107".into()),
409 err.span_label(span, label.as_str());
416 let mut arg_count_correct = explicit_lifetimes;
417 let mut unexpected_spans = vec![];
419 if arg_count_correct.is_ok()
420 && (!infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes)
422 arg_count_correct = check_kind_count(
424 param_counts.lifetimes,
425 param_counts.lifetimes,
426 arg_counts.lifetimes,
428 &mut unexpected_spans,
430 .and(arg_count_correct);
432 // FIXME(const_generics:defaults)
433 if !infer_args || arg_counts.consts > param_counts.consts {
434 arg_count_correct = check_kind_count(
439 arg_counts.lifetimes + arg_counts.types,
440 &mut unexpected_spans,
442 .and(arg_count_correct);
444 // Note that type errors are currently be emitted *after* const errors.
445 if !infer_args || arg_counts.types > param_counts.types - defaults.types - has_self as usize
447 arg_count_correct = check_kind_count(
449 param_counts.types - defaults.types - has_self as usize,
450 param_counts.types - has_self as usize,
452 arg_counts.lifetimes,
453 &mut unexpected_spans,
455 .and(arg_count_correct);
458 arg_count_correct.map_err(|reported_err| GenericArgCountMismatch {
459 reported: if reported_err { Some(ErrorReported) } else { None },
460 invalid_args: unexpected_spans,
464 /// Report an error that a generic argument did not match the generic parameter that was
466 fn generic_arg_mismatch_err(sess: &Session, arg: &GenericArg<'_>, kind: &'static str) {
467 let mut err = struct_span_err!(
471 "{} provided when a {} was expected",
475 // This note will be true as long as generic parameters are strictly ordered by their kind.
476 err.note(&format!("{} arguments must be provided before {} arguments", kind, arg.descr()));
480 /// Creates the relevant generic argument substitutions
481 /// corresponding to a set of generic parameters. This is a
482 /// rather complex function. Let us try to explain the role
483 /// of each of its parameters:
485 /// To start, we are given the `def_id` of the thing we are
486 /// creating the substitutions for, and a partial set of
487 /// substitutions `parent_substs`. In general, the substitutions
488 /// for an item begin with substitutions for all the "parents" of
489 /// that item -- e.g., for a method it might include the
490 /// parameters from the impl.
492 /// Therefore, the method begins by walking down these parents,
493 /// starting with the outermost parent and proceed inwards until
494 /// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
495 /// first to see if the parent's substitutions are listed in there. If so,
496 /// we can append those and move on. Otherwise, it invokes the
497 /// three callback functions:
499 /// - `args_for_def_id`: given the `DefId` `P`, supplies back the
500 /// generic arguments that were given to that parent from within
501 /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
502 /// might refer to the trait `Foo`, and the arguments might be
503 /// `[T]`. The boolean value indicates whether to infer values
504 /// for arguments whose values were not explicitly provided.
505 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
506 /// instantiate a `GenericArg`.
507 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
508 /// creates a suitable inference variable.
509 pub fn create_substs_for_generic_args<'b>(
512 parent_substs: &[subst::GenericArg<'tcx>],
514 self_ty: Option<Ty<'tcx>>,
515 arg_count_correct: bool,
516 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool),
517 mut provided_kind: impl FnMut(&GenericParamDef, &GenericArg<'_>) -> subst::GenericArg<'tcx>,
518 mut inferred_kind: impl FnMut(
519 Option<&[subst::GenericArg<'tcx>]>,
522 ) -> subst::GenericArg<'tcx>,
523 ) -> SubstsRef<'tcx> {
524 // Collect the segments of the path; we need to substitute arguments
525 // for parameters throughout the entire path (wherever there are
526 // generic parameters).
527 let mut parent_defs = tcx.generics_of(def_id);
528 let count = parent_defs.count();
529 let mut stack = vec![(def_id, parent_defs)];
530 while let Some(def_id) = parent_defs.parent {
531 parent_defs = tcx.generics_of(def_id);
532 stack.push((def_id, parent_defs));
535 // We manually build up the substitution, rather than using convenience
536 // methods in `subst.rs`, so that we can iterate over the arguments and
537 // parameters in lock-step linearly, instead of trying to match each pair.
538 let mut substs: SmallVec<[subst::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count);
539 // Iterate over each segment of the path.
540 while let Some((def_id, defs)) = stack.pop() {
541 let mut params = defs.params.iter().peekable();
543 // If we have already computed substitutions for parents, we can use those directly.
544 while let Some(¶m) = params.peek() {
545 if let Some(&kind) = parent_substs.get(param.index as usize) {
553 // `Self` is handled first, unless it's been handled in `parent_substs`.
555 if let Some(¶m) = params.peek() {
556 if param.index == 0 {
557 if let GenericParamDefKind::Type { .. } = param.kind {
561 .unwrap_or_else(|| inferred_kind(None, param, true)),
569 // Check whether this segment takes generic arguments and the user has provided any.
570 let (generic_args, infer_args) = args_for_def_id(def_id);
573 generic_args.iter().flat_map(|generic_args| generic_args.args.iter()).peekable();
575 // If we encounter a type or const when we expect a lifetime, we infer the lifetimes.
576 // If we later encounter a lifetime, we know that the arguments were provided in the
577 // wrong order. `force_infer_lt` records the type or const that forced lifetimes to be
578 // inferred, so we can use it for diagnostics later.
579 let mut force_infer_lt = None;
582 // We're going to iterate through the generic arguments that the user
583 // provided, matching them with the generic parameters we expect.
584 // Mismatches can occur as a result of elided lifetimes, or for malformed
585 // input. We try to handle both sensibly.
586 match (args.peek(), params.peek()) {
587 (Some(&arg), Some(¶m)) => {
588 match (arg, ¶m.kind) {
589 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
590 | (GenericArg::Type(_), GenericParamDefKind::Type { .. })
591 | (GenericArg::Const(_), GenericParamDefKind::Const) => {
592 substs.push(provided_kind(param, arg));
596 (GenericArg::Type(_), GenericParamDefKind::Lifetime)
597 | (GenericArg::Const(_), GenericParamDefKind::Lifetime) => {
598 // We expected a lifetime argument, but got a type or const
599 // argument. That means we're inferring the lifetimes.
600 substs.push(inferred_kind(None, param, infer_args));
601 force_infer_lt = Some(arg);
605 // We expected one kind of parameter, but the user provided
606 // another. This is an error. However, if we already know that
607 // the arguments don't match up with the parameters, we won't issue
608 // an additional error, as the user already knows what's wrong.
609 if arg_count_correct {
610 Self::generic_arg_mismatch_err(tcx.sess, arg, kind.descr());
613 // We've reported the error, but we want to make sure that this
614 // problem doesn't bubble down and create additional, irrelevant
615 // errors. In this case, we're simply going to ignore the argument
616 // and any following arguments. The rest of the parameters will be
618 while args.next().is_some() {}
623 (Some(&arg), None) => {
624 // We should never be able to reach this point with well-formed input.
625 // There are two situations in which we can encounter this issue.
627 // 1. The number of arguments is incorrect. In this case, an error
628 // will already have been emitted, and we can ignore it. This case
629 // also occurs when late-bound lifetime parameters are present, yet
630 // the lifetime arguments have also been explicitly specified by the
632 // 2. We've inferred some lifetimes, which have been provided later (i.e.
633 // after a type or const). We want to throw an error in this case.
635 if arg_count_correct {
636 let kind = arg.descr();
637 assert_eq!(kind, "lifetime");
639 force_infer_lt.expect("lifetimes ought to have been inferred");
640 Self::generic_arg_mismatch_err(tcx.sess, provided, kind);
646 (None, Some(¶m)) => {
647 // If there are fewer arguments than parameters, it means
648 // we're inferring the remaining arguments.
649 substs.push(inferred_kind(Some(&substs), param, infer_args));
653 (None, None) => break,
658 tcx.intern_substs(&substs)
661 /// Given the type/lifetime/const arguments provided to some path (along with
662 /// an implicit `Self`, if this is a trait reference), returns the complete
663 /// set of substitutions. This may involve applying defaulted type parameters.
664 /// Also returns back constriants on associated types.
669 /// T: std::ops::Index<usize, Output = u32>
670 /// ^1 ^^^^^^^^^^^^^^2 ^^^^3 ^^^^^^^^^^^4
673 /// 1. The `self_ty` here would refer to the type `T`.
674 /// 2. The path in question is the path to the trait `std::ops::Index`,
675 /// which will have been resolved to a `def_id`
676 /// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type
677 /// parameters are returned in the `SubstsRef`, the associated type bindings like
678 /// `Output = u32` are returned in the `Vec<ConvertedBinding...>` result.
680 /// Note that the type listing given here is *exactly* what the user provided.
682 /// For (generic) associated types
685 /// <Vec<u8> as Iterable<u8>>::Iter::<'a>
688 /// We have the parent substs are the substs for the parent trait:
689 /// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated
690 /// type itself: `['a]`. The returned `SubstsRef` concatenates these two
691 /// lists: `[Vec<u8>, u8, 'a]`.
