pythongh-125038: redundant GET_ITER and GET_AITER are removed from genexpr code

Adds CHECK_ITERABLE instruction. It checks that TOS is iterable or
async iterable. Redundant GET_ITER and GET_AITER instructions are
removed from generator expression code.

Author: efimov-mikhail

Doc/library/dis.rst

@@ -670,6 +670,14 @@ result back on the stack.
    .. versionadded:: 3.5
 
 
+.. opcode:: CHECK_ITERABLE (is_async)
+
+   Checks that ``STACK[-1]`` is iterable or async iterable, depending on
+   oparg value.
+
+   .. versionadded:: 3.14
+
+
 .. opcode:: TO_BOOL
 
    Implements ``STACK[-1] = bool(STACK[-1])``.

Include/internal/pycore_magic_number.h

@@ -262,6 +262,7 @@ Known values:
     Python 3.14a1 3607 (Add pseudo instructions JUMP_IF_TRUE/FALSE)
     Python 3.14a1 3608 (Add support for slices)
     Python 3.14a2 3609 (Add LOAD_SMALL_INT and LOAD_CONST_IMMORTAL instructions, remove RETURN_CONST)
+    Python 3.14a2 3610 (Add CHECK_ITERABLE)
 
     Python 3.15 will start with 3650
 
@@ -274,7 +275,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3609
+#define PYC_MAGIC_NUMBER 3610
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \

Include/internal/pycore_opcode_metadata.h

@@ -1798,6 +1798,12 @@ async def run():
         res = self.loop.run_until_complete(run())
         self.assertEqual(res, [i * 2 for i in range(1, 10)])
 
+    def test_async_gen_expression_incorrect(self):
+        err_msg = "'async for' requires an object with " \
+            "__aiter__ method, got int"
+        with self.assertRaisesRegex(TypeError, err_msg):
+            g = (x async for x in 42)
+
     def test_asyncgen_nonstarted_hooks_are_cancellable(self):
         # See https://bugs.python.org/issue38013
         messages = []