---
expr_op := expr_op OR expr_op
  expr_op := NOT expr_op
    NOT := "!"
      ! "!" (1, 1)
    expr_op := expr_op ? attrpath
      ID := "ID"
        ID "builtins" (1, 3)
      ? := "?"
        ? "?" (1, 12)
      ID := "ID"
        ID "nixVersion" (1, 14)
  OR := "OR"
    OR "||" (1, 25)
  expr_op := expr_op EQ expr_op
    expr_app := expr_app expr_select
      expr_app := expr_app expr_select
        expr_select := expr_simple . attrpath
          ID := "ID"
            ID "builtins" (1, 28)
          . := "."
            . "." (1, 36)
          ID := "ID"
            ID "compareVersions" (1, 37)
        ID := "ID"
          ID "requiredVersion" (1, 53)
      expr_select := expr_simple . attrpath
        ID := "ID"
          ID "builtins" (1, 69)
        . := "."
          . "." (1, 77)
        ID := "ID"
          ID "nixVersion" (1, 78)
    EQ := "EQ"
      EQ "==" (1, 89)
    INT := "INT"
      INT "1" (1, 92)