Make the "out" modifier when calling a method optional if the result is being discarded

[ekolis]

In this function:

public static bool IsBoolean(string s)
{
	return bool.TryParse(s, out _);
}

the out modifier is superfluous as the result is being discarded anyway. It would be easier to write as:

public static bool IsBoolean(string s)
{
	return bool.TryParse(s, _);
}

or maybe even

public static bool IsBoolean(string s)
{
	return bool.TryParse(s);
}

[CyrusNajmabadi]

public static bool IsBoolean(string s)
{
	return bool.TryParse(s);
}

This would make it a breaking change then for bool to add a TryParse function that didn't have an out param in the future.

[DavidArno]

Whilst @CyrusNajmabadi is right that the second example would cause problems, I think there is merit in the other version:

public static bool IsBoolean(string s)
{
	return bool.TryParse(s, _);
}

The need for an out with the discard does seem overkill.

[uygary]

out is part of the signature, and it's quite useful for method resolution and explicitly knowing which overload will be invoked.

void Main()
{
	var foo = new Foo();
	var x = 4;
	var _ = 2;
	
	foo.Bar(x, _);
	Console.WriteLine(_);
	
	foo.Bar(x, out _);
	Console.WriteLine(_);
}

public class Foo
{
	public void Bar(int x, out int y)
	{
		y = x;
		Console.WriteLine("Yes.");
	}
	
	public void Bar(int x, int y)
	{
		Console.WriteLine("Nope.");
	}
}

Building method resolution based on whether a parameter is used down the line or not... I really don't think this is a good idea to being with.

[DavidArno]

@uygary,

You make a good point. Sadly, the team didn't make using _ as a variable a compilation error when they introduced discards. So dropping the out on an out parameter discard could cause confusion.

So this is a nice idea that likely won't happen.