Extension of MMultiset.map to several base types

Util/MMultiset/MMultisetFacts.v

@@ -74,6 +74,7 @@ Section MMultisetFacts.
       | H : id (?x =/= ?y) |- _ => change (x =/= y) in H
     end.
   
+  (* FIXME: Does it work with several [FMultisetsOn] instances? *)
   Ltac msetdec_step := 
     match goal with
       (* Simplifying equalities *)