rust/src/librustc_mir
bors bc072ed0ca Auto merge of #47144 - estebank:moved-closure-arg, r=nikomatsakis
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;
  |         ----- borrowed data cannot be moved into here...
7 |     give_any(|y| x = Some(y));
  |              ---          ^ cannot be moved outside of its closure
  |              |
  |              ...because it cannot outlive this closure
```

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;
  |         ^^^^^
```

Fix #45983.
2018-01-22 05:30:37 +00:00
..