Allow specifying only a subset of generic type parameters explicitly instead of all vs none

TypeScript Version: 2.3.0
https://www.typescriptlang.org/play/
Code

class Greeter<T, S> {
    greeting: T;
    constructor(message: T, message2: S) {
        this.greeting = message;
    }

}

let greeter = new Greeter<string>("Hello", "world");

Expected behavior:

The compiler should infer S to be string.

Actual behavior:
Error:

Supplied parameters do not match any signature of call target.

The compiler expects either all generic parameters to be specified explicitly or none at all.

Start with the TypeScript 2.3 generic class example in the issue and reproduce the error in the linked TypeScript playground. Investigate generic call-site inference for new Greeter<string>("Hello", "world"); done means the explicit T is accepted while S is inferred as string, with coverage for the reported behavior.