[Issue 19793] no postblit is called if cast is used for structs

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19793

--- Comment #1 from Илья Ярошенко <ilyayaroshenko at gmail.com> ---
Maybe related to https://issues.dlang.org/show_bug.cgi?id=19774

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