def stale.go

yaml-for-bend@0.1.1.0 · scan.bend:540

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

540# Keys left behind are no longer possible. Keys go stale oldest first, so
541# a level whose oldest possible key is still fresh has nothing stale at or
542# below it, and the search stops there.
543def stale.go(keys: List<&2, SKey>, +at: T.Mark) -> Result<&2, &2, T.Error, List<&2, SKey>>:
544  match keys:
545    case Nil{}:
546      Done{[]}
547    case Con{k, +rest}:
548      match k:
549        case SKey{+possible, +required, +number, +kat, +tab, +low}:
550          +old = Bool.and(possible, is_stale(kat, at))
551          when(Result<&2, &2, T.Error, List<&2, SKey>>, Bool.not(low.stale(low, at)), u => Done{SKey{possible, required, number, kat, tab, low} <> rest},
552            u => when(Result<&2, &2, T.Error, List<&2, SKey>>, Bool.and(old, required),
553              u => Fail{T.Error{"could not find expected ':' while scanning a simple key", kat, T.Syntax{}}},
554              u => stale.cons(Bool.and(possible, Bool.not(old)), required, number, kat, tab, stale.go(rest, at))))