bc9ae36dba
us to construct trait-references and do other things without forcing a full evaluation of the supertraits. One downside of this scheme is that we must invoke `ensure_super_predicates` before using any construct that might require knowing about the super-predicates.
35 lines
1.1 KiB
Rust
35 lines
1.1 KiB
Rust
// Copyright 2015 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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// Example cycle where a bound on `T` uses a shorthand for `T`. This
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// creates a cycle because we have to know the bounds on `T` to figure
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// out what trait defines `Item`, but we can't know the bounds on `T`
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// without knowing how to handle `T::Item`.
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//
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// Note that in the future cases like this could perhaps become legal,
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// if we got more fine-grained about our cycle detection or changed
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// how we handle `T::Item` resolution.
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use std::ops::Add;
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// Preamble.
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trait Trait { type Item; }
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struct A<T>
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where T : Trait,
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T : Add<T::Item>
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//~^ ERROR unsupported cyclic reference between types/traits detected
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{
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data: T
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}
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fn main() {
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}
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