fix: raise ParseError instead of AssertionError on unmatched '}' (#604)

An unmatched '}' (e.g. parser.parse('}')) reached an internal assertion
(c_parser.py:127: assert len(self._scope_stack) > 1) rather than returning
through the usual ParseError path. Callers that catch ParseError to handle
parse failures would not catch the AssertionError.

Replace the bare assert with an explicit ParseError so malformed input
travels the documented error path. Fixes #603.

Author: patchwright

pycparser/c_parser.py

@@ -124,7 +124,8 @@ def _push_scope(self) -> None:
         self._scope_stack.append(dict())
 
     def _pop_scope(self) -> None:
-        assert len(self._scope_stack) > 1
+        if len(self._scope_stack) <= 1:
+            raise ParseError("Unmatched '}'")
         self._scope_stack.pop()
 
     def _add_typedef_name(self, name: str, coord: Optional[Coord]) -> None:

tests/test_c_parser.py

@@ -3783,3 +3783,11 @@ def test_case_empty_statement(self):
 
     # ~ unittest.TextTestRunner(verbosity=2).run(suite)
     unittest.main()
+
+class TestUnmatchedRbrace(unittest.TestCase):
+    """Regression for #603: unmatched '}' raises ParseError, not AssertionError."""
+
+    def test_unmatched_rbrace_raises_parse_error(self):
+        parser = c_parser.CParser()
+        with self.assertRaises(ParseError):
+            parser.parse("}", filename="test.c")