692 fn create_substs_for_ast_path<'a>(
696 parent_substs: &[subst::GenericArg<'tcx>],
697 generic_args: &'a hir::GenericArgs<'_>,
699 self_ty: Option<Ty<'tcx>>,
700 ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Result<(), GenericArgCountMismatch>)
702 // If the type is parameterized by this region, then replace this
703 // region with the current anon region binding (in other words,
704 // whatever & would get replaced with).
706 "create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
708 def_id, self_ty, generic_args
711 let tcx = self.tcx();
712 let generic_params = tcx.generics_of(def_id);
714 if generic_params.has_self {
715 if generic_params.parent.is_some() {
716 // The parent is a trait so it should have at least one subst
717 // for the `Self` type.
718 assert!(!parent_substs.is_empty())
720 // This item (presumably a trait) needs a self-type.
721 assert!(self_ty.is_some());
724 assert!(self_ty.is_none() && parent_substs.is_empty());
727 let arg_count_correct = Self::check_generic_arg_count(
732 GenericArgPosition::Type,
737 let is_object = self_ty.map_or(false, |ty| ty == self.tcx().types.trait_object_dummy_self);
738 let default_needs_object_self = |param: &ty::GenericParamDef| {
739 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
740 if is_object && has_default {
741 let self_param = tcx.types.self_param;
742 if tcx.at(span).type_of(param.def_id).walk().any(|ty| ty == self_param) {
743 // There is no suitable inference default for a type parameter
744 // that references self, in an object type.
753 let mut missing_type_params = vec![];
754 let mut inferred_params = vec![];
755 let substs = Self::create_substs_for_generic_args(
761 arg_count_correct.is_ok(),
762 // Provide the generic args, and whether types should be inferred.
765 (Some(generic_args), infer_args)
767 // The last component of this tuple is unimportant.
771 // Provide substitutions for parameters for which (valid) arguments have been provided.
772 |param, arg| match (¶m.kind, arg) {
773 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
774 self.ast_region_to_region(<, Some(param)).into()
776 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
777 if let (hir::TyKind::Infer, false) = (&ty.kind, self.allow_ty_infer()) {
778 inferred_params.push(ty.span);
781 self.ast_ty_to_ty(&ty).into()
784 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
785 self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
789 // Provide substitutions for parameters for which arguments are inferred.
790 |substs, param, infer_args| {
792 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
793 GenericParamDefKind::Type { has_default, .. } => {
794 if !infer_args && has_default {
795 // No type parameter provided, but a default exists.
797 // If we are converting an object type, then the
798 // `Self` parameter is unknown. However, some of the
799 // other type parameters may reference `Self` in their
800 // defaults. This will lead to an ICE if we are not
802 if default_needs_object_self(param) {
803 missing_type_params.push(param.name.to_string());
806 // This is a default type parameter.
809 tcx.at(span).type_of(param.def_id).subst_spanned(
817 } else if infer_args {
818 // No type parameters were provided, we can infer all.
820 if !default_needs_object_self(param) { Some(param) } else { None };
821 self.ty_infer(param, span).into()
823 // We've already errored above about the mismatch.
827 GenericParamDefKind::Const => {
828 // FIXME(const_generics:defaults)
830 // No const parameters were provided, we can infer all.
831 let ty = tcx.at(span).type_of(param.def_id);
832 self.ct_infer(ty, Some(param), span).into()
834 // We've already errored above about the mismatch.
835 tcx.consts.err.into()
841 if !inferred_params.is_empty() {
842 // We always collect the spans for placeholder types when evaluating `fn`s, but we
843 // only want to emit an error complaining about them if infer types (`_`) are not
844 // allowed. `allow_ty_infer` gates this behavior.
845 crate::collect::placeholder_type_error(
854 self.complain_about_missing_type_params(
858 generic_args.args.is_empty(),
861 // Convert associated-type bindings or constraints into a separate vector.
862 // Example: Given this:
864 // T: Iterator<Item = u32>
866 // The `T` is passed in as a self-type; the `Item = u32` is
867 // not a "type parameter" of the `Iterator` trait, but rather
868 // a restriction on `<T as Iterator>::Item`, so it is passed
870 let assoc_bindings = generic_args
874 let kind = match binding.kind {
875 hir::TypeBindingKind::Equality { ref ty } => {
876 ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty))
878 hir::TypeBindingKind::Constraint { ref bounds } => {
879 ConvertedBindingKind::Constraint(bounds)
882 ConvertedBinding { item_name: binding.ident, kind, span: binding.span }
887 "create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
888 generic_params, self_ty, substs
891 (substs, assoc_bindings, arg_count_correct)
894 crate fn create_substs_for_associated_item(
899 item_segment: &hir::PathSegment<'_>,
900 parent_substs: SubstsRef<'tcx>,
901 ) -> SubstsRef<'tcx> {
902 if tcx.generics_of(item_def_id).params.is_empty() {
903 self.prohibit_generics(slice::from_ref(item_segment));
907 self.create_substs_for_ast_path(
911 item_segment.generic_args(),
912 item_segment.infer_args,
919 /// On missing type parameters, emit an E0393 error and provide a structured suggestion using
920 /// the type parameter's name as a placeholder.
921 fn complain_about_missing_type_params(
923 missing_type_params: Vec<String>,
926 empty_generic_args: bool,
928 if missing_type_params.is_empty() {
932 missing_type_params.iter().map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
933 let mut err = struct_span_err!(
937 "the type parameter{} {} must be explicitly specified",
938 pluralize!(missing_type_params.len()),
942 self.tcx().def_span(def_id),
944 "type parameter{} {} must be specified for this",
945 pluralize!(missing_type_params.len()),
949 let mut suggested = false;
950 if let (Ok(snippet), true) = (
951 self.tcx().sess.source_map().span_to_snippet(span),
952 // Don't suggest setting the type params if there are some already: the order is
953 // tricky to get right and the user will already know what the syntax is.
956 if snippet.ends_with('>') {
957 // The user wrote `Trait<'a, T>` or similar. To provide an accurate suggestion
958 // we would have to preserve the right order. For now, as clearly the user is
959 // aware of the syntax, we do nothing.
961 // The user wrote `Iterator`, so we don't have a type we can suggest, but at
962 // least we can clue them to the correct syntax `Iterator<Type>`.
966 "set the type parameter{plural} to the desired type{plural}",
967 plural = pluralize!(missing_type_params.len()),
969 format!("{}<{}>", snippet, missing_type_params.join(", ")),
970 Applicability::HasPlaceholders,
979 "missing reference{} to {}",
980 pluralize!(missing_type_params.len()),
986 "because of the default `Self` reference, type parameters must be \
987 specified on object types",
992 /// Instantiates the path for the given trait reference, assuming that it's
993 /// bound to a valid trait type. Returns the `DefId` of the defining trait.
994 /// The type _cannot_ be a type other than a trait type.
996 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
997 /// are disallowed. Otherwise, they are pushed onto the vector given.
998 pub fn instantiate_mono_trait_ref(
1000 trait_ref: &hir::TraitRef<'_>,
1002 ) -> ty::TraitRef<'tcx> {
1003 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
1005 self.ast_path_to_mono_trait_ref(
1006 trait_ref.path.span,
1007 trait_ref.trait_def_id(),
1009 trait_ref.path.segments.last().unwrap(),
1013 /// The given trait-ref must actually be a trait.
1014 pub(super) fn instantiate_poly_trait_ref_inner(
1016 trait_ref: &hir::TraitRef<'_>,
1018 constness: Constness,
1020 bounds: &mut Bounds<'tcx>,
1022 ) -> Result<(), GenericArgCountMismatch> {
1023 let trait_def_id = trait_ref.trait_def_id();
1025 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
1027 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
1029 let path_span = if let [segment] = &trait_ref.path.segments[..] {
1030 // FIXME: `trait_ref.path.span` can point to a full path with multiple
1031 // segments, even though `trait_ref.path.segments` is of length `1`. Work
1032 // around that bug here, even though it should be fixed elsewhere.
1033 // This would otherwise cause an invalid suggestion. For an example, look at
1034 // `src/test/ui/issues/issue-28344.rs`.
1039 let (substs, assoc_bindings, arg_count_correct) = self.create_substs_for_ast_trait_ref(
1043 trait_ref.path.segments.last().unwrap(),
1045 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
1047 bounds.trait_bounds.push((poly_trait_ref, span, constness));
1049 let mut dup_bindings = FxHashMap::default();
1050 for binding in &assoc_bindings {
1051 // Specify type to assert that error was already reported in `Err` case.
1052 let _: Result<_, ErrorReported> = self.add_predicates_for_ast_type_binding(
1053 trait_ref.hir_ref_id,
1061 // Okay to ignore `Err` because of `ErrorReported` (see above).
1065 "instantiate_poly_trait_ref({:?}, bounds={:?}) -> {:?}",
1066 trait_ref, bounds, poly_trait_ref
1072 /// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct
1073 /// a full trait reference. The resulting trait reference is returned. This may also generate
1074 /// auxiliary bounds, which are added to `bounds`.
1079 /// poly_trait_ref = Iterator<Item = u32>
1083 /// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`.
1085 /// **A note on binders:** against our usual convention, there is an implied bounder around
1086 /// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions.
