import ast
import functools
import inspect


def masked(mask: int):
    '''
    Convert arithmetic operations that occur within the decorated function body in such a way that
    the result is reduced using the given bitmask. All additions, subtractions, multiplications,
    left shifts, and taking powers is augmented by introducing a bitwise and with the given mask.
    '''
    def decorator(function):
        code = inspect.getsource(function)
        tree = ast.parse(code, mode='exec')

        class Postprocessor(ast.NodeTransformer):
            name = None 
            def visit_BinOp(self, node: ast.BinOp):
                node = self.generic_visit(node)
                if not isinstance(node.op, (ast.Add, ast.Mult, ast.Sub, ast.LShift, ast.Pow)):
                    return node
                return ast.BinOp(node, ast.BitAnd(), ast.Constant(mask))
            def visit_FunctionDef(self, node: ast.FunctionDef):
                node = self.generic_visit(node)
                if self.name is None:
                    node.name = self.name = F'__wrapped_{node.name}'
                    for k in range(len(node.decorator_list)):
                        if node.decorator_list[k].func.id == masked.__name__:
                            del node.decorator_list[:k + 1]
                            break
                return node

        pp = Postprocessor()
        fixed = ast.fix_missing_locations(pp.visit(tree))
        eval(compile(fixed, function.__code__.co_filename, 'exec'))
        return functools.wraps(function)(eval(pp.name))

    return decorator

@masked(0xFFFF)
def test(x: int) -> int:
    return x * 0xBAAD