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

[d-bugmail at puremagic.com]

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

--- Comment #2 from deadalnix <deadalnix at gmail.com> ---
`__os2` can only be false if no exception was thrown. There is no reason to
emit any exception handling code in such function, even in the instances where
the bound check might fail.

In fact, the whole point of scope success is "run this when the scope is exited
using regular control flow rather than exception handling", so there is no
reason to emit any exception handling code ever when dealing with
scope(success).

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