Improve error message on unclosed interpolation/string, closes #794

Author: José Valim

lib/elixir/src/elixir_interpolation.erl

@@ -19,8 +19,8 @@ extract(Line, _File, _Interpol, [], _Buffer, [], _Output, Last) ->
 extract(Line, File, _Interpol, [Last|Remaining], Buffer, [], Output, Last) ->
   finish_extraction(Line, File, Buffer, Output, Remaining);
 
-extract(Line, _File, _Interpol, [Last], _Buffer, Search, _Output, Last) ->
-  { error, { Line, io_lib:format("unexpected end of string: ~ts", [[hd(Search)]]), [Last] } };
+extract(Line, _File, _Interpol, End, _Buffer, Search, _Output, Last) when End == [Last]; End == [] ->
+  { error, { Line, io_lib:format("missing terminator: ~ts", [[Last]]), [] } };
 
 extract(Line, File, Interpol, [$\n|Rest], Buffer, Search, Output, Last) ->
   extract(Line+1, File, Interpol, Rest, [$\n|Buffer], Search, Output, Last);

lib/elixir/test/erlang/string_test.erl

@@ -98,7 +98,8 @@ bin_string_with_escaped_interpolation_test() ->
   {<<"f#{'o}o">>, _} = eval("\"f\\#{'o}o\"").
 
 invalid_string_interpolation_test() ->
-  ?assertError({'Elixir.SyntaxError', _, _, _, _}, eval("\"f#{{}o\"")).
+  ?assertError({'Elixir.TokenMissingError', _, _, _, _}, eval("\"f#{some\"")),
+  ?assertError({'Elixir.TokenMissingError', _, _, _, _}, eval("\"f#{1+")).
 
 unterminated_string_interpolation_test() ->
   ?assertError({'Elixir.TokenMissingError', _, _, _, _}, eval("\"foo")).