Overlapping type
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- Dominant language
- Python
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Description
This is an rough idea from the recent discussion of whether to use object/Any or _KT for arguments of certain methods like pop or __sub__. E.g.:
class MyPoppable[KT, VT]:
def pop(self, x: X) -> VT: ...
What should X be? Using KT (or KT | None) finds type errors like the following:
poppable: MyPoppable[str]
poppable.pop(123)
But has a problem with overlapping types:
def foo(x: int | str):
poppable.pop(x)
On the other hand, using object doesn't catch type errors like poppable.pop(123).
The solution would be able to specify that any partially overlapping type would be accepted:
class MyPoppable[KT, VT]:
def pop(self, x: Overlapping[KT]) -> VT: ...
MyPoppable[str]().pop() would accept str, str | None, Literal["x"], str | int, etc., but not e.g. plain int.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the overlapping-type examples in the issue and review the recent discussion they reference. Define the intended semantics for an Overlapping type, including unions, literals, and non-overlapping types; done means the behavior and typing rules are agreed upon.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100