1087 /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>`
1088 /// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be
1089 /// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly,
1091 pub fn instantiate_poly_trait_ref(
1093 poly_trait_ref: &hir::PolyTraitRef<'_>,
1094 constness: Constness,
1096 bounds: &mut Bounds<'tcx>,
1097 ) -> Result<(), GenericArgCountMismatch> {
1098 self.instantiate_poly_trait_ref_inner(
1099 &poly_trait_ref.trait_ref,
1100 poly_trait_ref.span,
1108 fn ast_path_to_mono_trait_ref(
1111 trait_def_id: DefId,
1113 trait_segment: &hir::PathSegment<'_>,
1114 ) -> ty::TraitRef<'tcx> {
1115 let (substs, assoc_bindings, _) =
1116 self.create_substs_for_ast_trait_ref(span, trait_def_id, self_ty, trait_segment);
1117 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
1118 ty::TraitRef::new(trait_def_id, substs)
1121 /// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit
1122 /// an error and attempt to build a reasonable structured suggestion.
1123 fn complain_about_internal_fn_trait(
1126 trait_def_id: DefId,
1127 trait_segment: &'a hir::PathSegment<'a>,
1129 let trait_def = self.tcx().trait_def(trait_def_id);
1131 if !self.tcx().features().unboxed_closures
1132 && trait_segment.generic_args().parenthesized != trait_def.paren_sugar
1134 // For now, require that parenthetical notation be used only with `Fn()` etc.
1135 let (msg, sugg) = if trait_def.paren_sugar {
1137 "the precise format of `Fn`-family traits' type parameters is subject to \
1141 trait_segment.ident,
1145 .and_then(|args| args.args.get(0))
1146 .and_then(|arg| match arg {
1147 hir::GenericArg::Type(ty) => {
1148 Some(print::to_string(print::NO_ANN, |s| s.print_type(ty)))
1152 .unwrap_or_else(|| "()".to_string()),
1157 .filter_map(|b| match (b.ident.as_str() == "Output", &b.kind) {
1158 (true, hir::TypeBindingKind::Equality { ty }) => {
1159 Some(print::to_string(print::NO_ANN, |s| s.print_type(ty)))
1164 .unwrap_or_else(|| "()".to_string()),
1168 ("parenthetical notation is only stable when used with `Fn`-family traits", None)
1170 let sess = &self.tcx().sess.parse_sess;
1171 let mut err = feature_err(sess, sym::unboxed_closures, span, msg);
1172 if let Some(sugg) = sugg {
1173 let msg = "use parenthetical notation instead";
1174 err.span_suggestion(span, msg, sugg, Applicability::MaybeIncorrect);
1180 fn create_substs_for_ast_trait_ref<'a>(
1183 trait_def_id: DefId,
1185 trait_segment: &'a hir::PathSegment<'a>,
1186 ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Result<(), GenericArgCountMismatch>)
1188 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})", trait_segment);
1190 self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment);
1192 self.create_substs_for_ast_path(
1196 trait_segment.generic_args(),
1197 trait_segment.infer_args,
1202 fn trait_defines_associated_type_named(
1204 trait_def_id: DefId,
1205 assoc_name: ast::Ident,
1208 .associated_items(trait_def_id)
1209 .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, trait_def_id)
1213 // Returns `true` if a bounds list includes `?Sized`.
1214 pub fn is_unsized(&self, ast_bounds: &[hir::GenericBound<'_>], span: Span) -> bool {
1215 let tcx = self.tcx();
1217 // Try to find an unbound in bounds.
1218 let mut unbound = None;
1219 for ab in ast_bounds {
1220 if let &hir::GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = ab {
1221 if unbound.is_none() {
1222 unbound = Some(&ptr.trait_ref);
1228 "type parameter has more than one relaxed default \
1229 bound, only one is supported"
1236 let kind_id = tcx.lang_items().require(SizedTraitLangItem);
1239 // FIXME(#8559) currently requires the unbound to be built-in.
1240 if let Ok(kind_id) = kind_id {
1241 if tpb.path.res != Res::Def(DefKind::Trait, kind_id) {
1244 "default bound relaxed for a type parameter, but \
1245 this does nothing because the given bound is not \
1246 a default; only `?Sized` is supported",
1251 _ if kind_id.is_ok() => {
1254 // No lang item for `Sized`, so we can't add it as a bound.
1261 /// This helper takes a *converted* parameter type (`param_ty`)
1262 /// and an *unconverted* list of bounds:
1265 /// fn foo<T: Debug>
1266 /// ^ ^^^^^ `ast_bounds` parameter, in HIR form
1268 /// `param_ty`, in ty form
1271 /// It adds these `ast_bounds` into the `bounds` structure.
1273 /// **A note on binders:** there is an implied binder around
1274 /// `param_ty` and `ast_bounds`. See `instantiate_poly_trait_ref`
1275 /// for more details.
1279 ast_bounds: &[hir::GenericBound<'_>],
1280 bounds: &mut Bounds<'tcx>,
1282 let mut trait_bounds = Vec::new();
1283 let mut region_bounds = Vec::new();
1285 let constness = self.default_constness_for_trait_bounds();
1286 for ast_bound in ast_bounds {
1288 hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => {
1289 trait_bounds.push((b, constness))
1291 hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::MaybeConst) => {
1292 trait_bounds.push((b, Constness::NotConst))
1294 hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {}
1295 hir::GenericBound::Outlives(ref l) => region_bounds.push(l),
1299 for (bound, constness) in trait_bounds {
1300 let _ = self.instantiate_poly_trait_ref(bound, constness, param_ty, bounds);
1303 bounds.region_bounds.extend(
1304 region_bounds.into_iter().map(|r| (self.ast_region_to_region(r, None), r.span)),
1308 /// Translates a list of bounds from the HIR into the `Bounds` data structure.
1309 /// The self-type for the bounds is given by `param_ty`.
1314 /// fn foo<T: Bar + Baz>() { }
1315 /// ^ ^^^^^^^^^ ast_bounds
1319 /// The `sized_by_default` parameter indicates if, in this context, the `param_ty` should be
1320 /// considered `Sized` unless there is an explicit `?Sized` bound. This would be true in the
1321 /// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`.
1323 /// `span` should be the declaration size of the parameter.
1324 pub fn compute_bounds(
1327 ast_bounds: &[hir::GenericBound<'_>],
1328 sized_by_default: SizedByDefault,
1331 let mut bounds = Bounds::default();
1333 self.add_bounds(param_ty, ast_bounds, &mut bounds);
1334 bounds.trait_bounds.sort_by_key(|(t, _, _)| t.def_id());
1336 bounds.implicitly_sized = if let SizedByDefault::Yes = sized_by_default {
1337 if !self.is_unsized(ast_bounds, span) { Some(span) } else { None }
1345 /// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates
1348 /// **A note on binders:** given something like `T: for<'a> Iterator<Item = &'a u32>`, the
1349 /// `trait_ref` here will be `for<'a> T: Iterator`. The `binding` data however is from *inside*
1350 /// the binder (e.g., `&'a u32`) and hence may reference bound regions.
1351 fn add_predicates_for_ast_type_binding(
1353 hir_ref_id: hir::HirId,
1354 trait_ref: ty::PolyTraitRef<'tcx>,
1355 binding: &ConvertedBinding<'_, 'tcx>,
1356 bounds: &mut Bounds<'tcx>,
1358 dup_bindings: &mut FxHashMap<DefId, Span>,
1360 ) -> Result<(), ErrorReported> {
1361 let tcx = self.tcx();
1364 // Given something like `U: SomeTrait<T = X>`, we want to produce a
1365 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
1366 // subtle in the event that `T` is defined in a supertrait of
1367 // `SomeTrait`, because in that case we need to upcast.
1369 // That is, consider this case:
1372 // trait SubTrait: SuperTrait<int> { }
1373 // trait SuperTrait<A> { type T; }
1375 // ... B: SubTrait<T = foo> ...
1378 // We want to produce `<B as SuperTrait<int>>::T == foo`.
1380 // Find any late-bound regions declared in `ty` that are not
1381 // declared in the trait-ref. These are not well-formed.
1385 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
1386 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
1387 if let ConvertedBindingKind::Equality(ty) = binding.kind {
1388 let late_bound_in_trait_ref =
1389 tcx.collect_constrained_late_bound_regions(&trait_ref);
1390 let late_bound_in_ty =
1391 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(ty));
1392 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
1393 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
1394 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
1395 let br_name = match *br {
1396 ty::BrNamed(_, name) => name,
1400 "anonymous bound region {:?} in binding but not trait ref",
1405 // FIXME: point at the type params that don't have appropriate lifetimes:
1406 // struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F);
1407 // ---- ---- ^^^^^^^
1412 "binding for associated type `{}` references lifetime `{}`, \
1413 which does not appear in the trait input types",
1423 if self.trait_defines_associated_type_named(trait_ref.def_id(), binding.item_name) {
1424 // Simple case: X is defined in the current trait.
1427 // Otherwise, we have to walk through the supertraits to find
1429 self.one_bound_for_assoc_type(
1430 || traits::supertraits(tcx, trait_ref),
1431 || trait_ref.print_only_trait_path().to_string(),
1434 || match binding.kind {
1435 ConvertedBindingKind::Equality(ty) => Some(ty.to_string()),
1441 let (assoc_ident, def_scope) =
1442 tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
1444 // We have already adjusted the item name above, so compare with `ident.modern()` instead
1445 // of calling `filter_by_name_and_kind`.
