Custom error when moving arg outside of its closure

When given the following code:

```rust
fn give_any<F: for<'r> FnOnce(&'r ())>(f: F) {
    f(&());
}

fn main() {
    let mut x = None;
    give_any(|y| x = Some(y));
}
```

provide a custom error:

```
error: borrowed data cannot be moved outside of its closure
 --> file.rs:7:27
  |
6 |     let mut x = None;
  |         ----- binding declared outside of closure
7 |     give_any(|y| x = Some(y));
  |              ---          ^ cannot be assigned to binding outside of its closure
  |              |
  |              closure you can't escape
```

instead of the generic lifetime error:

```
error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
 --> file.rs:7:27
  |
7 |     give_any(|y| x = Some(y));
  |                           ^
  |
note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 7:14...
 --> file.rs:7:14
  |
7 |     give_any(|y| x = Some(y));
  |              ^^^^^^^^^^^^^^^
note: ...so that expression is assignable (expected &(), found &())
 --> file.rs:7:27
  |
7 |     give_any(|y| x = Some(y));
  |                           ^
note: but, the lifetime must be valid for the block suffix following statement 0 at 6:5...
 --> file.rs:6:5
  |
6 | /     let mut x = None;
7 | |     give_any(|y| x = Some(y));
8 | | }
  | |_^
note: ...so that variable is valid at time of its declaration
 --> file.rs:6:9
  |
6 |     let mut x = None;
  |         ^^^^^
```
This commit is contained in:
Esteban Küber 2018-01-02 15:25:53 -08:00
parent bb345a0be3
commit 846042161c
4 changed files with 67 additions and 2 deletions

View file

@ -16,5 +16,5 @@ fn with_int<F>(f: F) where F: FnOnce(&isize) {
fn main() {
let mut x = None;
with_int(|y| x = Some(y));
//~^ ERROR cannot infer
//~^ ERROR borrowed data cannot be moved outside of its closure
}

View file

@ -0,0 +1,19 @@
// Copyright 2018 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.
fn give_any<F: for<'r> FnOnce(&'r ())>(f: F) {
f(&());
}
fn main() {
let x = None;
give_any(|y| x = Some(y));
//~^ ERROR borrowed data cannot be moved outside of its closure
}

View file

@ -0,0 +1,12 @@
error: borrowed data cannot be moved outside of its closure
--> $DIR/issue-45983.rs:17:27
|
16 | let x = None;
| - binding declared outside of closure
17 | give_any(|y| x = Some(y));
| --- ^ cannot be assigned to binding outside of its closure
| |
| closure you can't escape
error: aborting due to previous error