AttributeError: 'Slice' object has no attribute 'qname' on fuzzed code

[correctmost]

Steps to reproduce

The following code triggers an AttributeError in astroid:

s = slice(-2)
@s()
@six.add_metaclass()
class a: ...

This bug was discovered by OSS-Fuzz:
https://issues.oss-fuzz.com/issues/409585564 (report not public yet)

Current behavior

Traceback (most recent call last):
  File "pylint/lint/pylinter.py", line 994, in get_ast
    return MANAGER.ast_from_file(filepath, modname, source=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/manager.py", line 165, in ast_from_file
    return AstroidBuilder(self).file_build(filepath, modname)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/builder.py", line 145, in file_build
    return self._post_build(module, builder, encoding)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/builder.py", line 173, in _post_build
    module = self._manager.visit_transforms(module)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/manager.py", line 129, in visit_transforms
    return self._transform.visit(node)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 162, in visit
    return self._visit(node)
           ^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 84, in _visit
    visited = self._visit_generic(value)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 112, in _visit_generic
    return [self._visit_generic(child) for child in node]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 112, in <listcomp>
    return [self._visit_generic(child) for child in node]
            ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 119, in _visit_generic
    return self._visit(node)
           ^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 87, in _visit
    return self._transform(node)
           ^^^^^^^^^^^^^^^^^^^^^
  File "astroid/transforms.py", line 67, in _transform
    ret = transform_func(node)
          ^^^^^^^^^^^^^^^^^^^^
  File "astroid/brain/brain_six.py", line 185, in transform_six_add_metaclass
    if func.qname() == SIX_ADD_METACLASS and decorator.args:
       ^^^^^^^^^^
AttributeError: 'Slice' object has no attribute 'qname'

Expected behavior

No crash

Version

ce81c29

[cdce8p]

Note that slice itself is not a callable, so the code above would fail in production as well.

>>> slice(-2)()
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    slice(-2)()
    ~~~~~~~~~^^
TypeError: 'slice' object is not callable

[Pierre-Sassoulas]

Thank you again for the fuzzing work @correctmost