IDEA-177895 Completion items with type casts derived from control flow are not suggested for 'this'

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

@@ -398,8 +398,13 @@ public class GuessManagerImpl extends GuessManager {
     private Map<PsiExpression, PsiType> myResult;
     private final PsiElement myForPlace;
 
-    private ExpressionTypeInstructionVisitor(PsiElement forPlace) {
-      myForPlace = forPlace;
+    private ExpressionTypeInstructionVisitor(@NotNull PsiElement forPlace) {
+      PsiElement parent = PsiUtil.skipParenthesizedExprUp(forPlace.getParent());
+      if (forPlace instanceof PsiThisExpression && parent instanceof PsiReferenceExpression) {
+        myForPlace = parent.getParent() instanceof PsiMethodCallExpression ? parent.getParent() : parent;
+      } else {
+        myForPlace = forPlace;
+      }
     }
 
     public Map<PsiExpression, PsiType> getResult() {

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

@@ -0,0 +1,15 @@
+public abstract class Super {
+
+    void foo() {
+      if (this instanceof Sub) {
+        this.subme<caret>
+      }
+    }
+
+
+}
+
+class Sub extends Zzza {
+  void subMethod() {}
+
+}

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

@@ -0,0 +1,15 @@
+public abstract class Super {
+
+    void foo() {
+      if (this instanceof Sub) {
+        ((Sub) this).subMethod();<caret>
+      }
+    }
+
+
+}
+
+class Sub extends Zzza {
+  void subMethod() {}
+
+}

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

@@ -33,7 +33,9 @@ class NormalCompletionDfaTest extends LightFixtureCompletionTestCase {
   void _testCastIncompleteInstanceofedQualifier() { doTest() }
 
   void testCastTooComplexInstanceofedQualifier() { doAntiTest() }
-  
+
+  void testCastInstanceofedThisQualifier() { doTest() }
+
   void testDontCastInstanceofedQualifier() { doTest() }
   void testDontCastPartiallyInstanceofedQualifier() { doAntiTest() }
   void testQualifierCastingWithUnknownAssignments() { doTest() }