The newly added support for `! &' uses the previous value of the_printed_command_except_trap or segfaults if none has been made yet:
$ bash -c ': X; ! & jobs' [1]+ Running : X & $ bash -c '! &' Segmentation fault
The newly added support for `! &' uses the previous value of the_printed_command_except_trap or segfaults if none has been made yet:
$ bash -c ': X; ! & jobs' [1]+ Running : X & $ bash -c '! &' Segmentation fault