https://issues.dlang.org/show_bug.cgi?id=12774

          Issue ID: 12774
           Summary: REG(2.066) ICE(optimize.c) Newing struct containing
                    union causes segfault
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: ice
          Severity: regression
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: yebblies@gmail.com
                CC: k.hara.pg@gmail.com

struct HasUnion
{
    union
    {
        int a, b;
    }
}

void main()
{
    auto x = new HasUnion();
}

This segfaults when trying to optimize `new HasUnion()`, which has been
expanded to `new HasUnion(0, )` with the second argument being NULL in the ast.

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