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;
9 use crate::middle::lang_items::SizedTraitLangItem;
10 use crate::middle::resolve_lifetime as rl;
11 use crate::require_c_abi_if_c_variadic;
12 use crate::util::common::ErrorReported;
13 use rustc::ty::subst::{self, InternalSubsts, Subst, SubstsRef};
14 use rustc::ty::{self, Const, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness};
15 use rustc::ty::{GenericParamDef, GenericParamDefKind};
17 use rustc_ast::util::lev_distance::find_best_match_for_name;
18 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
19 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId};
21 use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
22 use rustc_hir::def_id::DefId;
23 use rustc_hir::intravisit::Visitor;
25 use rustc_hir::{Constness, ExprKind, GenericArg, GenericArgs};
26 use rustc_session::lint::builtin::{AMBIGUOUS_ASSOCIATED_ITEMS, LATE_BOUND_LIFETIME_ARGUMENTS};
27 use rustc_session::parse::feature_err;
28 use rustc_session::Session;
29 use rustc_span::symbol::sym;
30 use rustc_span::{MultiSpan, Span, DUMMY_SP};
31 use rustc_target::spec::abi;
32 use rustc_trait_selection::traits;
33 use rustc_trait_selection::traits::astconv_object_safety_violations;
34 use rustc_trait_selection::traits::error_reporting::report_object_safety_error;
35 use rustc_trait_selection::traits::wf::object_region_bounds;
37 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 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 constraints 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.normalize_to_macros_2_0()` instead
1445 // of calling `filter_by_name_and_kind`.
1447 .associated_items(candidate.def_id())
1448 .filter_by_name_unhygienic(assoc_ident.name)
1450 i.kind == ty::AssocKind::Type && i.ident.normalize_to_macros_2_0() == assoc_ident
1452 .expect("missing associated type");
1454 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
1455 let msg = format!("associated type `{}` is private", binding.item_name);
1456 tcx.sess.span_err(binding.span, &msg);
1458 tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
1462 .entry(assoc_ty.def_id)
1463 .and_modify(|prev_span| {
1468 "the value of the associated type `{}` (from trait `{}`) \
1469 is already specified",
1471 tcx.def_path_str(assoc_ty.container.id())
1473 .span_label(binding.span, "re-bound here")
1474 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
1477 .or_insert(binding.span);
1480 match binding.kind {
1481 ConvertedBindingKind::Equality(ref ty) => {
1482 // "Desugar" a constraint like `T: Iterator<Item = u32>` this to
1483 // the "projection predicate" for:
1485 // `<T as Iterator>::Item = u32`
1486 bounds.projection_bounds.push((
1487 candidate.map_bound(|trait_ref| ty::ProjectionPredicate {
1488 projection_ty: ty::ProjectionTy::from_ref_and_name(
1498 ConvertedBindingKind::Constraint(ast_bounds) => {
1499 // "Desugar" a constraint like `T: Iterator<Item: Debug>` to
1501 // `<T as Iterator>::Item: Debug`
1503 // Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty`
1504 // parameter to have a skipped binder.
1505 let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);
1506 self.add_bounds(param_ty, ast_bounds, bounds);
1516 item_segment: &hir::PathSegment<'_>,
1518 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
1519 self.normalize_ty(span, self.tcx().at(span).type_of(did).subst(self.tcx(), substs))
1522 fn conv_object_ty_poly_trait_ref(
1525 trait_bounds: &[hir::PolyTraitRef<'_>],
1526 lifetime: &hir::Lifetime,
1528 let tcx = self.tcx();
1530 let mut bounds = Bounds::default();
1531 let mut potential_assoc_types = Vec::new();
1532 let dummy_self = self.tcx().types.trait_object_dummy_self;
1533 for trait_bound in trait_bounds.iter().rev() {
1534 if let Err(GenericArgCountMismatch {
1535 invalid_args: cur_potential_assoc_types, ..
1536 }) = self.instantiate_poly_trait_ref(
1538 Constness::NotConst,
1542 potential_assoc_types.extend(cur_potential_assoc_types.into_iter());
1546 // Expand trait aliases recursively and check that only one regular (non-auto) trait
1547 // is used and no 'maybe' bounds are used.
1548 let expanded_traits =
1549 traits::expand_trait_aliases(tcx, bounds.trait_bounds.iter().map(|&(a, b, _)| (a, b)));
1550 let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
1551 expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
1552 if regular_traits.len() > 1 {
1553 let first_trait = ®ular_traits[0];
1554 let additional_trait = ®ular_traits[1];
1555 let mut err = struct_span_err!(
1557 additional_trait.bottom().1,
1559 "only auto traits can be used as additional traits in a trait object"
1561 additional_trait.label_with_exp_info(
1563 "additional non-auto trait",
1566 first_trait.label_with_exp_info(&mut err, "first non-auto trait", "first use");
1570 if regular_traits.is_empty() && auto_traits.is_empty() {
1575 "at least one trait is required for an object type"
1578 return tcx.types.err;
1581 // Check that there are no gross object safety violations;
1582 // most importantly, that the supertraits don't contain `Self`,
1584 for item in ®ular_traits {
1585 let object_safety_violations =
1586 astconv_object_safety_violations(tcx, item.trait_ref().def_id());
1587 if !object_safety_violations.is_empty() {
1588 report_object_safety_error(
1591 item.trait_ref().def_id(),
1592 object_safety_violations,
1595 return tcx.types.err;
1599 // Use a `BTreeSet` to keep output in a more consistent order.
