This is implemented as a Clang frontend tool, and currently does two
things:
- Ensure for all fields wrapped in {Nonnull,}GCPtr<T>, T inherits from
JS::Cell
- Ensure for all fields not wrapped in {Nonnull,}GCPtr, that the type
does not inherit from JS::Cell (otherwise it should be wrapped in a
Ptr class).
In the future, this tool could be extended further. For example, we may
consider validating all implementations of Cell::visit_impl.
