Implementation with existential lifetime issue

[zakarumych]

I believe the next code should compile:

trait Trait<'a> {}
struct SomeType<'a> { data: &'a str }
impl<'a, 'b: 'a> Trait<'a> for SomeType<'b> {}

fn foo<T: for<'a> Trait<'a>>(t: T) {}

fn main() {
    let data = "qwerty";
    let some_type: SomeType<'static> = SomeType { data: data };
    foo(some_type);
}

Because 'static: 'a for any 'a
Or, maybe I missed something?

[zakarumych]

Of course if implementation could be rewritten as such impl<'a, 'b> Trait<'a> for SomeType<'b> {}. i.e. removing relation between 'b and 'a. Than this synthetic example would compile. But it could be impossible in many cases.

[nikomatsakis]

I agree it should compile; there are some long-standing issues with our handling of for<> bounds. The plan is to clean up them via a larger initiative (rust-lang/rust-roadmap-2017#8).

[cjgillot]

This now compiles.