1600 let mut associated_types: FxHashMap<Span, BTreeSet<DefId>> = FxHashMap::default();
1602 let regular_traits_refs_spans = bounds
1605 .filter(|(trait_ref, _, _)| !tcx.trait_is_auto(trait_ref.def_id()));
1607 for (base_trait_ref, span, constness) in regular_traits_refs_spans {
1608 assert_eq!(constness, Constness::NotConst);
1610 for trait_ref in traits::elaborate_trait_ref(tcx, base_trait_ref) {
1612 "conv_object_ty_poly_trait_ref: observing object predicate `{:?}`",
1616 ty::Predicate::Trait(pred, _) => {
1617 associated_types.entry(span).or_default().extend(
1618 tcx.associated_items(pred.def_id())
1619 .in_definition_order()
1620 .filter(|item| item.kind == ty::AssocKind::Type)
1621 .map(|item| item.def_id),
1624 ty::Predicate::Projection(pred) => {
1625 // A `Self` within the original bound will be substituted with a
1626 // `trait_object_dummy_self`, so check for that.
1627 let references_self = pred.skip_binder().ty.walk().any(|t| t == dummy_self);
1629 // If the projection output contains `Self`, force the user to
1630 // elaborate it explicitly to avoid a lot of complexity.
1632 // The "classicaly useful" case is the following:
1634 // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
1639 // Here, the user could theoretically write `dyn MyTrait<Output = X>`,
1640 // but actually supporting that would "expand" to an infinitely-long type
1641 // `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`.
1643 // Instead, we force the user to write
1644 // `dyn MyTrait<MyOutput = X, Output = X>`, which is uglier but works. See
1645 // the discussion in #56288 for alternatives.
1646 if !references_self {
1647 // Include projections defined on supertraits.
1648 bounds.projection_bounds.push((pred, span));
1656 for (projection_bound, _) in &bounds.projection_bounds {
1657 for def_ids in associated_types.values_mut() {
1658 def_ids.remove(&projection_bound.projection_def_id());
1662 self.complain_about_missing_associated_types(
1664 potential_assoc_types,
1668 // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
1669 // `dyn Trait + Send`.
1670 auto_traits.sort_by_key(|i| i.trait_ref().def_id());
1671 auto_traits.dedup_by_key(|i| i.trait_ref().def_id());
1672 debug!("regular_traits: {:?}", regular_traits);
1673 debug!("auto_traits: {:?}", auto_traits);
1675 // Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
1676 // removing the dummy `Self` type (`trait_object_dummy_self`).
1677 let trait_ref_to_existential = |trait_ref: ty::TraitRef<'tcx>| {
1678 if trait_ref.self_ty() != dummy_self {
1679 // FIXME: There appears to be a missing filter on top of `expand_trait_aliases`,
1680 // which picks up non-supertraits where clauses - but also, the object safety
1681 // completely ignores trait aliases, which could be object safety hazards. We
1682 // `delay_span_bug` here to avoid an ICE in stable even when the feature is
1683 // disabled. (#66420)
1684 tcx.sess.delay_span_bug(
1687 "trait_ref_to_existential called on {:?} with non-dummy Self",
1692 ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
1695 // Erase the `dummy_self` (`trait_object_dummy_self`) used above.
1696 let existential_trait_refs = regular_traits
1698 .map(|i| i.trait_ref().map_bound(|trait_ref| trait_ref_to_existential(trait_ref)));
1699 let existential_projections = bounds.projection_bounds.iter().map(|(bound, _)| {
1700 bound.map_bound(|b| {
1701 let trait_ref = trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1702 ty::ExistentialProjection {
1704 item_def_id: b.projection_ty.item_def_id,
1705 substs: trait_ref.substs,
1710 // Calling `skip_binder` is okay because the predicates are re-bound.
1711 let regular_trait_predicates = existential_trait_refs
1712 .map(|trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder()));
1713 let auto_trait_predicates = auto_traits
1715 .map(|trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()));
1716 let mut v = regular_trait_predicates
1717 .chain(auto_trait_predicates)
1719 existential_projections
1720 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())),
1722 .collect::<SmallVec<[_; 8]>>();
1723 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1725 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1727 // Use explicitly-specified region bound.
1728 let region_bound = if !lifetime.is_elided() {
1729 self.ast_region_to_region(lifetime, None)
1731 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1732 if tcx.named_region(lifetime.hir_id).is_some() {
1733 self.ast_region_to_region(lifetime, None)
1735 self.re_infer(None, span).unwrap_or_else(|| {
1740 "the lifetime bound for this object type cannot be deduced \
1741 from context; please supply an explicit bound"
1744 tcx.lifetimes.re_static
1749 debug!("region_bound: {:?}", region_bound);
1751 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1752 debug!("trait_object_type: {:?}", ty);
1756 /// When there are any missing associated types, emit an E0191 error and attempt to supply a
1757 /// reasonable suggestion on how to write it. For the case of multiple associated types in the
1758 /// same trait bound have the same name (as they come from different super-traits), we instead
1759 /// emit a generic note suggesting using a `where` clause to constraint instead.
1760 fn complain_about_missing_associated_types(
1762 associated_types: FxHashMap<Span, BTreeSet<DefId>>,
1763 potential_assoc_types: Vec<Span>,
1764 trait_bounds: &[hir::PolyTraitRef<'_>],
1766 if !associated_types.values().any(|v| !v.is_empty()) {
1769 let tcx = self.tcx();
1770 // FIXME: Marked `mut` so that we can replace the spans further below with a more
1771 // appropriate one, but this should be handled earlier in the span assignment.
1772 let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types
1774 .map(|(span, def_ids)| {
1775 (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
1778 let mut names = vec![];
1780 // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
1781 // `issue-22560.rs`.
1782 let mut trait_bound_spans: Vec<Span> = vec![];
1783 for (span, items) in &associated_types {
1784 if !items.is_empty() {
1785 trait_bound_spans.push(*span);
1787 for assoc_item in items {
1788 let trait_def_id = assoc_item.container.id();
1790 "`{}` (from trait `{}`)",
1792 tcx.def_path_str(trait_def_id),
1797 match (&potential_assoc_types[..], &trait_bounds) {
1798 ([], [bound]) => match &bound.trait_ref.path.segments[..] {
1799 // FIXME: `trait_ref.path.span` can point to a full path with multiple
1800 // segments, even though `trait_ref.path.segments` is of length `1`. Work
1801 // around that bug here, even though it should be fixed elsewhere.
