Constant evaluation error: attempted to read undefined bytes

[Thinkofname]

I saw that #51086 was closed when #51225 was merged so I thought it would fix the same error on my own code as well however as of nightly: rustc 1.28.0-nightly (aa094a43c 2018-06-01) it still happens.

Code:

#[derive(PartialEq, Eq, Clone, Copy)]
pub struct Stat {
    pub id: u8,
    pub index: usize,
}

impl Stat {
    pub const STUDENT_HAPPINESS: Stat = Stat{
        id: 0,
        index: 0,
    };
    pub const STUDENT_HUNGER: Stat = Stat{
        id: 0,
        index: Self::STUDENT_HAPPINESS.index + 1,
    };

}

pub fn from_index(id: u8, index: usize) -> Option<Stat> {
    let stat = Stat{id, index};
    match stat {
        Stat::STUDENT_HAPPINESS => Some(Stat::STUDENT_HAPPINESS),
        Stat::STUDENT_HUNGER => Some(Stat::STUDENT_HUNGER),
        _ => None,
    }
}

fn main() { }

Playground: http://play.rust-lang.org/?gist=cf51c77c20f06ca15f1dc2cc4fa779b0&version=nightly&mode=debug

From what I can tell its an alignment issue because changing id from a u8 to a u64 fixes the issue.