IDEA-123870 Completion does not suggest expected methods after instanceof

java/java-analysis-impl/src/com/intellij/codeInsight/guess/impl/ExpressionTypeMemoryState.java

@@ -26,6 +26,7 @@ import com.intellij.psi.PsiType;
 import com.intellij.util.containers.HashMap;
 import gnu.trove.THashMap;
 import gnu.trove.TObjectHashingStrategy;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Map;
 
@@ -110,7 +111,10 @@ public class ExpressionTypeMemoryState extends DfaMemoryStateImpl {
     return super.toString() + " states=[" + new HashMap<PsiExpression, PsiType>(myStates) + "]";
   }
 
-  public void setExpressionType(PsiExpression expression, PsiType type) {
-    myStates.put(expression, type);
+  public void setExpressionType(PsiExpression expression, @NotNull PsiType type) {
+    PsiType prev = myStates.get(expression);
+    if (prev == null || !type.isAssignableFrom(prev)) {
+      myStates.put(expression, type);
+    }
   }
 }

java/java-tests/testData/codeInsight/completion/normal/CastTwice.java

@@ -0,0 +1,14 @@
+public class Class2 {
+    void test(Object o) {
+        if (o instanceof B && ((A)o).a() && o.<caret>
+    }
+}
+
+
+interface A {
+    boolean a();
+}
+
+interface B extends A {
+    boolean b();
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/NormalCompletionDfaTest.groovy

@@ -40,7 +40,12 @@ class NormalCompletionDfaTest extends LightFixtureCompletionTestCase {
   void testCastQualifierForPrivateFieldReference() { doTest(); }
   void testOrAssignmentDfa() { doTest(); }
   void testFieldWithCastingCaret() { doTest(); }
-  
+
+  void testCastTwice() {
+    configureByTestName()
+    myFixture.assertPreferredCompletionItems 0, 'b', 'a'
+  }
+
   void testPublicMethodExtendsProtected() {
     myFixture.addClass '''
 package foo;