ICE when trying to move from reference in union

[matthewjasper]

The following code ICEs, when it should produce a cannot move error

union U<'a> {
    x: &'a String,
}

fn f(u: U<'_>) -> String {
    unsafe { *u.x }
}

[matthewjasper]

Worse, the following compiles:

#![feature(untagged_unions)]

union U<'a> {
    x: &'a mut String,
}

fn f(u: U<'_>) -> String {
    unsafe { *u.x }
}

[hellow554]

regression from stable-to-beta and stable-to-nightly

[pnkfelix]

triage: P-high