[Issue 23472] scope(sucess) generate exception handling code.

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23472

--- Comment #5 from kinke <kinke at gmx.net> ---
Almost - this basically corresponds to what the backend generates for the happy
path without exception, except that the assignments to `ret` need to be
constructions (`TOK.construct`) in order not to break in-place construction of
the return value for non-POD return types.

Such an invasive rewrite should be feasible in the frontend, but would
presumably be quite a bit of work, for little gain IMO.

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