[WIP] Implement subroutine opcodes

Author: Peppece

eth/vm/rstack.py

@@ -1,5 +1,7 @@
 from typing import (
     List,
+    Tuple,
+    Union,
 )
 
 from eth.exceptions import (
@@ -33,7 +35,7 @@ class RStack:
     __slots__ = ['values', '_append', '_pop_typed', '__len__']
 
     def __init__(self) -> None:
-        values: List[int] = []
+        values: List[Tuple[type, Union[int, bytes]]] = []
         self.values = values
         self._append = values.append
         self._pop_typed = values.pop