example: two functions: "sub" and "add". both have type signatures (int,int) -> int yet the types will not help you to proof you are using the functions correct

example: two functions: "sub" and "add". both have type signatures (int,int) -> int yet the types will not help you to proof you are using the functions correctly, and the types are also not helping that the output of these functions is always as promised by the documentation.