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Suggest named lifetime in ADT with hrtb

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This commit is contained in:
Esteban Küber 2020-02-11 12:37:12 -08:00
parent 24be307b53
commit bde96776a1
3 changed files with 87 additions and 10 deletions
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52
src/librustc_typeck/collect.rs
View File

@ -364,14 +364,52 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
);
match self.node() {
hir::Node::Field(_)
| hir::Node::Variant(_)
| hir::Node::Ctor(_)
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(..), .. }) => {
// The suggestion is only valid if this is not an ADT.
hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
let item =
self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
match &item.kind {
hir::ItemKind::Enum(_, generics)
| hir::ItemKind::Struct(_, generics)
| hir::ItemKind::Union(_, generics) => {
// FIXME: look for an appropriate lt name if `'a` is already used
let (lt_sp, sugg) = match &generics.params[..] {
[] => (generics.span, "<'a>".to_string()),
[bound, ..] => (bound.span.shrink_to_lo(), "'a, ".to_string()),
};
let suggestions = vec![
(lt_sp, sugg),
(
span,
format!(
"{}::{}",
// Replace the existing lifetimes with a new named lifetime.
self.tcx
.replace_late_bound_regions(&poly_trait_ref, |_| {
self.tcx.mk_region(ty::ReEarlyBound(
ty::EarlyBoundRegion {
def_id: item_def_id,
index: 0,
name: Symbol::intern("'a"),
},
))
})
.0,
item_segment.ident
),
),
];
err.multipart_suggestion(
"use a fully qualified path with explicit lifetimes",
suggestions,
Applicability::MaybeIncorrect,
);
}
_ => {}
}
}
hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(..), .. })
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(..), .. }) => {}
hir::Node::Item(_)
| hir::Node::ForeignItem(_)
| hir::Node::TraitItem(_)

11
src/test/ui/associated-types/associated-types-project-from-hrtb-in-struct.rs
View File

@ -7,18 +7,25 @@ pub trait Foo<T> {
fn get(&self, t: T) -> Self::A;
}
struct SomeStruct<I : for<'x> Foo<&'x isize>> {
struct SomeStruct<I: for<'x> Foo<&'x isize>> {
field: I::A
//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
}
enum SomeEnum<I: for<'x> Foo<&'x isize>> {
TupleVariant(I::A),
//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
StructVariant { field: I::A },
//~^ ERROR cannot extract an associated type from a higher-ranked trait bound in this context
}
// FIXME(eddyb) This one doesn't even compile because of the unsupported syntax.
// struct AnotherStruct<I : for<'x> Foo<&'x isize>> {
// field: <I as for<'y> Foo<&'y isize>>::A
// }
struct YetAnotherStruct<'a, I : for<'x> Foo<&'x isize>> {
struct YetAnotherStruct<'a, I: for<'x> Foo<&'x isize>> {
field: <I as Foo<&'a isize>>::A
}

34
src/test/ui/associated-types/associated-types-project-from-hrtb-in-struct.stderr
View File

@ -3,6 +3,38 @@ error[E0212]: cannot extract an associated type from a higher-ranked trait bound
|
LL | field: I::A
| ^^^^
|
help: use a fully qualified path with explicit lifetimes
|
LL | struct SomeStruct<'a, I: for<'x> Foo<&'x isize>> {
LL | field: <I as Foo<&'a isize>>::A
|
error: aborting due to previous error
error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
--> $DIR/associated-types-project-from-hrtb-in-struct.rs:16:18
|
LL | TupleVariant(I::A),
| ^^^^
|
help: use a fully qualified path with explicit lifetimes
|
LL | enum SomeEnum<'a, I: for<'x> Foo<&'x isize>> {
LL | TupleVariant(<I as Foo<&'a isize>>::A),
|
error[E0212]: cannot extract an associated type from a higher-ranked trait bound in this context
--> $DIR/associated-types-project-from-hrtb-in-struct.rs:18:28
|
LL | StructVariant { field: I::A },
| ^^^^
|
help: use a fully qualified path with explicit lifetimes
|
LL | enum SomeEnum<'a, I: for<'x> Foo<&'x isize>> {
LL | TupleVariant(I::A),
LL |
LL | StructVariant { field: <I as Foo<&'a isize>>::A },
|
error: aborting due to 3 previous errors