What types does the following function expect for the arguments a and b, and what type does it return?
What should an IDE tell the user about the types of a and b in the completion popup?
function foo(a, b) { return a + b; }
What should an IDE tell the user about the types of a and b in the completion popup?
function foo(a, b) { return a + b; }
(Numeric, Numeric) -> Numeric
But what if + is also String concatenation? Or any other overloading of "+". Then maybe the type of a and b is Something_that_can_be_+ed. The user can then think "ok, I'll pass a couple of Ints to obtain an Int, or a couple of Strings to obtain a String!". This also seems useful to me.
var price = document.querySelector('input#price').value; // "10"
var tax = document.querySelector('input#tax').value; // "1"
var total = foo(price, tax); // "101"
I find this type of fast feedback improves programmer productivity. It means that you get warned straight away, and don't have to do a trip through the debugger to find the problem.
Just because the compiler can infer that a specific type could be passed to a function, that does not mean that the developer intended that function to be used with that type.