diff options
Diffstat (limited to 'Lib/dataclasses.py')
| -rw-r--r-- | Lib/dataclasses.py | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index 3f85d85..b327462 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -808,8 +808,10 @@ def _get_field(cls, a_name, a_type, default_kw_only): raise TypeError(f'field {f.name} is a ClassVar but specifies ' 'kw_only') - # For real fields, disallow mutable defaults for known types. - if f._field_type is _FIELD and isinstance(f.default, (list, dict, set)): + # For real fields, disallow mutable defaults. Use unhashable as a proxy + # indicator for mutability. Read the __hash__ attribute from the class, + # not the instance. + if f._field_type is _FIELD and f.default.__class__.__hash__ is None: raise ValueError(f'mutable default {type(f.default)} for field ' f'{f.name} is not allowed: use default_factory') |