Add checks for functions with missing alternatives
There is a forgotten compiler option -emf (clm's -funcmayfail) which emits errors when a function may be missing alternatives.
This is a common error when constructors are later added to a type and not considered in all functions matching on that type. I just ran it on Cloogle and found several such issues, also in Platform.
It would be good to use -emf in CI to prevent this kind of errors.