1 //! Conversion from AST representation of types to the `ty.rs` representation.
2 //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
3 //! instance of `AstConv`.
5 use errors::{Applicability, DiagnosticId};
6 use crate::hir::{self, GenericArg, GenericArgs, ExprKind};
7 use crate::hir::def::{CtorOf, Res, DefKind};
8 use crate::hir::def_id::DefId;
9 use crate::hir::HirVec;
11 use crate::middle::resolve_lifetime as rl;
12 use crate::namespace::Namespace;
13 use rustc::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
15 use rustc::ty::{self, DefIdTree, Ty, TyCtxt, ToPredicate, TypeFoldable};
16 use rustc::ty::{GenericParamDef, GenericParamDefKind};
17 use rustc::ty::subst::{Kind, Subst, InternalSubsts, SubstsRef};
18 use rustc::ty::wf::object_region_bounds;
19 use rustc::mir::interpret::ConstValue;
20 use rustc_target::spec::abi;
21 use crate::require_c_abi_if_c_variadic;
22 use smallvec::SmallVec;
24 use syntax::feature_gate::{GateIssue, emit_feature_err};
26 use syntax::util::lev_distance::find_best_match_for_name;
27 use syntax::symbol::sym;
28 use syntax_pos::{DUMMY_SP, Span, MultiSpan};
29 use crate::util::common::ErrorReported;
30 use crate::util::nodemap::FxHashMap;
32 use std::collections::BTreeSet;
36 use super::{check_type_alias_enum_variants_enabled};
37 use rustc_data_structures::fx::FxHashSet;
40 pub struct PathSeg(pub DefId, pub usize);
42 pub trait AstConv<'gcx, 'tcx> {
43 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
45 /// Returns the set of bounds in scope for the type parameter with
47 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
48 -> &'tcx ty::GenericPredicates<'tcx>;
50 /// What lifetime should we use when a lifetime is omitted (and not elided)?
51 fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
52 -> Option<ty::Region<'tcx>>;
54 /// What type should we use when a type is omitted?
55 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
57 /// Same as ty_infer, but with a known type parameter definition.
58 fn ty_infer_for_def(&self,
59 _def: &ty::GenericParamDef,
60 span: Span) -> Ty<'tcx> {
64 /// Projecting an associated type from a (potentially)
65 /// higher-ranked trait reference is more complicated, because of
66 /// the possibility of late-bound regions appearing in the
67 /// associated type binding. This is not legal in function
68 /// signatures for that reason. In a function body, we can always
69 /// handle it because we can use inference variables to remove the
70 /// late-bound regions.
71 fn projected_ty_from_poly_trait_ref(&self,
74 poly_trait_ref: ty::PolyTraitRef<'tcx>)
77 /// Normalize an associated type coming from the user.
78 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
80 /// Invoked when we encounter an error from some prior pass
81 /// (e.g., resolve) that is translated into a ty-error. This is
82 /// used to help suppress derived errors typeck might otherwise
84 fn set_tainted_by_errors(&self);
86 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
89 struct ConvertedBinding<'tcx> {
90 item_name: ast::Ident,
96 enum GenericArgPosition {
98 Value, // e.g., functions
102 impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
103 pub fn ast_region_to_region(&self,
104 lifetime: &hir::Lifetime,
105 def: Option<&ty::GenericParamDef>)
108 let tcx = self.tcx();
109 let lifetime_name = |def_id| {
110 tcx.hir().name_by_hir_id(tcx.hir().as_local_hir_id(def_id).unwrap()).as_interned_str()
113 let r = match tcx.named_region(lifetime.hir_id) {
114 Some(rl::Region::Static) => {
115 tcx.lifetimes.re_static
118 Some(rl::Region::LateBound(debruijn, id, _)) => {
119 let name = lifetime_name(id);
120 tcx.mk_region(ty::ReLateBound(debruijn,
121 ty::BrNamed(id, name)))
124 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
125 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
128 Some(rl::Region::EarlyBound(index, id, _)) => {
129 let name = lifetime_name(id);
130 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
137 Some(rl::Region::Free(scope, id)) => {
138 let name = lifetime_name(id);
139 tcx.mk_region(ty::ReFree(ty::FreeRegion {
141 bound_region: ty::BrNamed(id, name)
144 // (*) -- not late-bound, won't change
148 self.re_infer(lifetime.span, def)
150 // This indicates an illegal lifetime
151 // elision. `resolve_lifetime` should have
152 // reported an error in this case -- but if
153 // not, let's error out.
154 tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
156 // Supply some dummy value. We don't have an
157 // `re_error`, annoyingly, so use `'static`.
158 tcx.lifetimes.re_static
163 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
170 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
171 /// returns an appropriate set of substitutions for this particular reference to `I`.
172 pub fn ast_path_substs_for_ty(&self,
175 item_segment: &hir::PathSegment)
178 let (substs, assoc_bindings, _) = item_segment.with_generic_args(|generic_args| {
179 self.create_substs_for_ast_path(
183 item_segment.infer_types,
188 assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
193 /// Report error if there is an explicit type parameter when using `impl Trait`.
195 tcx: TyCtxt<'_, '_, '_>,
197 seg: &hir::PathSegment,
198 generics: &ty::Generics,
200 let explicit = !seg.infer_types;
201 let impl_trait = generics.params.iter().any(|param| match param.kind {
202 ty::GenericParamDefKind::Type {
203 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
208 if explicit && impl_trait {
209 let mut err = struct_span_err! {
213 "cannot provide explicit type parameters when `impl Trait` is \
214 used in argument position."
223 /// Checks that the correct number of generic arguments have been provided.
224 /// Used specifically for function calls.
225 pub fn check_generic_arg_count_for_call(
226 tcx: TyCtxt<'_, '_, '_>,
229 seg: &hir::PathSegment,
230 is_method_call: bool,
232 let empty_args = P(hir::GenericArgs {
233 args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
235 let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
236 Self::check_generic_arg_count(
240 if let Some(ref args) = seg.args {
246 GenericArgPosition::MethodCall
248 GenericArgPosition::Value
250 def.parent.is_none() && def.has_self, // `has_self`
251 seg.infer_types || suppress_mismatch, // `infer_types`
255 /// Checks that the correct number of generic arguments have been provided.
256 /// This is used both for datatypes and function calls.
257 fn check_generic_arg_count(
258 tcx: TyCtxt<'_, '_, '_>,
261 args: &hir::GenericArgs,
262 position: GenericArgPosition,
265 ) -> (bool, Option<Vec<Span>>) {
266 // At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
267 // that lifetimes will proceed types. So it suffices to check the number of each generic
268 // arguments in order to validate them with respect to the generic parameters.
