Bug: S1125 code fix does not add ! when transforming x == false.

analyzers/src/SonarAnalyzer.CSharp/Rules/BooleanLiteralUnnecessaryCodeFix.cs

@@ -223,10 +223,28 @@ private static SyntaxNode FindNodeToKeep(BinaryExpressionSyntax binary)
 
             #endregion
 
+            #region ==/!= one side boolean
+
+            if (binary.IsKind(SyntaxKind.EqualsExpression))
+            {
+                // edge case [condition == false] -> !condition
+                if (CSharpEquivalenceChecker.AreEquivalent(binary.Right, CSharpSyntaxHelper.FalseLiteralExpression))
+                {
+                    return SyntaxFactory.PrefixUnaryExpression(SyntaxKind.LogicalNotExpression, binary.Left);
+                }
+                // edge case [false == condition] -> !condition
+                if (CSharpEquivalenceChecker.AreEquivalent(binary.Left, CSharpSyntaxHelper.FalseLiteralExpression))
+                {
+                    return SyntaxFactory.PrefixUnaryExpression(SyntaxKind.LogicalNotExpression, binary.Right);
+                }
+            }
+
             return CSharpEquivalenceChecker.AreEquivalent(binary.Left, CSharpSyntaxHelper.TrueLiteralExpression)
                    || CSharpEquivalenceChecker.AreEquivalent(binary.Left, CSharpSyntaxHelper.FalseLiteralExpression)
                 ? binary.Right
                 : binary.Left;
+
+            #endregion
         }
 
         private static bool TwoSidesAreDifferentBooleans(BinaryExpressionSyntax binary) =>

analyzers/tests/SonarAnalyzer.Test/TestCases/BooleanLiteralUnnecessary.Fixed.cs

@@ -34,15 +34,15 @@ public BooleanLiteralUnnecessary(bool a, bool b, bool? c, Item item)
             var x = false;                  // Fixed
             x = true;              // Fixed
             x = true;                     // Fixed
-            x = a;                    // Fixed
+            x = !a;                    // Fixed
             x = !a;                    // Fixed
 
             x = a;                // Fixed
             x = a;                  // Fixed
             x = a;                  // Fixed
             x = a;                 // Fixed
             x = !a;                  // Fixed
-            x = a;                 // Fixed
+            x = !a;                 // Fixed
             x = a;                  // Fixed
             x = false is a;                 // Error [CS9135]
             x = true is a;                  // Error [CS9135]
@@ -211,7 +211,17 @@ class Repro7999CodeFixError
     {
         void Method(bool cond)
         {
-            if (cond) { } // Fixed
+            if (!cond) { }  // Fixed
+            if (cond) { }  // Fixed
+
+            if (cond) { }   // Fixed
+            if (!cond) { }   // Fixed
+
+            if (!cond) { }  // Fixed
+            if (cond) { }  // Fixed
+
+            if (cond) { }   // Fixed
+            if (!cond) { }   // Fixed
         }
     }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/BooleanLiteralUnnecessary.cs

@@ -228,7 +228,17 @@ class Repro7999CodeFixError
     {
         void Method(bool cond)
         {
-            if (cond == false) { } // Noncompliant, TP but code fix is wrong - it should be fixed to "if (!cond)"
+            if (cond == false) { }  // Noncompliant
+            if (cond != false) { }  // Noncompliant
+
+            if (cond == true) { }   // Noncompliant
+            if (cond != true) { }   // Noncompliant
+
+            if (false == cond) { }  // Noncompliant
+            if (false != cond) { }  // Noncompliant
+
+            if (true == cond) { }   // Noncompliant
+            if (true != cond) { }   // Noncompliant
         }
     }