Should we allow nullable boolean ternary operator and let it return null value?

[Thaina]

bool? maybeCondition = null;

int? i = maybeCondition ? 0 : 1; // will result as null

long l = maybeCondition ? 1 : 0 ?? -1; // ternary expression would be null so then we can append null coalescing?

// if it is impossible because operator precedence we can use parenthesis anyway
string s = (maybeCondition ? "yes" : "no") ?? "maybe";

[siegfriedpammer]

This would be a massive breaking change for existing code. Also there is no syntactic difference making it harder to read. IMHO

[Thaina]

How can it be breaking changes?

In the current code, ternary operator only work on bool expression and error when it used on expression that result on bool?, so there should be nowhere using it on any expression that not return exact true or false

If this suddenly work it should affect no existing code that can compiled properly, instead it will only affect new code

[CyrusNajmabadi]

using System;
public class C {
    public void M() {
        int? maybeCondition = null;
        var v = maybeCondition > 0 ? 1 : 2; 
    }
}

This is already legal code. 'v' is an int. It cannot become an int? (or null) just because maybeCondition is null.

[Thaina]

@CyrusNajmabadi Oh right, sorry, I forgot ((int?)null) > 0 is not result in nullable, it just normal bool and false, and I don't intend to change that, it was actually sample code unrelated to my proposal

Let me change the example code a bit

[jilles-sg]

Using existing mechanisms, these could be written like

int? i = maybeCondition switch { true => 0, false => 1, null => null };

long l = maybeCondition switch { true => 1, false => 0, null => -1 };

string s = maybeCondition switch { true => "yes", false => "no", null => "maybe" };

[Thaina]

Yes, I have already write this way at first. And I felt true false null and => is unnecessary annoying and distracted when it always have just these 3 states