java completion: suggest only denotable method return types (IDEA-194462)

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

@@ -21,6 +21,7 @@ import com.intellij.codeInsight.lookup.PsiTypeLookupItem;
 import com.intellij.patterns.ElementPattern;
 import com.intellij.psi.*;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.psi.util.PsiTypesUtil;
 import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.Consumer;
 import com.intellij.util.ProcessingContext;
@@ -60,7 +61,7 @@ class MethodReturnTypeProvider extends CompletionProvider<CompletionParameters>
       @Nullable
       @Override
       public PsiType visitType(PsiType type) {
-        if (!(type instanceof PsiPrimitiveType) && myProcessed.add(type)) {
+        if (!(type instanceof PsiPrimitiveType) && PsiTypesUtil.isDenotableType(type, position) && myProcessed.add(type)) {
           int priority = type.equalsToText(CommonClassNames.JAVA_LANG_OBJECT) ? 1 : 1000 - myProcessed.size();
           consumer.consume(PrioritizedLookupElement.withPriority(PsiTypeLookupItem.createLookupItem(type, position), priority));
         }

java/java-tests/testData/codeInsight/completion/smartType/SuggestMethodReturnTypeAnonymous.java

@@ -0,0 +1,7 @@
+public class Main {
+
+  public <caret>x main() {
+    return new Object(){};
+  }
+
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartTypeCompletionTest.java

@@ -1170,6 +1170,11 @@ public class SmartTypeCompletionTest extends LightFixtureCompletionTestCase {
     myFixture.assertPreferredCompletionItems(0, "Serializable", "CharSequence", "Object");
   }
 
+  public void testSuggestMethodReturnTypeAnonymous() {
+    configureByTestName();
+    assertOrderedEquals(myFixture.getLookupElementStrings(), "Object");
+  }
+
   public void testSuggestCastReturnTypeByCalledMethod() { doTest(); }
 
   public void testOnlyInterfacesInImplements() { doTest(); }