S2583 FP: When using nullable boolean in if-elseif-else.

[ndsvw]

Description

used SonarQube version: 8.9.1

A nullable boolean can have 3 values (true, false, null).

When using "if", "else if" and "else" to write conditions for all 3 cases, S2583 shows a false positive.

Repro steps

Write this code:

		var b = (bool?)objectArg;
		
		if(b == true) {
			Console.WriteLine("true");	
		} else if(b == false) {
			Console.WriteLine("false");	
		} else {
			Console.WriteLine("null");	
		}

Our code:

Expected behavior

It's not a bug.

"b == false" is not underlined red.

There is no description "Change this condition so that it does not always evaluate to 'true'; some subsequent code is never executed." because it is wrong.

Actual behavior

It underlines "b == false" red with the description "Change this condition so that it does not always evaluate to 'true'; some subsequent code is never executed."

The else part has a red background because SonarDotnet thinks, it will never be executed.

Related information

• SonarScanner for .NET version (if used): sonar-scanner-4.6.1.2450
• Operating System: Windows 10
• SonarQube version: 8.9.1

[pavel-mikula-sonarsource]

Hi @ndsvw,

Thank you for reporting this case. I can confirm it as False Positive. Looks like we don't build proper set of possible constraints for this case.

[pavel-mikula-sonarsource]

The key is that var b = (bool?)objectArg; needs to be in the way. It works well for bool? b argument and bool? b = null; statement.

[mary-georgiou-sonarsource]

Fixed by #7750