[WIP] Implement subroutine opcodes

Author: Peppece

eth/abc.py

@@ -1593,13 +1593,13 @@ def stack_dup(self, position: int) -> None:
     #
     # Return Stack Managemement
     #
-    @abstract_method
+    @abstractmethod
     def rstack_push_int(self) -> Callable[[int], None]:
         """
         Push integer onto the return stack.
         """
 
-    @abstract_method
+    @abstractmethod
     def rstack_pop1_int(self) -> Callable[[int], None]:
         """
         Pop integer off the return stack and return it.

eth/vm/rstack.py

@@ -11,12 +11,11 @@
     validate_stack_int,
 )
 
-from eth.utils import (
+from eth_utils import (
     big_endian_to_int,
     ValidationError,
 )
 
-import collections.UserList as rstack
 """
 This module simply implements for the return stack the exact same design used for the data stack.
 As this stack must simply push_int or pop1_int any time a subroutine is accessed or left, only those two functions are provided.
@@ -28,14 +27,14 @@ class RStack():
     VM Return Stack
     """
 
-    __slots__ = ['values', '_append', '_pop_int', '__len__']
+    __slots__ = ['values', '_append', '_pop_typed', '__len__']
 
     def __init__(self) -> None:
-        values: List[int]
-        self.values = rstack.data
-        self._append = rstack.data.append
-        self._pop_typed = rstack.data.pop
-        self.__len__ = rstack.data.__len__
+        values: List[int] = []
+        self.values = values
+        self._append = values.append
+        self._pop_typed = values.pop
+        self.__len__ = values.__len__
 
     def push_int(self) -> int:
         if len(self.values) > 1023:
@@ -49,18 +48,3 @@ def push_int(self) -> int:
     def pop1_int(self) -> int:
         #
         # Note: This function is optimized for speed over readability.
-        #
-        if not self.values:
-            raise InsufficientStack("Wanted 1 stack item as int, had none")
-        else:
-            item_type, popped = self._pop_typed()
-            if item_type is int:
-                return popped  # type: ignore
-            elif item_type is bytes:
-                return big_endian_to_int(popped)  # type: ignore
-            else:
-                raise ValidationError(
-                "Stack must always be bytes or int, "
-                f"got {item_type!r} type, val {value!r}"
-                ) 
-