Allow ?? return

[ahdung]

x ?? throw ex is great, I hope also can do x ?? return to instead of:

var result = await FooAsync().ConfigureAwait(false);
if (result == null)
  return; // jump out of method
  // or return something if method with return parameter.

Use(result);

[Joe4evr]

#867

[huoyaoyuan]

This was rejected because the team want to extend the meaning of return in the future, thus don't want a feature adds limitation.