Seemingly incorrect error about use of uninitialized value

[DaGenix]

The following program:

fn test() -> (u32, u32) {
    return (0, 0);
}

fn main() {
    let mut X0: u32;
    let mut X1: u32;
    (X0, X1) = test();
}

Gives me the error:

multi-bind-issue.rs:9:5: 9:7 error: use of possibly uninitialized variable: X0
multi-bind-issue.rs:9 (X0, X1) = test();
^~
multi-bind-issue.rs:9:9: 9:11 error: use of possibly uninitialized variable: X1
multi-bind-issue.rs:9 (X0, X1) = test();
^~
error: aborting due to 2 previous errors

Which seems wrong, since the use its complaining about is the initialization of the variables.

Compiled with: 8883099

[Aatch]

You are trying to pattern match outside of a let/match, so this code wouldn't work anyway. Its just that the checker for unintialized variables gets to the tuple expression first.

This is just an unclear error message, not a bug.

[DaGenix]

Ok, makes sense. Isn't it still an issue though that the error message is very unhelpful? Someone coming from a language that allows this type of construct (I think Scala does) will be confused.

[brson]

I don't understand why this parses. What is (X0, X1) = test();?

[nikomatsakis]

I think it parses because we accept an arbitrary expression on the LHS, but certainly there should be some point, either in typeck or before, that enforces that the LHS is an lvalue...perhaps there isn't?

[klutzy]

(X0, X1) = test(); part is related to #7507