IDEA-204461 DFA: Make final getter stable if it gets a final field

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaExpressionFactory.java

@@ -26,10 +26,7 @@ import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.*;
 import com.intellij.psi.impl.JavaConstantExpressionEvaluator;
-import com.intellij.psi.util.InheritanceUtil;
-import com.intellij.psi.util.PropertyUtilBase;
-import com.intellij.psi.util.PsiTreeUtil;
-import com.intellij.psi.util.PsiUtil;
+import com.intellij.psi.util.*;
 import com.intellij.util.ObjectUtils;
 import com.intellij.util.containers.ContainerUtil;
 import com.siyeh.ig.psiutils.ClassUtils;
@@ -378,9 +375,12 @@ public class DfaExpressionFactory {
 
   private static final class GetterDescriptor implements VariableDescriptor {
     private final @NotNull PsiMethod myGetter;
+    private final boolean myStable;
 
     GetterDescriptor(@NotNull PsiMethod getter) {
       myGetter = getter;
+      PsiField field = PsiUtil.canBeOverridden(getter) ? null : PropertyUtil.getFieldOfGetter(getter);
+      myStable = field != null && field.hasModifierProperty(PsiModifier.FINAL);
     }
 
     @NotNull
@@ -397,7 +397,7 @@ public class DfaExpressionFactory {
 
     @Override
     public boolean isStable() {
-      return false;
+      return myStable;
     }
 
     @Override

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

@@ -42,7 +42,7 @@ class BrokenAlignment {
 
   private static class Data {
     @Nullable final String text;
-    @Nullable final Data inner;
+    @Nullable Data inner;
 
     Data(@Nullable String text, Data inner) {
       this.text = text;

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

@@ -0,0 +1,34 @@
+import java.io.File;
+
+final class MyClass {
+  
+  
+  void test(Point p) {
+    if (p.getX() == p.getY()) {
+      unknown();
+      if (<warning descr="Condition 'p.getX() == p.getY()' is always 'true'">p.getX() == p.getY()</warning>) {}
+    }
+  }
+  
+  native void unknown();
+  
+  void testFile(File f) {
+    if (!f.exists()) {
+      unknown();
+      if (!f.exists()) {}
+    }
+  }
+  
+  final class Point {
+    final int x;
+    final int y;
+    
+    Point(int x, int y) {
+      this.x = x;
+      this.y = y;
+    }
+    
+    public int getX() {return x;}
+    public int getY() {return y;}
+  }
+}