Now we get warning 56 ("this match case is unreachable"). Is this considered ok (or should warning 11 be raised) ? I did not follow the discussion about "_ -> ." clauses, but I don't see offhand why this should be a different warning number.
This has to be a different warning, because if a case is only unreachable (rather than unused), you cannot just remove it, but have to replace it by a refutation case.
Note that 56 is a subcase of 11: you only get warning 56 if both 11 and 56 are turned on.