4726bb46b0
the object trait matches the required trait during trait selection. The existing code was checking that the object trait WOULD match (in a probe), but never executing the match outside of a probe. This corrects various regressions observed in the wild, including issue #26952. Fixes #26952.
34 lines
1.1 KiB
Rust
34 lines
1.1 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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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>) -> &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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