Tree.first: def of bolt@1.27.0.0
Import: import bolt@1.27.0.0/src/syntax/tree.bend as Tree
Lines 54-66 of bolt@1.27.0.0/src/syntax/tree.bend: https://jend.leeeet.dev/read.txt?path=bolt@1.27.0.0/src/syntax/tree.bend&start_line=54&end_line=66

import Base
import bolt@1.27.0.0/src/syntax/lex.bend as Lex

# the token a leaf holds; a group's open, a statement's first token
def first(nn: Node) -> Maybe<&2, Lex.Tok>:
  match nn:
    case Leaf{tok}:
      Some{tok}
    case Group{open, kids, close}:
      Some{open}
    case Stmt{kind, kids, body}:
      first(kids)
    case NNil{}:
      None{}
    case NCons{h, t}:
      first(h)

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/syntax/lex.bend&name=Tok
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/syntax/tree.bend&name=Node