java completion: don't insert method type arguments if they weren't inferred (IDEA-198368)

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

@@ -0,0 +1,18 @@
+import java.util.Comparator;
+
+class T {
+
+  {
+    new TreeSet<>(Ordering.natural()<caret>)
+  }
+}
+
+abstract class Ordering<T> implements Comparator<T> {
+  static <C extends Comparable> Ordering<C> natural() {
+  }
+}
+
+class TreeSet<E> {
+  TreeSet(Comparator<? super E> c) {
+  }
+}