Support for singleton types in unions with Enum #7693
Conversation
There was a problem hiding this comment.
Thanks for the PR! Looks great.
(I'll give @Michael0x2a a chance to have a look before merging since he's our resident expert on literal types.)
mypy/checker.py
Outdated
| if typ.last_known_value: | ||
| return typ.last_known_value | ||
| elif typ.type.is_enum and len(typ.type.names) == 1: | ||
| key, = typ.type.names |
There was a problem hiding this comment.
I believe the names dict can also contain reference to methods, which shouldn't be counted as an enum values.
I'd try refactoring out the "get all enum values" check on lines ~4794 to ~4798 of this file into a separate helper function and call it here instead of using typ.type.names directly, and maybe also add a test case making sure mypy doesn't do anything weird if we have an single-value enum that also defines a method.
mypy/checker.py
Outdated
| @@ -4761,7 +4762,8 @@ def is_singleton_type(typ: Type) -> bool: | |||
| typ = get_proper_type(typ) | |||
| # TODO: Also make this return True if the type is a bool LiteralType. | |||
| # Also make this return True if the type corresponds to ... (ellipsis) or NotImplemented? | |||
| return isinstance(typ, NoneType) or (isinstance(typ, LiteralType) and typ.is_enum_literal()) | |||
| return (isinstance(typ, NoneType) or (isinstance(typ, LiteralType) and typ.is_enum_literal()) | |||
| or (isinstance(typ, Instance) and typ.type.is_enum and len(typ.type.names) == 1)) | |||
There was a problem hiding this comment.
See other comment about typ.type.names -- the same fix should be done here.
This PR adds supports for singleton types in unions using
Enums as described in PEP 484 (without usingFinal).As suggested by @Michael0x2a in the corresponding issue, adding another case to the
is_singleton_typeandcoerce_to_literalfunctions allows mypy to recognize anEnumwith 1 value as a singleton type.Fixes #7279