269 let param_counts = def.own_counts();
270 let arg_counts = args.own_counts();
271 let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
272 let infer_consts = position != GenericArgPosition::Type && arg_counts.consts == 0;
274 let mut defaults: ty::GenericParamCount = Default::default();
275 for param in &def.params {
277 GenericParamDefKind::Lifetime => {}
278 GenericParamDefKind::Type { has_default, .. } => {
279 defaults.types += has_default as usize
281 GenericParamDefKind::Const => {
282 // FIXME(const_generics:defaults)
287 if position != GenericArgPosition::Type && !args.bindings.is_empty() {
288 AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
291 // Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
292 let mut reported_late_bound_region_err = None;
293 if !infer_lifetimes {
294 if let Some(span_late) = def.has_late_bound_regions {
295 let msg = "cannot specify lifetime arguments explicitly \
296 if late bound lifetime parameters are present";
297 let note = "the late bound lifetime parameter is introduced here";
298 let span = args.args[0].span();
299 if position == GenericArgPosition::Value
300 && arg_counts.lifetimes != param_counts.lifetimes {
301 let mut err = tcx.sess.struct_span_err(span, msg);
302 err.span_note(span_late, note);
304 reported_late_bound_region_err = Some(true);
306 let mut multispan = MultiSpan::from_span(span);
307 multispan.push_span_label(span_late, note.to_string());
308 tcx.lint_hir(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
309 args.args[0].id(), multispan, msg);
310 reported_late_bound_region_err = Some(false);
315 let check_kind_count = |kind, required, permitted, provided, offset| {
317 "check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}",
324 // We enforce the following: `required` <= `provided` <= `permitted`.
325 // For kinds without defaults (i.e., lifetimes), `required == permitted`.
326 // For other kinds (i.e., types), `permitted` may be greater than `required`.
327 if required <= provided && provided <= permitted {
328 return (reported_late_bound_region_err.unwrap_or(false), None);
331 // Unfortunately lifetime and type parameter mismatches are typically styled
332 // differently in diagnostics, which means we have a few cases to consider here.
333 let (bound, quantifier) = if required != permitted {
334 if provided < required {
335 (required, "at least ")
336 } else { // provided > permitted
337 (permitted, "at most ")
343 let mut potential_assoc_types: Option<Vec<Span>> = None;
344 let (spans, label) = if required == permitted && provided > permitted {
345 // In the case when the user has provided too many arguments,
346 // we want to point to the unexpected arguments.
347 let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
349 .map(|arg| arg.span())
351 potential_assoc_types = Some(spans.clone());
352 (spans, format!( "unexpected {} argument", kind))
354 (vec![span], format!(
355 "expected {}{} {} argument{}",
359 if bound != 1 { "s" } else { "" },
363 let mut err = tcx.sess.struct_span_err_with_code(
366 "wrong number of {} arguments: expected {}{}, found {}",
372 DiagnosticId::Error("E0107".into())
375 err.span_label(span, label.as_str());
379 (provided > required, // `suppress_error`
380 potential_assoc_types)
383 if reported_late_bound_region_err.is_none()
384 && (!infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes) {
387 param_counts.lifetimes,
388 param_counts.lifetimes,
389 arg_counts.lifetimes,
393 // FIXME(const_generics:defaults)
394 if !infer_consts || arg_counts.consts > param_counts.consts {
400 arg_counts.lifetimes + arg_counts.types,
403 // Note that type errors are currently be emitted *after* const errors.
405 || arg_counts.types > param_counts.types - defaults.types - has_self as usize {
408 param_counts.types - defaults.types - has_self as usize,
409 param_counts.types - has_self as usize,
411 arg_counts.lifetimes,
414 (reported_late_bound_region_err.unwrap_or(false), None)
418 /// Creates the relevant generic argument substitutions
419 /// corresponding to a set of generic parameters. This is a
420 /// rather complex function. Let us try to explain the role
421 /// of each of its parameters:
423 /// To start, we are given the `def_id` of the thing we are
424 /// creating the substitutions for, and a partial set of
425 /// substitutions `parent_substs`. In general, the substitutions
426 /// for an item begin with substitutions for all the "parents" of
427 /// that item -- e.g., for a method it might include the
428 /// parameters from the impl.
430 /// Therefore, the method begins by walking down these parents,
431 /// starting with the outermost parent and proceed inwards until
432 /// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
433 /// first to see if the parent's substitutions are listed in there. If so,
434 /// we can append those and move on. Otherwise, it invokes the
435 /// three callback functions:
437 /// - `args_for_def_id`: given the `DefId` `P`, supplies back the
438 /// generic arguments that were given to that parent from within
439 /// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
440 /// might refer to the trait `Foo`, and the arguments might be
441 /// `[T]`. The boolean value indicates whether to infer values
442 /// for arguments whose values were not explicitly provided.
443 /// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
444 /// instantiate a `Kind`.
445 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
446 /// creates a suitable inference variable.
447 pub fn create_substs_for_generic_args<'a, 'b>(
448 tcx: TyCtxt<'a, 'gcx, 'tcx>,
450 parent_substs: &[Kind<'tcx>],
452 self_ty: Option<Ty<'tcx>>,
453 args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
454 provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
455 inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
456 ) -> SubstsRef<'tcx> {
457 // Collect the segments of the path; we need to substitute arguments
458 // for parameters throughout the entire path (wherever there are
459 // generic parameters).
460 let mut parent_defs = tcx.generics_of(def_id);
461 let count = parent_defs.count();
462 let mut stack = vec![(def_id, parent_defs)];
463 while let Some(def_id) = parent_defs.parent {
464 parent_defs = tcx.generics_of(def_id);
465 stack.push((def_id, parent_defs));
468 // We manually build up the substitution, rather than using convenience
469 // methods in `subst.rs`, so that we can iterate over the arguments and
470 // parameters in lock-step linearly, instead of trying to match each pair.
471 let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
473 // Iterate over each segment of the path.
474 while let Some((def_id, defs)) = stack.pop() {
475 let mut params = defs.params.iter().peekable();
477 // If we have already computed substitutions for parents, we can use those directly.
478 while let Some(¶m) = params.peek() {
479 if let Some(&kind) = parent_substs.get(param.index as usize) {
487 // `Self` is handled first, unless it's been handled in `parent_substs`.
489 if let Some(¶m) = params.peek() {
490 if param.index == 0 {
491 if let GenericParamDefKind::Type { .. } = param.kind {
492 substs.push(self_ty.map(|ty| ty.into())
493 .unwrap_or_else(|| inferred_kind(None, param, true)));
500 // Check whether this segment takes generic arguments and the user has provided any.
501 let (generic_args, infer_types) = args_for_def_id(def_id);
503 let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
507 // We're going to iterate through the generic arguments that the user
508 // provided, matching them with the generic parameters we expect.
509 // Mismatches can occur as a result of elided lifetimes, or for malformed
510 // input. We try to handle both sensibly.
511 match (args.peek(), params.peek()) {
512 (Some(&arg), Some(¶m)) => {
513 match (arg, ¶m.kind) {
514 (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
515 | (GenericArg::Type(_), GenericParamDefKind::Type { .. })
516 | (GenericArg::Const(_), GenericParamDefKind::Const) => {
517 substs.push(provided_kind(param, arg));
521 (GenericArg::Type(_), GenericParamDefKind::Lifetime)
522 | (GenericArg::Const(_), GenericParamDefKind::Lifetime) => {
523 // We expected a lifetime argument, but got a type or const
524 // argument. That means we're inferring the lifetimes.
525 substs.push(inferred_kind(None, param, infer_types));
529 // We expected one kind of parameter, but the user provided
530 // another. This is an error, but we need to handle it
531 // gracefully so we can report sensible errors.
532 // In this case, we're simply going to infer this argument.
538 // We should never be able to reach this point with well-formed input.
539 // Getting to this point means the user supplied more arguments than
540 // there are parameters.
