Incorrect "moving prohibited due to outstanding loan" error when destructuring vector with owned contents

[bstrie]

fn main() {
    let split = [~1, ~2];

    match split {
        [] => die!(),
        [_head, ..tail] => tail
    };
}

I'm not 100% sure if this should be legal, but the error message it gives is baffling:

$ rustc split2.rs
split2.rs:4:10: 4:15 error: moving out of immutable local variable prohibited due to outstanding loan
split2.rs:4     match split {
                      ^~~~~
split2.rs:4:10: 4:15 note: loan of immutable local variable granted here
split2.rs:4     match split {
                      ^~~~~
error: aborting due to previous error

Note that the error only occurs if you create a head binding. Replacing _head with _ causes this error to go away.

[nikomatsakis]

Actually this is legit. The error message should be improved, but there's an issue on that already: #4715

The problem is that the head binding induces a move, but the ..tail is effectively a borrow, which means that this pattern is both moving out of vec[0] and then borrowing vec[1...]. Since the borrow checker doesn't consider indicates, this results in an error.

[nikomatsakis]

The fix, by the way, is "[copy head, ..tail]"

[nikomatsakis]

or "[ref head, ..tail]"