gh-109118: Make comprehensions work within annotation scopes, but without inlining

Lib/test/test_type_params.py

@@ -436,9 +436,11 @@ class C[T]:
  class Inner[U](make_base(T for _ in (1,)), make_base(T)):
  pass
  """
- with self.assertRaisesRegex(SyntaxError,
- "Cannot use comprehension in annotation scope within class scope"):
- run_code(code)
+ ns = run_code(code)
+ inner = ns["C"].Inner
+ base1, base2, _ = inner.__bases__
+ self.assertEqual(list(base1.__arg__), [ns["C"].__type_params__[0]])
+ self.assertEqual(base2.__arg__, "class")
 
  def test_listcomp_in_nested_class(self):
  code = """
@@ -464,9 +466,11 @@ class C[T]:
  class Inner[U](make_base([T for _ in (1,)]), make_base(T)):
  pass
  """
- with self.assertRaisesRegex(SyntaxError,
- "Cannot use comprehension in annotation scope within class scope"):
- run_code(code)
+ ns = run_code(code)
+ inner = ns["C"].Inner
+ base1, base2, _ = inner.__bases__
+ self.assertEqual(base1.__arg__, [ns["C"].__type_params__[0]])
+ self.assertEqual(base2.__arg__, "class")
 
  def test_gen_exp_in_generic_method(self):
  code = """
@@ -475,27 +479,33 @@ class C[T]:
  def meth[U](x: (T for _ in (1,)), y: T):
  pass
  """
- with self.assertRaisesRegex(SyntaxError,
- "Cannot use comprehension in annotation scope within class scope"):
- run_code(code)
+ ns = run_code(code)
+ meth = ns["C"].meth
+ self.assertEqual(list(meth.__annotations__["x"]), [ns["C"].__type_params__[0]])
+ self.assertEqual(meth.__annotations__["y"], "class")
 
  def test_nested_scope_in_generic_alias(self):
  code = """
- class C[T]:
+ T = "global"
+ class C:
  T = "class"
  {}
  """
  error_cases = [
- "type Alias3[T] = (T for _ in (1,))",
- "type Alias4 = (T for _ in (1,))",
- "type Alias5[T] = [T for _ in (1,)]",
- "type Alias6 = [T for _ in (1,)]",
+ "type Alias[T] = (T for _ in (1,))",
+ "type Alias = (T for _ in (1,))",
+ "type Alias[T] = [T for _ in (1,)]",
+ "type Alias = [T for _ in (1,)]",
  ]
  for case in error_cases:
  with self.subTest(case=case):
- with self.assertRaisesRegex(SyntaxError,
- r"Cannot use [a-z]+ in annotation scope within class scope"):
- run_code(code.format(case))
+ ns = run_code(code.format(case))
+ alias = ns["C"].Alias
+ value = list(alias.__value__)[0]
+ if alias.__type_params__:
+ self.assertIs(value, alias.__type_params__[0])
+ else:
+ self.assertEqual(value, "global")
 
  def test_lambda_in_alias_in_class(self):
  code = """

Python/compile.c

@@ -371,6 +371,9 @@ static PyCodeObject *optimize_and_assemble(struct compiler *, int addNone);
 
 #define CAPSULE_NAME "compile.c compiler unit"
 
+static inline bool in_class_like_block(struct compiler *c) {
+ return c->u->u_ste->ste_type == ClassBlock || c->u->u_ste->ste_can_see_class_scope;
+}
 
 static int
 compiler_setup(struct compiler *c, mod_ty mod, PyObject *filename,
@@ -5460,7 +5463,7 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
  PySTEntryObject *entry,
  inlined_comprehension_state *state)
 {
- int in_class_block = (c->u->u_ste->ste_type == ClassBlock) && !c->u->u_in_inlined_comp;
+ int in_class_block = in_class_like_block(c) && !c->u->u_in_inlined_comp;
  c->u->u_in_inlined_comp++;
  // iterate over names bound in the comprehension and ensure we isolate
  // them from the outer scope as needed

Python/symtable.c

@@ -810,7 +810,8 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
  // free vars in comprehension that are locals in outer scope can
  // now simply be locals, unless they are free in comp children,
  // or if the outer scope is a class block
- if (!is_free_in_any_child(comp, k) && ste->ste_type != ClassBlock) {
+ if (!is_free_in_any_child(comp, k) && ste->ste_type != ClassBlock
+ && !ste->ste_can_see_class_scope) {
  if (PySet_Discard(comp_free, k) < 0) {
  return 0;
  }
@@ -2589,18 +2590,6 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
  identifier scope_name, asdl_comprehension_seq *generators,
  expr_ty elt, expr_ty value)
 {
- if (st->st_cur->ste_can_see_class_scope) {
- // gh-109118
- PyErr_Format(PyExc_SyntaxError,
- "Cannot use comprehension in annotation scope within class scope");
- PyErr_RangedSyntaxLocationObject(st->st_filename,
- e->lineno,
- e->col_offset + 1,
- e->end_lineno,
- e->end_col_offset + 1);
- VISIT_QUIT(st, 0);
- }
-
  int is_generator = (e->kind == GeneratorExp_kind);
  comprehension_ty outermost = ((comprehension_ty)
  asdl_seq_GET(generators, 0));