If the given argument to the out parameter is not correctly initialized (eg. void initialized variable), calling dtor for the argument is absolutely unsafe. That's the reason why my patch was rejected by Walter.
Alternative language semantics in my thought is:
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If an out parameter typed T exists, and
1. T has elaborate destructor
2. T.init represents logically invalid object (T is nested struct, and/or T has @disable this();)
Automatic blit initializing for the out parameter would be unsafe.
So semantic analysis would reject such a out parameter declaration.
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