message: Add a `getImpl()` utility method to the `TypeBase` class as a convenience for derived class to access their associated TypeStorage (NFC)
diff: @@ -165,6 +165,9 @@ public:
  Args... args) {
  return false;
  }
  +
  + /// Utility for easy access to the storage instance.
  + ImplType *getImpl() { return static_cast<ImplType *>(type); }
  };
  using ImplType = TypeStorage;
  