More precise error message when escaping a regex with a ref (elixir-lang#14560)

Author: sabiwara

lib/elixir/src/elixir_quote.erl

@@ -160,15 +160,7 @@ do_escape(BitString, _) when is_bitstring(BitString) ->
   end;
 
 do_escape(Map, Q) when is_map(Map) ->
-  TT =
-    [if
-      ?OTP_RELEASE >= 28, is_reference(V) ->
-        argument_error(<<('Elixir.Kernel':inspect(Map, []))/binary, " contains a reference (",
-                         ('Elixir.Kernel':inspect(V, []))/binary, ") and therefore it cannot be escaped ",
-                         "(it must be defined within a function instead). ", (bad_escape_hint())/binary>>);
-      true ->
-        {do_quote(K, Q), do_quote(V, Q)}
-     end || {K, V} <- lists:sort(maps:to_list(Map))],
+  TT = [escape_map_key_value(K, V, Map, Q) || {K, V} <- lists:sort(maps:to_list(Map))],
   {'%{}', [], TT};
 
 do_escape([], _) ->
@@ -202,6 +194,29 @@ do_escape(Fun, _) when is_function(Fun) ->
 do_escape(Other, _) ->
   bad_escape(Other).
 
+escape_map_key_value(K, V, Map, Q) ->
+  MaybeRef = if
+    ?OTP_RELEASE < 28 -> nil;
+    is_reference(V) -> V;
+    is_tuple(V) -> find_tuple_ref(V, 1);
+    true -> nil
+  end,
+  if
+    is_reference(MaybeRef) ->
+      argument_error(<<('Elixir.Kernel':inspect(Map, []))/binary, " contains a reference (",
+                        ('Elixir.Kernel':inspect(MaybeRef, []))/binary, ") and therefore it cannot be escaped ",
+                        "(it must be defined within a function instead). ", (bad_escape_hint())/binary>>);
+    true ->
+      {do_quote(K, Q), do_quote(V, Q)}
+    end.
+
+find_tuple_ref(Tuple, Index) when Index > tuple_size(Tuple) -> nil;
+find_tuple_ref(Tuple, Index) ->
+  case element(Index, Tuple) of
+    Ref when is_reference(Ref) -> Ref;
+    _ -> find_tuple_ref(Tuple, Index + 1)
+  end.
+
 bad_escape(Arg) ->
   argument_error(<<"cannot escape ", ('Elixir.Kernel':inspect(Arg, []))/binary, ". ",
                    (bad_escape_hint())/binary>>).