Shared via mypy Playground

main.py

from dataclasses import dataclass
from typing import TypeVar, Generic, Callable, Dict, Any
import sys

T_Input = TypeVar("T_Input")

class _RegisteredType(Generic[T_Input]):
    def __init__(self, name: str):
        self.name = name

@dataclass
class Request(Generic[T_Input]):
    r_type: _RegisteredType[T_Input]
    state: T_Input 

class C:
    def __init__(self):
        self._r_types: Dict[str, Callable[[Any], Any]] = {}
    
    def create_request_type(self, r_type: str, f: Callable[[Request[T_Input]], Any]) -> _RegisteredType[T_Input]:
        self._r_types[r_type] = f
        return _RegisteredType(r_type)
    
    def send_request(self, request: Request[Any]) -> Any:
        r_type = request.r_type.name
        f_to_call = self._r_types[r_type]
        return f_to_call(request)

# --- Example ---

def int_request_handler(req: Request[int]) -> str:
    return f"Handling int inside request: {req.state}"

c = C()
int_type = c.create_request_type("INT_OP", int_request_handler)

# Works
req1 = Request(r_type=int_type, state=42)
c.send_request(req1)

# Must fail
req_fail = Request(r_type=int_type, state="wrong")