def first

bolt@1.27.0.0 · src/syntax/tree.bend:54

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

54# the token a leaf holds; a group's open, a statement's first token
55def first(nn: Node) -> Maybe<&2, Lex.Tok>:
56  match nn:
57    case Leaf{tok}:
58      Some{tok}
59    case Group{open, kids, close}:
60      Some{open}
61    case Stmt{kind, kids, body}:
62      first(kids)
63    case NNil{}:
64      None{}
65    case NCons{h, t}:
66      first(h)