Uninitialized scalar field

The field will contain an arbitrary value left over from earlier computations. A scalar field is not initialized by the constructor
/src/mongo/db/query/optimizer/explain.cpp:500: UNINIT_CTOR 121476 Class member declaration for "_canAppend".
/src/mongo/db/query/optimizer/explain.cpp:325: UNINIT_CTOR 121476 Non-static class member "_canAppend" is not initialized in this constructor nor in any functions that it calls.