1802 // This would otherwise cause an invalid suggestion. For an example, look at
1803 // `src/test/ui/issues/issue-28344.rs` where instead of the following:
1805 // error[E0191]: the value of the associated type `Output`
1806 // (from trait `std::ops::BitXor`) must be specified
1807 // --> $DIR/issue-28344.rs:4:17
1809 // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
1810 // | ^^^^^^ help: specify the associated type:
1811 // | `BitXor<Output = Type>`
1815 // error[E0191]: the value of the associated type `Output`
1816 // (from trait `std::ops::BitXor`) must be specified
1817 // --> $DIR/issue-28344.rs:4:17
1819 // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8);
1820 // | ^^^^^^^^^^^^^ help: specify the associated type:
1821 // | `BitXor::bitor<Output = Type>`
1822 [segment] if segment.args.is_none() => {
1823 trait_bound_spans = vec![segment.ident.span];
1824 associated_types = associated_types
1826 .map(|(_, items)| (segment.ident.span, items))
1834 trait_bound_spans.sort();
1835 let mut err = struct_span_err!(
1839 "the value of the associated type{} {} must be specified",
1840 pluralize!(names.len()),
1843 let mut suggestions = vec![];
1844 let mut types_count = 0;
1845 let mut where_constraints = vec![];
1846 for (span, assoc_items) in &associated_types {
1847 let mut names: FxHashMap<_, usize> = FxHashMap::default();
1848 for item in assoc_items {
1850 *names.entry(item.ident.name).or_insert(0) += 1;
1852 let mut dupes = false;
1853 for item in assoc_items {
1854 let prefix = if names[&item.ident.name] > 1 {
1855 let trait_def_id = item.container.id();
1857 format!("{}::", tcx.def_path_str(trait_def_id))
1861 if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
1862 err.span_label(sp, format!("`{}{}` defined here", prefix, item.ident));
1865 if potential_assoc_types.len() == assoc_items.len() {
1866 // Only suggest when the amount of missing associated types equals the number of
1867 // extra type arguments present, as that gives us a relatively high confidence
1868 // that the user forgot to give the associtated type's name. The canonical
1869 // example would be trying to use `Iterator<isize>` instead of
1870 // `Iterator<Item = isize>`.
1871 for (potential, item) in potential_assoc_types.iter().zip(assoc_items.iter()) {
1872 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(*potential) {
1873 suggestions.push((*potential, format!("{} = {}", item.ident, snippet)));
1876 } else if let (Ok(snippet), false) =
1877 (tcx.sess.source_map().span_to_snippet(*span), dupes)
1880 assoc_items.iter().map(|item| format!("{} = Type", item.ident)).collect();
1881 let code = if snippet.ends_with('>') {
1882 // The user wrote `Trait<'a>` or similar and we don't have a type we can
1883 // suggest, but at least we can clue them to the correct syntax
1884 // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
1886 format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
1888 // The user wrote `Iterator`, so we don't have a type we can suggest, but at
1889 // least we can clue them to the correct syntax `Iterator<Item = Type>`.
1890 format!("{}<{}>", snippet, types.join(", "))
1892 suggestions.push((*span, code));
1894 where_constraints.push(*span);
1897 let where_msg = "consider introducing a new type parameter, adding `where` constraints \
1898 using the fully-qualified path to the associated types";
1899 if !where_constraints.is_empty() && suggestions.is_empty() {
1900 // If there are duplicates associated type names and a single trait bound do not
1901 // use structured suggestion, it means that there are multiple super-traits with
1902 // the same associated type name.
1903 err.help(where_msg);
1905 if suggestions.len() != 1 {
1906 // We don't need this label if there's an inline suggestion, show otherwise.
1907 for (span, assoc_items) in &associated_types {
1908 let mut names: FxHashMap<_, usize> = FxHashMap::default();
1909 for item in assoc_items {
1911 *names.entry(item.ident.name).or_insert(0) += 1;
1913 let mut label = vec![];
1914 for item in assoc_items {
1915 let postfix = if names[&item.ident.name] > 1 {
1916 let trait_def_id = item.container.id();
1917 format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
1921 label.push(format!("`{}`{}", item.ident, postfix));
1923 if !label.is_empty() {
1927 "associated type{} {} must be specified",
1928 pluralize!(label.len()),
1935 if !suggestions.is_empty() {
1936 err.multipart_suggestion(
1937 &format!("specify the associated type{}", pluralize!(types_count)),
1939 Applicability::HasPlaceholders,
1941 if !where_constraints.is_empty() {
1942 err.span_help(where_constraints, where_msg);
1948 fn report_ambiguous_associated_type(
1955 let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
1956 if let (Some(_), Ok(snippet)) = (
1957 self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
1958 self.tcx().sess.source_map().span_to_snippet(span),
1960 err.span_suggestion(
1962 "you are looking for the module in `std`, not the primitive type",
1963 format!("std::{}", snippet),
1964 Applicability::MachineApplicable,
1967 err.span_suggestion(
1969 "use fully-qualified syntax",
1970 format!("<{} as {}>::{}", type_str, trait_str, name),
1971 Applicability::HasPlaceholders,
1977 // Search for a bound on a type parameter which includes the associated item
1978 // given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter
1979 // This function will fail if there are no suitable bounds or there is
1981 fn find_bound_for_assoc_item(
1983 ty_param_def_id: DefId,
1984 assoc_name: ast::Ident,
1986 ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported> {
1987 let tcx = self.tcx();
1990 "find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})",
1991 ty_param_def_id, assoc_name, span,
1994 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1996 debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
1998 let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
1999 let param_name = tcx.hir().ty_param_name(param_hir_id);
2000 self.one_bound_for_assoc_type(
2002 traits::transitive_bounds(
2004 predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref()),
2007 || param_name.to_string(),
2014 // Checks that `bounds` contains exactly one element and reports appropriate
2015 // errors otherwise.