543 (None, Some(¶m)) => {
544 // If there are fewer arguments than parameters, it means
545 // we're inferring the remaining arguments.
546 substs.push(inferred_kind(Some(&substs), param, infer_types));
550 (None, None) => break,
555 tcx.intern_substs(&substs)
558 /// Given the type/lifetime/const arguments provided to some path (along with
559 /// an implicit `Self`, if this is a trait reference) returns the complete
560 /// set of substitutions. This may involve applying defaulted type parameters.
562 /// Note that the type listing given here is *exactly* what the user provided.
563 fn create_substs_for_ast_path(&self,
566 generic_args: &hir::GenericArgs,
568 self_ty: Option<Ty<'tcx>>)
569 -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>)
571 // If the type is parameterized by this region, then replace this
572 // region with the current anon region binding (in other words,
573 // whatever & would get replaced with).
574 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
576 def_id, self_ty, generic_args);
578 let tcx = self.tcx();
579 let generic_params = tcx.generics_of(def_id);
581 // If a self-type was declared, one should be provided.
582 assert_eq!(generic_params.has_self, self_ty.is_some());
584 let has_self = generic_params.has_self;
585 let (_, potential_assoc_types) = Self::check_generic_arg_count(
590 GenericArgPosition::Type,
595 let is_object = self_ty.map_or(false, |ty| {
596 ty == self.tcx().types.trait_object_dummy_self
598 let default_needs_object_self = |param: &ty::GenericParamDef| {
599 if let GenericParamDefKind::Type { has_default, .. } = param.kind {
600 if is_object && has_default {
601 if tcx.at(span).type_of(param.def_id).has_self_ty() {
602 // There is no suitable inference default for a type parameter
603 // that references self, in an object type.
612 let substs = Self::create_substs_for_generic_args(
618 // Provide the generic args, and whether types should be inferred.
619 |_| (Some(generic_args), infer_types),
620 // Provide substitutions for parameters for which (valid) arguments have been provided.
622 match (¶m.kind, arg) {
623 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
624 self.ast_region_to_region(<, Some(param)).into()
626 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
627 self.ast_ty_to_ty(&ty).into()
629 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
630 self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
635 // Provide substitutions for parameters for which arguments are inferred.
636 |substs, param, infer_types| {
638 GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
639 GenericParamDefKind::Type { has_default, .. } => {
640 if !infer_types && has_default {
641 // No type parameter provided, but a default exists.
643 // If we are converting an object type, then the
644 // `Self` parameter is unknown. However, some of the
645 // other type parameters may reference `Self` in their
646 // defaults. This will lead to an ICE if we are not
648 if default_needs_object_self(param) {
649 struct_span_err!(tcx.sess, span, E0393,
650 "the type parameter `{}` must be explicitly specified",
653 .span_label(span, format!(
654 "missing reference to `{}`", param.name))
656 "because of the default `Self` reference, type parameters \
657 must be specified on object types"))
661 // This is a default type parameter.
664 tcx.at(span).type_of(param.def_id)
665 .subst_spanned(tcx, substs.unwrap(), Some(span))
668 } else if infer_types {
669 // No type parameters were provided, we can infer all.
670 if !default_needs_object_self(param) {
671 self.ty_infer_for_def(param, span).into()
673 self.ty_infer(span).into()
676 // We've already errored above about the mismatch.
680 GenericParamDefKind::Const => {
681 // FIXME(const_generics:defaults)
682 // We've already errored above about the mismatch.
683 tcx.consts.err.into()
689 let assoc_bindings = generic_args.bindings.iter().map(|binding| {
691 item_name: binding.ident,
692 ty: self.ast_ty_to_ty(&binding.ty),
697 debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
698 generic_params, self_ty, substs);
700 (substs, assoc_bindings, potential_assoc_types)
703 /// Instantiates the path for the given trait reference, assuming that it's
704 /// bound to a valid trait type. Returns the `DefId` of the defining trait.
705 /// The type _cannot_ be a type other than a trait type.
707 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
708 /// are disallowed. Otherwise, they are pushed onto the vector given.
709 pub fn instantiate_mono_trait_ref(&self,
710 trait_ref: &hir::TraitRef,
712 -> ty::TraitRef<'tcx>
714 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
716 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
717 trait_ref.trait_def_id(),
719 trait_ref.path.segments.last().unwrap())
722 /// The given trait-ref must actually be a trait.
723 pub(super) fn instantiate_poly_trait_ref_inner(&self,
724 trait_ref: &hir::TraitRef,
726 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
728 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
730 let trait_def_id = trait_ref.trait_def_id();
732 debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
734 self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
736 let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
740 trait_ref.path.segments.last().unwrap(),
742 let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
744 let mut dup_bindings = FxHashMap::default();
745 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
746 // specify type to assert that error was already reported in Err case:
747 let predicate: Result<_, ErrorReported> =
748 self.ast_type_binding_to_poly_projection_predicate(
749 trait_ref.hir_ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
750 // okay to ignore Err because of ErrorReported (see above)
751 Some((predicate.ok()?, binding.span))
754 debug!("instantiate_poly_trait_ref({:?}, projections={:?}) -> {:?}",
755 trait_ref, poly_projections, poly_trait_ref);
756 (poly_trait_ref, potential_assoc_types)
759 pub fn instantiate_poly_trait_ref(&self,
760 poly_trait_ref: &hir::PolyTraitRef,
762 poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
763 -> (ty::PolyTraitRef<'tcx>, Option<Vec<Span>>)
765 self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
766 poly_projections, false)
769 fn ast_path_to_mono_trait_ref(&self,
773 trait_segment: &hir::PathSegment)
774 -> ty::TraitRef<'tcx>
776 let (substs, assoc_bindings, _) =
777 self.create_substs_for_ast_trait_ref(span,
781 assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
782 ty::TraitRef::new(trait_def_id, substs)
785 fn create_substs_for_ast_trait_ref(
790 trait_segment: &hir::PathSegment,
791 ) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'tcx>>, Option<Vec<Span>>) {
792 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
795 let trait_def = self.tcx().trait_def(trait_def_id);
797 if !self.tcx().features().unboxed_closures &&
798 trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
799 != trait_def.paren_sugar {
800 // For now, require that parenthetical notation be used only with `Fn()` etc.
801 let msg = if trait_def.paren_sugar {
802 "the precise format of `Fn`-family traits' type parameters is subject to change. \
803 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
805 "parenthetical notation is only stable when used with `Fn`-family traits"
807 emit_feature_err(&self.tcx().sess.parse_sess, sym::unboxed_closures,
808 span, GateIssue::Language, msg);
811 trait_segment.with_generic_args(|generic_args| {
812 self.create_substs_for_ast_path(span,
815 trait_segment.infer_types,
820 fn trait_defines_associated_type_named(&self,
822 assoc_name: ast::Ident)
825 self.tcx().associated_items(trait_def_id).any(|item| {
826 item.kind == ty::AssocKind::Type &&
827 self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
831 fn ast_type_binding_to_poly_projection_predicate(
833 hir_ref_id: hir::HirId,
834 trait_ref: ty::PolyTraitRef<'tcx>,
835 binding: &ConvertedBinding<'tcx>,
837 dup_bindings: &mut FxHashMap<DefId, Span>)
838 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
840 let tcx = self.tcx();
843 // Given something like `U: SomeTrait<T = X>`, we want to produce a
844 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
845 // subtle in the event that `T` is defined in a supertrait of
846 // `SomeTrait`, because in that case we need to upcast.
