70 lines
1.6 KiB
Rust
70 lines
1.6 KiB
Rust
trait Foo<A> {
|
|
fn get(&self, A: &A) {}
|
|
}
|
|
|
|
trait Bar {
|
|
type Out;
|
|
}
|
|
|
|
impl<T> Foo<T> for [isize; 0] {
|
|
// OK, T is used in `Foo<T>`.
|
|
}
|
|
|
|
impl<T, U> Foo<T> for [isize; 1] {
|
|
//~^ ERROR the type parameter `U` is not constrained
|
|
}
|
|
|
|
impl<T, U> Foo<T> for [isize; 2]
|
|
where
|
|
T: Bar<Out = U>,
|
|
{
|
|
// OK, `U` is now constrained by the output type parameter.
|
|
}
|
|
|
|
impl<T: Bar<Out = U>, U> Foo<T> for [isize; 3] {
|
|
// OK, same as above but written differently.
|
|
}
|
|
|
|
impl<T, U> Foo<T> for U {
|
|
//~^ ERROR conflicting implementations of trait `Foo<_>` for type `[isize; 0]`
|
|
}
|
|
|
|
impl<T, U> Bar for T {
|
|
//~^ ERROR the type parameter `U` is not constrained
|
|
|
|
type Out = U;
|
|
|
|
// Using `U` in an associated type within the impl is not good enough!
|
|
}
|
|
|
|
impl<T, U> Bar for T
|
|
where
|
|
T: Bar<Out = U>,
|
|
{
|
|
//~^^^^ ERROR the type parameter `U` is not constrained by the impl trait, self type, or predicates
|
|
//~| ERROR conflicting implementations of trait `Bar`
|
|
// This crafty self-referential attempt is still no good.
|
|
}
|
|
|
|
impl<T, U, V> Foo<T> for T
|
|
where
|
|
(T, U): Bar<Out = V>,
|
|
{
|
|
//~^^^^ ERROR the type parameter `U` is not constrained
|
|
//~| ERROR the type parameter `V` is not constrained
|
|
//~| ERROR conflicting implementations of trait `Foo<[isize; 0]>` for type `[isize; 0]`
|
|
|
|
// Here, `V` is bound by an output type parameter, but the inputs
|
|
// are not themselves constrained.
|
|
}
|
|
|
|
impl<T, U, V> Foo<(T, U)> for T
|
|
where
|
|
(T, U): Bar<Out = V>,
|
|
{
|
|
//~^^^^ ERROR conflicting implementations of trait `Foo<([isize; 0], _)>` for type `[isize; 0]`
|
|
// As above, but both T and U ARE constrained.
|
|
}
|
|
|
|
fn main() {}
|