Proposed resolution:

Table 88 (section 27.4.3) -- Position type requirements be updated to include increment and decrement operators.

expression        return type     operational    note

++p               fpos&           p += O(1)
p++               fpos            { P tmp = p;
                                    ++p;
                                    return tmp; }
--p               fpos&           p -= O(1)
p--               fpos            { P tmp = p;
                                    --p;
                                    return tmp; }