translate-c: Incorrect code generated for cast-to-union

[ehaas]

Zig Version

0.10.0-dev.870+65aa33319

Steps to Reproduce

Run zig translate-c on the following:

union U {
    long l;
    double d;
};

void foo(void) {
    union U u = (union U) 42L;
}

Expected Behavior

The union cast should be translated into something like this:

var u: union_U = union_U{ .l = @as(c_long, 42) };

Actual Behavior

The union cast is translated like this, which does not compile:

var u: union_U = @as(union_U, @as(c_long, 42));