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'_
in dyn Trait
just like ordinary elision
cc #48468
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
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// Check that the `'_` in `dyn Trait + '_` acts like ordinary elision, | ||
// and not like an object lifetime default. | ||
// | ||
// cc #48468 | ||
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#![feature(dyn_trait)] | ||
#![feature(underscore_lifetimes)] | ||
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fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> { | ||
// ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static` | ||
Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime | ||
} | ||
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fn b<T>(items: &[T]) -> Box<dyn Iterator<Item=&T> + '_> { | ||
Box::new(items.iter()) // OK, equivalent to c | ||
} | ||
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fn c<'a, T>(items: &'a [T]) -> Box<dyn Iterator<Item=&'a T> + 'a> { | ||
Box::new(items.iter()) // OK, equivalent to b | ||
} | ||
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fn main() { } |
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src/test/ui/underscore-lifetime/dyn-trait-underscore.stderr
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error[E0495]: cannot infer an appropriate lifetime for autoref due to conflicting requirements | ||
--> $DIR/dyn-trait-underscore.rs:21:20 | ||
| | ||
LL | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime | ||
| ^^^^ | ||
| | ||
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the function body at 19:1... | ||
--> $DIR/dyn-trait-underscore.rs:19:1 | ||
| | ||
LL | / fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> { | ||
LL | | // ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static` | ||
LL | | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime | ||
LL | | } | ||
| |_^ | ||
note: ...so that reference does not outlive borrowed content | ||
--> $DIR/dyn-trait-underscore.rs:21:14 | ||
| | ||
LL | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime | ||
| ^^^^^ | ||
= note: but, the lifetime must be valid for the static lifetime... | ||
= note: ...so that the expression is assignable: | ||
expected std::boxed::Box<std::iter::Iterator<Item=&T> + 'static> | ||
found std::boxed::Box<std::iter::Iterator<Item=&T>> | ||
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error: aborting due to previous error | ||
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For more information about this error, try `rustc --explain E0495`. |