OptionalAssignedToNull: added optional (sic!) warning on optional == null comparison

Fixes IDEA-187578 Inspection to detect when Optional is compared with null

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/optionalNull/afterOptionalComparison.java

@@ -0,0 +1,20 @@
+// "Fix all 'Null value for Optional type' problems in file" "true"
+import java.util.List;
+import java.util.Optional;
+import java.util.OptionalInt;
+
+public class Test {
+  void test(Optional<String> opt) {
+    if(!opt.isPresent()) {
+      System.out.println("null!");
+    }
+  }
+
+  void test2 (Optional<String> opt) {
+      /*comment*/
+      if(opt.isPresent()) {
+      System.out.println("null!");
+    }
+  }
+
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/optionalNull/afterOptionalNull.java

@@ -16,7 +16,7 @@ public class Test {
   }
 
   OptionalInt opt() {
-    return OptionalInt.empty();
+    return (/*comment*/OptionalInt.empty());
   }
 
   void m(Optional<String> opt) {}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/optionalNull/beforeOptionalComparison.java

@@ -0,0 +1,19 @@
+// "Fix all 'Null value for Optional type' problems in file" "true"
+import java.util.List;
+import java.util.Optional;
+import java.util.OptionalInt;
+
+public class Test {
+  void test(Optional<String> opt) {
+    if(opt =<caret>= null) {
+      System.out.println("null!");
+    }
+  }
+
+  void test2 (Optional<String> opt) {
+    if(opt !=/*comment*/ null) {
+      System.out.println("null!");
+    }
+  }
+
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/optionalNull/beforeOptionalNull.java

@@ -16,7 +16,7 @@ public class Test {
   }
 
   OptionalInt opt() {
-    return null;
+    return (/*comment*/null);
   }
 
   void m(Optional<String> opt) {}