Extend iteration by index to strings and bytes

Author: markshannon

Include/cpython/object.h

@@ -239,6 +239,9 @@ struct _typeobject {
      * Otherwise, limited to MAX_VERSIONS_PER_CLASS (defined elsewhere).
      */
     uint16_t tp_versions_used;
+    /* Returns the object at the index given, or NULL if out-of-bounds
+     * Never raises an exception. */
+    iterindexfunc tp_iterindex;
 };
 
 #define _Py_ATTR_CACHE_UNUSED (30000)  // (see tp_versions_used)

Include/internal/pycore_magic_number.h

@@ -281,7 +281,7 @@ Known values:
     Python 3.15a1 3651 (Simplify LOAD_CONST)
     Python 3.15a1 3652 (Virtual iterators)
     Python 3.15a1 3653 (Fix handling of opcodes that may leave operands on the stack when optimizing LOAD_FAST)
-    Python 3.15a1 3654 (Specialize GET_ITER)
+    Python 3.15a1 3654 (Specialize GET_ITER. Add FOR_ITER_INDEX)
 
 
     Python 3.16 will start with 3700