Optional Parameters in any order

[TonyValenti]

Right now I write code like the following:

public void Foo(IComparer<T> MyComparer = default, FooObject Foo = default, AnotherObject Another = default){
  MyComparer ??= Comparer<T>.Default;
  Foo ??= FooObject.Default;
  Another ??= AnotherObject.Default;
}

and I call it like follows:

Foo(MyComparer); //This is nice.
Foo(default, new FooObject()); //Not as much.
Foo(Another: new AnotherObject); //Don't like at all.

It would be really nice if C# could infer the position of optional parameters by their type so I could simply say:

Foo(MyComparer());
Foo(new FooObject());
Foo(new AnotherObject());

[HaloFour]

Considering that methods can have multiple optional parameters of the same type I don't see how that could work. It also sounds like an unmitigated nightmare where it affects overload resolution.

The C# compiler does now allow you to specify optional parameters in any order by name, so the third example: Foo(Another: new AnotherObject()); does work. Is that not sufficient?