Handle error in Macro.to_string/1, closes #13102

Author: josevalim

Diff for: lib/elixir/lib/code/normalizer.ex

@@ -349,13 +349,15 @@ defmodule Code.Normalizer do
         meta
       end
 
+    last = List.last(args)
+
     cond do
-      Keyword.has_key?(meta, :do) or match?([{{:__block__, _, [:do]}, _} | _], List.last(args)) ->
+      Keyword.has_key?(meta, :do) or match?([{{:__block__, _, [:do]}, _} | _], last) ->
         # def foo do :ok end
         # def foo, do: :ok
         normalize_kw_blocks(form, meta, args, state)
 
-      match?([{:do, _} | _], List.last(args)) ->
+      match?([{:do, _} | _], last) and Keyword.keyword?(last) ->
         # Non normalized kw blocks
         line = state.parent_meta[:line]
         meta = meta ++ [do: [line: line], end: [line: line]]

Diff for: lib/elixir/test/elixir/code_normalizer/quoted_ast_test.exs

@@ -229,6 +229,12 @@ defmodule Code.Normalizer.QuotedASTTest do
     test "invalid block" do
       assert quoted_to_string({:__block__, [], {:bar, [], []}}) ==
                "{:__block__, [], {:bar, [], []}}"
+
+      assert quoted_to_string({:foo, [], [{:do, :ok}, :not_keyword]}) ==
+               "foo({:do, :ok}, :not_keyword)"
+
+      assert quoted_to_string({:foo, [], [[{:do, :ok}, :not_keyword]]}) ==
+               "foo([{:do, :ok}, :not_keyword])"
     end
 
     test "not in" do