848 // That is, consider this case:
851 // trait SubTrait: SuperTrait<int> { }
852 // trait SuperTrait<A> { type T; }
854 // ... B : SubTrait<T=foo> ...
857 // We want to produce `<B as SuperTrait<int>>::T == foo`.
859 // Find any late-bound regions declared in `ty` that are not
860 // declared in the trait-ref. These are not wellformed.
864 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
865 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
866 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
867 let late_bound_in_ty =
868 tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
869 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
870 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
871 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
872 let br_name = match *br {
873 ty::BrNamed(_, name) => name,
877 "anonymous bound region {:?} in binding but not trait ref",
881 struct_span_err!(tcx.sess,
884 "binding for associated type `{}` references lifetime `{}`, \
885 which does not appear in the trait input types",
886 binding.item_name, br_name)
891 let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
893 // Simple case: X is defined in the current trait.
896 // Otherwise, we have to walk through the supertraits to find
898 let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
899 self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
901 self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
902 binding.item_name, binding.span)
905 let (assoc_ident, def_scope) =
906 tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
907 let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
908 i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident
909 }).expect("missing associated type");
911 if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
912 let msg = format!("associated type `{}` is private", binding.item_name);
913 tcx.sess.span_err(binding.span, &msg);
915 tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
918 dup_bindings.entry(assoc_ty.def_id)
919 .and_modify(|prev_span| {
920 struct_span_err!(self.tcx().sess, binding.span, E0719,
921 "the value of the associated type `{}` (from the trait `{}`) \
922 is already specified",
924 tcx.def_path_str(assoc_ty.container.id()))
925 .span_label(binding.span, "re-bound here")
926 .span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
929 .or_insert(binding.span);
932 Ok(candidate.map_bound(|trait_ref| {
933 ty::ProjectionPredicate {
934 projection_ty: ty::ProjectionTy::from_ref_and_name(
944 fn ast_path_to_ty(&self,
947 item_segment: &hir::PathSegment)
950 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
953 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
957 /// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
958 /// removing the dummy `Self` type (`trait_object_dummy_self`).
959 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
960 -> ty::ExistentialTraitRef<'tcx> {
961 if trait_ref.self_ty() != self.tcx().types.trait_object_dummy_self {
962 bug!("trait_ref_to_existential called on {:?} with non-dummy Self", trait_ref);
964 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
967 fn conv_object_ty_poly_trait_ref(&self,
969 trait_bounds: &[hir::PolyTraitRef],
970 lifetime: &hir::Lifetime)
973 let tcx = self.tcx();
975 let mut projection_bounds = Vec::new();
976 let mut potential_assoc_types = Vec::new();
977 let dummy_self = self.tcx().types.trait_object_dummy_self;
978 // FIXME: we want to avoid collecting into a `Vec` here, but simply cloning the iterator is
979 // not straightforward due to the borrow checker.
980 let bound_trait_refs: Vec<_> = trait_bounds
984 let (trait_ref, cur_potential_assoc_types) = self.instantiate_poly_trait_ref(
987 &mut projection_bounds
989 potential_assoc_types.extend(cur_potential_assoc_types.into_iter().flatten());
990 (trait_ref, trait_bound.span)
994 // Expand trait aliases recursively and check that only one regular (non-auto) trait
995 // is used and no 'maybe' bounds are used.
996 let expanded_traits = traits::expand_trait_aliases(tcx, bound_trait_refs.iter().cloned());
997 let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
998 expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
999 if regular_traits.len() > 1 {
1000 let first_trait = ®ular_traits[0];
1001 let additional_trait = ®ular_traits[1];
1002 let mut err = struct_span_err!(tcx.sess, additional_trait.bottom().1, E0225,
1003 "only auto traits can be used as additional traits in a trait object"
1005 additional_trait.label_with_exp_info(&mut err,
1006 "additional non-auto trait", "additional use");
1007 first_trait.label_with_exp_info(&mut err,
1008 "first non-auto trait", "first use");
1012 if regular_traits.is_empty() && auto_traits.is_empty() {
1013 span_err!(tcx.sess, span, E0224,
1014 "at least one non-builtin trait is required for an object type");
1015 return tcx.types.err;
1018 // Check that there are no gross object safety violations;
1019 // most importantly, that the supertraits don't contain `Self`,
1021 for item in ®ular_traits {
1022 let object_safety_violations =
1023 tcx.global_tcx().astconv_object_safety_violations(item.trait_ref().def_id());
1024 if !object_safety_violations.is_empty() {
1025 tcx.report_object_safety_error(
1027 item.trait_ref().def_id(),
1028 object_safety_violations
1030 .map(|mut err| err.emit());
1031 return tcx.types.err;
1035 // Use a `BTreeSet` to keep output in a more consistent order.
1036 let mut associated_types = BTreeSet::default();
1038 let regular_traits_refs = bound_trait_refs
1040 .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()))
1041 .map(|(trait_ref, _)| trait_ref);
1042 for trait_ref in traits::elaborate_trait_refs(tcx, regular_traits_refs) {
1043 debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", trait_ref);
1045 ty::Predicate::Trait(pred) => {
1047 .extend(tcx.associated_items(pred.def_id())
1048 .filter(|item| item.kind == ty::AssocKind::Type)
1049 .map(|item| item.def_id));
1051 ty::Predicate::Projection(pred) => {
1052 // A `Self` within the original bound will be substituted with a
1053 // `trait_object_dummy_self`, so check for that.
1054 let references_self =
1055 pred.skip_binder().ty.walk().any(|t| t == dummy_self);
1057 // If the projection output contains `Self`, force the user to
1058 // elaborate it explicitly to avoid a lot of complexity.
1060 // The "classicaly useful" case is the following:
1062 // trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
1067 // Here, the user could theoretically write `dyn MyTrait<Output = X>`,
1068 // but actually supporting that would "expand" to an infinitely-long type
1069 // `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`.
1071 // Instead, we force the user to write `dyn MyTrait<MyOutput = X, Output = X>`,
1072 // which is uglier but works. See the discussion in #56288 for alternatives.
1073 if !references_self {
1074 // Include projections defined on supertraits.
1075 projection_bounds.push((pred, DUMMY_SP))
1082 for (projection_bound, _) in &projection_bounds {
1083 associated_types.remove(&projection_bound.projection_def_id());
1086 if !associated_types.is_empty() {
1087 let names = associated_types.iter().map(|item_def_id| {
1088 let assoc_item = tcx.associated_item(*item_def_id);
1089 let trait_def_id = assoc_item.container.id();
1091 "`{}` (from the trait `{}`)",
1093 tcx.def_path_str(trait_def_id),
1095 }).collect::<Vec<_>>().join(", ");
1096 let mut err = struct_span_err!(
1100 "the value of the associated type{} {} must be specified",
1101 if associated_types.len() == 1 { "" } else { "s" },
1104 let (suggest, potential_assoc_types_spans) =
1105 if potential_assoc_types.len() == associated_types.len() {
1106 // Only suggest when the amount of missing associated types equals the number of
1107 // extra type arguments present, as that gives us a relatively high confidence
1108 // that the user forgot to give the associtated type's name. The canonical
1109 // example would be trying to use `Iterator<isize>` instead of
1110 // `Iterator<Item = isize>`.
