6f99a27886
This implements RFC 39. Omitted lifetimes in return values will now be
inferred to more useful defaults, and an error is reported if a lifetime
in a return type is omitted and one of the two lifetime elision rules
does not specify what it should be.
This primarily breaks two uncommon code patterns. The first is this:
unsafe fn get_foo_out_of_thin_air() -> &Foo {
...
}
This should be changed to:
unsafe fn get_foo_out_of_thin_air() -> &'static Foo {
...
}
The second pattern that needs to be changed is this:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed {
Owned(format!("hello world"))
}
Change code like this to:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed<'static> {
Owned(format!("hello world"))
}
Closes #15552.
[breaking-change]
34 lines
997 B
Rust
34 lines
997 B
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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struct direct<'a> {
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f: &'a int
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}
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struct indirect1 {
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// Here the lifetime parameter of direct is bound by the fn()
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g: |direct|: 'static
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}
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struct indirect2<'a> {
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// But here it is set to 'a
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g: |direct<'a>|: 'static
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}
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fn take_direct<'a,'b>(p: direct<'a>) -> direct<'b> { p } //~ ERROR mismatched types
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//~^ ERROR cannot infer
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fn take_indirect1(p: indirect1) -> indirect1 { p }
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fn take_indirect2<'a,'b>(p: indirect2<'a>) -> indirect2<'b> { p } //~ ERROR mismatched types
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//~^ ERROR cannot infer
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fn main() {}
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