mutability is not inherited through fixed-length vectors

[nikomatsakis]

The following program:

type two_ints = [int * 2];

fn main() {
    let mut foo: two_ints = [0, 1];
    foo[0] = foo[1];
}

erroneously yields:

/Users/nmatsakis/tmp/foo.rs:5:4: 5:9 error: assigning to immutable vec content
/Users/nmatsakis/tmp/foo.rs:5     foo[0] = foo[1];
                                  ^~~~~
error: aborting due to previous error

Note that using a ~[] vec compiles successfully.