Rollup merge of #69048 - estebank:hrlt-assoc, r=nagisa
Suggestion when encountering assoc types from hrtb When encountering E0212, detect whether this is a representable case or not, i.e. if it's happening on an `fn` or on an ADT. If the former, provide a structured suggestion, otherwise note that this can't be represented in Rust. Fix #69000.
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Dylan DPC
GitHub
commit
8d00adf289
9 changed files with 226 additions and 20 deletions
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@ -278,6 +278,17 @@ impl ItemCtxt<'tcx> {
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pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
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AstConv::ast_ty_to_ty(self, ast_ty)
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}
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pub fn hir_id(&self) -> hir::HirId {
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self.tcx
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.hir()
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.as_local_hir_id(self.item_def_id)
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.expect("Non-local call to local provider is_const_fn")
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}
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pub fn node(&self) -> hir::Node<'tcx> {
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self.tcx.hir().get(self.hir_id())
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}
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}
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impl AstConv<'tcx> for ItemCtxt<'tcx> {
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@ -290,15 +301,7 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
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}
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fn default_constness_for_trait_bounds(&self) -> ast::Constness {
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// FIXME: refactor this into a method
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let hir_id = self
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.tcx
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.hir()
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.as_local_hir_id(self.item_def_id)
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.expect("Non-local call to local provider is_const_fn");
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let node = self.tcx.hir().get(hir_id);
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if let Some(fn_like) = FnLikeNode::from_node(node) {
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if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
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fn_like.constness()
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} else {
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ast::Constness::NotConst
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@ -352,14 +355,80 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
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self.tcx().mk_projection(item_def_id, item_substs)
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} else {
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// There are no late-bound regions; we can just ignore the binder.
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struct_span_err!(
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let mut err = struct_span_err!(
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self.tcx().sess,
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span,
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E0212,
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"cannot extract an associated type from a higher-ranked trait bound \
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in this context"
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)
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.emit();
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);
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match self.node() {
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hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
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let item =
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self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
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match &item.kind {
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hir::ItemKind::Enum(_, generics)
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| hir::ItemKind::Struct(_, generics)
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| hir::ItemKind::Union(_, generics) => {
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// FIXME: look for an appropriate lt name if `'a` is already used
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let (lt_sp, sugg) = match &generics.params[..] {
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[] => (generics.span, "<'a>".to_string()),
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[bound, ..] => (bound.span.shrink_to_lo(), "'a, ".to_string()),
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};
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let suggestions = vec![
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(lt_sp, sugg),
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(
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span,
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format!(
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"{}::{}",
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// Replace the existing lifetimes with a new named lifetime.
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self.tcx
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.replace_late_bound_regions(&poly_trait_ref, |_| {
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self.tcx.mk_region(ty::ReEarlyBound(
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ty::EarlyBoundRegion {
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def_id: item_def_id,
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index: 0,
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name: Symbol::intern("'a"),
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},
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))
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})
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.0,
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item_segment.ident
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),
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),
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];
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err.multipart_suggestion(
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"use a fully qualified path with explicit lifetimes",
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suggestions,
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Applicability::MaybeIncorrect,
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);
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}
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_ => {}
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}
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}
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hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..), .. })
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| hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(..), .. })
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| hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(..), .. }) => {}
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hir::Node::Item(_)
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| hir::Node::ForeignItem(_)
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| hir::Node::TraitItem(_)
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| hir::Node::ImplItem(_) => {
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err.span_suggestion(
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span,
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"use a fully qualified path with inferred lifetimes",
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format!(
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"{}::{}",
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// Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
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self.tcx.anonymize_late_bound_regions(&poly_trait_ref).skip_binder(),
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item_segment.ident
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),
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Applicability::MaybeIncorrect,
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);
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}
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_ => {}
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}
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err.emit();
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self.tcx().types.err
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}
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}
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@ -0,0 +1,37 @@
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#![allow(dead_code, unused_variables)]
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// run-rustfix
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// Check projection of an associated type out of a higher-ranked trait-bound
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// in the context of a function signature.
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pub trait Foo<T> {
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type A;
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fn get(&self, t: T) -> Self::A;
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}
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fn foo2<I : for<'x> Foo<&'x isize>>(
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x: <I as Foo<&isize>>::A)
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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{
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// This case is illegal because we have to instantiate `'x`, and
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// we don't know what region to instantiate it with.
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//
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// This could perhaps be made equivalent to the examples below,
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// specifically for fn signatures.
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}
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fn foo3<I : for<'x> Foo<&'x isize>>(
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x: <I as Foo<&isize>>::A)
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{
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// OK, in this case we spelled out the precise regions involved, though we left one of
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// them anonymous.
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}
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fn foo4<'a, I : for<'x> Foo<&'x isize>>(
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x: <I as Foo<&'a isize>>::A)
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{
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// OK, in this case we spelled out the precise regions involved.
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}
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pub fn main() {}
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@ -1,3 +1,5 @@
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#![allow(dead_code, unused_variables)]
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// run-rustfix
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// Check projection of an associated type out of a higher-ranked trait-bound
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// in the context of a function signature.
