I still see under the heading 'Choose between explicit type declaration or implicit type inference' the following: > Sum(x: Integer, u: Integer): Int = return

I still see under the heading 'Choose between explicit type declaration or implicit type inference' the following: > Sum(x: Integer, u: Integer): Int = return x * y > or > Sum(x: Integer, u: Integer): = return x * y Clearly, x * y is not the sum. And y isn't in the argument list, u is. And in both cases the return statement is unnecessary and should be omitted.