RFC: 1026 function overloading

[aljazerzen]

No description provided.

[aljazerzen]

This is what happens with scalars currently:

      create scalar type A extending str;
      create scalar type B extending A;
   
      create function foo(a: str) -> str using ("matched str");
      create function foo(a: A) -> str using ("matched A");
   
      select foo(<str>"hello"); # error: please disambiguate between the two function
                                # I would say this is incorrect, it should "match str"

      select foo(<A>"hello");   # matched A
                                # correct

      select foo(<B>"hello");   # internal server error: function edgedbpub."..." is not unique
                                # obviously bad