mirror of https://github.com/rust-lang/rust.git
70 lines
1.6 KiB
Rust
70 lines
1.6 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]
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where
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T: Bar<Out = U>,
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{
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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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//~^ ERROR conflicting implementations of trait `Foo<_>` for type `[isize; 0]`
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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
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T: Bar<Out = U>,
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{
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//~^^^^ ERROR the type parameter `U` is not constrained by the impl trait, self type, or predicates
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//~| ERROR conflicting implementations of trait `Bar`
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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
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(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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//~| ERROR conflicting implementations of trait `Foo<[isize; 0]>` for type `[isize; 0]`
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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
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(T, U): Bar<Out = V>,
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{
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//~^^^^ ERROR conflicting implementations of trait `Foo<([isize; 0], _)>` for type `[isize; 0]`
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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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