Function parameter matching type guard.

param_match.py

"""
This defines a decorator that works kind of like a type-guard (https://peps.python.org/pep-0647/) for the arguments
of a function.

The usefulness of this is for functions that "defer" their arguments to another function, e.g. places where you 
would call functools.wraps().

@same_params_as(f)
@functools.wraps(f)
def passes_args_through(*a, **kw):
   return f(*a, **kw)
"""

from typing import Callable, ParamSpec, TypeAlias

# pyright: reportMissingTypeArgument=true

_P = ParamSpec("_P")

_MatchFunc: TypeAlias = Callable[_P, object]
_MatchDecorator: TypeAlias = Callable[[_MatchFunc[_P]], _MatchFunc[_P]]

def same_params_as(_matching_func: _MatchFunc[_P]) -> _MatchDecorator[_P]:
    """For the purposes of static type checking, mark a function as having the same param spec as another."""
    return lambda f: f


"""
def f(a): pass

@same_params_as(f)
def b(*a, **kw): pass


b()  # test - this should be flagged as missing parameter 'a'
"""