2016 fn one_bound_for_assoc_type<I>(
2018 all_candidates: impl Fn() -> I,
2019 ty_param_name: impl Fn() -> String,
2020 assoc_name: ast::Ident,
2022 is_equality: impl Fn() -> Option<String>,
2023 ) -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
2025 I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
2027 let mut matching_candidates = all_candidates()
2028 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
2030 let bound = match matching_candidates.next() {
2031 Some(bound) => bound,
2033 self.complain_about_assoc_type_not_found(
2039 return Err(ErrorReported);
2043 debug!("one_bound_for_assoc_type: bound = {:?}", bound);
2045 if let Some(bound2) = matching_candidates.next() {
2046 debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2);
2048 let is_equality = is_equality();
2049 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(matching_candidates);
2050 let mut err = if is_equality.is_some() {
2051 // More specific Error Index entry.
2056 "ambiguous associated type `{}` in bounds of `{}`",
2065 "ambiguous associated type `{}` in bounds of `{}`",
2070 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
2072 let mut where_bounds = vec![];
2073 for bound in bounds {
2074 let bound_id = bound.def_id();
2075 let bound_span = self
2077 .associated_items(bound_id)
2078 .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_id)
2079 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
2081 if let Some(bound_span) = bound_span {
2085 "ambiguous `{}` from `{}`",
2087 bound.print_only_trait_path(),
2090 if let Some(constraint) = &is_equality {
2091 where_bounds.push(format!(
2092 " T: {trait}::{assoc} = {constraint}",
2093 trait=bound.print_only_trait_path(),
2095 constraint=constraint,
2098 err.span_suggestion(
2100 "use fully qualified syntax to disambiguate",
2104 bound.print_only_trait_path(),
2107 Applicability::MaybeIncorrect,
2112 "associated type `{}` could derive from `{}`",
2114 bound.print_only_trait_path(),
2118 if !where_bounds.is_empty() {
2120 "consider introducing a new type parameter `T` and adding `where` constraints:\
2121 \n where\n T: {},\n{}",
2123 where_bounds.join(",\n"),
2127 if !where_bounds.is_empty() {
2128 return Err(ErrorReported);
2134 fn complain_about_assoc_type_not_found<I>(
2136 all_candidates: impl Fn() -> I,
2137 ty_param_name: &str,
2138 assoc_name: ast::Ident,
2141 I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
2143 // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
2144 // valid span, so we point at the whole path segment instead.
2145 let span = if assoc_name.span != DUMMY_SP { assoc_name.span } else { span };
2146 let mut err = struct_span_err!(
2150 "associated type `{}` not found for `{}`",
2155 let all_candidate_names: Vec<_> = all_candidates()
2156 .map(|r| self.tcx().associated_items(r.def_id()).in_definition_order())
2159 |item| if item.kind == ty::AssocKind::Type { Some(item.ident.name) } else { None },
2163 if let (Some(suggested_name), true) = (
2164 find_best_match_for_name(all_candidate_names.iter(), &assoc_name.as_str(), None),
2165 assoc_name.span != DUMMY_SP,
2167 err.span_suggestion(
2169 "there is an associated type with a similar name",
2170 suggested_name.to_string(),
2171 Applicability::MaybeIncorrect,
2174 err.span_label(span, format!("associated type `{}` not found", assoc_name));
2180 // Create a type from a path to an associated type.
2181 // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
2182 // and item_segment is the path segment for `D`. We return a type and a def for
2184 // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
2185 // parameter or `Self`.
2186 pub fn associated_path_to_ty(
2188 hir_ref_id: hir::HirId,
2192 assoc_segment: &hir::PathSegment<'_>,
2193 permit_variants: bool,
2194 ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
2195 let tcx = self.tcx();
2196 let assoc_ident = assoc_segment.ident;
2198 debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
2200 // Check if we have an enum variant.
2201 let mut variant_resolution = None;
2202 if let ty::Adt(adt_def, _) = qself_ty.kind {
2203 if adt_def.is_enum() {
2204 let variant_def = adt_def
2207 .find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did));
2208 if let Some(variant_def) = variant_def {
2209 if permit_variants {
2210 tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
2211 self.prohibit_generics(slice::from_ref(assoc_segment));
2212 return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
2214 variant_resolution = Some(variant_def.def_id);
2220 // Find the type of the associated item, and the trait where the associated
2221 // item is declared.
2222 let bound = match (&qself_ty.kind, qself_res) {
2223 (_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
2224 // `Self` in an impl of a trait -- we have a concrete self type and a
2226 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
2227 Some(trait_ref) => trait_ref,
2229 // A cycle error occurred, most likely.
2230 return Err(ErrorReported);
2234 self.one_bound_for_assoc_type(
2235 || traits::supertraits(tcx, ty::Binder::bind(trait_ref)),
2236 || "Self".to_string(),
2242 (&ty::Param(_), Res::SelfTy(Some(param_did), None))
2243 | (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
2244 self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
2247 if variant_resolution.is_some() {
2248 // Variant in type position
2249 let msg = format!("expected type, found variant `{}`", assoc_ident);
2250 tcx.sess.span_err(span, &msg);
2251 } else if qself_ty.is_enum() {
2252 let mut err = struct_span_err!(
2256 "no variant named `{}` found for enum `{}`",
2261 let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
2262 if let Some(suggested_name) = find_best_match_for_name(
2263 adt_def.variants.iter().map(|variant| &variant.ident.name),
2264 &assoc_ident.as_str(),
2267 err.span_suggestion(
2269 "there is a variant with a similar name",
2270 suggested_name.to_string(),
2271 Applicability::MaybeIncorrect,
2276 format!("variant not found in `{}`", qself_ty),
2280 if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
2281 let sp = tcx.sess.source_map().def_span(sp);
2282 err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
2286 } else if !qself_ty.references_error() {
2287 // Don't print `TyErr` to the user.
