add tp_as_mapping slots for str & tuple.

src/runtime/str.cpp

@@ -2987,6 +2987,9 @@ void setupStr() {
     str_cls->tp_as_sequence->sq_repeat = (ssizeargfunc)string_repeat;
     str_cls->tp_as_sequence->sq_slice = str_slice;
 
+    str_cls->tp_as_mapping->mp_length = (lenfunc)str_length;
+    str_cls->tp_as_mapping->mp_subscript = (binaryfunc)strGetitem<CAPI>;
+
     str_cls->tp_new = (newfunc)strNewPacked;
 
     basestring_cls->giveAttr("__doc__",

src/runtime/tuple.cpp

@@ -811,6 +811,9 @@ void setupTuple() {
     tuple_cls->tp_as_sequence->sq_contains = (objobjproc)tuplecontains;
     tuple_cls->tp_iter = tupleIter;
 
+    tuple_cls->tp_as_mapping->mp_length = (lenfunc)tuplelength;
+    tuple_cls->tp_as_mapping->mp_subscript = (binaryfunc)tupleGetitem<CAPI>;
+
     FunctionMetadata* hasnext = FunctionMetadata::create((void*)tupleiterHasnextUnboxed, BOOL, 1);
     hasnext->addVersion((void*)tupleiterHasnext, BOXED_BOOL);
     tuple_iterator_cls->giveAttr("__hasnext__", new BoxedFunction(hasnext));