QWeakPointer: don't let IfCompatible<X> make accidental SMFsHEADdev

The IfCompatible constraint did not exclude the case where is_same<X,
T>, so it made accidental copy and move SMFs. This is a problem
because the normal SMFs all work fine with a forward-declared T, but
conversion construction and assignment inspects X, e.g. by going
through QSharedPointer<X> or checking std::is_virtual_base_of, which
require types to be complete.

Hot-fix by excluding T from IfCompatible<X>. All functions that use
this constraint are already also available as overloads for T, except
the QObject private ctor, for which this patch therefore adds a new
overload.

Fixes the FTBFS described in QTBUG-138246, but not the bug itself,
which is also about QSharedPointer and qxp::is_virtual_base_of.

Amends 014d7ac65417ed9b5ffb85cca24d16564ff5005a.

[ChangeLog][QtCore][QWeakPointer] Fixed a regression whereby the
QWeakPointer<T> copy or move constructors and/or assignment operators
may fail to compile for forward-declared (incomplete) T.

Task-number: QTBUG-138246
Pick-to: 6.10 6.9 6.8 6.5
Change-Id: I0b098732cd7dbb373ff2b2dee8deaac3859127a5
Reviewed-by: Fabian Kosmale <[email protected]>
Reviewed-by: Milian Wolff <[email protected]>

0 files changed, 0 insertions, 0 deletions