JavaCompletionUtil: do not add an unnecessary cast if hierarchy signature has several levels

Fixes IDEA-185554 Redundant cast on autocompletion

java/java-impl/src/com/intellij/codeInsight/completion/JavaCompletionUtil.java

@@ -366,7 +366,7 @@ public class JavaCompletionUtil {
           PsiClassType.ClassResolveResult plainResult = ((PsiClassType)plainQualifier).resolveGenerics();
           PsiClass plainClass = plainResult.getElement();
           HierarchicalMethodSignature signature = method.getHierarchicalMethodSignature();
-          if (plainClass != null && StreamEx.of(signature.getSuperSignatures()).prepend(signature)
+          if (plainClass != null && StreamEx.ofTree(signature, s -> StreamEx.of(s.getSuperSignatures()))
             .anyMatch(sig -> MethodSignatureUtil.findMethodBySignature(plainClass, sig, true) != null)) {
             PsiClass castClass = ((PsiClassType)castType).resolveGenerics().getElement();
 

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

@@ -0,0 +1,18 @@
+class MyTest {
+    interface Container<K, V> {
+        V read(K k);
+    }
+
+    interface Container2<K, V> extends Container<K, V> {
+        V read(K k);
+    }
+
+    interface Container3<K, V> extends Container2<K, V> {
+        V read(K k);
+    }
+
+    void test(Container3<String, String> c3) {
+        Container<String, String> c = c3;
+        c.re<caret>
+    }
+}

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

@@ -0,0 +1,18 @@
+class MyTest {
+    interface Container<K, V> {
+        V read(K k);
+    }
+
+    interface Container2<K, V> extends Container<K, V> {
+        V read(K k);
+    }
+
+    interface Container3<K, V> extends Container2<K, V> {
+        V read(K k);
+    }
+
+    void test(Container3<String, String> c3) {
+        Container<String, String> c = c3;
+        c.read()
+    }
+}

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

@@ -54,6 +54,7 @@ class NormalCompletionDfaTest extends NormalCompletionTestCase {
   void testGenericTypeDfa() { doTest() }
   void testNoUnnecessaryCastDfa() { doTest() }
   void testNoUnnecessaryCastRawDfa() { doTest() }
+  void testNoUnnecessaryCastDeepHierarchy() { doTest() }
   void testInstanceOfAfterFunction() { doTest() }
   void testComplexInstanceOfDfa() {
     configureByTestName()