1447 .associated_items(candidate.def_id())
1448 .filter_by_name_unhygienic(assoc_ident.name)
1449 .find(|i| i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident)
1450 .expect("missing associated type");
1452 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
1453 let msg = format!("associated type `{}` is private", binding.item_name);
1454 tcx.sess.span_err(binding.span, &msg);
1456 tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
1460 .entry(assoc_ty.def_id)
1461 .and_modify(|prev_span| {
1466 "the value of the associated type `{}` (from trait `{}`) \
1467 is already specified",
1469 tcx.def_path_str(assoc_ty.container.id())
1471 .span_label(binding.span, "re-bound here")
1472 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
1475 .or_insert(binding.span);
1478 match binding.kind {
1479 ConvertedBindingKind::Equality(ref ty) => {
1480 // "Desugar" a constraint like `T: Iterator<Item = u32>` this to
1481 // the "projection predicate" for:
1483 // `<T as Iterator>::Item = u32`
1484 bounds.projection_bounds.push((
1485 candidate.map_bound(|trait_ref| ty::ProjectionPredicate {
1486 projection_ty: ty::ProjectionTy::from_ref_and_name(
1496 ConvertedBindingKind::Constraint(ast_bounds) => {
1497 // "Desugar" a constraint like `T: Iterator<Item: Debug>` to
1499 // `<T as Iterator>::Item: Debug`
1501 // Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty`
1502 // parameter to have a skipped binder.
1503 let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);
1504 self.add_bounds(param_ty, ast_bounds, bounds);
1514 item_segment: &hir::PathSegment<'_>,
1516 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
1517 self.normalize_ty(span, self.tcx().at(span).type_of(did).subst(self.tcx(), substs))
1520 fn conv_object_ty_poly_trait_ref(
1523 trait_bounds: &[hir::PolyTraitRef<'_>],
1524 lifetime: &hir::Lifetime,
1526 let tcx = self.tcx();
1528 let mut bounds = Bounds::default();
1529 let mut potential_assoc_types = Vec::new();
1530 let dummy_self = self.tcx().types.trait_object_dummy_self;
1531 for trait_bound in trait_bounds.iter().rev() {
1532 if let Err(GenericArgCountMismatch {
1533 invalid_args: cur_potential_assoc_types, ..
1534 }) = self.instantiate_poly_trait_ref(
1536 Constness::NotConst,
1540 potential_assoc_types.extend(cur_potential_assoc_types.into_iter());
1544 // Expand trait aliases recursively and check that only one regular (non-auto) trait
1545 // is used and no 'maybe' bounds are used.
1546 let expanded_traits =
1547 traits::expand_trait_aliases(tcx, bounds.trait_bounds.iter().map(|&(a, b, _)| (a, b)));
1548 let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
1549 expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
1550 if regular_traits.len() > 1 {
1551 let first_trait = ®ular_traits[0];
1552 let additional_trait = ®ular_traits[1];
1553 let mut err = struct_span_err!(
1555 additional_trait.bottom().1,
1557 "only auto traits can be used as additional traits in a trait object"
1559 additional_trait.label_with_exp_info(
1561 "additional non-auto trait",
1564 first_trait.label_with_exp_info(&mut err, "first non-auto trait", "first use");
1568 if regular_traits.is_empty() && auto_traits.is_empty() {
1573 "at least one trait is required for an object type"
1576 return tcx.types.err;
1579 // Check that there are no gross object safety violations;
1580 // most importantly, that the supertraits don't contain `Self`,
1582 for item in ®ular_traits {
1583 let object_safety_violations =
1584 astconv_object_safety_violations(tcx, item.trait_ref().def_id());
1585 if !object_safety_violations.is_empty() {
1586 report_object_safety_error(
1589 item.trait_ref().def_id(),
1590 object_safety_violations,
1593 return tcx.types.err;
1597 // Use a `BTreeSet` to keep output in a more consistent order.
1598 let mut associated_types: FxHashMap<Span, BTreeSet<DefId>> = FxHashMap::default();
1600 let regular_traits_refs_spans = bounds
1603 .filter(|(trait_ref, _, _)| !tcx.trait_is_auto(trait_ref.def_id()));
1605 for (base_trait_ref, span, constness) in regular_traits_refs_spans {
1606 assert_eq!(constness, Constness::NotConst);
1608 for trait_ref in traits::elaborate_trait_ref(tcx, base_trait_ref) {
1610 "conv_object_ty_poly_trait_ref: observing object predicate `{:?}`",
1614 ty::Predicate::Trait(pred, _) => {
1615 associated_types.entry(span).or_default().extend(
1616 tcx.associated_items(pred.def_id())
1617 .in_definition_order()
1618 .filter(|item| item.kind == ty::AssocKind::Type)
1619 .map(|item| item.def_id),
1622 ty::Predicate::Projection(pred) => {
1623 // A `Self` within the original bound will be substituted with a
1624 // `trait_object_dummy_self`, so check for that.
1625 let references_self = pred.skip_binder().ty.walk().any(|t| t == dummy_self);
1627 // If the projection output contains `Self`, force the user to
1628 // elaborate it explicitly to avoid a lot of complexity.
1630 // The "classicaly useful" case is the following:
1632 // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
1637 // Here, the user could theoretically write `dyn MyTrait<Output = X>`,
1638 // but actually supporting that would "expand" to an infinitely-long type
1639 // `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`.
1641 // Instead, we force the user to write
1642 // `dyn MyTrait<MyOutput = X, Output = X>`, which is uglier but works. See
1643 // the discussion in #56288 for alternatives.
1644 if !references_self {
1645 // Include projections defined on supertraits.
1646 bounds.projection_bounds.push((pred, span));
1654 for (projection_bound, _) in &bounds.projection_bounds {
1655 for def_ids in associated_types.values_mut() {
1656 def_ids.remove(&projection_bound.projection_def_id());
1660 self.complain_about_missing_associated_types(
1662 potential_assoc_types,
1666 // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
1667 // `dyn Trait + Send`.
1668 auto_traits.sort_by_key(|i| i.trait_ref().def_id());
1669 auto_traits.dedup_by_key(|i| i.trait_ref().def_id());
1670 debug!("regular_traits: {:?}", regular_traits);
1671 debug!("auto_traits: {:?}", auto_traits);
1673 // Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
1674 // removing the dummy `Self` type (`trait_object_dummy_self`).
1675 let trait_ref_to_existential = |trait_ref: ty::TraitRef<'tcx>| {
1676 if trait_ref.self_ty() != dummy_self {
1677 // FIXME: There appears to be a missing filter on top of `expand_trait_aliases`,
1678 // which picks up non-supertraits where clauses - but also, the object safety
1679 // completely ignores trait aliases, which could be object safety hazards. We
1680 // `delay_span_bug` here to avoid an ICE in stable even when the feature is
1681 // disabled. (#66420)
1682 tcx.sess.delay_span_bug(
1685 "trait_ref_to_existential called on {:?} with non-dummy Self",
1690 ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
1693 // Erase the `dummy_self` (`trait_object_dummy_self`) used above.
1694 let existential_trait_refs = regular_traits
1696 .map(|i| i.trait_ref().map_bound(|trait_ref| trait_ref_to_existential(trait_ref)));
1697 let existential_projections = bounds.projection_bounds.iter().map(|(bound, _)| {
1698 bound.map_bound(|b| {
1699 let trait_ref = trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1700 ty::ExistentialProjection {
1702 item_def_id: b.projection_ty.item_def_id,
1703 substs: trait_ref.substs,
1708 // Calling `skip_binder` is okay because the predicates are re-bound.
1709 let regular_trait_predicates = existential_trait_refs
1710 .map(|trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder()));
1711 let auto_trait_predicates = auto_traits
1713 .map(|trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()));
1714 let mut v = regular_trait_predicates
1715 .chain(auto_trait_predicates)
1717 existential_projections
1718 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())),
1720 .collect::<SmallVec<[_; 8]>>();
1721 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1723 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1725 // Use explicitly-specified region bound.
1726 let region_bound = if !lifetime.is_elided() {
1727 self.ast_region_to_region(lifetime, None)
1729 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1730 if tcx.named_region(lifetime.hir_id).is_some() {
1731 self.ast_region_to_region(lifetime, None)
1733 self.re_infer(None, span).unwrap_or_else(|| {
1738 "the lifetime bound for this object type cannot be deduced \
1739 from context; please supply an explicit bound"
1742 tcx.lifetimes.re_static
1747 debug!("region_bound: {:?}", region_bound);
1749 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1750 debug!("trait_object_type: {:?}", ty);
1754 /// When there are any missing associated types, emit an E0191 error and attempt to supply a
1755 /// reasonable suggestion on how to write it. For the case of multiple associated types in the
1756 /// same trait bound have the same name (as they come from different super-traits), we instead
1757 /// emit a generic note suggesting using a `where` clause to constraint instead.
