Auto merge of #85158 - JulianKnodt:array_const_val, r=cjgillot

Mir-Opt for copying enums with large discrepancies

I have been meaning to make this for quite a while, based off of this [hackmd](https://hackmd.io/`@ft4bxUsFT5CEUBmRKYHr7w/rJM8BBPzD).`

I'm not sure where to put this opt now that I've made it, so I'd appreciate suggestions on that!
It's also one long chain of statements, not sure if there's a more friendly format to make it.

r? `@tmiasko`
I would `r` oli but he's on leave so he suggested I `r` tmiasko or wesleywiser.

Author: bors