elixir: Fix exception on literal empty list

Issue kanaka#190

elixir/lib/mix/tasks/step3_env.ex

@@ -58,6 +58,7 @@ defmodule Mix.Tasks.Step3Env do
   end
   defp eval_bindings(_bindings, _env), do: throw({:error, "Unbalanced let* bindings"})
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, ast, meta}, env), do: eval_list(ast, env, meta)
   defp eval(ast, env), do: eval_ast(ast, env)
 

elixir/lib/mix/tasks/step4_if_fn_do.ex

@@ -67,6 +67,7 @@ defmodule Mix.Tasks.Step4IfFnDo do
   end
   defp eval_bindings(_bindings, _env), do: throw({:error, "Unbalanced let* bindings"})
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, ast, meta}, env), do: eval_list(ast, env, meta)
   defp eval(ast, env), do: eval_ast(ast, env)
 

elixir/lib/mix/tasks/step5_tco.ex

@@ -67,6 +67,7 @@ defmodule Mix.Tasks.Step5Tco do
   end
   defp eval_bindings(_bindings, _env), do: throw({:error, "Unbalanced let* bindings"})
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, ast, meta}, env), do: eval_list(ast, env, meta)
   defp eval(ast, env), do: eval_ast(ast, env)
 

elixir/lib/mix/tasks/step6_file.ex

@@ -90,6 +90,7 @@ defmodule Mix.Tasks.Step6File do
   end
   defp eval_bindings(_bindings, _env), do: throw({:error, "Unbalanced let* bindings"})
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, ast, meta}, env), do: eval_list(ast, env, meta)
   defp eval(ast, env), do: eval_ast(ast, env)
 

elixir/lib/mix/tasks/step7_quote.ex

@@ -114,6 +114,7 @@ defmodule Mix.Tasks.Step7Quote do
   end
   defp quasiquote(ast, _env), do: list([{:symbol, "quote"}, ast])
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, ast, meta}, env), do: eval_list(ast, env, meta)
   defp eval(ast, env), do: eval_ast(ast, env)
 

elixir/lib/mix/tasks/step8_macros.ex

@@ -159,6 +159,7 @@ defmodule Mix.Tasks.Step8Macros do
     end
   end
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, _list, _meta} = ast, env) do
     case macroexpand(ast, env) do
       {:list, list, meta} -> eval_list(list, env, meta)

elixir/lib/mix/tasks/step9_try.ex

@@ -159,6 +159,7 @@ defmodule Mix.Tasks.Step9Try do
     end
   end
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, _list, _meta} = ast, env) do
     case macroexpand(ast, env) do
       {:list, list, meta} -> eval_list(list, env, meta)

elixir/lib/mix/tasks/stepA_mal.ex

@@ -178,6 +178,7 @@ defmodule Mix.Tasks.StepAMal do
     end
   end
 
+  defp eval({:list, [], _} = empty_ast, env), do: empty_ast
   defp eval({:list, _list, _meta} = ast, env) do
     case macroexpand(ast, env) do
       {:list, list, meta} -> eval_list(list, env, meta)