pathologic input: O(n^2) with link ref. defs #238
Description
Input generated with this leads to O(n^2) in time and space (output size):
$ python -c 'N=1000; print("[x]: " + "x" * N + "\n[x]" * N)'
{{ message }}
Input generated with this leads to O(n^2) in time and space (output size):
$ python -c 'N=1000; print("[x]: " + "x" * N + "\n[x]" * N)'