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@ -1,8 +1,8 @@
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error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
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--> $DIR/associated-types-project-from-hrtb-in-fn.rs:11:8
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--> $DIR/associated-types-project-from-hrtb-in-fn.rs:13:8
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LL | x: I::A)
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| ^^^^
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| ^^^^ help: use a fully qualified path with inferred lifetimes: `<I as Foo<&isize>>::A`
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error: aborting due to previous error
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@ -7,18 +7,25 @@ pub trait Foo<T> {
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fn get(&self, t: T) -> Self::A;
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}
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struct SomeStruct<I : for<'x> Foo<&'x isize>> {
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struct SomeStruct<I: for<'x> Foo<&'x isize>> {
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field: I::A
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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}
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enum SomeEnum<I: for<'x> Foo<&'x isize>> {
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TupleVariant(I::A),
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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StructVariant { field: I::A },
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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}
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// FIXME(eddyb) This one doesn't even compile because of the unsupported syntax.
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// struct AnotherStruct<I : for<'x> Foo<&'x isize>> {
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// field: <I as for<'y> Foo<&'y isize>>::A
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// }
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struct YetAnotherStruct<'a, I : for<'x> Foo<&'x isize>> {
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struct YetAnotherStruct<'a, I: for<'x> Foo<&'x isize>> {
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field: <I as Foo<&'a isize>>::A
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}
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@ -3,6 +3,38 @@ error[E0212]: cannot extract an associated type from a higher-ranked trait bound
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LL | field: I::A
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| ^^^^
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help: use a fully qualified path with explicit lifetimes
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LL | struct SomeStruct<'a, I: for<'x> Foo<&'x isize>> {
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LL | field: <I as Foo<&'a isize>>::A
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error: aborting due to previous error
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error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
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--> $DIR/associated-types-project-from-hrtb-in-struct.rs:16:18
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LL | TupleVariant(I::A),
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| ^^^^
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help: use a fully qualified path with explicit lifetimes
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LL | enum SomeEnum<'a, I: for<'x> Foo<&'x isize>> {
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LL | TupleVariant(<I as Foo<&'a isize>>::A),
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error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
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--> $DIR/associated-types-project-from-hrtb-in-struct.rs:18:28
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LL | StructVariant { field: I::A },
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| ^^^^
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help: use a fully qualified path with explicit lifetimes
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LL | enum SomeEnum<'a, I: for<'x> Foo<&'x isize>> {
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LL | TupleVariant(I::A),
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LL |
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LL | StructVariant { field: <I as Foo<&'a isize>>::A },
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error: aborting due to 3 previous errors
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@ -0,0 +1,38 @@
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#![allow(dead_code)]
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// run-rustfix
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// Check projection of an associated type out of a higher-ranked trait-bound
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// in the context of a method definition in a trait.
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pub trait Foo<T> {
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type A;
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fn get(&self, t: T) -> Self::A;
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}
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trait SomeTrait<I : for<'x> Foo<&'x isize>> {
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fn some_method(&self, arg: <I as Foo<&isize>>::A);
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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}
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trait AnotherTrait<I : for<'x> Foo<&'x isize>> {
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fn some_method(&self, arg: <I as Foo<&isize>>::A);
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}
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trait YetAnotherTrait<I : for<'x> Foo<&'x isize>> {
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fn some_method<'a>(&self, arg: <I as Foo<&'a isize>>::A);
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}
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trait Banana<'a> {
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type Assoc: Default;
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}
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struct Peach<X>(std::marker::PhantomData<X>);
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impl<X: for<'a> Banana<'a>> Peach<X> {
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fn mango(&self) -> <X as Banana<'_>>::Assoc {
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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Default::default()
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}
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}
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pub fn main() {}
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@ -1,3 +1,5 @@
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#![allow(dead_code)]
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// run-rustfix
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// Check projection of an associated type out of a higher-ranked trait-bound
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// in the context of a method definition in a trait.
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@ -20,4 +22,17 @@ trait YetAnotherTrait<I : for<'x> Foo<&'x isize>> {
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fn some_method<'a>(&self, arg: <I as Foo<&'a isize>>::A);
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}
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trait Banana<'a> {
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type Assoc: Default;
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}
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struct Peach<X>(std::marker::PhantomData<X>);
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impl<X: for<'a> Banana<'a>> Peach<X> {
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fn mango(&self) -> X::Assoc {
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//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
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Default::default()
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}
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}
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pub fn main() {}
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@ -1,8 +1,14 @@
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error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
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--> $DIR/associated-types-project-from-hrtb-in-trait-method.rs:11:32
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--> $DIR/associated-types-project-from-hrtb-in-trait-method.rs:13:32
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LL | fn some_method(&self, arg: I::A);
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| ^^^^
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| ^^^^ help: use a fully qualified path with inferred lifetimes: `<I as Foo<&isize>>::A`
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error: aborting due to previous error
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error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
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--> $DIR/associated-types-project-from-hrtb-in-trait-method.rs:32:24
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LL | fn mango(&self) -> X::Assoc {
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| ^^^^^^^^ help: use a fully qualified path with inferred lifetimes: `<X as Banana<'_>>::Assoc`
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error: aborting due to 2 previous errors
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