On Sunday, 17 June 2018 at 10:58:29 UTC, Cauterite wrote:
Is there a reason scope(success) needs to set up for exception
handling?
Or is this a bug / potential enhancement ?
If you had no exception handling in place, you'd need to
duplicate code in the output. For instance:
void foo()
{
scope(success) writeln("success!");
if (a) return;
if (b) return;
throw new Exception;
}
This would have to be lowered to:
void foo()
{
if (a) { writeln("success!"); return; }
if (b) { writeln("success!"); return; }
throw new Exception;
writeln("success!"); // maybe omitted with flow analysis
}
Now imagine there were 20 places you return from the function
early. Now imagine this is in a loop body, where you can leave it
via goto, break, continue, return, or end-of-block. And wrapped
in several if statements.
You generate smaller code with the exception handling system. The
compiler only has to pay attention to scope guards in the code
that handles it directly, instead of at every flow control
statement. Add to that the fact that -betterC is pretty recent
and scope guards are more than ten years old, and you get this
hole in the compiler.