Problems if TypEr cannot guess the type of arguments

[EarlPitts]

When I'm searching for the set of functions to test, I'm already taking advantage of the type signatures of the arguments.
But there are cases, when TypEr cannot infer the type of the arguments, and gives back any() instead.
E.g.:

f(I) ->
    I.

and

f(I) ->
    I + 1.

results in two different "functions"

[{"msg_test.erl",{msg_test,go,1},["number()"]}]
[{"msg_test.erl",{msg_test,go,1},["any()"]}]