Index.walk: def of bolt@1.27.0.0
Import: import bolt@1.27.0.0/src/rules/pedantic/index.bend as Index
Lines 43-65 of bolt@1.27.0.0/src/rules/pedantic/index.bend: https://jend.leeeet.dev/read.txt?path=bolt@1.27.0.0/src/rules/pedantic/index.bend&start_line=43&end_line=65

import Base
import bolt@1.27.0.0/src/finding.bend as F
import bolt@1.27.0.0/src/syntax/lex.bend as Lex
import bolt@1.27.0.0/src/syntax/tree.bend as Tree
import bolt@1.27.0.0/src/rules/calls.bend as Calls

# every List.get / String.get call at a computed index, but self's own
def walk(nn: Tree.Node, +path: String, +fixed: List<&2, String>, +self: String) -> List<&2, F.Finding>:
  match nn:
    case Tree.NCons{Tree.Leaf{Lex.Tok{k, +t, +l, +c}}, Tree.NCons{Tree.Group{Lex.Tok{_, +o, _, _}, +kids, _}, rest}}:
      +list = named(t, self, "List.get")
      +as = Calls.args(kids)
      +get = Bool.and(String.eq(o, "("), Bool.or(list, named(t, self, "String.get")))
      +fire = Bool.and(get, Bool.and(Bool.not(literal(Calls.arg(as, Bool.pick(Nat, list, 3n, 1n)))),
        Bool.not(held(list, Calls.arg(as, 2n), fixed))))
      +more = List.concat(&2, F.Finding, [walk(kids, path, fixed, self), walk(rest, path, fixed, self)])
      Bool.pick(List<&2, F.Finding>, fire,
        F.Finding{path, l, c, U32.from_nat(String.length(t)), "index",
          t ++ " in a recursive def walks the list from its head on every step, which is quadratic; recurse over the list itself."} <> more,
        more)
    case Tree.NCons{Tree.Group{open, +kids, close}, rest}:
      List.concat(&2, F.Finding, [walk(kids, path, fixed, self), walk(rest, path, fixed, self)])
    case Tree.NCons{Tree.Stmt{kind, +kids, body}, rest}:
      List.concat(&2, F.Finding, [walk(kids, path, fixed, self), walk(body, path, fixed, self),
        walk(rest, path, fixed, self)])
    case Tree.NCons{h, rest}:
      walk(rest, path, fixed, self)
    case other:
      Nil{}

Uses (20):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.not
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.or
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.pick
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.concat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  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
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.eq
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.length
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.from_nat
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/finding.bend&name=Finding
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/calls.bend&name=arg
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/calls.bend&name=args
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/pedantic/index.bend&name=held
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/pedantic/index.bend&name=literal
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/pedantic/index.bend&name=named
  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