Concrete generics support

[sobolevn]

Right now it is impossible to write a code like this one:

from classes import typeclass
from typing import List

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

@some.instance(List[int])
def _some_list_int(instance: List[int]) -> int:
    ...

Because, you cannot check that some variable has type List[int] in runtime.

Maybe we can use runtime typecheckers? Like: https://github.com/erezsh/runtype

Related #8

[sobolevn]

Or https://github.com/beartype/beartype

[sobolevn]

My current design:

from typing import List, TYPE_CHECKING

if not TYPE_CHECKING:
    reveal_type = print

from phantom import Phantom
from phantom.predicates import collection, generic

class ListOfInt(
    List[int],
    Phantom,
    predicate=collection.every(generic.of_type(int)),
):
    ...



from classes import typeclass

@typeclass
def sum_all(instance) -> int:
    ...

@sum_all.instance(List[int], delegate=ListOfInt)
def _sum_list_of_int(instance: List[int]) -> int:
    return sum(x for x in instance)

l = [1, 2, 3]
reveal_type(sum_all(l))

It both typechecks (I need to fix my plugin, though) and works in runtime.