Redefining Literal class variable in subclass has 'Incompatible type'

[AugPro]

Are you reporting a bug, or opening a feature request?

Bug

Please insert below the code you are checking with mypy,

or a mock-up repro if the source is private. We would appreciate
if you try to simplify your case to a minimal repro.

from typing import Literal

class A:
    foo : Literal['bar', 'spam']= 'bar'
    
class B(A):
    foo = 'spam'

What is the actual behavior/output?

main.py:7: error: Incompatible types in assignment (expression has type "str", base class "A" defined the type as "Union[Literal['bar'], Literal['spam']]")
Found 1 error in 1 file (checked 1 source file)

What is the behavior/output you expect?

I expected no error, as B.foo is still of type Literal['bar', 'spam']

What are the versions of mypy and Python you are using?

mypy == 0.770
Python == 3.8

What are the mypy flags you are using? (For example --strict-optional)

no flags

[msullivan]

Yup, that looks like a bug. Does it work as a workaround if you repeat the type annotation in the subclass?

[AugPro]

yes it does ! It also works if I overwrite foo in __init__ method for instance, and in that case no need to repeat type annotation

[peterschutt]

Is this the same issue?

from typing import Generic, List, Literal, TypeVar

T = TypeVar("T", bound=str)


class Thing(Generic[T]):
    collection: List[T] 
    word: T


class SubThing(Thing[Literal["word"]]):
    collection = ["word"]
    word = "word"

test.py:14: error: Incompatible types in assignment (expression has type "str", base class "Thing" defined the type as "Literal['word']")
Found 1 error in 1 file (checked 1 source file)

Mypy seems happy with the collection override but not word.

py == 3.8.5
mypy == 0.782

[embray]

Ditto with

$ mypy --version
mypy 0.812

and no additional flags.

[willfrey]

Just ran into this issue with 0.910.

[xsevy]

there's still the same problem 0.930

[cebasfu93]

Also ran into this bug with version 0.910

[amickael]

Is this fixed? Still running into this issue in 0.982

[JelleZijlstra]

This was fixed in 57de8db which isn't in 0.982.