Message in French (Français)
When called from '<var>X</var>', rewriting a node of type '<var>Type Name</var>' must return a non-null value of the same type. Alternatively, override '<var>Y</var>' and change it to not visit children of this type.
Unlocalized message
When called from '<var>X</var>', rewriting a node of type '<var>Type Name</var>' must return a non-null value of the same type. Alternatively, override '<var>Y</var>' and change it to not visit children of this type.
Search by Google