When comparing the
call against the function call operators, the implied object
argument is compared against the implicit object parameter of the
function call operator.
When comparing the call against a
surrogate call function, the implied object argument is compared
against the first parameter of the surrogate call function.
conversion function from which the surrogate call function was
derived will be used in the conversion sequence for that
parameter since it converts the implied object argument to the
appropriate function pointer or reference required by that first
— end note