The ability to do member nullability narrowing on constructors

[JonasAlmaas]

It would be nice if there was a way to specify that a constructor will set a specific member/property.

You can do this with a checker function and the MemberNotNull attribute. But there is really no need to do an extra check.

Maybe something like this?:

public class MyClass
{
	public string Foo;
	public string? Bar;

	public MyClass(string foo) {
		this.Foo = foo;
	}

	[MemberNotNull(nameof(MyClass.Bar))]
	public MyClass(string foo, string bar) {
		this.Foo = foo;
		this.Bar = bar;
	}
}

Todays usage (without MemberNotNull)

var test = new MyClass("Test", "abc");
string teststr = test.Bar; // I get a nullability warning here

[RikkiGibson]

See also #4563