Trait constant inside struct field

#1

Could you help me with this gist? Is this actually invalid code or a compiler bug? If it is invalid, why is it?

https://play.rust-lang.org/?gist=d1c12027c6fb9753e0a7859c5ee489e6&version=stable&mode=debug

#2

I think this is https://github.com/rust-lang/rust/issues/50308