Open
Description
Given the following snippet:
struct State {
val: u8,
xy: bool,
}
struct Test {
vec: Vec<State>,
}
impl Test {
fn new() -> Self {
Test { vec: Vec::new() }
}
fn get_mut(&mut self, id: usize) -> Result<&mut u8, Option<&mut State>> {
match self.vec.get_mut(id) {
Some(State { ref mut val, ref xy }) /*if true*/ => Ok(val),
other => Err(other),
}
}
}This compiles just fine. Now uncomment the if true match guard and compile fails:
error[E0505]: cannot move out of `_` because it is borrowed
--> src/lib.rs:18:13
|
15 | fn get_mut(&mut self, id: usize) -> Result<&mut u8, Option<&mut State>> {
| - let's call the lifetime of this reference `'1`
16 | match self.vec.get_mut(id) {
17 | Some(State { ref mut val, ref xy }) if true => Ok(val),
| ----------- ------- returning this value requires that borrow lasts for `'1`
| |
| borrow of value occurs here
18 | other => Err(other),
| ^^^^^ move out of value occurs here
Why does the insignificant match guard affect the borrowck?
Tested both on stable 1.38.0 and 1.40.0-nightly (032a53a 2019-10-03).