I wrote a warning when nullary methods return U...
I wrote a warning when nullary methods return U...

I wrote a warning when nullary methods return Unit. I wimped out of
including it in this patch because we had about 200 of them, and that's
what is fixed in this patch. I will add the warning to some kind of
"-Xlint" feature after 2.9.

This is motivated at least partly by the resolution of #4506, which
indicates the distinction between "def foo()" and "def foo" will
continue to jab its pointy stick into our eyes, so I believe we have a
minimal duty of at least following our own advice about what they mean
and not making a semirandom choice as to whether a method has parens or
not. Review by community.


KhanSuleyman/scala-parser-combinators,searler/scala-parser-combinators,l15k4/scala-parser-combinators