[Issue 19430] wrong code for `this =`, corrupted memory issue

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19430

--- Comment #3 from Stanislav Blinov <stanislav.blinov at gmail.com> ---
You forgot a `puts` in the two-argument constructor. There are exactly two
instances being constructed. One by returning from `sum`, the other one is `c`
in main. First "d" in output is from assignment, second is on exiting main. All
seems quite legit, i.e. WAD.

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