[Issue 18232] Union methods fail to initialize local variables to .init

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18232

--- Comment #3 from hsteoh at quickfur.ath.cx ---
Minimized code:
------
union U {
    int method() {
        int x;
        return x;
    }
}
------

The disassembly shows that x is never initialized to 0, and a garbage value is
returned.

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