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Cannot assign twice to immutable variable with 'l: while break 'l {} as initializer #62115
Description
With:
fn _f() {
let _x = 'label: while break 'label {};
}we get:
warning[E0384]: cannot assign twice to immutable variable `_x`
--> src/lib.rs:2:14
|
2 | let _x = 'label: while break 'label {};
| -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot assign twice to immutable variable
| |
| first assignment to `_x`
| help: make this binding mutable: `mut _x`
|
= warning: this error has been downgraded to a warning for backwards compatibility with previous releases
= warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
= note: for more information, try `rustc --explain E0729`
This seems wrong. At least from a source view, _x is assigned to once.
Current MIR dump:
fn _f() -> () {
let mut _0: (); // return place in scope 0 at src/lib.rs:1:9: 1:9
let _1: (); // "_x" in scope 0 at src/lib.rs:2:9: 2:11
scope 1 {
}
bb0: {
StorageLive(_1); // bb0[0]: scope 0 at src/lib.rs:2:9: 2:11
StorageDead(_1); // bb0[1]: scope 0 at src/lib.rs:3:1: 3:2
return; // bb0[2]: scope 0 at src/lib.rs:3:2: 3:2
}
}This might possibly be fixed by #61988.
Activity
pnkfelix commentedon Jun 25, 2019
@eddyb points out that the first bullet item of PR #61872 says that it fixes this.
Centril commentedon Jun 25, 2019
Great. Then we'll just need to add a regression test to https://github.com/rust-lang/rust/blob/07e5297faf2966a77c466b0b5ad936c0deb828ac/src/test/ui/nll/assign-while-to-immutable.rs once the PR is merged.
eddyb commentedon Jun 25, 2019
@Centril once it's merged? @matthewjasper could add this test and close this issue as part of the PR.
Auto merge of #61872 - matthewjasper:refactor-mir-drop-gen, r=nikomat…