Two neighbor step in char 0 #16926

Job	Run time
doctest (1.10, ubuntu-latest)	27m 17s
test (1.6, short, ubuntu-latest)	1h 31m 10s
doctest (1.11-nightly, ubuntu-latest)	25m 56s
test (1.6, long, ubuntu-latest)	43m 48s
doctest (nightly, ubuntu-latest)	36m 31s
test (1.10, short, ubuntu-latest)	1h 11m 31s
doctest (1.10, ubuntu-latest, depwarn=error)	26m 55s
test (1.10, long, ubuntu-latest)	33m 16s
doctest (1.10, macOS, RPTU)	12m 27s
test (1.11-nightly, short, ubuntu-latest)	1h 22m 34s
test (1.11-nightly, long, ubuntu-latest)	45m 22s
test (nightly, short, ubuntu-latest)	1h 40m 50s
test (nightly, long, ubuntu-latest)	53m 10s
test (1.10, short, ubuntu-latest, depwarn=error)	1h 16m 6s
test (1.10, long, ubuntu-latest, depwarn=error)	33m 38s
test (1.10, short, macOS, RPTU)	13m 49s
test (1.10, long, macOS, RPTU)	11m 39s
test (1.10, book, ubuntu-latest)	41m 55s
test (nightly, book, ubuntu-latest)	58m 4s
	14h 45m 58s

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