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Support `Literal` types

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
38/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
tooling

Research direction

Start by tracing how typeclass, AssociatedType, Supports, and @some.instance handle delegated types, then compare that path with the Literal[1] example. Done means the example type-checks and some(1) resolves correctly through the Literal registration, with the existing delegate behavior preserved.

Written by the indexing model from the issue text.

Description

enhancement

After we have delegate in-place we can use Literal types.

But, now they are not supported.
Ideally, something like this should work:

from classes import typeclass, AssociatedType, Supports
from typing_extensions import Literal

class SomeDelegate(object):
    ...  # TODO: write proper `__instancecheck__`

class A(AssociatedType):
    ...

@typeclass(A)
def some(instance) -> int:
    ...

@some.instance(Literal[1], delegate=SomeDelegate)
def _some_tuple(instance: Literal[1]) -> int:
    return instance

def test(i: Supports[A]):
    return some(i)

some(1)
Dominant language
Python
Stars
730
Forks
30
No merged PRs in 30d

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