1111 (true, potential_assoc_types)
1115 let mut suggestions = Vec::new();
1116 for (i, item_def_id) in associated_types.iter().enumerate() {
1117 let assoc_item = tcx.associated_item(*item_def_id);
1120 format!("associated type `{}` must be specified", assoc_item.ident),
1122 if item_def_id.is_local() {
1124 tcx.def_span(*item_def_id),
1125 format!("`{}` defined here", assoc_item.ident),
1129 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
1130 potential_assoc_types_spans[i],
1133 potential_assoc_types_spans[i],
1134 format!("{} = {}", assoc_item.ident, snippet),
1139 if !suggestions.is_empty() {
1140 let msg = format!("if you meant to specify the associated {}, write",
1141 if suggestions.len() == 1 { "type" } else { "types" });
1142 err.multipart_suggestion(
1145 Applicability::MaybeIncorrect,
1151 // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
1152 // `dyn Trait + Send`.
1153 auto_traits.sort_by_key(|i| i.trait_ref().def_id());
1154 auto_traits.dedup_by_key(|i| i.trait_ref().def_id());
1155 debug!("regular_traits: {:?}", regular_traits);
1156 debug!("auto_traits: {:?}", auto_traits);
1158 // Erase the `dummy_self` (`trait_object_dummy_self`) used above.
1159 let existential_trait_refs = regular_traits.iter().map(|i| {
1160 i.trait_ref().map_bound(|trait_ref| self.trait_ref_to_existential(trait_ref))
1162 let existential_projections = projection_bounds.iter().map(|(bound, _)| {
1163 bound.map_bound(|b| {
1164 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
1165 ty::ExistentialProjection {
1167 item_def_id: b.projection_ty.item_def_id,
1168 substs: trait_ref.substs,
1173 // Calling `skip_binder` is okay because the predicates are re-bound.
1174 let regular_trait_predicates = existential_trait_refs.map(
1175 |trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder()));
1176 let auto_trait_predicates = auto_traits.into_iter().map(
1177 |trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()));
1179 regular_trait_predicates
1180 .chain(auto_trait_predicates)
1181 .chain(existential_projections
1182 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
1183 .collect::<SmallVec<[_; 8]>>();
1184 v.sort_by(|a, b| a.stable_cmp(tcx, b));
1186 let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
1188 // Use explicitly-specified region bound.
1189 let region_bound = if !lifetime.is_elided() {
1190 self.ast_region_to_region(lifetime, None)
1192 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
1193 if tcx.named_region(lifetime.hir_id).is_some() {
1194 self.ast_region_to_region(lifetime, None)
1196 self.re_infer(span, None).unwrap_or_else(|| {
1197 span_err!(tcx.sess, span, E0228,
1198 "the lifetime bound for this object type cannot be deduced \
1199 from context; please supply an explicit bound");
1200 tcx.lifetimes.re_static
1205 debug!("region_bound: {:?}", region_bound);
1207 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
1208 debug!("trait_object_type: {:?}", ty);
1212 fn report_ambiguous_associated_type(
1219 let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
1220 if let (Some(_), Ok(snippet)) = (
1221 self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
1222 self.tcx().sess.source_map().span_to_snippet(span),
1224 err.span_suggestion(
1226 "you are looking for the module in `std`, not the primitive type",
1227 format!("std::{}", snippet),
1228 Applicability::MachineApplicable,
1231 err.span_suggestion(
1233 "use fully-qualified syntax",
1234 format!("<{} as {}>::{}", type_str, trait_str, name),
1235 Applicability::HasPlaceholders
1241 // Search for a bound on a type parameter which includes the associated item
1242 // given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter
1243 // This function will fail if there are no suitable bounds or there is
1245 fn find_bound_for_assoc_item(&self,
1246 ty_param_def_id: DefId,
1247 assoc_name: ast::Ident,
1249 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1251 let tcx = self.tcx();
1253 let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
1254 let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
1256 // Check that there is exactly one way to find an associated type with the
1258 let suitable_bounds = traits::transitive_bounds(tcx, bounds)
1259 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
1261 let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
1262 let param_name = tcx.hir().ty_param_name(param_hir_id);
1263 self.one_bound_for_assoc_type(suitable_bounds,
1264 ¶m_name.as_str(),
1269 // Checks that `bounds` contains exactly one element and reports appropriate
1270 // errors otherwise.
1271 fn one_bound_for_assoc_type<I>(&self,
1273 ty_param_name: &str,
1274 assoc_name: ast::Ident,
1276 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
1277 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
1279 let bound = match bounds.next() {
1280 Some(bound) => bound,
1282 struct_span_err!(self.tcx().sess, span, E0220,
1283 "associated type `{}` not found for `{}`",
1286 .span_label(span, format!("associated type `{}` not found", assoc_name))
1288 return Err(ErrorReported);
1292 if let Some(bound2) = bounds.next() {
1293 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
1294 let mut err = struct_span_err!(
1295 self.tcx().sess, span, E0221,
1296 "ambiguous associated type `{}` in bounds of `{}`",
1299 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
1301 for bound in bounds {
1302 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
1303 item.kind == ty::AssocKind::Type &&
1304 self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
1306 .and_then(|item| self.tcx().hir().span_if_local(item.def_id));
1308 if let Some(span) = bound_span {
1309 err.span_label(span, format!("ambiguous `{}` from `{}`",
1313 span_note!(&mut err, span,
1314 "associated type `{}` could derive from `{}`",
1325 // Create a type from a path to an associated type.
1326 // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
1327 // and item_segment is the path segment for `D`. We return a type and a def for
1329 // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
1330 // parameter or `Self`.
1331 pub fn associated_path_to_ty(
1333 hir_ref_id: hir::HirId,
1337 assoc_segment: &hir::PathSegment,
1338 permit_variants: bool,
1339 ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
1340 let tcx = self.tcx();
1341 let assoc_ident = assoc_segment.ident;
1343 debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
1345 self.prohibit_generics(slice::from_ref(assoc_segment));
1347 // Check if we have an enum variant.
1348 let mut variant_resolution = None;
1349 if let ty::Adt(adt_def, _) = qself_ty.sty {
1350 if adt_def.is_enum() {
1351 let variant_def = adt_def.variants.iter().find(|vd| {
1352 tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did)
1354 if let Some(variant_def) = variant_def {
1355 if permit_variants {
1356 check_type_alias_enum_variants_enabled(tcx, span);
1357 tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
1358 return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
1360 variant_resolution = Some(variant_def.def_id);
1366 // Find the type of the associated item, and the trait where the associated
1367 // item is declared.
1368 let bound = match (&qself_ty.sty, qself_res) {
1369 (_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
1370 // `Self` in an impl of a trait -- we have a concrete self type and a
1372 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
1373 Some(trait_ref) => trait_ref,
1375 // A cycle error occurred, most likely.
1376 return Err(ErrorReported);
1380 let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
1381 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_ident));
1383 self.one_bound_for_assoc_type(candidates, "Self", assoc_ident, span)?
