SONARJAVA-7282 False negative java:S2168: not reported when the outer null check is written !(helper != null)

java-checks-test-sources/default/src/main/files/non-compiling/checks/DoubleCheckedLockingCheckSample.java

@@ -17,5 +17,18 @@ public UnknownType unknownType() {
    }
   }
 
+  public UnknownType unknownTypeNegated() {
+   if (!(unknownType != null)) {
+//     ^^^^^^^^^^^^^^^^^^^^^^>
+     synchronized (Helper.class) { // Noncompliant {{Remove this dangerous instance of double-checked locking.}}
+//   ^^^^^^^^^^^^
+       if (!(unknownType != null)) {
+//         ^^^^^^^^^^^^^^^^^^^^^^<
+         this.unknownType = new UnknownType();
+       }
+     }
+   }
+  }
+
   class Helper  { }
 }

java-checks-test-sources/default/src/main/java/checks/DoubleCheckedLockingCheckSample.java

@@ -14,6 +14,42 @@ public Helper classicCase() {
     return helper;
   }
 
+  public Helper classicCaseNegated() {
+    if (!(helper != null))
+//      ^^^^^^^^^^^^^^^^^>
+      synchronized (this) { // Noncompliant {{Remove this dangerous instance of double-checked locking.}}
+//    ^^^^^^^^^^^^
+        if (helper == null)
+//          ^^^^^^^^^^^^^^<
+          helper = new Helper();
+      }
+    return helper;
+  }
+
+  public Helper classicCaseInnerNegated() {
+    if (helper == null)
+//      ^^^^^^^^^^^^^^>
+      synchronized (this) { // Noncompliant {{Remove this dangerous instance of double-checked locking.}}
+//    ^^^^^^^^^^^^
+        if (!(helper != null))
+//          ^^^^^^^^^^^^^^^^^<
+          helper = new Helper();
+      }
+    return helper;
+  }
+
+  public Helper classicCaseRepeatedNegations() {
+    if (((!!(helper == null))))
+//      ^^^^^^^^^^^^^^^^^^^^^^>
+      synchronized (this) { // Noncompliant {{Remove this dangerous instance of double-checked locking.}}
+//    ^^^^^^^^^^^^
+        if (!(!(!(helper != null))))
+//          ^^^^^^^^^^^^^^^^^^^^^^^<
+          helper = new Helper();
+      }
+    return helper;
+  }
+
   public Helper fieldIsNotActuallyInitializedHere() {
     if (helper == null)
       synchronized (this) { // Compliant - field is not initialized in this method actually
@@ -250,6 +286,24 @@ public synchronized Helper synchronizedClassicCase() {
     return helper;
   }
 
+  public Helper negatedNullEqualityOuter() {
+    if (!(helper == null))
+      synchronized (this) { // Compliant
+        if (helper == null)
+          helper = new Helper();
+      }
+    return helper;
+  }
+
+  public Helper doubleNegatedNotEqualInner() {
+    if (helper == null)
+      synchronized (this) {
+        if (!!(helper != null))
+          helper = new Helper();
+      }
+    return helper;
+  }
+
   static class Helper { }
 }
 

java-checks/src/main/java/org/sonar/java/checks/synchronization/DoubleCheckedLockingCheck.java

@@ -16,7 +16,14 @@
  */
 package org.sonar.java.checks.synchronization;
 
+import java.util.Arrays;
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
 import org.sonar.check.Rule;
+import org.sonar.java.model.ExpressionUtils;
 import org.sonar.java.model.ModifiersUtils;
 import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
 import org.sonar.plugins.java.api.JavaFileScannerContext;
@@ -34,19 +41,15 @@
 import org.sonar.plugins.java.api.tree.SynchronizedStatementTree;
 import org.sonar.plugins.java.api.tree.SyntaxToken;
 import org.sonar.plugins.java.api.tree.Tree;
-
-import java.util.Arrays;
-import java.util.Deque;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Optional;
-import java.util.stream.Stream;
+import org.sonar.plugins.java.api.tree.UnaryExpressionTree;
 
 import static org.sonar.plugins.java.api.tree.Tree.Kind.EQUAL_TO;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.IDENTIFIER;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.IF_STATEMENT;
+import static org.sonar.plugins.java.api.tree.Tree.Kind.LOGICAL_COMPLEMENT;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.MEMBER_SELECT;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.METHOD;
+import static org.sonar.plugins.java.api.tree.Tree.Kind.NOT_EQUAL_TO;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.NULL_LITERAL;
 import static org.sonar.plugins.java.api.tree.Tree.Kind.SYNCHRONIZED_STATEMENT;
 
@@ -90,10 +93,18 @@ private static Optional<IfFieldEqNull> isIfFieldEqNull(Tree tree) {
       return Optional.empty();
     }
     IfStatementTree ifTree = (IfStatementTree) tree;
-    if (!ifTree.condition().is(EQUAL_TO)) {
+
+    ExpressionTree condition = ExpressionUtils.skipParentheses(ifTree.condition());
+    boolean negated = false;
+    while (condition.is(LOGICAL_COMPLEMENT)) {
+      negated = !negated;
+      condition = ExpressionUtils.skipParentheses(((UnaryExpressionTree) condition).expression());
+    }
+    if (!condition.is(negated ? NOT_EQUAL_TO : EQUAL_TO)) {
       return Optional.empty();
     }
-    BinaryExpressionTree eqRelation = (BinaryExpressionTree) ifTree.condition();
+
+    BinaryExpressionTree eqRelation = (BinaryExpressionTree) condition;
     if (eqRelation.rightOperand().is(NULL_LITERAL)) {
       return isField(eqRelation.leftOperand()).map(f -> new IfFieldEqNull(ifTree, f));
     }