QL: Add a query that finds missing noinline or nomagic annotations.

ql/src/queries/performance/MissingNoinline.ql

@@ -0,0 +1,23 @@
+/**
+ * @name Missing `noinline` or `nomagic` annotation
+ * @description When a predicate is factored out to improve join-ordering, it should be marked as `noinline` or `nomagic`.
+ * @kind problem
+ * @problem.severity error
+ * @id ql/missing-noinline
+ * @tags performance
+ * @precision high
+ */
+
+import ql
+
+from QLDoc doc, Predicate decl
+where
+  doc.getContents().matches(["%join order%", "%join-order%"]) and
+  decl.getQLDoc() = doc and
+  not decl.getAnAnnotation() instanceof NoInline and
+  not decl.getAnAnnotation() instanceof NoMagic and
+  not decl.getAnAnnotation() instanceof NoOpt and
+  // If it's marked as inline it's probably because the QLDoc says something like
+  // "this predicate is inlined because it gives a better join-order".
+  not decl.getAnAnnotation() instanceof Inline
+select decl, "This predicate might be inlined."