internal compiler error: const expr(33: Msg::Start) of type main::Msg has size 1 instead of 16

[nnethercote]

This Rust code makes rustc stop with an internal compile error.

fn main() {
    enum Msg {
        Start,
        Measure(Fn() -> usize),
    }

    let _ = Msg::Start;
}

[mitaa]

This seems to be the same issue as, or at least related to, #16812

Changing the example to

fn main() {
    enum Msg {
        Start(usize),
        Measure([u8]),
    }


    let _ = Msg::Start;
}

yields the same error message: Unexpected type returned from struct_tail

[arielb1]

cc #25388

[steveklabnik]

This no longer ICEs!