"Dynamic metaclass not supported" false positive on generics
Nobody has claimed this yet.
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
from typing import TypeVar, Generic
T = TypeVar("T")
class FooMetaclass(type, Generic[T]): pass
class Foo(metaclass=FooMetaclass[T]): # error: Dynamic metaclass not supported for "Foo"
pass
https://mypy-play.net/?mypy=master&python=3.10&gist=d4b169a5ece08ed0607b19fff8e9b749
according to the documentation:
Mypy does not understand dynamically-computed metaclasses, such as
class A(metaclass=f()): ...
however this isn't dynamically computed, it's just a generic so mypy should be able to understand it statically
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 reproducing the example in the linked mypy-play case and reading the metaclass-support documentation, especially its limitations. Trace how the generic metaclass expression is classified versus a dynamically computed metaclass. Done means this example no longer reports the false positive, while genuinely dynamic metaclasses retain their documented behavior and regression coverage is added.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers, devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100