1758 fn complain_about_missing_associated_types(
1760 associated_types: FxHashMap<Span, BTreeSet<DefId>>,
1761 potential_assoc_types: Vec<Span>,
1762 trait_bounds: &[hir::PolyTraitRef<'_>],
1764 if !associated_types.values().any(|v| !v.is_empty()) {
1767 let tcx = self.tcx();
1768 // FIXME: Marked `mut` so that we can replace the spans further below with a more
1769 // appropriate one, but this should be handled earlier in the span assignment.
1770 let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types
1772 .map(|(span, def_ids)| {
1773 (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
1776 let mut names = vec![];
1778 // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
1779 // `issue-22560.rs`.
1780 let mut trait_bound_spans: Vec<Span> = vec![];
1781 for (span, items) in &associated_types {
1782 if !items.is_empty() {
1783 trait_bound_spans.push(*span);
1785 for assoc_item in items {
1786 let trait_def_id = assoc_item.container.id();
1788 "`{}` (from trait `{}`)",
1790 tcx.def_path_str(trait_def_id),
1795 match (&potential_assoc_types[..], &trait_bounds) {
1796 ([], [bound]) => match &bound.trait_ref.path.segments[..] {
1797 // FIXME: `trait_ref.path.span` can point to a full path with multiple
1798 // segments, even though `trait_ref.path.segments` is of length `1`. Work
1799 // around that bug here, even though it should be fixed elsewhere.
1800 // This would otherwise cause an invalid suggestion. For an example, look at
1801 // `src/test/ui/issues/issue-28344.rs` where instead of the following:
1803 // error[E0191]: the value of the associated type `Output`
1804 // (from trait `std::ops::BitXor`) must be specified
1805 // --> $DIR/issue-28344.rs:4:17
1807 // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
1808 // | ^^^^^^ help: specify the associated type:
1809 // | `BitXor<Output = Type>`
1813 // error[E0191]: the value of the associated type `Output`
1814 // (from trait `std::ops::BitXor`) must be specified
1815 // --> $DIR/issue-28344.rs:4:17
1817 // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
1818 // | ^^^^^^^^^^^^^ help: specify the associated type:
1819 // | `BitXor::bitor<Output = Type>`
1820 [segment] if segment.args.is_none() => {
1821 trait_bound_spans = vec![segment.ident.span];
1822 associated_types = associated_types
1824 .map(|(_, items)| (segment.ident.span, items))
1832 trait_bound_spans.sort();
1833 let mut err = struct_span_err!(
1837 "the value of the associated type{} {} must be specified",
1838 pluralize!(names.len()),
1841 let mut suggestions = vec![];
1842 let mut types_count = 0;
1843 let mut where_constraints = vec![];
1844 for (span, assoc_items) in &associated_types {
1845 let mut names: FxHashMap<_, usize> = FxHashMap::default();
1846 for item in assoc_items {
1848 *names.entry(item.ident.name).or_insert(0) += 1;
1850 let mut dupes = false;
1851 for item in assoc_items {
1852 let prefix = if names[&item.ident.name] > 1 {
1853 let trait_def_id = item.container.id();
1855 format!("{}::", tcx.def_path_str(trait_def_id))
1859 if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
1860 err.span_label(sp, format!("`{}{}` defined here", prefix, item.ident));
1863 if potential_assoc_types.len() == assoc_items.len() {
1864 // Only suggest when the amount of missing associated types equals the number of
1865 // extra type arguments present, as that gives us a relatively high confidence
1866 // that the user forgot to give the associtated type's name. The canonical
1867 // example would be trying to use `Iterator<isize>` instead of
1868 // `Iterator<Item = isize>`.
1869 for (potential, item) in potential_assoc_types.iter().zip(assoc_items.iter()) {
1870 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(*potential) {
1871 suggestions.push((*potential, format!("{} = {}", item.ident, snippet)));
1874 } else if let (Ok(snippet), false) =
1875 (tcx.sess.source_map().span_to_snippet(*span), dupes)
1878 assoc_items.iter().map(|item| format!("{} = Type", item.ident)).collect();
1879 let code = if snippet.ends_with('>') {
1880 // The user wrote `Trait<'a>` or similar and we don't have a type we can
1881 // suggest, but at least we can clue them to the correct syntax
1882 // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
1884 format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
1886 // The user wrote `Iterator`, so we don't have a type we can suggest, but at
1887 // least we can clue them to the correct syntax `Iterator<Item = Type>`.
1888 format!("{}<{}>", snippet, types.join(", "))
1890 suggestions.push((*span, code));
1892 where_constraints.push(*span);
1895 let where_msg = "consider introducing a new type parameter, adding `where` constraints \
1896 using the fully-qualified path to the associated types";
1897 if !where_constraints.is_empty() && suggestions.is_empty() {
1898 // If there are duplicates associated type names and a single trait bound do not
1899 // use structured suggestion, it means that there are multiple super-traits with
1900 // the same associated type name.
1901 err.help(where_msg);
1903 if suggestions.len() != 1 {
1904 // We don't need this label if there's an inline suggestion, show otherwise.
1905 for (span, assoc_items) in &associated_types {
1906 let mut names: FxHashMap<_, usize> = FxHashMap::default();
1907 for item in assoc_items {
1909 *names.entry(item.ident.name).or_insert(0) += 1;
1911 let mut label = vec![];
1912 for item in assoc_items {
1913 let postfix = if names[&item.ident.name] > 1 {
1914 let trait_def_id = item.container.id();
1915 format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
1919 label.push(format!("`{}`{}", item.ident, postfix));
1921 if !label.is_empty() {
1925 "associated type{} {} must be specified",
1926 pluralize!(label.len()),
1933 if !suggestions.is_empty() {
1934 err.multipart_suggestion(
1935 &format!("specify the associated type{}", pluralize!(types_count)),
1937 Applicability::HasPlaceholders,
1939 if !where_constraints.is_empty() {
1940 err.span_help(where_constraints, where_msg);
1946 fn report_ambiguous_associated_type(
1953 let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
1954 if let (Some(_), Ok(snippet)) = (
1955 self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
1956 self.tcx().sess.source_map().span_to_snippet(span),
1958 err.span_suggestion(
1960 "you are looking for the module in `std`, not the primitive type",
1961 format!("std::{}", snippet),
1962 Applicability::MachineApplicable,
1965 err.span_suggestion(
1967 "use fully-qualified syntax",
1968 format!("<{} as {}>::{}", type_str, trait_str, name),
1969 Applicability::HasPlaceholders,
1975 // Search for a bound on a type parameter which includes the associated item
1976 // given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter
1977 // This function will fail if there are no suitable bounds or there is
1979 fn find_bound_for_assoc_item(
1981 ty_param_def_id: DefId,
1982 assoc_name: ast::Ident,
1984 ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported> {
1985 let tcx = self.tcx();
1988 "find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})",
1989 ty_param_def_id, assoc_name, span,
1992 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1994 debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
1996 let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
1997 let param_name = tcx.hir().ty_param_name(param_hir_id);
1998 self.one_bound_for_assoc_type(
2000 traits::transitive_bounds(
2002 predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref()),
2005 || param_name.to_string(),
2012 // Checks that `bounds` contains exactly one element and reports appropriate
2013 // errors otherwise.
2014 fn one_bound_for_assoc_type<I>(
2016 all_candidates: impl Fn() -> I,
2017 ty_param_name: impl Fn() -> String,
2018 assoc_name: ast::Ident,
2020 is_equality: impl Fn() -> Option<String>,
2021 ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
2023 I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
2025 let mut matching_candidates = all_candidates()
2026 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
2028 let bound = match matching_candidates.next() {
2029 Some(bound) => bound,
2031 self.complain_about_assoc_type_not_found(
2037 return Err(ErrorReported);
2041 debug!("one_bound_for_assoc_type: bound = {:?}", bound);
2043 if let Some(bound2) = matching_candidates.next() {
2044 debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2);
2046 let is_equality = is_equality();
2047 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(matching_candidates);
2048 let mut err = if is_equality.is_some() {
2049 // More specific Error Index entry.
2054 "ambiguous associated type `{}` in bounds of `{}`",
2063 "ambiguous associated type `{}` in bounds of `{}`",
2068 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
2070 let mut where_bounds = vec![];
2071 for bound in bounds {
2072 let bound_id = bound.def_id();
2073 let bound_span = self
2075 .associated_items(bound_id)
2076 .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_id)
2077 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
2079 if let Some(bound_span) = bound_span {
2083 "ambiguous `{}` from `{}`",
2085 bound.print_only_trait_path(),
2088 if let Some(constraint) = &is_equality {
2089 where_bounds.push(format!(
2090 " T: {trait}::{assoc} = {constraint}",
2091 trait=bound.print_only_trait_path(),
2093 constraint=constraint,
2096 err.span_suggestion(
2098 "use fully qualified syntax to disambiguate",
2102 bound.print_only_trait_path(),
2105 Applicability::MaybeIncorrect,
2110 "associated type `{}` could derive from `{}`",
2112 bound.print_only_trait_path(),
2116 if !where_bounds.is_empty() {
2118 "consider introducing a new type parameter `T` and adding `where` constraints:\
2119 \n where\n T: {},\n{}",
2121 where_bounds.join(",\n"),
2125 if !where_bounds.is_empty() {
2126 return Err(ErrorReported);
2132 fn complain_about_assoc_type_not_found<I>(
2134 all_candidates: impl Fn() -> I,
2135 ty_param_name: &str,
2136 assoc_name: ast::Ident,
2139 I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
2141 // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
2142 // valid span, so we point at the whole path segment instead.
