Use union instead of join for unifying types
Open
Nobody has claimed this yet.
bug
needs discussion
priority-0-high
topic-join-v-union
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
@erictraut has gathered a long list of problems caused by mypy's behavior of using the "join" operator to unify types in various contexts.
- #12053
- #12009
- #11934
- #11440
- #11618
- #10740
- #10442
- #7884
- #7835
- #7616
- #6968
- #6079
- #5512
- #5128
- #4134
- #3339
I believe that we should change this behavior.
If someone opens a PR to do this, it would be interesting to see what the results look like in mypy-primer and mypy's CI.
Contributor guide
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 by reviewing the linked issues (#12053, #12009, #11934, #11440, #11618, #10740, #10442, #7884, #7835, #7616, #6968, #6079, #5512, #5128, #4134, and #3339) to map the affected contexts. Then compare results in mypy-primer and mypy's CI; done means the unification behavior has been changed and its effects are understood across those checks.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100