Syntax highlighting is thrown off by `<<`

[RalfJung]

Consider this code:

pub fn f() {
    g::<u32>();
}
pub fn g<T>() -> std::mem::MaybeUninit<[T; 1 << 2]> {
    std::mem::MaybeUninit::uninit()
}

fn main() {
    f();
}

On the playground, fn main does not get syntax highlighting:

Seems like the << in a type is throwing it off and then it can't parse the rest of the file any more, or so?

[shepmaster]

Looks like an upstream issue and someone has already proposed a PR: ajaxorg/ace#5572.