A comment why this fixes the problem would be good. @xeno-by explained it to me this way: `e.tpe <:< c.typeOf[MappedToBase]` should always be true following the method signature. However during implicit search (and only during implicit search) macros are successfully called with invalid type arguments in certain situations, which is a bug. This means the condition is invalidated and c.abort(...) will stop this branch of implicit search. But c.abort should never happen when calling the macro normally.