Ok just reuse the main_function from Runner for now

lib/benchee/benchmark/repeated_measurement.ex

@@ -116,7 +116,7 @@ defmodule Benchee.Benchmark.RepeatedMeasurement do
          }
        )
        when iterations > 1 do
-    main = main_function(function, input)
+    main = Runner.main_function(function, input)
     # with no before/after each we can safely omit them and don't get the hit
     # on run time measurements (See PR discussions for this for more info #127)
     fn -> RepeatN.repeat_n(main, iterations) end
@@ -131,17 +131,12 @@ defmodule Benchee.Benchmark.RepeatedMeasurement do
       RepeatN.repeat_n(
         fn ->
           new_input = Hooks.run_before_each(scenario, scenario_context)
-          main = main_function(function, new_input)
+          main = Runner.main_function(function, new_input)
           return_value = main.()
           Hooks.run_after_each(return_value, scenario, scenario_context)
         end,
         iterations
       )
     end
   end
-
-  # TODO: temporarily duplicated
-  @no_input Benchee.Benchmark.no_input()
-  defp main_function(function, @no_input), do: function
-  defp main_function(function, input), do: fn -> function.(input) end
 end

lib/benchee/benchmark/runner.ex

@@ -212,6 +212,6 @@ defmodule Benchee.Benchmark.Runner do
   end
 
   @no_input Benchmark.no_input()
-  defp main_function(function, @no_input), do: function
-  defp main_function(function, input), do: fn -> function.(input) end
+  def main_function(function, @no_input), do: function
+  def main_function(function, input), do: fn -> function.(input) end
 end