Detect recursive 'source' earlier

Off-by-one error, though still functional. The recursive source is now
detected immediately as the file is source'd the second time.

Also remove an outdated comment re. KconfigError.

1 files changed, 2 insertions, 2 deletions

diff --git a/kconfiglib.py b/kconfiglib.py
index c6a51f9..b96bd19 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -1483,10 +1483,11 @@ class Kconfig(object):
         # Jumps to the beginning of a sourced Kconfig file, saving the previous
         # position and file object
 
+        self._filestack.append((self._file, self._filename, self._linenr))
+
         # Check for recursive 'source'
         for _, name, _ in self._filestack:
             if name == filename:
-                # KconfigParseError might have been a better name, but too late
                 raise KconfigError(
                     "\n{}:{}: Recursive 'source' of '{}' detected. Check that "
                     "environment variables are set correctly.\n"
@@ -1496,7 +1497,6 @@ class Kconfig(object):
                                       for _, name, linenr
                                       in reversed(self._filestack))))
 
-        self._filestack.append((self._file, self._filename, self._linenr))
         try:
             self._file = self._open(filename)
         except IOError as e: