Java: Don't cause endless recursive calls of the equals() method in the inspection "Objects compared with '=='", handle qualified 'this' (IDEA-164038)

plugins/InspectionGadgets/src/com/siyeh/ig/equality/EqualityOperatorComparesObjectsInspection.java

@@ -32,6 +32,7 @@ import com.siyeh.ig.psiutils.ParenthesesUtils;
 import org.jetbrains.annotations.Nls;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 public class EqualityOperatorComparesObjectsInspection extends BaseInspection {
 
@@ -211,13 +212,24 @@ public class EqualityOperatorComparesObjectsInspection extends BaseInspection {
       }
       if (lhs instanceof PsiThisExpression || rhs instanceof PsiThisExpression) {
         final PsiMethod method = PsiTreeUtil.getParentOfType(expression, PsiMethod.class);
-        if (method != null && "equals".equals(method.getName())) {
-          return;
+        if (method != null && "equals".equals(method.getName()) && method.getParameterList().getParametersCount() == 1) {
+          final PsiClass containingClass = method.getContainingClass();
+          if (isThisQualifier(lhs, containingClass) || isThisQualifier(rhs, containingClass)) {
+            return;
+          }
         }
       }
       final String operationText = expression.getOperationSign().getText();
       final String prefix = tokenType.equals(JavaTokenType.NE) ? "!" : "";
       registerError(expression, operationText, prefix);
     }
+
+    private static boolean isThisQualifier(@Nullable PsiExpression expression, @Nullable PsiClass psiClass) {
+      if (expression instanceof PsiThisExpression) {
+        final PsiJavaCodeReferenceElement qualifier = ((PsiThisExpression)expression).getQualifier();
+        return qualifier == null || psiClass != null && qualifier.isReferenceTo(psiClass);
+      }
+      return false;
+    }
   }
 }

plugins/InspectionGadgets/test/com/siyeh/igfixes/equality/replace_equality_with_equals/CompareOtherQualifiedThisInEqualsMethod.after.java

@@ -0,0 +1,13 @@
+class Outer {
+  class Inner {
+    private Outer outer() {
+      return Outer.this;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      return (obj instanceof Inner) &&
+              Outer.this.equals(((Inner) obj).outer());
+    }
+  }
+}

plugins/InspectionGadgets/test/com/siyeh/igfixes/equality/replace_equality_with_equals/CompareOtherQualifiedThisInEqualsMethod.java

@@ -0,0 +1,13 @@
+class Outer {
+  class Inner {
+    private Outer outer() {
+      return Outer.this;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      return (obj instanceof Inner) &&
+              Outer.this <caret>== ((Inner) obj).outer();
+    }
+  }
+}

plugins/InspectionGadgets/test/com/siyeh/igfixes/equality/replace_equality_with_equals/CompareSameQualifiedThisInEqualsMethod.java

@@ -0,0 +1,14 @@
+class Demo {
+  private Object field;
+
+  @Override
+  public boolean equals(Object obj) {
+    if (Demo.this <caret>== obj) {
+      return true;
+    }
+    else {
+      Demo other = (Demo)obj;
+      return field == other.field;
+    }
+  }
+}

plugins/InspectionGadgets/testsrc/com/siyeh/ig/fixes/equality/EqualityOperatorComparesObjectsInspectionTestBase.java

@@ -31,6 +31,8 @@ public abstract class EqualityOperatorComparesObjectsInspectionTestBase extends
   public void testSimpleObjectComparison() { doTest(true, false); }
   public void testNegatedObjectComparison() { doTest(false, false); }
   public void testCompareThisInEqualsMethod() { assertQuickfixNotAvailable(); }
+  public void testCompareSameQualifiedThisInEqualsMethod() { assertQuickfixNotAvailable(); }
+  public void testCompareOtherQualifiedThisInEqualsMethod() { doTest(true, false); }
   public void testCompareFieldInEqualsMethod() { doTest(true, false); }
 
   @Override