Tree.depth_to.up: def of bolt@1.27.0.0
Import: import bolt@1.27.0.0/src/syntax/tree.bend as Tree
Lines 189-195 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=189&end_line=195

import Base

# one more group above the one found below, when one was
def depth_to.up(below: Nat) -> Nat:
  match below:
    case Zero{}:
      0n
    case Succ{p}:
      Succ{Succ{p}}

Uses (1):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat