qdoc generates {-proxy.html} pages if the target of a \relate is not valid. In Qt COre /6.6.0, these are the following pages:

./qtcore/qforeach-proxy.html
./qtcore/qfunctionpointer-proxy.html
./qtcore/qoverload-proxy.html
./qtcore/qpair-proxy.html
./qtcore/qtassert-proxy.html
./qtcore/qtclasshelpermacros-proxy.html
./qtcore/qtdarwinhelpers-proxy.html
./qtcore/qtenvironmentvariables-proxy.html
./qtcore/qtminmax-proxy.html
./qtcore/qtpreprocessorsupport-proxy.html
./qtcore/qtresource-proxy.html
./qtcore/qtswap-proxy.html
./qtcore/qttranslation-proxy.html
./qtcore/qttypetraits-proxy.html
./qtcore/qtversion-proxy.html
./qtcore/qtversionchecks-proxy.html
./qtcore/qtypeinfo-proxy.html