The VersionContext type is currently declared in a single header file (src/mongo/db/version_context.h) but the definitions are split between two source files (src/mongo/db/version_context.cpp) and src/mongo/db/version_context_decoration.cpp).

This split is due to the need to use VersionContext from within server_base (where OperationContext is not available), yet still allow implementing methods such as VersionContext::getDecoration(OperationContext*).

An alternative design would be to move the methods that receive an OperationContext parameter to a new VersionContextDecoration class. This would allow a 1-to-1 correspondence between header and source files, potentially preventing confusion and linking problems.