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Suggest Explicit Lifetime for Associated Type Bindings #123245

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Suggest Explicit Lifetime for Associated Type Bindings #123245

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d5113ef
Add tests
veera-sivarajan Mar 30, 2024
169b379
Suggest Explicit Lifetime for Associated Type Bindings
veera-sivarajan Mar 30, 2024
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56 changes: 47 additions & 9 deletions compiler/rustc_resolve/src/late.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1634,7 +1634,6 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
#[instrument(level = "debug", skip(self))]
fn resolve_anonymous_lifetime(&mut self, lifetime: &Lifetime, elided: bool) {
debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);

let kind =
if elided { MissingLifetimeKind::Ampersand } else { MissingLifetimeKind::Underscore };
let missing_lifetime =
Expand Down Expand Up @@ -1685,14 +1684,53 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
..
} = &rib.kind
{
diag.multipart_suggestion(
"consider introducing a higher-ranked lifetime here",
vec![
(span.shrink_to_lo(), "for<'a> ".into()),
(lifetime.ident.span.shrink_to_hi(), "'a ".into()),
],
Applicability::MachineApplicable,
);
// hacky way to check if lifetime suggestion is for
// an associated type binding
let is_associated_type_binding = lifetime.ident.span
!= self.r.tcx.sess.source_map().span_extend_to_prev_char(
lifetime.ident.span,
'=',
false,
);
if is_associated_type_binding {
for upper_rib in self.lifetime_ribs[0..i].iter().rev() {
if let LifetimeRibKind::Generics {
kind: LifetimeBinderKind::Function,
span: function_span,
..
} = upper_rib.kind
{
let type_parameter_span = self
.r
.tcx
.sess
.source_map()
.span_through_char(function_span, '<')
.shrink_to_hi();
diag.multipart_suggestion(
"consider adding an explicit lifetime here",
vec![
(type_parameter_span, "'a, ".into()),
(
lifetime.ident.span.shrink_to_hi(),
"'a ".into(),
),
],
Applicability::MaybeIncorrect,
);
break;
}
}
} else {
diag.multipart_suggestion(
"consider introducing a higher-ranked lifetime here",
vec![
(span.shrink_to_lo(), "for<'a> ".into()),
(lifetime.ident.span.shrink_to_hi(), "'a ".into()),
],
Applicability::MachineApplicable,
);
}
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There is existing diagnostic code in rustc_resolve::late::diagnostics. We should adapt and reuse add_missing_lifetime_specifiers_label and suggest_introducing_lifetime.

break;
}
}
Expand Down
28 changes: 28 additions & 0 deletions tests/ui/lifetimes/suggest-explicit-lifetime-for-associated-types-issue-122025.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
struct MyType;

fn foo<F>()
where
F: Iterator<Item = &MyType>, //~ `&` without an explicit lifetime name cannot be used here
{
}

fn bar() {
fn baz<F>()
where
F: Iterator<Item = &MyType>, //~ `&` without an explicit lifetime name cannot be used here
{
}
}

fn function<T>()
where
T: Iterator<Item = &MyType>, //~ `&` without an explicit lifetime name cannot be used here
{
fn lambda<A>()
where
A: Iterator<Item = &u8>, //~ `&` without an explicit lifetime name cannot be used here
{
}
}

fn main() {}
55 changes: 55 additions & 0 deletions tests/ui/lifetimes/suggest-explicit-lifetime-for-associated-types-issue-122025.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/suggest-explicit-lifetime-for-associated-types-issue-122025.rs:5:24
|
LL | F: Iterator<Item = &MyType>,
| ^ explicit lifetime name needed here
|
help: consider adding an explicit lifetime here
|
LL ~ fn foo<'a, F>()
LL | where
LL ~ F: Iterator<Item = &'a MyType>,
|

error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/suggest-explicit-lifetime-for-associated-types-issue-122025.rs:12:28
|
LL | F: Iterator<Item = &MyType>,
| ^ explicit lifetime name needed here
|
help: consider adding an explicit lifetime here
|
LL ~ fn baz<'a, F>()
LL | where
LL ~ F: Iterator<Item = &'a MyType>,
|

error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/suggest-explicit-lifetime-for-associated-types-issue-122025.rs:19:24
|
LL | T: Iterator<Item = &MyType>,
| ^ explicit lifetime name needed here
|
help: consider adding an explicit lifetime here
|
LL ~ fn function<'a, T>()
LL | where
LL ~ T: Iterator<Item = &'a MyType>,
|

error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/suggest-explicit-lifetime-for-associated-types-issue-122025.rs:23:28
|
LL | A: Iterator<Item = &u8>,
| ^ explicit lifetime name needed here
|
help: consider adding an explicit lifetime here
|
LL ~ fn lambda<'a, A>()
LL | where
LL ~ A: Iterator<Item = &'a u8>,
|

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0637`.
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