substitutions in trait predicates
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b-naber
parent
760a6654fb
commit
da2cf9b9d1
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@ -112,12 +112,15 @@ pub enum SizedByDefault {
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No,
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}
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#[derive(Debug)]
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struct ConvertedBinding<'a, 'tcx> {
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item_name: Ident,
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kind: ConvertedBindingKind<'a, 'tcx>,
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gen_args: &'a GenericArgs<'a>,
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span: Span,
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}
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#[derive(Debug)]
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enum ConvertedBindingKind<'a, 'tcx> {
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Equality(Ty<'tcx>),
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Constraint(&'a [hir::GenericBound<'a>]),
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@ -323,6 +326,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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let tcx = self.tcx();
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let generics = tcx.generics_of(def_id);
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debug!("generics: {:?}", generics);
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if generics.has_self {
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if generics.parent.is_some() {
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@ -557,7 +561,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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ConvertedBindingKind::Constraint(bounds)
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}
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};
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ConvertedBinding { item_name: binding.ident, kind, span: binding.span }
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ConvertedBinding {
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item_name: binding.ident,
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kind,
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gen_args: binding.gen_args,
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span: binding.span,
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}
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})
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.collect();
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@ -918,61 +927,28 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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dup_bindings: &mut FxHashMap<DefId, Span>,
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path_span: Span,
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) -> Result<(), ErrorReported> {
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// Given something like `U: SomeTrait<T = X>`, we want to produce a
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// predicate like `<U as SomeTrait>::T = X`. This is somewhat
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// subtle in the event that `T` is defined in a supertrait of
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// `SomeTrait`, because in that case we need to upcast.
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//
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// That is, consider this case:
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//
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// ```
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// trait SubTrait: SuperTrait<i32> { }
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// trait SuperTrait<A> { type T; }
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//
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// ... B: SubTrait<T = foo> ...
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// ```
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//
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// We want to produce `<B as SuperTrait<i32>>::T == foo`.
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debug!(
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"add_predicates_for_ast_type_binding(hir_ref_id {:?}, trait_ref {:?}, binding {:?}, bounds {:?}",
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hir_ref_id, trait_ref, binding, bounds
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);
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let tcx = self.tcx();
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if !speculative {
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// Given something like `U: SomeTrait<T = X>`, we want to produce a
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// predicate like `<U as SomeTrait>::T = X`. This is somewhat
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// subtle in the event that `T` is defined in a supertrait of
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// `SomeTrait`, because in that case we need to upcast.
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//
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// That is, consider this case:
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//
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// ```
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// trait SubTrait: SuperTrait<i32> { }
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// trait SuperTrait<A> { type T; }
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//
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// ... B: SubTrait<T = foo> ...
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// ```
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//
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// We want to produce `<B as SuperTrait<i32>>::T == foo`.
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// Find any late-bound regions declared in `ty` that are not
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// declared in the trait-ref. These are not well-formed.
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//
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// Example:
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//
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// for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
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// for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
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if let ConvertedBindingKind::Equality(ty) = binding.kind {
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let late_bound_in_trait_ref =
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tcx.collect_constrained_late_bound_regions(&trait_ref);
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let late_bound_in_ty =
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tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(ty));
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debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
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debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
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// FIXME: point at the type params that don't have appropriate lifetimes:
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// struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F);
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// ---- ---- ^^^^^^^
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self.validate_late_bound_regions(
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late_bound_in_trait_ref,
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late_bound_in_ty,
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|br_name| {
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struct_span_err!(
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tcx.sess,
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binding.span,
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E0582,
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"binding for associated type `{}` references {}, \
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which does not appear in the trait input types",
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binding.item_name,
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br_name
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)
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},
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);
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}
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}
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let candidate =
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if self.trait_defines_associated_type_named(trait_ref.def_id(), binding.item_name) {
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// Simple case: X is defined in the current trait.
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@ -1030,6 +1006,72 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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.or_insert(binding.span);
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}
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// Include substitutions for generic parameters of associated types
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let projection_ty = candidate.map_bound(|trait_ref| {
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let item_segment = hir::PathSegment {
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ident: assoc_ty.ident,
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hir_id: None,
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res: None,
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args: Some(binding.gen_args),
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infer_args: false,
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};
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let substs_trait_ref_and_assoc_item = self.create_substs_for_associated_item(
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tcx,
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path_span,
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assoc_ty.def_id,
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&item_segment,
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trait_ref.substs,
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);
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debug!(
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"add_predicates_for_ast_type_binding: substs for trait-ref and assoc_item: {:?}",
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substs_trait_ref_and_assoc_item
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);
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ty::ProjectionTy {
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item_def_id: assoc_ty.def_id,
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substs: substs_trait_ref_and_assoc_item,
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}
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});
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if !speculative {
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// Find any late-bound regions declared in `ty` that are not
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// declared in the trait-ref or assoc_ty. These are not well-formed.
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//
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// Example:
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//
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// for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
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// for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
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if let ConvertedBindingKind::Equality(ty) = binding.kind {
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let late_bound_in_trait_ref =
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tcx.collect_constrained_late_bound_regions(&projection_ty);
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let late_bound_in_ty =
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tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(ty));
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debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
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debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
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// FIXME: point at the type params that don't have appropriate lifetimes:
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// struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F);
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// ---- ---- ^^^^^^^
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self.validate_late_bound_regions(
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late_bound_in_trait_ref,
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late_bound_in_ty,
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|br_name| {
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struct_span_err!(
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tcx.sess,
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binding.span,
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E0582,
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"binding for associated type `{}` references {}, \
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which does not appear in the trait input types",
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binding.item_name,
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br_name
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)
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},
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);
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}
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}
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match binding.kind {
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ConvertedBindingKind::Equality(ref ty) => {
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// "Desugar" a constraint like `T: Iterator<Item = u32>` this to
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@ -1037,13 +1079,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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//
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// `<T as Iterator>::Item = u32`
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bounds.projection_bounds.push((
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candidate.map_bound(|trait_ref| ty::ProjectionPredicate {
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projection_ty: ty::ProjectionTy::from_ref_and_name(
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tcx,
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trait_ref,
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binding.item_name,
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),
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ty,
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projection_ty.map_bound(|projection_ty| {
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debug!(
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"add_predicates_for_ast_type_binding: projection_ty {:?}, substs: {:?}",
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projection_ty, projection_ty.substs
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);
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ty::ProjectionPredicate { projection_ty, ty }
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}),
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binding.span,
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));
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@ -1055,7 +1096,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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//
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// Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty`
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// parameter to have a skipped binder.
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let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);
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let param_ty =
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tcx.mk_projection(assoc_ty.def_id, projection_ty.skip_binder().substs);
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self.add_bounds(param_ty, ast_bounds, bounds);
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}
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}
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