Given a QTaggedPointer, users may write taggedPtr = {}; to mean "reset it". This is error-prone: due to overload resolution, this actually ends up calling QTaggedPointer<T>::operator=(T *), which changes the pointer but *not* the tag, and not the implicitly declared QTaggedPointer<T>:operator=(const QTaggedPointer<T> &) which would reset both pointer and tag. Given the idiomatic usage of {} is indeed to perform a full reset (cf. std::exchange(obj, {}), std::take, etc.), work around this by disabling the operator= overload for pointers in case an initializer list is passed. In other words, make `={}` fall back to the implicitly declared overload. Note, this breaks some usages, such as taggedPtr = {rawPtr}; but at least we get a compile error for these, and they don't look common at all. [ChangeLog][QtCore][QTaggedPointer] The operator assignment taking a raw pointer has been reimplemented in order to avoid subtle issues when assigning `{}` to a QTaggedPointer. This will cause code that assigns a braced-init-list to a QTaggedPointer object to stop compiling (for instance, `tagPtr = {ptr}` is now ill-formed). Change-Id: I5e572a9b0f119ddb2df17f1797934933dff2ba7b Task-number: QTBUG-106070 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>