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#![feature(precise_capturing_in_traits)]
trait LifetimeParam<'a> {
fn test() -> impl Sized;
}
// Refining via capturing fewer lifetimes than the trait definition.
impl<'a> LifetimeParam<'a> for i32 {
fn test() -> impl Sized + use<> {}
//~^ WARN impl trait in impl method captures fewer lifetimes than in trait
}
// If the lifetime is substituted, then we don't refine anything.
impl LifetimeParam<'static> for u32 {
fn test() -> impl Sized + use<> {}
// Ok
}
trait TypeParam<T> {
fn test() -> impl Sized;
}
// Indirectly capturing a lifetime param through a type param substitution.
impl<'a> TypeParam<&'a ()> for i32 {
fn test() -> impl Sized + use<> {}
//~^ WARN impl trait in impl method captures fewer lifetimes than in trait
}
// Two of them, but only one is captured...
impl<'a, 'b> TypeParam<(&'a (), &'b ())> for u32 {
fn test() -> impl Sized + use<'b> {}
//~^ WARN impl trait in impl method captures fewer lifetimes than in trait
}
// What if we don't capture a type param? That should be an error otherwise.
impl<T> TypeParam<T> for u64 {
fn test() -> impl Sized + use<> {}
//~^ ERROR `impl Trait` must mention all type parameters in scope in `use<...>`
}
fn main() {}
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