Anyone can help me? Why compiler is throwing this error?:

** (ArgumentError) argument error
(stdlib 3.13) :lists.keyfind(:counter, 1, :SyncKey)
(elixir 1.10.4) src/elixir_utils.erl:45: :elixir_utils.var_context/2
(stdlib 3.13) lists.erl:1354: :lists.mapfoldl/3

Here is the source:

defmodule Problem do
  def sample,
    do: {
      :foldercreate,
      {:FolderHierarchy, :FolderCreate,
       [
         {:FolderHierarchy, :SyncKey, :reqres},
         {:FolderHierarchy, :ParentId, :req},
         {:FolderHierarchy, :DisplayName, :req},
         {:FolderHierarchy, :Type, :req},
         {:FolderHierarchy, :Status, :res},
         {:FolderHierarchy, :ServerId, :res}
       ]}
    }

    defmacro res_cmd() do
      {fnname, {namespace,container,lista}} = sample()
      quote do
        def unquote(fnname)(:res, pars) do
            {
              unquote(namespace),
              unquote(container),
              unquote(lista)
                |> Enum.filter(fn {_, _, ty} -> ty == :res or ty == :reqres end)
                |> Enum.map(fn {a,b,_c} -> {a,b,pars[b]} end)
            }
        end
      end
    end
end

defmodule Injected do
  require Problem
  Problem.res_cmd()
end