2288 self.report_ambiguous_associated_type(
2290 &qself_ty.to_string(),
2295 return Err(ErrorReported);
2299 let trait_did = bound.def_id();
2300 let (assoc_ident, def_scope) =
2301 tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
2303 // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
2304 // of calling `filter_by_name_and_kind`.
2306 .associated_items(trait_did)
2307 .in_definition_order()
2309 i.kind.namespace() == Namespace::TypeNS
2310 && i.ident.normalize_to_macros_2_0() == assoc_ident
2312 .expect("missing associated type");
2314 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, assoc_segment, bound);
2315 let ty = self.normalize_ty(span, ty);
2317 let kind = DefKind::AssocTy;
2318 if !item.vis.is_accessible_from(def_scope, tcx) {
2319 let msg = format!("{} `{}` is private", kind.descr(item.def_id), assoc_ident);
2320 tcx.sess.span_err(span, &msg);
2322 tcx.check_stability(item.def_id, Some(hir_ref_id), span);
2324 if let Some(variant_def_id) = variant_resolution {
2325 tcx.struct_span_lint_hir(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| {
2326 let mut err = lint.build("ambiguous associated item");
2327 let mut could_refer_to = |kind: DefKind, def_id, also| {
2328 let note_msg = format!(
2329 "`{}` could{} refer to the {} defined here",
2334 err.span_note(tcx.def_span(def_id), ¬e_msg);
2337 could_refer_to(DefKind::Variant, variant_def_id, "");
2338 could_refer_to(kind, item.def_id, " also");
2340 err.span_suggestion(
2342 "use fully-qualified syntax",
2343 format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
2344 Applicability::MachineApplicable,
2350 Ok((ty, kind, item.def_id))
2356 opt_self_ty: Option<Ty<'tcx>>,
2358 trait_segment: &hir::PathSegment<'_>,
2359 item_segment: &hir::PathSegment<'_>,
2361 let tcx = self.tcx();
2363 let trait_def_id = tcx.parent(item_def_id).unwrap();
2365 debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id);
2367 let self_ty = if let Some(ty) = opt_self_ty {
2370 let path_str = tcx.def_path_str(trait_def_id);
2372 let def_id = self.item_def_id();
2374 debug!("qpath_to_ty: self.item_def_id()={:?}", def_id);
2376 let parent_def_id = def_id
2377 .and_then(|def_id| tcx.hir().as_local_hir_id(def_id))
2378 .map(|hir_id| tcx.hir().get_parent_did(hir_id));
2380 debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id);
2382 // If the trait in segment is the same as the trait defining the item,
2383 // use the `<Self as ..>` syntax in the error.
2384 let is_part_of_self_trait_constraints = def_id == Some(trait_def_id);
2385 let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id);
2387 let type_name = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait {
2393 self.report_ambiguous_associated_type(
2397 item_segment.ident.name,
2399 return tcx.types.err;
2402 debug!("qpath_to_ty: self_type={:?}", self_ty);
2404 let trait_ref = self.ast_path_to_mono_trait_ref(span, trait_def_id, self_ty, trait_segment);
2406 let item_substs = self.create_substs_for_associated_item(
2414 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
2416 self.normalize_ty(span, tcx.mk_projection(item_def_id, item_substs))
2419 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment<'a>>>(
2423 let mut has_err = false;
2424 for segment in segments {
2425 let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
2426 for arg in segment.generic_args().args {
2427 let (span, kind) = match arg {
2428 hir::GenericArg::Lifetime(lt) => {
2434 (lt.span, "lifetime")
2436 hir::GenericArg::Type(ty) => {
2444 hir::GenericArg::Const(ct) => {
2452 let mut err = struct_span_err!(
2456 "{} arguments are not allowed for this type",
2459 err.span_label(span, format!("{} argument not allowed", kind));
2461 if err_for_lt && err_for_ty && err_for_ct {
2466 // Only emit the first error to avoid overloading the user with error messages.
2467 if let [binding, ..] = segment.generic_args().bindings {
2469 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
2475 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) {
2476 let mut err = struct_span_err!(
2480 "associated type bindings are not allowed here"
2482 err.span_label(span, "associated type not allowed here").emit();
2485 // FIXME(eddyb, varkor) handle type paths here too, not just value ones.
2486 pub fn def_ids_for_value_path_segments(
2488 segments: &[hir::PathSegment<'_>],
2489 self_ty: Option<Ty<'tcx>>,
2493 // We need to extract the type parameters supplied by the user in
2494 // the path `path`. Due to the current setup, this is a bit of a
2495 // tricky-process; the problem is that resolve only tells us the
2496 // end-point of the path resolution, and not the intermediate steps.
2497 // Luckily, we can (at least for now) deduce the intermediate steps
2498 // just from the end-point.
2500 // There are basically five cases to consider:
2502 // 1. Reference to a constructor of a struct:
2504 // struct Foo<T>(...)
2506 // In this case, the parameters are declared in the type space.
2508 // 2. Reference to a constructor of an enum variant:
2510 // enum E<T> { Foo(...) }
2512 // In this case, the parameters are defined in the type space,
2513 // but may be specified either on the type or the variant.
2515 // 3. Reference to a fn item or a free constant:
2519 // In this case, the path will again always have the form
2520 // `a::b::foo::<T>` where only the final segment should have
2521 // type parameters. However, in this case, those parameters are
2522 // declared on a value, and hence are in the `FnSpace`.
2524 // 4. Reference to a method or an associated constant:
2526 // impl<A> SomeStruct<A> {
2530 // Here we can have a path like
2531 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
2532 // may appear in two places. The penultimate segment,
2533 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
2534 // final segment, `foo::<B>` contains parameters in fn space.
2536 // The first step then is to categorize the segments appropriately.
2538 let tcx = self.tcx();
2540 assert!(!segments.is_empty());
2541 let last = segments.len() - 1;
2543 let mut path_segs = vec![];
2546 // Case 1. Reference to a struct constructor.
2547 DefKind::Ctor(CtorOf::Struct, ..) => {
2548 // Everything but the final segment should have no
2549 // parameters at all.