1385 (&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
1386 (&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
1387 self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
1390 if variant_resolution.is_some() {
1391 // Variant in type position
1392 let msg = format!("expected type, found variant `{}`", assoc_ident);
1393 tcx.sess.span_err(span, &msg);
1394 } else if qself_ty.is_enum() {
1395 let mut err = tcx.sess.struct_span_err(
1397 &format!("no variant `{}` in enum `{}`", assoc_ident, qself_ty),
1400 let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
1401 if let Some(suggested_name) = find_best_match_for_name(
1402 adt_def.variants.iter().map(|variant| &variant.ident.name),
1403 &assoc_ident.as_str(),
1406 err.span_suggestion(
1408 "there is a variant with a similar name",
1409 suggested_name.to_string(),
1410 Applicability::MaybeIncorrect,
1413 err.span_label(span, format!("variant not found in `{}`", qself_ty));
1416 if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
1417 let sp = tcx.sess.source_map().def_span(sp);
1418 err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
1422 } else if !qself_ty.references_error() {
1423 // Don't print `TyErr` to the user.
1424 self.report_ambiguous_associated_type(
1426 &qself_ty.to_string(),
1428 &assoc_ident.as_str(),
1431 return Err(ErrorReported);
1435 let trait_did = bound.def_id();
1436 let (assoc_ident, def_scope) =
1437 tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
1438 let item = tcx.associated_items(trait_did).find(|i| {
1439 Namespace::from(i.kind) == Namespace::Type &&
1440 i.ident.modern() == assoc_ident
1441 }).expect("missing associated type");
1443 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
1444 let ty = self.normalize_ty(span, ty);
1446 let kind = DefKind::AssocTy;
1447 if !item.vis.is_accessible_from(def_scope, tcx) {
1448 let msg = format!("{} `{}` is private", kind.descr(), assoc_ident);
1449 tcx.sess.span_err(span, &msg);
1451 tcx.check_stability(item.def_id, Some(hir_ref_id), span);
1453 if let Some(variant_def_id) = variant_resolution {
1454 let mut err = tcx.struct_span_lint_hir(
1455 AMBIGUOUS_ASSOCIATED_ITEMS,
1458 "ambiguous associated item",
1461 let mut could_refer_to = |kind: DefKind, def_id, also| {
1462 let note_msg = format!("`{}` could{} refer to {} defined here",
1463 assoc_ident, also, kind.descr());
1464 err.span_note(tcx.def_span(def_id), ¬e_msg);
1466 could_refer_to(DefKind::Variant, variant_def_id, "");
1467 could_refer_to(kind, item.def_id, " also");
1469 err.span_suggestion(
1471 "use fully-qualified syntax",
1472 format!("<{} as {}>::{}", qself_ty, "Trait", assoc_ident),
1473 Applicability::HasPlaceholders,
1477 Ok((ty, kind, item.def_id))
1480 fn qpath_to_ty(&self,
1482 opt_self_ty: Option<Ty<'tcx>>,
1484 trait_segment: &hir::PathSegment,
1485 item_segment: &hir::PathSegment)
1488 let tcx = self.tcx();
1489 let trait_def_id = tcx.parent(item_def_id).unwrap();
1491 self.prohibit_generics(slice::from_ref(item_segment));
1493 let self_ty = if let Some(ty) = opt_self_ty {
1496 let path_str = tcx.def_path_str(trait_def_id);
1497 self.report_ambiguous_associated_type(
1501 &item_segment.ident.as_str(),
1503 return tcx.types.err;
1506 debug!("qpath_to_ty: self_type={:?}", self_ty);
1508 let trait_ref = self.ast_path_to_mono_trait_ref(span,
1513 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
1515 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
1518 pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(
1519 &self, segments: T) -> bool {
1520 let mut has_err = false;
1521 for segment in segments {
1522 segment.with_generic_args(|generic_args| {
1523 let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
1524 for arg in &generic_args.args {
1525 let (span, kind) = match arg {
1526 hir::GenericArg::Lifetime(lt) => {
1527 if err_for_lt { continue }
1530 (lt.span, "lifetime")
1532 hir::GenericArg::Type(ty) => {
1533 if err_for_ty { continue }
1538 hir::GenericArg::Const(ct) => {
1539 if err_for_ct { continue }
1544 let mut err = struct_span_err!(
1548 "{} arguments are not allowed for this type",
1551 err.span_label(span, format!("{} argument not allowed", kind));
1553 if err_for_lt && err_for_ty && err_for_ct {
1557 for binding in &generic_args.bindings {
1559 Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
1567 pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_, '_, '_>, span: Span) {
1568 let mut err = struct_span_err!(tcx.sess, span, E0229,
1569 "associated type bindings are not allowed here");
1570 err.span_label(span, "associated type not allowed here").emit();
1573 // FIXME(eddyb, varkor) handle type paths here too, not just value ones.
1574 pub fn def_ids_for_value_path_segments(
1576 segments: &[hir::PathSegment],
1577 self_ty: Option<Ty<'tcx>>,
1581 // We need to extract the type parameters supplied by the user in
1582 // the path `path`. Due to the current setup, this is a bit of a
1583 // tricky-process; the problem is that resolve only tells us the
1584 // end-point of the path resolution, and not the intermediate steps.
1585 // Luckily, we can (at least for now) deduce the intermediate steps
1586 // just from the end-point.
1588 // There are basically five cases to consider:
1590 // 1. Reference to a constructor of a struct:
1592 // struct Foo<T>(...)
1594 // In this case, the parameters are declared in the type space.
1596 // 2. Reference to a constructor of an enum variant:
1598 // enum E<T> { Foo(...) }
1600 // In this case, the parameters are defined in the type space,
1601 // but may be specified either on the type or the variant.
1603 // 3. Reference to a fn item or a free constant:
1607 // In this case, the path will again always have the form
1608 // `a::b::foo::<T>` where only the final segment should have
1609 // type parameters. However, in this case, those parameters are
1610 // declared on a value, and hence are in the `FnSpace`.
1612 // 4. Reference to a method or an associated constant:
1614 // impl<A> SomeStruct<A> {
1618 // Here we can have a path like
1619 // `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
1620 // may appear in two places. The penultimate segment,
1621 // `SomeStruct::<A>`, contains parameters in TypeSpace, and the
1622 // final segment, `foo::<B>` contains parameters in fn space.
1624 // The first step then is to categorize the segments appropriately.
1626 let tcx = self.tcx();
1628 assert!(!segments.is_empty());
1629 let last = segments.len() - 1;
1631 let mut path_segs = vec![];
1634 // Case 1. Reference to a struct constructor.
1635 DefKind::Ctor(CtorOf::Struct, ..) => {
1636 // Everything but the final segment should have no
1637 // parameters at all.
1638 let generics = tcx.generics_of(def_id);
1639 // Variant and struct constructors use the
1640 // generics of their parent type definition.
1641 let generics_def_id = generics.parent.unwrap_or(def_id);
1642 path_segs.push(PathSeg(generics_def_id, last));
1645 // Case 2. Reference to a variant constructor.
1646 DefKind::Ctor(CtorOf::Variant, ..)
1647 | DefKind::Variant => {
1648 let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
1649 let (generics_def_id, index) = if let Some(adt_def) = adt_def {
1650 debug_assert!(adt_def.is_enum());
1652 } else if last >= 1 && segments[last - 1].args.is_some() {
1653 // Everything but the penultimate segment should have no
1654 // parameters at all.
