Tag wrong heredoc start as SyntaxError instead of TokenMissingError

Author: José Valim

lib/elixir/src/elixir_tokenizer.erl

@@ -627,9 +627,8 @@ extract_heredoc(Line0, Rest0, Marker) ->
           {error, {ErrorLine, io_lib:format(Message, [Terminator, Line0]), []}}
       end;
     error ->
-      Terminator = [Marker, Marker, Marker],
-      Message = "heredoc start ~ts must be followed by a new line",
-      {error, {Line0, io_lib:format(Message, [Terminator]), []}}
+      Message = "heredoc start must be followed by a new line after ",
+      {error, {Line0, io_lib:format(Message, []), [Marker, Marker, Marker]}}
   end.
 
 %% Remove spaces from heredoc based on the position of the final quotes.

lib/elixir/test/elixir/kernel/errors_test.exs

@@ -54,8 +54,8 @@ defmodule Kernel.ErrorsTest do
   end
 
   test :heredoc_start do
-    assert_compile_fail TokenMissingError,
-      "nofile:1: heredoc start \"\"\" must be followed by a new line",
+    assert_compile_fail SyntaxError,
+      "nofile:1: heredoc start must be followed by a new line after \"\"\"",
       '"""bar\n"""'
   end