2550 let generics = tcx.generics_of(def_id);
2551 // Variant and struct constructors use the
2552 // generics of their parent type definition.
2553 let generics_def_id = generics.parent.unwrap_or(def_id);
2554 path_segs.push(PathSeg(generics_def_id, last));
2557 // Case 2. Reference to a variant constructor.
2558 DefKind::Ctor(CtorOf::Variant, ..) | DefKind::Variant => {
2559 let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
2560 let (generics_def_id, index) = if let Some(adt_def) = adt_def {
2561 debug_assert!(adt_def.is_enum());
2563 } else if last >= 1 && segments[last - 1].args.is_some() {
2564 // Everything but the penultimate segment should have no
2565 // parameters at all.
2566 let mut def_id = def_id;
2568 // `DefKind::Ctor` -> `DefKind::Variant`
2569 if let DefKind::Ctor(..) = kind {
2570 def_id = tcx.parent(def_id).unwrap()
2573 // `DefKind::Variant` -> `DefKind::Enum`
2574 let enum_def_id = tcx.parent(def_id).unwrap();
2575 (enum_def_id, last - 1)
2577 // FIXME: lint here recommending `Enum::<...>::Variant` form
2578 // instead of `Enum::Variant::<...>` form.
2580 // Everything but the final segment should have no
2581 // parameters at all.
2582 let generics = tcx.generics_of(def_id);
2583 // Variant and struct constructors use the
2584 // generics of their parent type definition.
2585 (generics.parent.unwrap_or(def_id), last)
2587 path_segs.push(PathSeg(generics_def_id, index));
2590 // Case 3. Reference to a top-level value.
2591 DefKind::Fn | DefKind::Const | DefKind::ConstParam | DefKind::Static => {
2592 path_segs.push(PathSeg(def_id, last));
2595 // Case 4. Reference to a method or associated const.
2596 DefKind::AssocFn | DefKind::AssocConst => {
2597 if segments.len() >= 2 {
2598 let generics = tcx.generics_of(def_id);
2599 path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
2601 path_segs.push(PathSeg(def_id, last));
2604 kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
2607 debug!("path_segs = {:?}", path_segs);
2612 // Check a type `Path` and convert it to a `Ty`.
2615 opt_self_ty: Option<Ty<'tcx>>,
2616 path: &hir::Path<'_>,
2617 permit_variants: bool,
2619 let tcx = self.tcx();
2622 "res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
2623 path.res, opt_self_ty, path.segments
2626 let span = path.span;
2628 Res::Def(DefKind::OpaqueTy, did) => {
2629 // Check for desugared `impl Trait`.
2630 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
2631 let item_segment = path.segments.split_last().unwrap();
2632 self.prohibit_generics(item_segment.1);
2633 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
2634 self.normalize_ty(span, tcx.mk_opaque(did, substs))
2636 Res::Def(DefKind::Enum, did)
2637 | Res::Def(DefKind::TyAlias, did)
2638 | Res::Def(DefKind::Struct, did)
2639 | Res::Def(DefKind::Union, did)
2640 | Res::Def(DefKind::ForeignTy, did) => {
2641 assert_eq!(opt_self_ty, None);
2642 self.prohibit_generics(path.segments.split_last().unwrap().1);
2643 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
2645 Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
2646 // Convert "variant type" as if it were a real type.
2647 // The resulting `Ty` is type of the variant's enum for now.
2648 assert_eq!(opt_self_ty, None);
2651 self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
2652 let generic_segs: FxHashSet<_> =
2653 path_segs.iter().map(|PathSeg(_, index)| index).collect();
2654 self.prohibit_generics(path.segments.iter().enumerate().filter_map(
2656 if !generic_segs.contains(&index) { Some(seg) } else { None }
2660 let PathSeg(def_id, index) = path_segs.last().unwrap();
2661 self.ast_path_to_ty(span, *def_id, &path.segments[*index])
2663 Res::Def(DefKind::TyParam, def_id) => {
2664 assert_eq!(opt_self_ty, None);
2665 self.prohibit_generics(path.segments);
2667 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2668 let item_id = tcx.hir().get_parent_node(hir_id);
2669 let item_def_id = tcx.hir().local_def_id(item_id);
2670 let generics = tcx.generics_of(item_def_id);
2671 let index = generics.param_def_id_to_index[&def_id];
2672 tcx.mk_ty_param(index, tcx.hir().name(hir_id))
2674 Res::SelfTy(Some(_), None) => {
2675 // `Self` in trait or type alias.
2676 assert_eq!(opt_self_ty, None);
2677 self.prohibit_generics(path.segments);
2678 tcx.types.self_param
2680 Res::SelfTy(_, Some(def_id)) => {
2681 // `Self` in impl (we know the concrete type).
2682 assert_eq!(opt_self_ty, None);
2683 self.prohibit_generics(path.segments);
2684 // Try to evaluate any array length constants.
2685 self.normalize_ty(span, tcx.at(span).type_of(def_id))
2687 Res::Def(DefKind::AssocTy, def_id) => {
2688 debug_assert!(path.segments.len() >= 2);
2689 self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
2694 &path.segments[path.segments.len() - 2],
2695 path.segments.last().unwrap(),
2698 Res::PrimTy(prim_ty) => {
2699 assert_eq!(opt_self_ty, None);
2700 self.prohibit_generics(path.segments);
2702 hir::PrimTy::Bool => tcx.types.bool,
2703 hir::PrimTy::Char => tcx.types.char,
2704 hir::PrimTy::Int(it) => tcx.mk_mach_int(it),
2705 hir::PrimTy::Uint(uit) => tcx.mk_mach_uint(uit),
2706 hir::PrimTy::Float(ft) => tcx.mk_mach_float(ft),
2707 hir::PrimTy::Str => tcx.mk_str(),
2711 self.set_tainted_by_errors();
2712 return self.tcx().types.err;
2714 _ => span_bug!(span, "unexpected resolution: {:?}", path.res),
2718 /// Parses the programmer's textual representation of a type into our
2719 /// internal notion of a type.