2143 let span = if assoc_name.span != DUMMY_SP { assoc_name.span } else { span };
2144 let mut err = struct_span_err!(
2148 "associated type `{}` not found for `{}`",
2153 let all_candidate_names: Vec<_> = all_candidates()
2154 .map(|r| self.tcx().associated_items(r.def_id()).in_definition_order())
2157 |item| if item.kind == ty::AssocKind::Type { Some(item.ident.name) } else { None },
2161 if let (Some(suggested_name), true) = (
2162 find_best_match_for_name(all_candidate_names.iter(), &assoc_name.as_str(), None),
2163 assoc_name.span != DUMMY_SP,
2165 err.span_suggestion(
2167 "there is an associated type with a similar name",
2168 suggested_name.to_string(),
2169 Applicability::MaybeIncorrect,
2172 err.span_label(span, format!("associated type `{}` not found", assoc_name));
2178 // Create a type from a path to an associated type.
2179 // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
2180 // and item_segment is the path segment for `D`. We return a type and a def for
2182 // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
2183 // parameter or `Self`.
2184 pub fn associated_path_to_ty(
2186 hir_ref_id: hir::HirId,
2190 assoc_segment: &hir::PathSegment<'_>,
2191 permit_variants: bool,
2192 ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
2193 let tcx = self.tcx();
2194 let assoc_ident = assoc_segment.ident;
2196 debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
2198 // Check if we have an enum variant.
2199 let mut variant_resolution = None;
2200 if let ty::Adt(adt_def, _) = qself_ty.kind {
2201 if adt_def.is_enum() {
2202 let variant_def = adt_def
2205 .find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did));
2206 if let Some(variant_def) = variant_def {
2207 if permit_variants {
2208 tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
2209 self.prohibit_generics(slice::from_ref(assoc_segment));
2210 return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
2212 variant_resolution = Some(variant_def.def_id);
2218 // Find the type of the associated item, and the trait where the associated
2219 // item is declared.
2220 let bound = match (&qself_ty.kind, qself_res) {
2221 (_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
2222 // `Self` in an impl of a trait -- we have a concrete self type and a
2224 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
2225 Some(trait_ref) => trait_ref,
2227 // A cycle error occurred, most likely.
2228 return Err(ErrorReported);
2232 self.one_bound_for_assoc_type(
2233 || traits::supertraits(tcx, ty::Binder::bind(trait_ref)),
2234 || "Self".to_string(),
2240 (&ty::Param(_), Res::SelfTy(Some(param_did), None))
2241 | (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
2242 self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
2245 if variant_resolution.is_some() {
2246 // Variant in type position
2247 let msg = format!("expected type, found variant `{}`", assoc_ident);
2248 tcx.sess.span_err(span, &msg);
2249 } else if qself_ty.is_enum() {
2250 let mut err = struct_span_err!(
2254 "no variant named `{}` found for enum `{}`",
2259 let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
2260 if let Some(suggested_name) = find_best_match_for_name(
2261 adt_def.variants.iter().map(|variant| &variant.ident.name),
2262 &assoc_ident.as_str(),
2265 err.span_suggestion(
2267 "there is a variant with a similar name",
2268 suggested_name.to_string(),
2269 Applicability::MaybeIncorrect,
2274 format!("variant not found in `{}`", qself_ty),
2278 if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
2279 let sp = tcx.sess.source_map().def_span(sp);
2280 err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
2284 } else if !qself_ty.references_error() {
2285 // Don't print `TyErr` to the user.
2286 self.report_ambiguous_associated_type(
2288 &qself_ty.to_string(),
2293 return Err(ErrorReported);
2297 let trait_did = bound.def_id();
2298 let (assoc_ident, def_scope) =
2299 tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
2301 // We have already adjusted the item name above, so compare with `ident.modern()` instead
2302 // of calling `filter_by_name_and_kind`.
2304 .associated_items(trait_did)
2305 .in_definition_order()
2306 .find(|i| i.kind.namespace() == Namespace::TypeNS && i.ident.modern() == assoc_ident)
2307 .expect("missing associated type");
2309 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, assoc_segment, bound);
2310 let ty = self.normalize_ty(span, ty);
2312 let kind = DefKind::AssocTy;
2313 if !item.vis.is_accessible_from(def_scope, tcx) {
2314 let msg = format!("{} `{}` is private", kind.descr(item.def_id), assoc_ident);
2315 tcx.sess.span_err(span, &msg);
2317 tcx.check_stability(item.def_id, Some(hir_ref_id), span);
2319 if let Some(variant_def_id) = variant_resolution {
2320 tcx.struct_span_lint_hir(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| {
2321 let mut err = lint.build("ambiguous associated item");
2322 let mut could_refer_to = |kind: DefKind, def_id, also| {
2323 let note_msg = format!(
2324 "`{}` could{} refer to the {} defined here",
2329 err.span_note(tcx.def_span(def_id), ¬e_msg);
2332 could_refer_to(DefKind::Variant, variant_def_id, "");
2333 could_refer_to(kind, item.def_id, " also");
2335 err.span_suggestion(
2337 "use fully-qualified syntax",
2338 format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
2339 Applicability::MachineApplicable,
2345 Ok((ty, kind, item.def_id))
2351 opt_self_ty: Option<Ty<'tcx>>,
2353 trait_segment: &hir::PathSegment<'_>,
2354 item_segment: &hir::PathSegment<'_>,
2356 let tcx = self.tcx();
2358 let trait_def_id = tcx.parent(item_def_id).unwrap();
2360 debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id);
2362 let self_ty = if let Some(ty) = opt_self_ty {
2365 let path_str = tcx.def_path_str(trait_def_id);
2367 let def_id = self.item_def_id();
2369 debug!("qpath_to_ty: self.item_def_id()={:?}", def_id);
2371 let parent_def_id = def_id
2372 .and_then(|def_id| tcx.hir().as_local_hir_id(def_id))
2373 .map(|hir_id| tcx.hir().get_parent_did(hir_id));
2375 debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id);
2377 // If the trait in segment is the same as the trait defining the item,
2378 // use the `<Self as ..>` syntax in the error.
2379 let is_part_of_self_trait_constraints = def_id == Some(trait_def_id);
2380 let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id);
2382 let type_name = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait {
2388 self.report_ambiguous_associated_type(
2392 item_segment.ident.name,
2394 return tcx.types.err;
2397 debug!("qpath_to_ty: self_type={:?}", self_ty);
2399 let trait_ref = self.ast_path_to_mono_trait_ref(span, trait_def_id, self_ty, trait_segment);
2401 let item_substs = self.create_substs_for_associated_item(
2409 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
2411 self.normalize_ty(span, tcx.mk_projection(item_def_id, item_substs))
2414 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment<'a>>>(
2418 let mut has_err = false;
2419 for segment in segments {
2420 let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
2421 for arg in segment.generic_args().args {
2422 let (span, kind) = match arg {
2423 hir::GenericArg::Lifetime(lt) => {
2429 (lt.span, "lifetime")
2431 hir::GenericArg::Type(ty) => {
2439 hir::GenericArg::Const(ct) => {
2447 let mut err = struct_span_err!(
2451 "{} arguments are not allowed for this type",
2454 err.span_label(span, format!("{} argument not allowed", kind));
2456 if err_for_lt && err_for_ty && err_for_ct {
2461 // Only emit the first error to avoid overloading the user with error messages.
2462 if let [binding, ..] = segment.generic_args().bindings {
2464 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
2470 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) {
2471 let mut err = struct_span_err!(
2475 "associated type bindings are not allowed here"
2477 err.span_label(span, "associated type not allowed here").emit();
2480 // FIXME(eddyb, varkor) handle type paths here too, not just value ones.
2481 pub fn def_ids_for_value_path_segments(
2483 segments: &[hir::PathSegment<'_>],
2484 self_ty: Option<Ty<'tcx>>,
2488 // We need to extract the type parameters supplied by the user in
2489 // the path `path`. Due to the current setup, this is a bit of a
2490 // tricky-process; the problem is that resolve only tells us the
2491 // end-point of the path resolution, and not the intermediate steps.
2492 // Luckily, we can (at least for now) deduce the intermediate steps
2493 // just from the end-point.
2495 // There are basically five cases to consider:
2497 // 1. Reference to a constructor of a struct:
2499 // struct Foo<T>(...)
2501 // In this case, the parameters are declared in the type space.
2503 // 2. Reference to a constructor of an enum variant:
2505 // enum E<T> { Foo(...) }
2507 // In this case, the parameters are defined in the type space,
2508 // but may be specified either on the type or the variant.
2510 // 3. Reference to a fn item or a free constant:
2514 // In this case, the path will again always have the form
2515 // `a::b::foo::<T>` where only the final segment should have
2516 // type parameters. However, in this case, those parameters are
2517 // declared on a value, and hence are in the `FnSpace`.
