[1 .] . . : 2

# (map (@ 1 0-0)
#   (.sequence
#     (string (@ 1 1-2) ‘1’)
#   )
#   (.result
#     (string (@ 1 12-13) ‘2’)
#   )
# )
# (map (@ 1 0-0)
#   (.sequence
#     (nothing (@ 1 3-4))
#   )
#   (.result
#     (string (@ 1 12-13) ‘2’)
#   )
# )
# :1:6–7: warning: ‘.’ outside alternation has no effect
#  [1 .] . . : 2
#        ^
# :1:8–9: warning: ‘.’ outside alternation has no effect
#  [1 .] . . : 2
#          ^
# :1:3–4: error: mapping of null sequence
#  [1 .] . . : 2
#     ^