Amends 207aae5560 to make it easy to
create human-friendly error messages. Since the functor-accepting member
functions are not removed from the API, the first compile error will be
that there is no suitable overload of the makeSlotObject helper, which.
With the assert helper, the first error message is easier to understand.
Change-Id: I4878ec35a44ddfa5dc9d9e358d81c3fd40389c0c
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>