1655 let mut def_id = def_id;
1657 // `DefKind::Ctor` -> `DefKind::Variant`
1658 if let DefKind::Ctor(..) = kind {
1659 def_id = tcx.parent(def_id).unwrap()
1662 // `DefKind::Variant` -> `DefKind::Enum`
1663 let enum_def_id = tcx.parent(def_id).unwrap();
1664 (enum_def_id, last - 1)
1666 // FIXME: lint here recommending `Enum::<...>::Variant` form
1667 // instead of `Enum::Variant::<...>` form.
1669 // Everything but the final segment should have no
1670 // parameters at all.
1671 let generics = tcx.generics_of(def_id);
1672 // Variant and struct constructors use the
1673 // generics of their parent type definition.
1674 (generics.parent.unwrap_or(def_id), last)
1676 path_segs.push(PathSeg(generics_def_id, index));
1679 // Case 3. Reference to a top-level value.
1682 | DefKind::ConstParam
1683 | DefKind::Static => {
1684 path_segs.push(PathSeg(def_id, last));
1687 // Case 4. Reference to a method or associated const.
1689 | DefKind::AssocConst => {
1690 if segments.len() >= 2 {
1691 let generics = tcx.generics_of(def_id);
1692 path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
1694 path_segs.push(PathSeg(def_id, last));
1697 kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
1700 debug!("path_segs = {:?}", path_segs);
1705 // Check a type `Path` and convert it to a `Ty`.
1706 pub fn res_to_ty(&self,
1707 opt_self_ty: Option<Ty<'tcx>>,
1709 permit_variants: bool)
1711 let tcx = self.tcx();
1713 debug!("res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
1714 path.res, opt_self_ty, path.segments);
1716 let span = path.span;
1718 Res::Def(DefKind::Existential, did) => {
1719 // Check for desugared impl trait.
1720 assert!(ty::is_impl_trait_defn(tcx, did).is_none());
1721 let item_segment = path.segments.split_last().unwrap();
1722 self.prohibit_generics(item_segment.1);
1723 let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
1726 tcx.mk_opaque(did, substs),
1729 Res::Def(DefKind::Enum, did)
1730 | Res::Def(DefKind::TyAlias, did)
1731 | Res::Def(DefKind::Struct, did)
1732 | Res::Def(DefKind::Union, did)
1733 | Res::Def(DefKind::ForeignTy, did) => {
1734 assert_eq!(opt_self_ty, None);
1735 self.prohibit_generics(path.segments.split_last().unwrap().1);
1736 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
1738 Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
1739 // Convert "variant type" as if it were a real type.
1740 // The resulting `Ty` is type of the variant's enum for now.
1741 assert_eq!(opt_self_ty, None);
1744 self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
1745 let generic_segs: FxHashSet<_> =
1746 path_segs.iter().map(|PathSeg(_, index)| index).collect();
1747 self.prohibit_generics(path.segments.iter().enumerate().filter_map(|(index, seg)| {
1748 if !generic_segs.contains(&index) {
1755 let PathSeg(def_id, index) = path_segs.last().unwrap();
1756 self.ast_path_to_ty(span, *def_id, &path.segments[*index])
1758 Res::Def(DefKind::TyParam, did) => {
1759 assert_eq!(opt_self_ty, None);
1760 self.prohibit_generics(&path.segments);
1762 let hir_id = tcx.hir().as_local_hir_id(did).unwrap();
1763 let item_id = tcx.hir().get_parent_node_by_hir_id(hir_id);
1764 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1765 let generics = tcx.generics_of(item_def_id);
1766 let index = generics.param_def_id_to_index[
1767 &tcx.hir().local_def_id_from_hir_id(hir_id)];
1768 tcx.mk_ty_param(index, tcx.hir().name_by_hir_id(hir_id).as_interned_str())
1770 Res::SelfTy(_, Some(def_id)) => {
1771 // `Self` in impl (we know the concrete type).
1772 assert_eq!(opt_self_ty, None);
1773 self.prohibit_generics(&path.segments);
1774 // Try to evaluate any array length constants
1775 self.normalize_ty(span, tcx.at(span).type_of(def_id))
1777 Res::SelfTy(Some(_), None) => {
1779 assert_eq!(opt_self_ty, None);
1780 self.prohibit_generics(&path.segments);
1783 Res::Def(DefKind::AssocTy, def_id) => {
1784 debug_assert!(path.segments.len() >= 2);
1785 self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
1786 self.qpath_to_ty(span,
1789 &path.segments[path.segments.len() - 2],
1790 path.segments.last().unwrap())
1792 Res::PrimTy(prim_ty) => {
1793 assert_eq!(opt_self_ty, None);
1794 self.prohibit_generics(&path.segments);
1796 hir::Bool => tcx.types.bool,
1797 hir::Char => tcx.types.char,
1798 hir::Int(it) => tcx.mk_mach_int(it),
1799 hir::Uint(uit) => tcx.mk_mach_uint(uit),
1800 hir::Float(ft) => tcx.mk_mach_float(ft),
1801 hir::Str => tcx.mk_str()
1805 self.set_tainted_by_errors();
1806 return self.tcx().types.err;
1808 _ => span_bug!(span, "unexpected resolution: {:?}", path.res)
1812 /// Parses the programmer's textual representation of a type into our
1813 /// internal notion of a type.
1814 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1815 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
1816 ast_ty.hir_id, ast_ty, ast_ty.node);
1818 let tcx = self.tcx();
1820 let result_ty = match ast_ty.node {
1821 hir::TyKind::Slice(ref ty) => {
1822 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1824 hir::TyKind::Ptr(ref mt) => {
1825 tcx.mk_ptr(ty::TypeAndMut {
1826 ty: self.ast_ty_to_ty(&mt.ty),
1830 hir::TyKind::Rptr(ref region, ref mt) => {
1831 let r = self.ast_region_to_region(region, None);
1832 debug!("Ref r={:?}", r);
1833 let t = self.ast_ty_to_ty(&mt.ty);
1834 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1836 hir::TyKind::Never => {
1839 hir::TyKind::Tup(ref fields) => {
1840 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
1842 hir::TyKind::BareFn(ref bf) => {
1843 require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1844 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1846 hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
1847 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1849 hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1850 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1851 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1852 self.ast_ty_to_ty(qself)
1854 self.res_to_ty(opt_self_ty, path, false)
1856 hir::TyKind::Def(item_id, ref lifetimes) => {
1857 let did = tcx.hir().local_def_id_from_hir_id(item_id.id);
1858 self.impl_trait_ty_to_ty(did, lifetimes)
1860 hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1861 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1862 let ty = self.ast_ty_to_ty(qself);
1864 let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
1869 self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
1870 .map(|(ty, _, _)| ty).unwrap_or(tcx.types.err)
1872 hir::TyKind::Array(ref ty, ref length) => {
1873 let length = self.ast_const_to_const(length, tcx.types.usize);
1874 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
1875 self.normalize_ty(ast_ty.span, array_ty)
1877 hir::TyKind::Typeof(ref _e) => {
1878 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1879 "`typeof` is a reserved keyword but unimplemented")
1880 .span_label(ast_ty.span, "reserved keyword")
1885 hir::TyKind::Infer => {
1886 // Infer also appears as the type of arguments or return
1887 // values in a ExprKind::Closure, or as
1888 // the type of local variables. Both of these cases are
1889 // handled specially and will not descend into this routine.
