feat[venom]: cleanup variable version handling (vyperlang#4404)

refactor `IRVariable` so that parsing cannot result in a nonzero
`.version` (it should only be modified by internal passes).

---------

Co-authored-by: Charles Cooper <[email protected]>

vyper/venom/basicblock.py

@@ -115,13 +115,20 @@ class IROperand:
     """
 
     value: Any
+    _hash: Optional[int]
+
+    def __init__(self, value: Any) -> None:
+        self.value = value
+        self._hash = None
 
     @property
     def name(self) -> str:
         return self.value
 
     def __hash__(self) -> int:
-        return hash(self.value)
+        if self._hash is None:
+            self._hash = hash(self.value)
+        return self._hash
 
     def __eq__(self, other) -> bool:
         if not isinstance(other, type(self)):
@@ -140,6 +147,7 @@ class IRLiteral(IROperand):
     value: int
 
     def __init__(self, value: int) -> None:
+        super().__init__(value)
         assert isinstance(value, int), "value must be an int"
         self.value = value
 
@@ -149,27 +157,25 @@ class IRVariable(IROperand):
     IRVariable represents a variable in IR. A variable is a string that starts with a %.
     """
 
-    value: str
-
-    def __init__(self, value: str, version: Optional[str | int] = None) -> None:
-        assert isinstance(value, str)
-        assert ":" not in value, "Variable name cannot contain ':'"
-        if version:
-            assert isinstance(value, str) or isinstance(value, int), "value must be an str or int"
-            value = f"{value}:{version}"
-        if value[0] != "%":
-            value = f"%{value}"
-        self.value = value
+    _name: str
+    version: Optional[int]
+
+    def __init__(self, name: str, version: int = 0) -> None:
+        super().__init__(name)
+        assert isinstance(name, str)
+        assert isinstance(version, int | None)
+        if not name.startswith("%"):
+            name = f"%{name}"
+        self._name = name
+        self.version = version
+        if version > 0:
+            self.value = f"{name}:{version}"
+        else:
+            self.value = name
 
     @property
     def name(self) -> str:
-        return self.value.split(":")[0]
-
-    @property
-    def version(self) -> int:
-        if ":" not in self.value:
-            return 0
-        return int(self.value.split(":")[1])
+        return self._name
 
 
 class IRLabel(IROperand):
@@ -184,7 +190,7 @@ class IRLabel(IROperand):
 
     def __init__(self, value: str, is_symbol: bool = False) -> None:
         assert isinstance(value, str), "value must be an str"
-        self.value = value
+        super().__init__(value)
         self.is_symbol = is_symbol
 
 
@@ -464,7 +470,7 @@ def remove_cfg_out(self, bb: "IRBasicBlock") -> None:
         self.cfg_out.remove(bb)
 
     def append_instruction(
-        self, opcode: str, *args: Union[IROperand, int], ret: IRVariable = None
+        self, opcode: str, *args: Union[IROperand, int], ret: Optional[IRVariable] = None
     ) -> Optional[IRVariable]:
         """
         Append an instruction to the basic block

vyper/venom/parser.py

@@ -170,13 +170,7 @@ def LABEL(self, label) -> IRLabel:
         return IRLabel(label[1:])
 
     def VAR_IDENT(self, var_ident) -> IRVariable:
-        parts = var_ident[1:].split(":", maxsplit=1)
-        assert 1 <= len(parts) <= 2
-        varname = parts[0]
-        version = None
-        if len(parts) > 1:
-            version = int(parts[1])
-        return IRVariable(varname, version=version)
+        return IRVariable(var_ident[1:])
 
     def CONST(self, val) -> IRLiteral:
         return IRLiteral(int(val))