63 lines
1.3 KiB
Rust
63 lines
1.3 KiB
Rust
trait Foo<A> {
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fn get(&self, A: &A) { }
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}
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trait Bar {
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type Out;
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}
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impl<T> Foo<T> for [isize;0] {
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// OK, T is used in `Foo<T>`.
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}
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impl<T,U> Foo<T> for [isize;1] {
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//~^ ERROR the type parameter `U` is not constrained
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}
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impl<T,U> Foo<T> for [isize;2] where T : Bar<Out=U> {
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// OK, `U` is now constrained by the output type parameter.
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}
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impl<T:Bar<Out=U>,U> Foo<T> for [isize;3] {
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// OK, same as above but written differently.
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}
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impl<T,U> Foo<T> for U {
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// OK, T, U are used everywhere. Note that the coherence check
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// hasn't executed yet, so no errors about overlap.
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}
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impl<T,U> Bar for T {
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//~^ ERROR the type parameter `U` is not constrained
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type Out = U;
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// Using `U` in an associated type within the impl is not good enough!
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}
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impl<T,U> Bar for T
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where T : Bar<Out=U>
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{
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//~^^^ ERROR the type parameter `U` is not constrained
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// This crafty self-referential attempt is still no good.
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}
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impl<T,U,V> Foo<T> for T
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where (T,U): Bar<Out=V>
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{
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//~^^^ ERROR the type parameter `U` is not constrained
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//~| ERROR the type parameter `V` is not constrained
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// Here, `V` is bound by an output type parameter, but the inputs
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// are not themselves constrained.
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}
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impl<T,U,V> Foo<(T,U)> for T
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where (T,U): Bar<Out=V>
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{
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// As above, but both T and U ARE constrained.
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}
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fn main() { }
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