String.join.go: def of Base
Import: import Base
Lines 2181-2186 of Base/base.bend: https://jend.leeeet.dev/read.txt?path=Base/base.bend&start_line=2181&end_line=2186

import Base

def String.join.go(xs: List<&2, String>, h: String, +sep: String) -> String:
  match xs:
    case Nil{}:
      h
    case h2 <> t:
      String.append(h, String.append(sep, String.join.go(t, h2, sep)))

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.append