gh-114053: Fix another edge case involving get_type_hints, PEP 695 and PEP 563

Lib/test/test_typing.py

@@ -4858,20 +4858,30 @@ def f(x: X): ...
 {'x': list[list[ForwardRef('X')]]}
  )
 
- def test_pep695_generic_with_future_annotations(self):
+ def test_pep695_generic_class_with_future_annotations(self):
+ original_globals = dict(ann_module695.__dict__)
+
  hints_for_A = get_type_hints(ann_module695.A)
  A_type_params = ann_module695.A.__type_params__
  self.assertIs(hints_for_A["x"], A_type_params[0])
  self.assertEqual(hints_for_A["y"].__args__[0], Unpack[A_type_params[1]])
  self.assertIs(hints_for_A["z"].__args__[0], A_type_params[2])
 
+ # should not have changed as a result of the get_type_hints() calls!
+ self.assertEqual(ann_module695.__dict__, original_globals)
+
+ def test_pep695_generic_class_with_future_annotations_and_local_shadowing(self):
  hints_for_B = get_type_hints(ann_module695.B)
- self.assertEqual(hints_for_B.keys(),{"x", "y", "z"})
+ self.assertEqual(hints_for_B,{"x": int, "y": str, "z": bytes})
+
+ def test_pep695_generic_class_with_future_annotations_name_clash_with_global_vars(self):
+ hints_for_C = get_type_hints(ann_module695.C)
  self.assertEqual(
- set(hints_for_B.values()) ^ set(ann_module695.B.__type_params__),
- set()
+ set(hints_for_C.values()),
+ set(ann_module695.C.__type_params__)
  )
 
+ def test_pep_695_generic_function_with_future_annotations(self):
  hints_for_generic_function = get_type_hints(ann_module695.generic_function)
  func_t_params = ann_module695.generic_function.__type_params__
  self.assertEqual(
@@ -4882,6 +4892,54 @@ def test_pep695_generic_with_future_annotations(self):
  self.assertIs(hints_for_generic_function["z"].__origin__, func_t_params[2])
  self.assertIs(hints_for_generic_function["zz"].__origin__, func_t_params[2])
 
+ def test_pep_695_generic_function_with_future_annotations_name_clash_with_global_vars(self):
+ self.assertEqual(
+ set(get_type_hints(ann_module695.generic_function_2).values()),
+ set(ann_module695.generic_function_2.__type_params__)
+ )
+
+ def test_pep_695_generic_method_with_future_annotations(self):
+ hints_for_generic_method = get_type_hints(ann_module695.D.generic_method)
+ params ={
+ param.__name__: param
+ for param in ann_module695.D.generic_method.__type_params__
+ }
+ self.assertEqual(
+ hints_for_generic_method,
+{"x": params["Foo"], "y": params["Bar"], "return": types.NoneType}
+ )
+
+ def test_pep_695_generic_method_with_future_annotations_name_clash_with_global_vars(self):
+ self.assertEqual(
+ set(get_type_hints(ann_module695.D.generic_method_2).values()),
+ set(ann_module695.D.generic_method_2.__type_params__)
+ )
+
+ def test_pep_695_generics_with_future_annotations_nested_in_function(self):
+ results = ann_module695.nested()
+
+ self.assertEqual(
+ set(results.hints_for_E.values()),
+ set(results.E.__type_params__)
+ )
+ self.assertEqual(
+ set(results.hints_for_E_meth.values()),
+ set(results.E.generic_method.__type_params__)
+ )
+ self.assertNotEqual(
+ set(results.hints_for_E_meth.values()),
+ set(results.E.__type_params__)
+ )
+ self.assertEqual(
+ set(results.hints_for_E_meth.values()).intersection(results.E.__type_params__),
+ set()
+ )
+
+ self.assertEqual(
+ set(results.hints_for_generic_func.values()),
+ set(results.generic_func.__type_params__)
+ )
+
  def test_extended_generic_rules_subclassing(self):
  class T1(Tuple[T, KT]): ...
  class T2(Tuple[T, ...]): ...

Lib/test/typinganndata/ann_module695.py

@@ -17,6 +17,56 @@ class B[T, *Ts, **P]:
  z: P
 
 
+Eggs = int
+Spam = str
+
+
+class C[Eggs, **Spam]:
+ x: Eggs
+ y: Spam
+
+
 def generic_function[T, *Ts, **P](
  x: T, *y: *Ts, z: P.args, zz: P.kwargs
 ) -> None: ...
+
+
+def generic_function_2[Eggs, **Spam](x: Eggs, y: Spam): pass
+
+
+class D:
+ Foo = int
+ Bar = str
+
+ def generic_method[Foo, **Bar](
+ self, x: Foo, y: Bar
+ ) -> None: ...
+
+ def generic_method_2[Eggs, **Spam](self, x: Eggs, y: Spam): pass
+
+
+def nested():
+ from types import SimpleNamespace
+ from typing import get_type_hints
+
+ Eggs = bytes
+ Spam = memoryview
+
+
+ class E[Eggs, **Spam]:
+ x: Eggs
+ y: Spam
+
+ def generic_method[Eggs, **Spam](self, x: Eggs, y: Spam): pass
+
+
+ def generic_function[Eggs, **Spam](x: Eggs, y: Spam): pass
+
+
+ return SimpleNamespace(
+ E=E,
+ hints_for_E=get_type_hints(E),
+ hints_for_E_meth=get_type_hints(E.generic_method),
+ generic_func=generic_function,
+ hints_for_generic_func=get_type_hints(generic_function)
+ )

Lib/typing.py

@@ -1060,15 +1060,24 @@ def _evaluate(self, globalns, localns, type_params=_sentinel, *, recursive_guard
  globalns = getattr(
  sys.modules.get(self.__forward_module__, None), '__dict__', globalns
  )
+
+ # type parameters require some special handling,
+ # as they exist in their own scope
+ # but `eval()` does not have a dedicated parameter for that scope.
+ # For classes, names in type parameter scopes should override
+ # names in the global scope (which here are called `localns`!),
+ # but should in turn be overridden by names in the class scope
+ # (which here are called `globalns`!)
  if type_params:
- # "Inject" type parameters into the local namespace
- # (unless they are shadowed by assignments *in* the local namespace),
- # as a way of emulating annotation scopes when calling `eval()`
- locals_to_pass ={param.__name__: param for param in type_params} | localns
- else:
- locals_to_pass = localns
+ globalns, localns = dict(globalns), dict(localns)
+ for param in type_params:
+ param_name = param.__name__
+ if not self.__forward_is_class__ or param_name not in globalns:
+ globalns[param_name] = param
+ localns.pop(param_name, None)
+
  type_ = _type_check(
- eval(self.__forward_code__, globalns, locals_to_pass),
+ eval(self.__forward_code__, globalns, localns),
  "Forward references must evaluate to types.",
  is_argument=self.__forward_is_argument__,
  allow_special_forms=self.__forward_is_class__,

Misc/NEWS.d/next/Library/2024-06-08-15-46-35.gh-issue-114053.Ub2XgJ.rst

@@ -0,0 +1,4 @@
+Fix edge-case bug where :func:`typing.get_type_hints` would produce
+incorrect results if type parameters in a class scope were overridden by
+assignments in a class scope and ``from __future__ import annotations``
+semantics were enabled. Patch by Alex Waygood.