Actually I didn't say anything about warnings when suggesting (4). If we adopted (4) we'd surely want a warning like (2) when main returns a type other than (), Void, or ExitCode. So I'm going to vote on that basis
Argl! My misunderstanding, sorry.
Would anyone change their vote if we change 4 to: -XNoWombat: 00WWWN / -XWombat 00IWWN]? I believe Malte will. Anyone else?
(For 3a, I did specify that -XWombat gives errors on types which aren't instances of ExitStatus)