Type inference broke down in Visual Studio 2017

[ArtemAvramenko]

TypeScript Version: 2.1.1

Code

class A {

    func(callback: () => void);
    func(callback: (code: number) => void);
    func(callback: Function) {
    }

    test() {
        this.func(code => { });
    }
}

Expected behavior:

Actual behavior:

[mhegazy]

If i were to guess, your VS 2015 was using 2.0 or earlier, your VS 2017 is using 2.1. If so, you can find more details about this in #11936.

it has always been any, the parameter help was showing the wrong overload in this case, but at build time the type was any silently, with TS 2.1, you should get an error under --noImplicitAny.

[ArtemAvramenko]

Why it is any? Function has two overloads, one of them is parameterless. If I specify parameter, it is definitely second overload with number parameter.

[mhegazy]

#11936 has discussion on why overload resolution works this way. it is mostly a design limitation. It is important to note, that previously it was any (though your hover in VS told you it was number), now it is still any, but will consistently report an error if --noImplicitany is enabled.