2720 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
2721 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})", ast_ty.hir_id, ast_ty, ast_ty.kind);
2723 let tcx = self.tcx();
2725 let result_ty = match ast_ty.kind {
2726 hir::TyKind::Slice(ref ty) => tcx.mk_slice(self.ast_ty_to_ty(&ty)),
2727 hir::TyKind::Ptr(ref mt) => {
2728 tcx.mk_ptr(ty::TypeAndMut { ty: self.ast_ty_to_ty(&mt.ty), mutbl: mt.mutbl })
2730 hir::TyKind::Rptr(ref region, ref mt) => {
2731 let r = self.ast_region_to_region(region, None);
2732 debug!("ast_ty_to_ty: r={:?}", r);
2733 let t = self.ast_ty_to_ty(&mt.ty);
2734 tcx.mk_ref(r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
2736 hir::TyKind::Never => tcx.types.never,
2737 hir::TyKind::Tup(ref fields) => {
2738 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
2740 hir::TyKind::BareFn(ref bf) => {
2741 require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
2742 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl, &[], None))
2744 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
2745 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
2747 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
2748 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
2749 let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself));
2750 self.res_to_ty(opt_self_ty, path, false)
2752 hir::TyKind::Def(item_id, ref lifetimes) => {
2753 let did = tcx.hir().local_def_id(item_id.id);
2754 self.impl_trait_ty_to_ty(did, lifetimes)
2756 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
2757 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
2758 let ty = self.ast_ty_to_ty(qself);
2760 let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.kind {
2765 self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
2766 .map(|(ty, _, _)| ty)
2767 .unwrap_or(tcx.types.err)
2769 hir::TyKind::Array(ref ty, ref length) => {
2770 let length = self.ast_const_to_const(length, tcx.types.usize);
2771 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
2772 self.normalize_ty(ast_ty.span, array_ty)
2774 hir::TyKind::Typeof(ref _e) => {
2779 "`typeof` is a reserved keyword but unimplemented"
2781 .span_label(ast_ty.span, "reserved keyword")
2786 hir::TyKind::Infer => {
2787 // Infer also appears as the type of arguments or return
2788 // values in a ExprKind::Closure, or as
2789 // the type of local variables. Both of these cases are
2790 // handled specially and will not descend into this routine.
2791 self.ty_infer(None, ast_ty.span)
2793 hir::TyKind::Err => tcx.types.err,
2796 debug!("ast_ty_to_ty: result_ty={:?}", result_ty);
2798 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
2802 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2803 pub fn const_param_def_id(&self, expr: &hir::Expr<'_>) -> Option<DefId> {
2804 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
2805 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
2806 let expr = match &expr.kind {
2807 ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
2808 block.expr.as_ref().unwrap()
2814 ExprKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
2815 Res::Def(DefKind::ConstParam, did) => Some(did),
2822 pub fn ast_const_to_const(
2824 ast_const: &hir::AnonConst,
2826 ) -> &'tcx ty::Const<'tcx> {
2827 debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
2829 let tcx = self.tcx();
2830 let def_id = tcx.hir().local_def_id(ast_const.hir_id);
2832 let expr = &tcx.hir().body(ast_const.body).value;
2834 let lit_input = match expr.kind {
2835 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
2836 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
2837 hir::ExprKind::Lit(ref lit) => {
2838 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
2845 if let Some(lit_input) = lit_input {
2846 // If an error occurred, ignore that it's a literal and leave reporting the error up to
2848 if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
2851 tcx.sess.delay_span_bug(expr.span, "ast_const_to_const: couldn't lit_to_const");
2855 let kind = if let Some(def_id) = self.const_param_def_id(expr) {
2856 // Find the name and index of the const parameter by indexing the generics of the
2857 // parent item and construct a `ParamConst`.
2858 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2859 let item_id = tcx.hir().get_parent_node(hir_id);
2860 let item_def_id = tcx.hir().local_def_id(item_id);
2861 let generics = tcx.generics_of(item_def_id);
2862 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
2863 let name = tcx.hir().name(hir_id);
2864 ty::ConstKind::Param(ty::ParamConst::new(index, name))
2866 ty::ConstKind::Unevaluated(def_id, InternalSubsts::identity_for_item(tcx, def_id), None)
2868 tcx.mk_const(ty::Const { val: kind, ty })
2871 pub fn impl_trait_ty_to_ty(
2874 lifetimes: &[hir::GenericArg<'_>],
2876 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
2877 let tcx = self.tcx();
2879 let generics = tcx.generics_of(def_id);
2881 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
2882 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
2883 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
2884 // Our own parameters are the resolved lifetimes.
2886 GenericParamDefKind::Lifetime => {
2887 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
2888 self.ast_region_to_region(lifetime, None).into()
2896 // Replace all parent lifetimes with `'static`.
2898 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
2899 _ => tcx.mk_param_from_def(param),
2903 debug!("impl_trait_ty_to_ty: substs={:?}", substs);
2905 let ty = tcx.mk_opaque(def_id, substs);
2906 debug!("impl_trait_ty_to_ty: {}", ty);
2910 pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> {
2912 hir::TyKind::Infer if expected_ty.is_some() => {
2913 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
2914 expected_ty.unwrap()
2916 _ => self.ast_ty_to_ty(ty),
2922 unsafety: hir::Unsafety,
2924 decl: &hir::FnDecl<'_>,
2925 generic_params: &[hir::GenericParam<'_>],
2926 ident_span: Option<Span>,
2927 ) -> ty::PolyFnSig<'tcx> {
2930 let tcx = self.tcx();
2932 // We proactively collect all the inferred type params to emit a single error per fn def.
