Cannot use the associated type of a trait with uninferred generic parameters.
Erroneous code example:
pub trait Foo<T> {
type A;
fn get(&self, t: T) -> Self::A;
}
fn foo2<I : for<'x> Foo<&'x isize>>(
field: I::A) {} // error!In this example, we have to instantiate 'x, and
we don’t know what lifetime to instantiate it with.
To fix this, spell out the precise lifetimes involved.
Example:
pub trait Foo<T> {
type A;
fn get(&self, t: T) -> Self::A;
}
fn foo3<I : for<'x> Foo<&'x isize>>(
x: <I as Foo<&isize>>::A) {} // ok!
fn foo4<'a, I : for<'x> Foo<&'x isize>>(
x: <I as Foo<&'a isize>>::A) {} // ok!