Should overloads be allowed?

def fooString( a : string)
def fooNumber( a : number)

a = { "ok", 1 };
b = typeof(a) == "string";
c,d = filterByBoolMask( b, a );
e = fooString( c );
f = fooNumber( d );

vs.

def foo( a : string) {
  return 1;
}

def foo(a : number) {
  return 2;
}

a = { "ok", 1 };
b = foo( a );  // { 1, 2 }