2519 // 4. Reference to a method or an associated constant:
2521 // impl<A> SomeStruct<A> {
2525 // Here we can have a path like
2526 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
2527 // may appear in two places. The penultimate segment,
2528 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
2529 // final segment, `foo::<B>` contains parameters in fn space.
2531 // The first step then is to categorize the segments appropriately.
2533 let tcx = self.tcx();
2535 assert!(!segments.is_empty());
2536 let last = segments.len() - 1;
2538 let mut path_segs = vec![];
2541 // Case 1. Reference to a struct constructor.
2542 DefKind::Ctor(CtorOf::Struct, ..) => {
2543 // Everything but the final segment should have no
2544 // parameters at all.
2545 let generics = tcx.generics_of(def_id);
2546 // Variant and struct constructors use the
2547 // generics of their parent type definition.
2548 let generics_def_id = generics.parent.unwrap_or(def_id);
2549 path_segs.push(PathSeg(generics_def_id, last));
2552 // Case 2. Reference to a variant constructor.
2553 DefKind::Ctor(CtorOf::Variant, ..) | DefKind::Variant => {
2554 let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
2555 let (generics_def_id, index) = if let Some(adt_def) = adt_def {
2556 debug_assert!(adt_def.is_enum());
2558 } else if last >= 1 && segments[last - 1].args.is_some() {
2559 // Everything but the penultimate segment should have no
2560 // parameters at all.
2561 let mut def_id = def_id;
2563 // `DefKind::Ctor` -> `DefKind::Variant`
2564 if let DefKind::Ctor(..) = kind {
2565 def_id = tcx.parent(def_id).unwrap()
2568 // `DefKind::Variant` -> `DefKind::Enum`
2569 let enum_def_id = tcx.parent(def_id).unwrap();
2570 (enum_def_id, last - 1)
2572 // FIXME: lint here recommending `Enum::<...>::Variant` form
2573 // instead of `Enum::Variant::<...>` form.
2575 // Everything but the final segment should have no
2576 // parameters at all.
2577 let generics = tcx.generics_of(def_id);
2578 // Variant and struct constructors use the
2579 // generics of their parent type definition.
2580 (generics.parent.unwrap_or(def_id), last)
2582 path_segs.push(PathSeg(generics_def_id, index));
2585 // Case 3. Reference to a top-level value.
2586 DefKind::Fn | DefKind::Const | DefKind::ConstParam | DefKind::Static => {
2587 path_segs.push(PathSeg(def_id, last));
2590 // Case 4. Reference to a method or associated const.
2591 DefKind::Method | DefKind::AssocConst => {
2592 if segments.len() >= 2 {
2593 let generics = tcx.generics_of(def_id);
2594 path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
2596 path_segs.push(PathSeg(def_id, last));
2599 kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
2602 debug!("path_segs = {:?}", path_segs);
2607 // Check a type `Path` and convert it to a `Ty`.
2610 opt_self_ty: Option<Ty<'tcx>>,
2611 path: &hir::Path<'_>,
2612 permit_variants: bool,
2614 let tcx = self.tcx();
2617 "res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
2618 path.res, opt_self_ty, path.segments
2621 let span = path.span;
2623 Res::Def(DefKind::OpaqueTy, did) => {
2624 // Check for desugared `impl Trait`.
2625 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
2626 let item_segment = path.segments.split_last().unwrap();
2627 self.prohibit_generics(item_segment.1);
2628 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
2629 self.normalize_ty(span, tcx.mk_opaque(did, substs))
2631 Res::Def(DefKind::Enum, did)
2632 | Res::Def(DefKind::TyAlias, did)
2633 | Res::Def(DefKind::Struct, did)
2634 | Res::Def(DefKind::Union, did)
2635 | Res::Def(DefKind::ForeignTy, did) => {
2636 assert_eq!(opt_self_ty, None);
2637 self.prohibit_generics(path.segments.split_last().unwrap().1);
2638 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
2640 Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
2641 // Convert "variant type" as if it were a real type.
2642 // The resulting `Ty` is type of the variant's enum for now.
2643 assert_eq!(opt_self_ty, None);
2646 self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
2647 let generic_segs: FxHashSet<_> =
2648 path_segs.iter().map(|PathSeg(_, index)| index).collect();
2649 self.prohibit_generics(path.segments.iter().enumerate().filter_map(
2651 if !generic_segs.contains(&index) { Some(seg) } else { None }
2655 let PathSeg(def_id, index) = path_segs.last().unwrap();
2656 self.ast_path_to_ty(span, *def_id, &path.segments[*index])
2658 Res::Def(DefKind::TyParam, def_id) => {
2659 assert_eq!(opt_self_ty, None);
2660 self.prohibit_generics(path.segments);
2662 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2663 let item_id = tcx.hir().get_parent_node(hir_id);
2664 let item_def_id = tcx.hir().local_def_id(item_id);
2665 let generics = tcx.generics_of(item_def_id);
2666 let index = generics.param_def_id_to_index[&def_id];
2667 tcx.mk_ty_param(index, tcx.hir().name(hir_id))
2669 Res::SelfTy(Some(_), None) => {
2670 // `Self` in trait or type alias.
2671 assert_eq!(opt_self_ty, None);
2672 self.prohibit_generics(path.segments);
2673 tcx.types.self_param
2675 Res::SelfTy(_, Some(def_id)) => {
2676 // `Self` in impl (we know the concrete type).
2677 assert_eq!(opt_self_ty, None);
2678 self.prohibit_generics(path.segments);
2679 // Try to evaluate any array length constants.
2680 self.normalize_ty(span, tcx.at(span).type_of(def_id))
2682 Res::Def(DefKind::AssocTy, def_id) => {
2683 debug_assert!(path.segments.len() >= 2);
2684 self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
2689 &path.segments[path.segments.len() - 2],
2690 path.segments.last().unwrap(),
2693 Res::PrimTy(prim_ty) => {
2694 assert_eq!(opt_self_ty, None);
2695 self.prohibit_generics(path.segments);
2697 hir::PrimTy::Bool => tcx.types.bool,
2698 hir::PrimTy::Char => tcx.types.char,
2699 hir::PrimTy::Int(it) => tcx.mk_mach_int(it),
2700 hir::PrimTy::Uint(uit) => tcx.mk_mach_uint(uit),
2701 hir::PrimTy::Float(ft) => tcx.mk_mach_float(ft),
2702 hir::PrimTy::Str => tcx.mk_str(),
2706 self.set_tainted_by_errors();
2707 return self.tcx().types.err;
2709 _ => span_bug!(span, "unexpected resolution: {:?}", path.res),
2713 /// Parses the programmer's textual representation of a type into our
2714 /// internal notion of a type.
2715 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
2716 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})", ast_ty.hir_id, ast_ty, ast_ty.kind);
2718 let tcx = self.tcx();
2720 let result_ty = match ast_ty.kind {
2721 hir::TyKind::Slice(ref ty) => tcx.mk_slice(self.ast_ty_to_ty(&ty)),
2722 hir::TyKind::Ptr(ref mt) => {
2723 tcx.mk_ptr(ty::TypeAndMut { ty: self.ast_ty_to_ty(&mt.ty), mutbl: mt.mutbl })
2725 hir::TyKind::Rptr(ref region, ref mt) => {
2726 let r = self.ast_region_to_region(region, None);
2727 debug!("ast_ty_to_ty: r={:?}", r);
2728 let t = self.ast_ty_to_ty(&mt.ty);
2729 tcx.mk_ref(r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
2731 hir::TyKind::Never => tcx.types.never,
2732 hir::TyKind::Tup(ref fields) => {
2733 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
2735 hir::TyKind::BareFn(ref bf) => {
2736 require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
2737 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl, &[], None))
2739 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
2740 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
2742 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
2743 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
2744 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself));
2745 self.res_to_ty(opt_self_ty, path, false)
2747 hir::TyKind::Def(item_id, ref lifetimes) => {
2748 let did = tcx.hir().local_def_id(item_id.id);
2749 self.impl_trait_ty_to_ty(did, lifetimes)
2751 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
2752 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
2753 let ty = self.ast_ty_to_ty(qself);
2755 let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.kind {
2760 self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
2761 .map(|(ty, _, _)| ty)
2762 .unwrap_or(tcx.types.err)
2764 hir::TyKind::Array(ref ty, ref length) => {
2765 let length = self.ast_const_to_const(length, tcx.types.usize);
2766 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
2767 self.normalize_ty(ast_ty.span, array_ty)
2769 hir::TyKind::Typeof(ref _e) => {
2774 "`typeof` is a reserved keyword but unimplemented"
2776 .span_label(ast_ty.span, "reserved keyword")
2781 hir::TyKind::Infer => {
2782 // Infer also appears as the type of arguments or return
2783 // values in a ExprKind::Closure, or as
2784 // the type of local variables. Both of these cases are
2785 // handled specially and will not descend into this routine.