2933 let mut visitor = PlaceholderHirTyCollector::default();
2934 for ty in decl.inputs {
2935 visitor.visit_ty(ty);
2937 let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
2938 let output_ty = match decl.output {
2939 hir::FnRetTy::Return(ref output) => {
2940 visitor.visit_ty(output);
2941 self.ast_ty_to_ty(output)
2943 hir::FnRetTy::DefaultReturn(..) => tcx.mk_unit(),
2946 debug!("ty_of_fn: output_ty={:?}", output_ty);
2949 ty::Binder::bind(tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi));
2951 if !self.allow_ty_infer() {
2952 // We always collect the spans for placeholder types when evaluating `fn`s, but we
2953 // only want to emit an error complaining about them if infer types (`_`) are not
2954 // allowed. `allow_ty_infer` gates this behavior.
2955 crate::collect::placeholder_type_error(
2957 ident_span.map(|sp| sp.shrink_to_hi()).unwrap_or(DUMMY_SP),
2960 ident_span.is_some(),
2964 // Find any late-bound regions declared in return type that do
2965 // not appear in the arguments. These are not well-formed.
2968 // for<'a> fn() -> &'a str <-- 'a is bad
2969 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
2970 let inputs = bare_fn_ty.inputs();
2971 let late_bound_in_args =
2972 tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned()));
2973 let output = bare_fn_ty.output();
2974 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
2975 for br in late_bound_in_ret.difference(&late_bound_in_args) {
2976 let lifetime_name = match *br {
2977 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
2978 ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
2980 let mut err = struct_span_err!(
2984 "return type references {} \
2985 which is not constrained by the fn input types",
2988 if let ty::BrAnon(_) = *br {
2989 // The only way for an anonymous lifetime to wind up
2990 // in the return type but **also** be unconstrained is
2991 // if it only appears in "associated types" in the
2992 // input. See #47511 for an example. In this case,
2993 // though we can easily give a hint that ought to be
2996 "lifetimes appearing in an associated type \
2997 are not considered constrained",
3006 /// Given the bounds on an object, determines what single region bound (if any) we can
3007 /// use to summarize this type. The basic idea is that we will use the bound the user
3008 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
3009 /// for region bounds. It may be that we can derive no bound at all, in which case
3010 /// we return `None`.
3011 fn compute_object_lifetime_bound(
3014 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
3015 ) -> Option<ty::Region<'tcx>> // if None, use the default
3017 let tcx = self.tcx();
3019 debug!("compute_opt_region_bound(existential_predicates={:?})", existential_predicates);
3021 // No explicit region bound specified. Therefore, examine trait
3022 // bounds and see if we can derive region bounds from those.
3023 let derived_region_bounds = object_region_bounds(tcx, existential_predicates);
3025 // If there are no derived region bounds, then report back that we
3026 // can find no region bound. The caller will use the default.
3027 if derived_region_bounds.is_empty() {
3031 // If any of the derived region bounds are 'static, that is always
3033 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
3034 return Some(tcx.lifetimes.re_static);
3037 // Determine whether there is exactly one unique region in the set
3038 // of derived region bounds. If so, use that. Otherwise, report an
3040 let r = derived_region_bounds[0];
3041 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
3046 "ambiguous lifetime bound, explicit lifetime bound required"
3054 /// Collects together a list of bounds that are applied to some type,
3055 /// after they've been converted into `ty` form (from the HIR
3056 /// representations). These lists of bounds occur in many places in
3060 /// trait Foo: Bar + Baz { }
3061 /// ^^^^^^^^^ supertrait list bounding the `Self` type parameter
3063 /// fn foo<T: Bar + Baz>() { }
3064 /// ^^^^^^^^^ bounding the type parameter `T`
3066 /// impl dyn Bar + Baz
3067 /// ^^^^^^^^^ bounding the forgotten dynamic type
3070 /// Our representation is a bit mixed here -- in some cases, we
3071 /// include the self type (e.g., `trait_bounds`) but in others we do
3072 #[derive(Default, PartialEq, Eq, Clone, Debug)]
3073 pub struct Bounds<'tcx> {
3074 /// A list of region bounds on the (implicit) self type. So if you
3075 /// had `T: 'a + 'b` this might would be a list `['a, 'b]` (but
3076 /// the `T` is not explicitly included).
3077 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
3079 /// A list of trait bounds. So if you had `T: Debug` this would be
3080 /// `T: Debug`. Note that the self-type is explicit here.
3081 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span, Constness)>,
3083 /// A list of projection equality bounds. So if you had `T:
3084 /// Iterator<Item = u32>` this would include `<T as
3085 /// Iterator>::Item => u32`. Note that the self-type is explicit
3087 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
3089 /// `Some` if there is *no* `?Sized` predicate. The `span`
3090 /// is the location in the source of the `T` declaration which can
3091 /// be cited as the source of the `T: Sized` requirement.
3092 pub implicitly_sized: Option<Span>,
3095 impl<'tcx> Bounds<'tcx> {
3096 /// Converts a bounds list into a flat set of predicates (like
3097 /// where-clauses). Because some of our bounds listings (e.g.,
3098 /// regions) don't include the self-type, you must supply the
3099 /// self-type here (the `param_ty` parameter).
3104 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
3105 // If it could be sized, and is, add the `Sized` predicate.
3106 let sized_predicate = self.implicitly_sized.and_then(|span| {
3107 tcx.lang_items().sized_trait().map(|sized| {
3108 let trait_ref = ty::Binder::bind(ty::TraitRef {
3110 substs: tcx.mk_substs_trait(param_ty, &[]),
3112 (trait_ref.without_const().to_predicate(), span)
3121 .map(|&(region_bound, span)| {
3122 // Account for the binder being introduced below; no need to shift `param_ty`
3123 // because, at present at least, it either only refers to early-bound regions,
3124 // or it's a generic associated type that deliberately has escaping bound vars.
3125 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
3126 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
3127 (ty::Binder::bind(outlives).to_predicate(), span)
3129 .chain(self.trait_bounds.iter().map(|&(bound_trait_ref, span, constness)| {
3130 let predicate = bound_trait_ref.with_constness(constness).to_predicate();
3134 self.projection_bounds
3136 .map(|&(projection, span)| (projection.to_predicate(), span)),