Valid to assign to field of struct in union?

[Johan Engelen via Digitalmars-d]

On Tuesday, 6 September 2016 at 12:56:24 UTC, Johan Engelen wrote:
> 
> The compiler allows it, but it leads to a bug with CTFE of this 
> code: the assert fails.

Before someone smart tries it, yes the code works with LDC, but 
wait... swap the order of `first` and `second` in the union, and 
BOOM!
Internally, CTFE of the code leads to a corrupt union initializer 
array. LDC and DMD do things a little differently in codegen. 
Oversimplified: LDC will use the first member of the union, DMD 
the last.