Raise ArgumentError on invalid binding in Code.eval_string/3 (#15146)

Previously, passing a non-list binding to `Code.eval_string/3` would crash
deep in Erlang code with a confusing `FunctionClauseError` in
`:elixir_erl_var.load_binding/6`.

Author: pnezis

lib/elixir/lib/code.ex

@@ -621,11 +621,17 @@ defmodule Code do
   def eval_string(string, binding \\ [], opts \\ [])
 
   def eval_string(string, binding, %Macro.Env{} = env) do
-    validated_eval_string(string, binding, env)
+    validated_eval_string(string, validate_binding(binding), env)
   end
 
   def eval_string(string, binding, opts) when is_list(opts) do
-    validated_eval_string(string, binding, opts)
+    validated_eval_string(string, validate_binding(binding), opts)
+  end
+
+  defp validate_binding(binding) when is_list(binding), do: binding
+
+  defp validate_binding(binding) do
+    raise ArgumentError, "binding must be a list, got: #{inspect(binding)}"
   end
 
   defp validated_eval_string(string, binding, opts_or_env) do

lib/elixir/test/elixir/code_test.exs

@@ -176,6 +176,16 @@ defmodule CodeTest do
                {"1", [{:c, 2}, {:b, "1"}, {:a, 1}]}
     end
 
+    test "raises on invalid binding type" do
+      assert_raise ArgumentError, "binding must be a list, got: :not_a_list", fn ->
+        Code.eval_string("1 + 1", :not_a_list)
+      end
+
+      assert_raise ArgumentError, "binding must be a list, got: %{}", fn ->
+        Code.eval_string("1 + 1", %{}, __ENV__)
+      end
+    end
+
     test "keeps caller in stacktrace" do
       try do
         Code.eval_string("<<a::size(b)>>", [a: :a, b: :b], file: "myfile")