42 lines
1.3 KiB
Rust
42 lines
1.3 KiB
Rust
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// 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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// Check that when there are vacuous predicates in the environment
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// (which make a fn uncallable) we don't erroneously cache those and
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// then consider them satisfied elsewhere. The current technique for
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// doing this is just to filter "global" predicates out of the
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// environment, which means that we wind up with an error in the
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// function `vacuous`, because even though `i32: Bar<u32>` is implied
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// by its where clause, that where clause never holds.
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trait Foo<X,Y>: Bar<X> {
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}
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trait Bar<X> { }
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fn vacuous<A>()
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where i32: Foo<u32, A>
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{
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// vacuous could never be called, because it requires that i32:
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// Bar<u32>. But the code doesn't check that this could never be
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// satisfied.
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require::<i32, u32>();
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//~^ ERROR the trait `Bar<u32>` is not implemented for the type `i32`
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}
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fn require<A,B>()
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where A: Bar<B>
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{
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}
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fn main() {
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require::<i32, u32>();
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}
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