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Rollup merge of #106747 - yanchen4791:issue-105507-fix, r=estebank
Add 'static lifetime suggestion when GAT implied 'static requirement from HRTB Fix for issue #105507 The problem: When generic associated types (GATs) are from higher-ranked trait bounds (HRTB), they are implied 'static requirement (see [Implied 'static requirement from higher-ranked trait bounds](https://blog.rust-lang.org/2022/10/28/gats-stabilization.html#implied-static-requirement-from-higher-ranked-trait-bounds) for more details). If the user did not explicitly specify the `'static` lifetime when using the GAT, the current error message will only point out the type `does not live long enough` where the type is used, but not where the GAT is specified and how to fix the problem. The solution: Add notes at the span where the problematic GATs are specified and suggestions of how to fix the problem by adding `'static` lifetime at the right spans.
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Original file line number | Diff line number | Diff line change |
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// run-rustfix | ||
// | ||
#![allow(warnings)] | ||
struct Wrapper<'a, T: ?Sized>(&'a T); | ||
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trait Project { | ||
type Projected<'a> where Self: 'a; | ||
fn project(this: Wrapper<'_, Self>) -> Self::Projected<'_>; | ||
} | ||
trait MyTrait {} | ||
trait ProjectedMyTrait {} | ||
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impl<T> Project for Option<T> { | ||
type Projected<'a> = Option<Wrapper<'a, T>> where T: 'a; | ||
fn project(this: Wrapper<'_, Self>) -> Self::Projected<'_> { | ||
this.0.as_ref().map(Wrapper) | ||
} | ||
} | ||
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impl<T: MyTrait> MyTrait for Option<Wrapper<'_, T>> {} | ||
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impl<T: ProjectedMyTrait> MyTrait for Wrapper<'_, T> {} | ||
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impl<T> ProjectedMyTrait for T | ||
where | ||
T: Project, | ||
for<'a> T::Projected<'a>: MyTrait, | ||
//~^ NOTE due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
//~| NOTE due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
{} | ||
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fn require_trait<T: MyTrait>(_: T) {} | ||
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fn foo<T : MyTrait + 'static + 'static, U : MyTrait + 'static + 'static>(wrap: Wrapper<'_, Option<T>>, wrap1: Wrapper<'_, Option<U>>) { | ||
//~^ HELP consider restricting the type parameter to the `'static` lifetime | ||
//~| HELP consider restricting the type parameter to the `'static` lifetime | ||
require_trait(wrap); | ||
//~^ ERROR `T` does not live long enough | ||
require_trait(wrap1); | ||
//~^ ERROR `U` does not live long enough | ||
} | ||
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fn main() {} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,43 @@ | ||
// run-rustfix | ||
// | ||
#![allow(warnings)] | ||
struct Wrapper<'a, T: ?Sized>(&'a T); | ||
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||
trait Project { | ||
type Projected<'a> where Self: 'a; | ||
fn project(this: Wrapper<'_, Self>) -> Self::Projected<'_>; | ||
} | ||
trait MyTrait {} | ||
trait ProjectedMyTrait {} | ||
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||
impl<T> Project for Option<T> { | ||
type Projected<'a> = Option<Wrapper<'a, T>> where T: 'a; | ||
fn project(this: Wrapper<'_, Self>) -> Self::Projected<'_> { | ||
this.0.as_ref().map(Wrapper) | ||
} | ||
} | ||
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impl<T: MyTrait> MyTrait for Option<Wrapper<'_, T>> {} | ||
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impl<T: ProjectedMyTrait> MyTrait for Wrapper<'_, T> {} | ||
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impl<T> ProjectedMyTrait for T | ||
where | ||
T: Project, | ||
for<'a> T::Projected<'a>: MyTrait, | ||
//~^ NOTE due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
//~| NOTE due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
{} | ||
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fn require_trait<T: MyTrait>(_: T) {} | ||
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fn foo<T : MyTrait, U : MyTrait>(wrap: Wrapper<'_, Option<T>>, wrap1: Wrapper<'_, Option<U>>) { | ||
//~^ HELP consider restricting the type parameter to the `'static` lifetime | ||
//~| HELP consider restricting the type parameter to the `'static` lifetime | ||
require_trait(wrap); | ||
//~^ ERROR `T` does not live long enough | ||
require_trait(wrap1); | ||
//~^ ERROR `U` does not live long enough | ||
} | ||
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fn main() {} |
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Original file line number | Diff line number | Diff line change |
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error: `T` does not live long enough | ||
--> $DIR/issue-105507.rs:37:5 | ||
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LL | require_trait(wrap); | ||
| ^^^^^^^^^^^^^^^^^^^ | ||
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note: due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
--> $DIR/issue-105507.rs:27:35 | ||
| | ||
LL | for<'a> T::Projected<'a>: MyTrait, | ||
| ^^^^^^^ | ||
help: consider restricting the type parameter to the `'static` lifetime | ||
| | ||
LL | fn foo<T : MyTrait + 'static, U : MyTrait + 'static>(wrap: Wrapper<'_, Option<T>>, wrap1: Wrapper<'_, Option<U>>) { | ||
| +++++++++ +++++++++ | ||
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error: `U` does not live long enough | ||
--> $DIR/issue-105507.rs:39:5 | ||
| | ||
LL | require_trait(wrap1); | ||
| ^^^^^^^^^^^^^^^^^^^^ | ||
| | ||
note: due to current limitations in the borrow checker, this implies a `'static` lifetime | ||
--> $DIR/issue-105507.rs:27:35 | ||
| | ||
LL | for<'a> T::Projected<'a>: MyTrait, | ||
| ^^^^^^^ | ||
help: consider restricting the type parameter to the `'static` lifetime | ||
| | ||
LL | fn foo<T : MyTrait + 'static, U : MyTrait + 'static>(wrap: Wrapper<'_, Option<T>>, wrap1: Wrapper<'_, Option<U>>) { | ||
| +++++++++ +++++++++ | ||
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error: aborting due to 2 previous errors | ||
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