def co.alias

yaml-for-bend@0.1.1.0 · compose.bend:493

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

493# An alias: a copy of its node, counted at the node's full size. An alias
494# inside the node it names would make a cycle, which a tree can't hold.
495def co.alias(co: Co, +name: String, +limit: Nat, +at: T.Mark) -> Result<&2, &2, T.Error, Co>:
496  match co:
497    case Co{+stack, +anchors, count, root, docs, opened, depth, copied}:
498      when(Result<&2, &2, T.Error, Co>, opens(stack, name),
499        u => Fail{content("found an alias to a node that holds it: " ++ name ++ " is recursive, and a tree can't hold a cycle", at)},
500        u => when(Result<&2, &2, T.Error, Co>, Bool.not(found(Map.has(&2, Anchored, anchors, name))),
501          u => Fail{content("found an alias to an unknown anchor: " ++ name, at)},
502          u => alias.got(Map.get(Anchored, Anchored{V.Null{}, 0n}, anchors, name), Co{stack, anchors, count, root, docs, opened, depth, copied}, limit, at)))