27 lines
741 B
Rust
27 lines
741 B
Rust
//@ run-pass
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#![allow(dead_code)]
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#![allow(unused_variables)]
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// Test that when we match a trait reference like `Foo<A>: Foo<?0t>`,
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// we unify with `?0t` with `A`. In this code, if we failed to do
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// that, then you get an unconstrained type-variable in `call`.
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//
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// Also serves as a regression test for issue #26952, though the test
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// was derived from another reported regression with the same cause.
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use std::marker::PhantomData;
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trait Trait<A> { fn foo(&self); }
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struct Type<A> { a: PhantomData<A> }
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fn as_trait<A>(t: &Type<A>) -> &dyn Trait<A> { loop { } }
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fn want<A,T:Trait<A>+?Sized>(t: &T) { }
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fn call<A>(p: Type<A>) {
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let q = as_trait(&p);
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want(q); // parameter A to `want` *would* be unconstrained
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}
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fn main() { }
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