Decide the fate of type_params in _eval_type and _evaluate

Feature or enhancement

Currently there are two places in our typing-related code that raise a DeprecationWarning when type_params parameter is not provided:

cpython/Lib/typing.py

Lines 432 to 442 in 07183eb

    
           def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=frozenset(), 
        
                          format=None, owner=None): 
        
               """Evaluate all forward references in the given type t. 
        
               For use of globalns and localns see the docstring for get_type_hints(). 
        
               recursive_guard is used to prevent infinite recursion with a recursive 
        
               ForwardRef. 
        
               """ 
        
               if type_params is _sentinel: 
        
                   _deprecation_warning_for_no_type_params_passed("typing._eval_type") 
        
                   type_params = ()

cpython/Lib/annotationlib.py

Lines 213 to 221 in 07183eb

    
           def _evaluate(self, globalns, localns, type_params=_sentinel, *, recursive_guard): 
        
               import typing 
        
               import warnings 
        
               if type_params is _sentinel: 
        
                   typing._deprecation_warning_for_no_type_params_passed( 
        
                       "typing.ForwardRef._evaluate" 
        
                   ) 
        
                   type_params = ()

The error message of this function says that the behavior will change in 3.15 to disallow this:

cpython/Lib/typing.py

Lines 410 to 420 in 07183eb

    
           def _deprecation_warning_for_no_type_params_passed(funcname: str) -> None: 
        
               import warnings 
        
               depr_message = ( 
        
                   f"Failing to pass a value to the 'type_params' parameter " 
        
                   f"of {funcname!r} is deprecated, as it leads to incorrect behaviour " 
        
                   f"when calling {funcname} on a stringified annotation " 
        
                   f"that references a PEP 695 type parameter. " 
        
                   f"It will be disallowed in Python 3.15." 
        
               ) 
        
               warnings.warn(depr_message, category=DeprecationWarning, stacklevel=3)

So, we have several options:

Adding TypeError('type_params parameter is not provided') when type_params is _sentinel
Changing type_params to not contain a default value
Do nothing?

CC @JelleZijlstra @AlexWaygood

I would like to work on this after we decide the fate of these functions :)

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Decide the fate of `type_params` in `_eval_type` and `_evaluate` #136021

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	def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=frozenset(),
	format=None, owner=None):
	"""Evaluate all forward references in the given type t.

	For use of globalns and localns see the docstring for get_type_hints().
	recursive_guard is used to prevent infinite recursion with a recursive
	ForwardRef.
	"""
	if type_params is _sentinel:
	_deprecation_warning_for_no_type_params_passed("typing._eval_type")
	type_params = ()

	def _evaluate(self, globalns, localns, type_params=_sentinel, *, recursive_guard):
	import typing
	import warnings

	if type_params is _sentinel:
	typing._deprecation_warning_for_no_type_params_passed(
	"typing.ForwardRef._evaluate"
	)
	type_params = ()

	def _deprecation_warning_for_no_type_params_passed(funcname: str) -> None:
	import warnings

	depr_message = (
	f"Failing to pass a value to the 'type_params' parameter "
	f"of {funcname!r} is deprecated, as it leads to incorrect behaviour "
	f"when calling {funcname} on a stringified annotation "
	f"that references a PEP 695 type parameter. "
	f"It will be disallowed in Python 3.15."
	)
	warnings.warn(depr_message, category=DeprecationWarning, stacklevel=3)

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Decide the fate of type_params in _eval_type and _evaluate #136021

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Decide the fate of `type_params` in `_eval_type` and `_evaluate` #136021