stage1: Create a new declaration scope for union enum types

Making the enum type share the scope with the parent union means every
declaration "bleeds" into the enum scope.
Let's mint a fresh empty scope for the enum type.

Thanks to @Vexu for the test case.

Closes #7532
e18abab55aLemonBoy committed on 12/24/2020, 1:57:12 PM· committed by Veikka Tuominenparent83646df
2 files changedLine totals unavailable