31 lines
895 B
Rust
31 lines
895 B
Rust
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// compile-flags: -Ztrait-solver=next
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// When we're solving `<T as Foo>::Assoc = i32`, we actually first solve
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// `<T as Foo>::Assoc = _#1t`, then unify `_#1t` with `i32`. That goal
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// with the inference variable is ambiguous when there are >1 param-env
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// candidates.
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// We don't unify the RHS of a projection goal eagerly when solving, both
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// for caching reasons and partly to make sure that we don't make the new
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// trait solver smarter than it should be.
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// This is (as far as I can tell) a forwards-compatible decision, but if you
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// make this test go from fail to pass, be sure you understand the implications!
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trait Foo {
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type Assoc;
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}
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trait Bar {}
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impl<T> Bar for T where T: Foo<Assoc = i32> {}
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fn needs_bar<T: Bar>() {}
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fn foo<T: Foo<Assoc = i32> + Foo<Assoc = u32>>() {
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needs_bar::<T>();
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//~^ ERROR type annotations needed: cannot satisfy `T: Bar`
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}
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fn main() {}
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