Raise when Access syntax used on non-keywords

Author: lexmag

lib/elixir/lib/access.ex

@@ -53,7 +53,7 @@ defmodule Access do
     :maps.find(key, map)
   end
 
-  def fetch(list, key) when is_list(list) do
+  def fetch(list, key) when is_list(list) and is_atom(key) do
     case :lists.keyfind(key, 1, list) do
       {^key, value} -> {:ok, value}
       false -> :error

lib/elixir/test/elixir/access_test.exs

@@ -36,6 +36,10 @@ defmodule AccessTest do
     assert Access.fetch([foo: :bar], :foo) == {:ok, :bar}
     assert Access.fetch([foo: :bar], :bar) == :error
 
+    assert_raise FunctionClauseError, fn ->
+      Access.fetch([{"foo", :bar}], "foo")
+    end
+
     assert Access.get([foo: :bar], :foo) == :bar
     assert Access.get_and_update([], :foo, fn nil -> {:ok, :baz} end) == {:ok, [foo: :baz]}
     assert Access.get_and_update([foo: :bar], :foo, fn :bar -> {:ok, :baz} end) == {:ok, [foo: :baz]}