> even C++ to some extent

C++ can also infer return types, the following is a valid C++14 function definition

    auto foo() {
        auto curry = [](auto x) {
            return [=](auto y) { return x + y; };
        };
        auto add42 = curry(42);
        return add42(58);
    }

which incidentally gets compiled to this:

    0000000000000000 <foo()>:
       0:	mov    $0x64,%eax
       5:	retq