This ensures that all visit_edges implementations include a call to
Base::visit_edges. In particular, this gives three nice benefits:
- The call can't be forgotten (the main benefit, of course).
- All of the calls look the same. In other words, always use "Base"
instead of the actual concrete class.
- Ensure the object has a call to JS_CELL or JS_OBJECT in the
definition. Otherwise, Base will not be defined and the call will
not compile.
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.
