MyPy reports errors when performing nested element access using a ``TypeVar``-parameterized generic type

Bug Report

Type variables and generics enable propagating finer-grained type information through objects like containers. However, it seems that MyPy has issues when this design pattern is used in a nested manner:

To Reproduce

import typing

T = typing.TypeVar("T")

class Container(typing.Generic[T]):
    def __init__(self, value : T) -> None:
        self.value = value

class A(Container[int]):
    pass

class B(Container[A]):
    pass

def get(x: Container[T]) -> T:
    return x.value


a = B(A(5))
reveal_type(a)

b = get(a)
reveal_type(b)

c1 = get(b)
reveal_type(c1)

# This is expected to match 'c1'
c2 = get(get(a))
reveal_type(c2)

MyPy-Play link: https://gist.github.com/mypy-play/40d62fe7a0fc28bf68bd9d156ba77c5b

a.py:20: note: Revealed type is "a.B"
a.py:23: note: Revealed type is "a.A"
a.py:26: note: Revealed type is "builtins.int"
a.py:30: note: Revealed type is "builtins.int"

Reference (PyRight):

/Users/wjakob/drjit-nanobind/a.py
  /Users/wjakob/drjit-nanobind/a.py:20:13 - information: Type of "a" is "B"
  /Users/wjakob/drjit-nanobind/a.py:23:13 - information: Type of "b" is "A"
  /Users/wjakob/drjit-nanobind/a.py:26:13 - information: Type of "c1" is "int"
  /Users/wjakob/drjit-nanobind/a.py:30:13 - information: Type of "c2" is "int"

Actual Behavior

a.py:20: note: Revealed type is "a.B"
a.py:23: note: Revealed type is "a.A"
a.py:26: note: Revealed type is "builtins.int"
a.py:29: error: Argument 1 to "get" has incompatible type "B"; expected "Container[Container[int]]"  [arg-type]
a.py:30: note: Revealed type is "builtins.int"
Found 1 error in 1 file (checked 1 source file)

Your Environment
Python 3.12.2, MyPy 1.8.0

Inizia con la riproduzione a.py dell’issue, usando Python 3.12.2 e MyPy 1.8.0, e confrontala con l’esempio MyPy-Play collegato. Analizza l’inferenza annidata di TypeVar per get(get(a)). Il lavoro è completato quando la chiamata annidata non produce alcun errore incompatible-argument e c2 viene rivelato come builtins.int, come c1.