They do not work with our qmltypes properly and have been deprecated for a long time, sadly they're still needed for pulling in enums from different namespaces / classes in a few places:

src/imports/wavefrontmesh/qwavefrontmesh.h
src/labs/wavefrontmesh/qwavefrontmesh_p.h
src/quick/items/qquickaccessibleattached_p.h
src/quick/items/qquickrectangle_p.h

(There are also a few uses in examples and tests but these are less important)

We need to figure out a solution for this.