49 lines
1.6 KiB
Rust
49 lines
1.6 KiB
Rust
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// Copyright 2016 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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// Regression test for #30225, which was an ICE that would trigger as
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// a result of a poor interaction between trait result caching and
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// type inference. Specifically, at that time, unification could cause
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// unrelated type variables to become instantiated, if subtyping
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// relationships existed. These relationships are now propagated
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// through obligations and hence everything works out fine.
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trait Foo<U,V> : Sized {
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fn foo(self, u: Option<U>, v: Option<V>) {}
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}
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struct A;
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struct B;
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impl Foo<A, B> for () {} // impl A
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impl Foo<u32, u32> for u32 {} // impl B, creating ambiguity
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fn toxic() {
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// cache the resolution <() as Foo<$0,$1>> = impl A
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let u = None;
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let v = None;
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Foo::foo((), u, v);
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}
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fn bomb() {
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let mut u = None; // type is Option<$0>
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let mut v = None; // type is Option<$1>
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let mut x = None; // type is Option<$2>
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Foo::foo(x.unwrap(),u,v); // register <$2 as Foo<$0, $1>>
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u = v; // mark $0 and $1 in a subtype relationship
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//~^ ERROR mismatched types
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x = Some(()); // set $2 = (), allowing impl selection
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// to proceed for <() as Foo<$0, $1>> = impl A.
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// kaboom, this *used* to trigge an ICE
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}
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fn main() {}
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