pub struct Foo<T: Copy> {
    map_keys: [u64; 64],
    map_vals: T,
}

impl<T: Copy> Foo<T> {
    pub fn new() -> Self {
        Foo {
            map_keys: [!0; 64],
            map_vals: unsafe { ::std::mem::zeroed() }
        }
    }
}

fn main() {
    Foo::<fn()>::new();
}