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.

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