Exclude enums that implement the BitmaskType trait

Author: rvermeulen

cpp/common/src/codingstandards/cpp/Type.qll

@@ -59,3 +59,31 @@ Type stripSpecifiers(Type type) {
   then result = stripSpecifiers(type.(SpecifiedType).getBaseType())
   else result = type
 }
+
+/**
+ * A type that implements the BitmaskType trait.
+ * https://en.cppreference.com/w/cpp/named_req/BitmaskType
+ */
+abstract class BitmaskType extends Type { }
+
+/**
+ * Holds if `enum` implements required overload `overload` to implement
+ * the BitmaskType trait.
+ */
+private predicate isRequiredEnumOverload(Enum enum, Function overload) {
+  overload.getName().regexpMatch("operator([&|^~]|&=|\\|=)") and
+  forex(Parameter p | p = overload.getAParameter() |
+    (
+      p.getType() = enum
+      or
+      p.getType().(ReferenceType).getBaseType() = enum
+    )
+  )
+}
+
+private class EnumBitmaskType extends BitmaskType, Enum {
+  EnumBitmaskType() {
+    // Implements all the required overload
+    count(Function overload | isRequiredEnumOverload(this, overload)) = 6
+  }
+}