let method calls on other instances not affect our fields (IDEA-92380)

java/java-impl/src/com/intellij/codeInspection/dataFlow/ControlFlowAnalyzer.java

@@ -1254,7 +1254,11 @@ class ControlFlowAnalyzer extends JavaElementVisitor {
         }
       }
 
-      addInstruction(new MethodCallInstruction(expression, createChainedVariableValue(expression)));
+      MethodCallInstruction callInstruction = new MethodCallInstruction(expression, createChainedVariableValue(expression));
+      if (!DfaValueFactory.isEffectivelyUnqualified(methodExpression)) {
+        callInstruction.setShouldFlushFields(false);
+      }
+      addInstruction(callInstruction);
 
       if (!myCatchStack.isEmpty()) {
         addMethodThrows(expression.resolveMethod());

java/java-impl/src/com/intellij/codeInspection/dataFlow/instructions/MethodCallInstruction.java

@@ -72,6 +72,10 @@ public class MethodCallInstruction extends Instruction {
     }
   }
 
+  public void setShouldFlushFields(boolean shouldFlushFields) {
+    myShouldFlushFields = shouldFlushFields;
+  }
+
   @Nullable
   public PsiType getResultType() {
     return myType;

java/java-impl/src/com/intellij/codeInspection/dataFlow/value/DfaValueFactory.java

@@ -154,7 +154,7 @@ public class DfaValueFactory {
     return null;
   }
 
-  private static boolean isEffectivelyUnqualified(PsiReferenceExpression refExpression) {
+  public static boolean isEffectivelyUnqualified(PsiReferenceExpression refExpression) {
     PsiExpression qualifier = refExpression.getQualifierExpression();
     if (qualifier == null) {
       return true;

java/java-tests/testData/inspection/dataFlow/fixture/EqualsHasNoSideEffects.java

@@ -0,0 +1,22 @@
+class DefaultObjectIdentifier {
+  String user;
+  String requestorClass;
+  public boolean equals(Object otherObject) {
+    if (otherObject == null || !(otherObject instanceof DefaultObjectIdentifier))
+      return false;
+    else {
+      DefaultObjectIdentifier identifier = (DefaultObjectIdentifier) otherObject;
+      if (user == null && identifier.user != null)
+        return false;
+      else if (requestorClass == null && identifier.requestorClass != null)
+        return false;
+      else if (((user == null && <warning descr="Condition 'identifier.user == null' is always 'true' when reached">identifier.user == null</warning>)
+                || (this.user.equals(identifier.user)))
+               &&
+               ((requestorClass == null && <warning descr="Condition 'identifier.requestorClass == null' is always 'true' when reached">identifier.requestorClass == null</warning>)
+                || this.requestorClass.equals(identifier.requestorClass)))
+        return true;
+      else
+        return false;
+    }
+  }}

java/java-tests/testData/inspection/dataFlow/fixture/MutableNotAnnotatedFieldsTreatment.java

@@ -54,12 +54,12 @@ class Foo {
     System.out.println(data.hashCode());
   }
 
-  void dontWarnWhenDoubleChecked_This_WithMethodCall() {
+  void warnWhenDoubleChecked_This_WithMethodCall() {
     if (data == null) {
       return;
     }
     System.out.println(data.hashCode());
-    if (data == null) {
+    if (<warning descr="Condition 'data == null' is always 'false'">data == null</warning>) {
       return;
     }
     System.out.println(data.hashCode());

java/java-tests/testData/inspection/dataFlow/fixture/MutableNullableFieldsTreatment.java

@@ -56,12 +56,12 @@ class Foo {
     System.out.println(data.hashCode());
   }
   
-  void dontWarnWhenDoubleChecked_This_WithMethodCall() {
+  void warnWhenDoubleChecked_This_WithMethodCall() {
     if (data == null) {
       return;
     }
     System.out.println(data.hashCode());
-    if (data == null) {
+    if (<warning descr="Condition 'data == null' is always 'false'">data == null</warning>) {
       return;
     }
     System.out.println(data.hashCode());

java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java

@@ -156,4 +156,6 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testTryWithResourcesInstanceOf() { doTest(); }
   public void testOmnipresentExceptions() { doTest(); }
 
+  public void testEqualsHasNoSideEffects() { doTest(); }
+
 }