Scan.key: def of yaml-for-bend@0.1.1.0
Import: import yaml-for-bend@0.1.1.0/scan.bend as Scan
Lines 1381-1386 of yaml-for-bend@0.1.1.0/scan.bend: https://jend.leeeet.dev/read.txt?path=yaml-for-bend@0.1.1.0/scan.bend&start_line=1381&end_line=1386

import Base
import yaml-for-bend@0.1.1.0/token.bend as T

# "? ": an explicit key.
def key(+st: Sc) -> Step:
  when(Step, sc.in_flow(st), u => key.rest(st),
    u => when(Step, sc.tab(st), u => fail(st, "found a tab character that violates indentation", sc.at(st)),
    u => when(Step, sc.allowed(st), u => key.rest(roll(st, sc.col(st), None{}, T.BMapStart{}, sc.at(st))),
      u => fail(st, "mapping keys are not allowed in this context", sc.at(st)))))

Uses (13):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=Sc
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=Step
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=fail
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=key.rest
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=roll
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=sc.allowed
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=sc.at
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=sc.col
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=sc.in_flow
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=sc.tab
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=when
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/token.bend&name=Tok