Incomplete/confusing error when match arm is a static constant

[o11c]

The following code gives an error pointing to the static FOO line, but not pointing to the FOO => line, so it's not obvious that the problem is really the match. I originally encountered this from (a form of) the bitflags! macro, which was doubly confusing.

pub struct Flags
{
    bits: uint,
}

static FOO: Flags = Flags{bits: 0x01};
static BAR: Flags = Flags{bits: 0x02};

// caller is guaranteed to only set one bit here.
pub fn frob(f: Flags)
{
    match f
    {
        FOO => {}
        BAR => {}
        _ => {}
    }
}

[huonw]

cc #6533, #13626, #13731, #14576.