2786 self.ty_infer(None, ast_ty.span)
2788 hir::TyKind::Err => tcx.types.err,
2791 debug!("ast_ty_to_ty: result_ty={:?}", result_ty);
2793 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
2797 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2798 pub fn const_param_def_id(&self, expr: &hir::Expr<'_>) -> Option<DefId> {
2799 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
2800 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
2801 let expr = match &expr.kind {
2802 ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
2803 block.expr.as_ref().unwrap()
2809 ExprKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
2810 Res::Def(DefKind::ConstParam, did) => Some(did),
2817 pub fn ast_const_to_const(
2819 ast_const: &hir::AnonConst,
2821 ) -> &'tcx ty::Const<'tcx> {
2822 debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
2824 let tcx = self.tcx();
2825 let def_id = tcx.hir().local_def_id(ast_const.hir_id);
2827 let expr = &tcx.hir().body(ast_const.body).value;
2829 let lit_input = match expr.kind {
2830 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
2831 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
2832 hir::ExprKind::Lit(ref lit) => {
2833 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
2840 if let Some(lit_input) = lit_input {
2841 // If an error occurred, ignore that it's a literal and leave reporting the error up to
2843 if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
2846 tcx.sess.delay_span_bug(expr.span, "ast_const_to_const: couldn't lit_to_const");
2850 let kind = if let Some(def_id) = self.const_param_def_id(expr) {
2851 // Find the name and index of the const parameter by indexing the generics of the
2852 // parent item and construct a `ParamConst`.
2853 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2854 let item_id = tcx.hir().get_parent_node(hir_id);
2855 let item_def_id = tcx.hir().local_def_id(item_id);
2856 let generics = tcx.generics_of(item_def_id);
2857 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
2858 let name = tcx.hir().name(hir_id);
2859 ty::ConstKind::Param(ty::ParamConst::new(index, name))
2861 ty::ConstKind::Unevaluated(def_id, InternalSubsts::identity_for_item(tcx, def_id), None)
2863 tcx.mk_const(ty::Const { val: kind, ty })
2866 pub fn impl_trait_ty_to_ty(
2869 lifetimes: &[hir::GenericArg<'_>],
2871 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
2872 let tcx = self.tcx();
2874 let generics = tcx.generics_of(def_id);
2876 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
2877 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
2878 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
2879 // Our own parameters are the resolved lifetimes.
2881 GenericParamDefKind::Lifetime => {
2882 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
2883 self.ast_region_to_region(lifetime, None).into()
2891 // Replace all parent lifetimes with `'static`.
2893 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
2894 _ => tcx.mk_param_from_def(param),
2898 debug!("impl_trait_ty_to_ty: substs={:?}", substs);
2900 let ty = tcx.mk_opaque(def_id, substs);
2901 debug!("impl_trait_ty_to_ty: {}", ty);
2905 pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> {
2907 hir::TyKind::Infer if expected_ty.is_some() => {
2908 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
2909 expected_ty.unwrap()
2911 _ => self.ast_ty_to_ty(ty),
2917 unsafety: hir::Unsafety,
2919 decl: &hir::FnDecl<'_>,
2920 generic_params: &[hir::GenericParam<'_>],
2921 ident_span: Option<Span>,
2922 ) -> ty::PolyFnSig<'tcx> {
2925 let tcx = self.tcx();
2927 // We proactively collect all the infered type params to emit a single error per fn def.
2928 let mut visitor = PlaceholderHirTyCollector::default();
2929 for ty in decl.inputs {
2930 visitor.visit_ty(ty);
2932 let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
2933 let output_ty = match decl.output {
2934 hir::FnRetTy::Return(ref output) => {
2935 visitor.visit_ty(output);
2936 self.ast_ty_to_ty(output)
2938 hir::FnRetTy::DefaultReturn(..) => tcx.mk_unit(),
2941 debug!("ty_of_fn: output_ty={:?}", output_ty);
2944 ty::Binder::bind(tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi));
2946 if !self.allow_ty_infer() {
2947 // We always collect the spans for placeholder types when evaluating `fn`s, but we
2948 // only want to emit an error complaining about them if infer types (`_`) are not
2949 // allowed. `allow_ty_infer` gates this behavior.
2950 crate::collect::placeholder_type_error(
2952 ident_span.map(|sp| sp.shrink_to_hi()).unwrap_or(DUMMY_SP),
2955 ident_span.is_some(),
2959 // Find any late-bound regions declared in return type that do
2960 // not appear in the arguments. These are not well-formed.
2963 // for<'a> fn() -> &'a str <-- 'a is bad
2964 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
2965 let inputs = bare_fn_ty.inputs();
2966 let late_bound_in_args =
2967 tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned()));
2968 let output = bare_fn_ty.output();
2969 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
2970 for br in late_bound_in_ret.difference(&late_bound_in_args) {
2971 let lifetime_name = match *br {
2972 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
2973 ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
2975 let mut err = struct_span_err!(
2979 "return type references {} \
2980 which is not constrained by the fn input types",
2983 if let ty::BrAnon(_) = *br {
2984 // The only way for an anonymous lifetime to wind up
2985 // in the return type but **also** be unconstrained is
2986 // if it only appears in "associated types" in the
2987 // input. See #47511 for an example. In this case,
2988 // though we can easily give a hint that ought to be
2991 "lifetimes appearing in an associated type \
2992 are not considered constrained",
3001 /// Given the bounds on an object, determines what single region bound (if any) we can
3002 /// use to summarize this type. The basic idea is that we will use the bound the user
3003 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
3004 /// for region bounds. It may be that we can derive no bound at all, in which case
3005 /// we return `None`.
3006 fn compute_object_lifetime_bound(
3009 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
3010 ) -> Option<ty::Region<'tcx>> // if None, use the default
3012 let tcx = self.tcx();
3014 debug!("compute_opt_region_bound(existential_predicates={:?})", existential_predicates);
3016 // No explicit region bound specified. Therefore, examine trait
3017 // bounds and see if we can derive region bounds from those.
3018 let derived_region_bounds = object_region_bounds(tcx, existential_predicates);
3020 // If there are no derived region bounds, then report back that we
3021 // can find no region bound. The caller will use the default.
3022 if derived_region_bounds.is_empty() {
3026 // If any of the derived region bounds are 'static, that is always
3028 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
3029 return Some(tcx.lifetimes.re_static);
3032 // Determine whether there is exactly one unique region in the set
3033 // of derived region bounds. If so, use that. Otherwise, report an
3035 let r = derived_region_bounds[0];
3036 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
3041 "ambiguous lifetime bound, explicit lifetime bound required"
3049 /// Collects together a list of bounds that are applied to some type,
3050 /// after they've been converted into `ty` form (from the HIR
3051 /// representations). These lists of bounds occur in many places in
3055 /// trait Foo: Bar + Baz { }
3056 /// ^^^^^^^^^ supertrait list bounding the `Self` type parameter
3058 /// fn foo<T: Bar + Baz>() { }
3059 /// ^^^^^^^^^ bounding the type parameter `T`
3061 /// impl dyn Bar + Baz
3062 /// ^^^^^^^^^ bounding the forgotten dynamic type
3065 /// Our representation is a bit mixed here -- in some cases, we
3066 /// include the self type (e.g., `trait_bounds`) but in others we do
3067 #[derive(Default, PartialEq, Eq, Clone, Debug)]
3068 pub struct Bounds<'tcx> {
3069 /// A list of region bounds on the (implicit) self type. So if you
3070 /// had `T: 'a + 'b` this might would be a list `['a, 'b]` (but
3071 /// the `T` is not explicitly included).
3072 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
3074 /// A list of trait bounds. So if you had `T: Debug` this would be
3075 /// `T: Debug`. Note that the self-type is explicit here.
3076 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span, Constness)>,
3078 /// A list of projection equality bounds. So if you had `T:
3079 /// Iterator<Item = u32>` this would include `<T as
3080 /// Iterator>::Item => u32`. Note that the self-type is explicit
3082 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
3084 /// `Some` if there is *no* `?Sized` predicate. The `span`
3085 /// is the location in the source of the `T` declaration which can
3086 /// be cited as the source of the `T: Sized` requirement.
3087 pub implicitly_sized: Option<Span>,
3090 impl<'tcx> Bounds<'tcx> {
3091 /// Converts a bounds list into a flat set of predicates (like
3092 /// where-clauses). Because some of our bounds listings (e.g.,
3093 /// regions) don't include the self-type, you must supply the
3094 /// self-type here (the `param_ty` parameter).
3099 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
3100 // If it could be sized, and is, add the `Sized` predicate.
3101 let sized_predicate = self.implicitly_sized.and_then(|span| {
3102 tcx.lang_items().sized_trait().map(|sized| {
3103 let trait_ref = ty::Binder::bind(ty::TraitRef {
3105 substs: tcx.mk_substs_trait(param_ty, &[]),
3107 (trait_ref.without_const().to_predicate(), span)
3116 .map(|&(region_bound, span)| {
3117 // Account for the binder being introduced below; no need to shift `param_ty`
3118 // because, at present at least, it either only refers to early-bound regions,
3119 // or it's a generic associated type that deliberately has escaping bound vars.
3120 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
3121 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
3122 (ty::Binder::bind(outlives).to_predicate(), span)
3124 .chain(self.trait_bounds.iter().map(|&(bound_trait_ref, span, constness)| {
3125 let predicate = bound_trait_ref.with_constness(constness).to_predicate();
3129 self.projection_bounds
3131 .map(|&(projection, span)| (projection.to_predicate(), span)),