Fix S2583 FP: certains configuration of conditions lead to wrong detection of dead code

[sebastien-lorrain]

Repro steps

/// <summary>
/// A certain combination of condition wrongly considers the else code as dead.
/// </summary>
private static void FalsePositive()
{
	FalsePositive2_Sub(true, false, false);
	FalsePositive2_Sub(true, false, true);

	FalsePositive2_Sub(true, true, true);
	FalsePositive2_Sub(true, true, false);

	FalsePositive2_Sub(false, false, false);
	FalsePositive2_Sub(false, false, true);

	FalsePositive2_Sub(false, true, true);
	FalsePositive2_Sub(false, true, false);

	// Outcome.
	Console.WriteLine((_test1 && _test2 && _test3 && _test4) ? "Went through each test condition" : "Missed at least one test condition");        //NOSONAR.
}

private static bool _test1 = false;
private static bool _test2 = false;
private static bool _test3 = false;
private static bool _test4 = false;

private static void FalsePositive_Sub(bool testCondition1, bool testCondition2, bool testCondition3)
{
	bool condition1 = testCondition1;
	bool condition2 = testCondition2;
	bool condition3 = condition2 && testCondition3;

	if (condition2 && condition3 && condition1)
	{
		_test1 = true;
	}

	else if (!condition2 && !condition1)
	{
		_test2 = true;
	}

	else if (condition2 && condition1 && !condition3)
	{
		_test3 = true;
	}

	else
	{
		_test4 = true;
	}
}

Expected behavior

Rule S2583 should not be triggered

Actual Behavior

The else code should not be considered as dead code, as at least one combination of conditions triggers it.

Related information

Sonar C# version 7.11

[andrei-epure-sonarsource]

thanks for the detailed repro, @SebastienLorrain !