1890 self.ty_infer(ast_ty.span)
1892 hir::TyKind::Err => {
1895 hir::TyKind::CVarArgs(lt) => {
1896 let va_list_did = match tcx.lang_items().va_list() {
1898 None => span_bug!(ast_ty.span,
1899 "`va_list` lang item required for variadics"),
1901 let region = self.ast_region_to_region(<, None);
1902 tcx.type_of(va_list_did).subst(tcx, &[region.into()])
1906 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1910 pub fn ast_const_to_const(
1912 ast_const: &hir::AnonConst,
1914 ) -> &'tcx ty::Const<'tcx> {
1915 debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
1917 let tcx = self.tcx();
1918 let def_id = tcx.hir().local_def_id_from_hir_id(ast_const.hir_id);
1920 let mut const_ = ty::Const {
1921 val: ConstValue::Unevaluated(
1923 InternalSubsts::identity_for_item(tcx, def_id),
1928 let mut expr = &tcx.hir().body(ast_const.body).value;
1930 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
1931 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
1932 if let ExprKind::Block(block, _) = &expr.node {
1933 if block.stmts.is_empty() {
1934 if let Some(trailing) = &block.expr {
1940 if let ExprKind::Path(ref qpath) = expr.node {
1941 if let hir::QPath::Resolved(_, ref path) = qpath {
1942 if let Res::Def(DefKind::ConstParam, def_id) = path.res {
1943 let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
1944 let item_id = tcx.hir().get_parent_node(node_id);
1945 let item_def_id = tcx.hir().local_def_id(item_id);
1946 let generics = tcx.generics_of(item_def_id);
1947 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(node_id)];
1948 let name = tcx.hir().name(node_id).as_interned_str();
1949 const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
1954 tcx.mk_const(const_)
1957 pub fn impl_trait_ty_to_ty(
1960 lifetimes: &[hir::GenericArg],
1962 debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
1963 let tcx = self.tcx();
1965 let generics = tcx.generics_of(def_id);
1967 debug!("impl_trait_ty_to_ty: generics={:?}", generics);
1968 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
1969 if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
1970 // Our own parameters are the resolved lifetimes.
1972 GenericParamDefKind::Lifetime => {
1973 if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
1974 self.ast_region_to_region(lifetime, None).into()
1982 // Replace all parent lifetimes with 'static.
1984 GenericParamDefKind::Lifetime => {
1985 tcx.lifetimes.re_static.into()
1987 _ => tcx.mk_param_from_def(param)
1991 debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
1993 let ty = tcx.mk_opaque(def_id, substs);
1994 debug!("impl_trait_ty_to_ty: {}", ty);
1998 pub fn ty_of_arg(&self,
2000 expected_ty: Option<Ty<'tcx>>)
2004 hir::TyKind::Infer if expected_ty.is_some() => {
2005 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
2006 expected_ty.unwrap()
2008 _ => self.ast_ty_to_ty(ty),
2012 pub fn ty_of_fn(&self,
2013 unsafety: hir::Unsafety,
2016 -> ty::PolyFnSig<'tcx> {
2019 let tcx = self.tcx();
2021 decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
2023 let output_ty = match decl.output {
2024 hir::Return(ref output) => self.ast_ty_to_ty(output),
2025 hir::DefaultReturn(..) => tcx.mk_unit(),
2028 debug!("ty_of_fn: output_ty={:?}", output_ty);
2030 let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
2038 // Find any late-bound regions declared in return type that do
2039 // not appear in the arguments. These are not well-formed.
2042 // for<'a> fn() -> &'a str <-- 'a is bad
2043 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
2044 let inputs = bare_fn_ty.inputs();
2045 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
2046 &inputs.map_bound(|i| i.to_owned()));
2047 let output = bare_fn_ty.output();
2048 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
2049 for br in late_bound_in_ret.difference(&late_bound_in_args) {
2050 let lifetime_name = match *br {
2051 ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
2052 ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
2054 let mut err = struct_span_err!(tcx.sess,
2057 "return type references {} \
2058 which is not constrained by the fn input types",
2060 if let ty::BrAnon(_) = *br {
2061 // The only way for an anonymous lifetime to wind up
2062 // in the return type but **also** be unconstrained is
2063 // if it only appears in "associated types" in the
2064 // input. See #47511 for an example. In this case,
2065 // though we can easily give a hint that ought to be
2067 err.note("lifetimes appearing in an associated type \
2068 are not considered constrained");
2076 /// Given the bounds on an object, determines what single region bound (if any) we can
2077 /// use to summarize this type. The basic idea is that we will use the bound the user
2078 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
2079 /// for region bounds. It may be that we can derive no bound at all, in which case
2080 /// we return `None`.
2081 fn compute_object_lifetime_bound(&self,
2083 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
2084 -> Option<ty::Region<'tcx>> // if None, use the default
2086 let tcx = self.tcx();
2088 debug!("compute_opt_region_bound(existential_predicates={:?})",
2089 existential_predicates);
2091 // No explicit region bound specified. Therefore, examine trait
2092 // bounds and see if we can derive region bounds from those.
2093 let derived_region_bounds =
2094 object_region_bounds(tcx, existential_predicates);
2096 // If there are no derived region bounds, then report back that we
2097 // can find no region bound. The caller will use the default.
2098 if derived_region_bounds.is_empty() {
2102 // If any of the derived region bounds are 'static, that is always
2104 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
2105 return Some(tcx.lifetimes.re_static);
2108 // Determine whether there is exactly one unique region in the set
2109 // of derived region bounds. If so, use that. Otherwise, report an
2111 let r = derived_region_bounds[0];
2112 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
2113 span_err!(tcx.sess, span, E0227,
2114 "ambiguous lifetime bound, explicit lifetime bound required");
2120 // A helper struct for conveniently grouping a set of bounds which we pass to
2121 // and return from functions in multiple places.
2122 #[derive(PartialEq, Eq, Clone, Debug)]
2123 pub struct Bounds<'tcx> {
2124 pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
2125 pub implicitly_sized: Option<Span>,
2126 pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
2127 pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
2130 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
2131 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
2132 -> Vec<(ty::Predicate<'tcx>, Span)>
2134 // If it could be sized, and is, add the `Sized` predicate.
2135 let sized_predicate = self.implicitly_sized.and_then(|span| {
2136 tcx.lang_items().sized_trait().map(|sized| {
2137 let trait_ref = ty::TraitRef {
2139 substs: tcx.mk_substs_trait(param_ty, &[])
2141 (trait_ref.to_predicate(), span)
2145 sized_predicate.into_iter().chain(
2146 self.region_bounds.iter().map(|&(region_bound, span)| {
2147 // Account for the binder being introduced below; no need to shift `param_ty`
2148 // because, at present at least, it can only refer to early-bound regions.
2149 let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
2150 let outlives = ty::OutlivesPredicate(param_ty, region_bound);
2151 (ty::Binder::dummy(outlives).to_predicate(), span)
2153 self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
2154 (bound_trait_ref.to_predicate(), span)
2157 self.projection_bounds.iter().map(|&(projection, span)| {
2158 (projection.to_predicate(), span)