Add test case for raising NotImplemented

Author: brianschubert

test-data/unit/check-statements.test

@@ -519,6 +519,13 @@ if object():
     raise BaseException from f # E: Exception must be derived from BaseException
 [builtins fixtures/exception.pyi]
 
+[case testRaiseNotImplementedFails]
+if object():
+    raise NotImplemented    # E: Exception must be derived from BaseException; did you mean "NotImplementedError"?
+if object():
+    raise NotImplemented()  # E: NotImplemented? not callable
+[builtins fixtures/notimplemented.pyi]
+
 [case testTryFinallyStatement]
 import typing
 try:

test-data/unit/fixtures/notimplemented.pyi

@@ -1,6 +1,5 @@
 # builtins stub used in NotImplemented related cases.
-from typing import Any, cast
-
+from typing import Any
 
 class object:
     def __init__(self) -> None: pass
@@ -10,5 +9,10 @@ class function: pass
 class bool: pass
 class int: pass
 class str: pass
-NotImplemented = cast(Any, None)
 class dict: pass
+
+class _NotImplementedType(Any):
+    __call__: NotImplemented  # type: ignore
+NotImplemented = _NotImplementedType()
+
+class BaseException: pass