Union inference regression in 3.1.2

[unthingable]

type C = Function0[Int] | Function0[String]

def foo(c: C): Unit = ()

foo(() => 1)

Output

3.1.1:

3.1.2:

[s5bug]

Additional note that foo( (() => 1): Function0[Int] ) (explicit ascription) compiles.

[odersky]

Can we find the commit that broke this?

[griggt]

First bad commit is 6ac8b47 from #14026