Add Missing Override query

ql/src/codeql_ql/ast/Ast.qll

@@ -228,10 +228,14 @@ class ClassPredicate extends TClassPredicate, Predicate {
 
   override string getAPrimaryQlClass() { result = "ClassPredicate" }
 
-  predicate isPrivate() {
+  override Class getParent() { result.getAClassPredicate() = this }
+
+  predicate isPrivate() { hasAnnotation("private") }
+
+  predicate hasAnnotation(string name) {
     exists(Generated::ClassMember member |
       pred = member.getChild(_) and
-      member.getAFieldOrChild().(Generated::Annotation).getName().getValue() = "private"
+      member.getAFieldOrChild().(Generated::Annotation).getName().getValue() = name
     )
   }
 

ql/src/queries/style/MissingOverride.ql

@@ -0,0 +1,20 @@
+/**
+ * @name Missing override annotation
+ * @description Predicates that overide another predicate should have an `override` annotation.
+ * @kind problem
+ * @problem.severity warning
+ * @precision very-high
+ * @id ql/missing-override
+ * @tags maintainability
+ */
+
+import ql
+
+string getQualifiedName(ClassPredicate p) {
+  result = p.getDeclaringType().getName() + "." + p.getName()
+}
+
+from ClassPredicate pred, ClassPredicate sup
+where pred.overrides(sup) and not pred.hasAnnotation("override")
+select pred, getQualifiedName(pred) + "overrides $@ but does not have an override annotation.", sup,
+  getQualifiedName(sup)

ql/test/queries/style/MissingOverride/MissingOverride.expected

@@ -0,0 +1 @@
+| Test.qll:12:3:12:33 | ClassPredicate | Wrong.testoverrides $@ but does not have an override annotation. | Test.qll:4:3:4:40 | ClassPredicate | Super.test |

ql/test/queries/style/MissingOverride/MissingOverride.qlref

@@ -0,0 +1 @@
+queries/style/MissingOverride.ql

ql/test/queries/style/MissingOverride/Test.qll

@@ -0,0 +1,13 @@
+import ql
+
+class Super extends AstNode {
+  predicate test(int i) { i = [1 .. 5] }
+}
+
+class Correct extends Super {
+  override predicate test(int i) { i = 3 }
+}
+
+class Wrong extends Super {
+  predicate test(int i) { i = 2 }
+}