feat: extreme-self-casting

Author: GreyElaina

challenges/extreme-self-casting/question.py

@@ -0,0 +1,39 @@
+"""
+TODO:
+
+make Fn[VnCallable] could be casted to a Callable with a Any value.
+you MUST NOT modify anything expect the `Fn.into_callable`'s annotation.
+"""
+
+from typing import Callable, TypeVar, Generic, Any, assert_type
+
+VnCallable = TypeVar("VnCallable", bound=Callable)
+
+class Fn(Generic[VnCallable]):
+    def __init__(self, f: VnCallable) -> None:
+        self.f = f
+
+    def into_callable(self) -> None:
+        ...
+
+
+def should_pass():
+    @Fn
+    def example(a: int, b: str, c: float, *, d: bool = False) -> None:
+        return
+
+    assert_type(example.f(1, "1", 1., d=False), None)
+
+    a: Any = 11111111
+
+    b = example.into_callable()(a, 1, "1", 1., d=False)
+
+    assert_type(b, None)
+
+
+def should_fail():
+    @Fn
+    def example(a: int, b: str, c: float, *, d: bool = False) -> None:
+        ...
+
+    example.into_callable()(1, "1", 1., d=False)