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.

[joonhocho]

I too am currently using currying as well as workaround, but it feels too hacky to me. I wish this can be resolved.

[alisd23]

For anyone else wondering about a workaround, as @alshain said you can use currying. The workaround for the above example would be:

function test<S>() {
  return function<T extends keyof S>(tValue: T): any {
    return null;
  };
}

test<SomeType>()('some-key');