feat: introduce block.prevrandao as alias for block.difficulty

docs/constants-and-vars.rst

@@ -11,11 +11,12 @@ Environment variables always exist in the namespace and are primarily used to pr
 Block and Transaction Properties
 --------------------------------
 
-==================== ================ =============================================
+==================== ================ =========================================================
 Name                 Type             Value
-==================== ================ =============================================
-``block.coinbase``   ``address``      Current block miner’s address
+==================== ================ =========================================================
+``block.coinbase``   ``address``      Current block miner's address
 ``block.difficulty`` ``uint256``      Current block difficulty
+``block.prevrandao`` ``uint256``      Current randomness beacon provided by the beacon chain
 ``block.number``     ``uint256``      Current block number
 ``block.prevhash``   ``bytes32``      Equivalent to ``blockhash(block.number - 1)``
 ``block.timestamp``  ``uint256``      Current block epoch timestamp
@@ -26,7 +27,11 @@ Name                 Type             Value
 ``msg.value``        ``uint256``      Number of wei sent with the message
 ``tx.origin``        ``address``      Sender of the transaction (full call chain)
 ``tx.gasprice``      ``uint256``      Gas price of current transaction in wei
-==================== ================ =============================================
+==================== ================ =========================================================
+
+.. note::
+
+    ``block.prevrandao`` is an alias for ``block.difficulty``. Since ``block.difficulty`` is considered deprecated according to `EIP-4399 <https://eips.ethereum.org/EIPS/eip-4399>`_ after "The Merge" (Paris hard fork), we recommend using ``block.prevrandao``.
 
 .. note::
 

tests/compiler/test_opcodes.py

@@ -43,7 +43,7 @@ def test_version_check(evm_version):
 
 def test_get_opcodes(evm_version):
     op = opcodes.get_opcodes()
-    if evm_version == "berlin":
+    if evm_version in ("paris", "berlin"):
         assert "CHAINID" in op
         assert op["SLOAD"][-1] == 2100
     elif evm_version == "istanbul":

tests/parser/syntax/test_block.py

@@ -138,6 +138,13 @@ def foo():
     """,
     """
 @external
+def foo():
+    x: uint256 = block.prevrandao + 185
+    if tx.origin == self:
+        y: Bytes[35] = concat(block.prevhash, b"dog")
+    """,
+    """
+@external
 def foo() -> uint256:
     return tx.gasprice
     """,

vyper/codegen/expr.py

@@ -42,13 +42,15 @@
     TypeCheckFailure,
     TypeMismatch,
     UnimplementedException,
+    VyperException,
 )
 from vyper.utils import (
     DECIMAL_DIVISOR,
     SizeLimits,
     bytes_to_int,
     is_checksum_encoded,
     string_to_bytes,
+    vyper_warn,
 )
 
 ENVIRONMENT_VARIABLES = {"block", "msg", "tx", "chain"}
@@ -279,7 +281,23 @@ def parse_Attribute(self):
                 return IRnode.from_list(["callvalue"], typ=BaseType("uint256"))
             elif key == "msg.gas":
                 return IRnode.from_list(["gas"], typ="uint256")
+            elif key == "block.prevrandao":
+                if not version_check(begin="paris"):
+                    warning = VyperException(
+                        "tried to use block.prevrandao in pre-Paris "
+                        "environment! Suggest using block.difficulty instead.",
+                        self.expr,
+                    )
+                    vyper_warn(str(warning))
+                return IRnode.from_list(["prevrandao"], typ="uint256")
             elif key == "block.difficulty":
+                if version_check(begin="paris"):
+                    warning = VyperException(
+                        "tried to use block.difficulty in post-Paris "
+                        "environment! Suggest using block.prevrandao instead.",
+                        self.expr,
+                    )
+                    vyper_warn(str(warning))
                 return IRnode.from_list(["difficulty"], typ="uint256")
             elif key == "block.timestamp":
                 return IRnode.from_list(["timestamp"], typ=BaseType("uint256"))

vyper/evm/opcodes.py

@@ -3,7 +3,7 @@
 from vyper.exceptions import CompilerPanic
 from vyper.typing import OpcodeGasCost, OpcodeMap, OpcodeRulesetMap, OpcodeRulesetValue, OpcodeValue
 
-active_evm_version: int = 3
+active_evm_version: int = 4
 
 # EVM version rules work as follows:
 # 1. Fork rules go from oldest (lowest value) to newest (highest value).
@@ -24,11 +24,12 @@
     "petersburg": 1,
     "istanbul": 2,
     "berlin": 3,
+    "paris": 4,
     # ETC Forks
     "atlantis": 0,
     "agharta": 1,
 }
-DEFAULT_EVM_VERSION: str = "berlin"
+DEFAULT_EVM_VERSION: str = "paris"
 
 
 # opcode as hex value
@@ -84,6 +85,7 @@
     "TIMESTAMP": (0x42, 0, 1, 2),
     "NUMBER": (0x43, 0, 1, 2),
     "DIFFICULTY": (0x44, 0, 1, 2),
+    "PREVRANDAO": (0x44, 0, 1, 2),
     "GASLIMIT": (0x45, 0, 1, 2),
     "CHAINID": (0x46, 0, 1, (None, None, 2)),
     "SELFBALANCE": (0x47, 0, 1, (None, None, 5)),

vyper/semantics/environment.py

@@ -11,6 +11,7 @@
     "block": {
         "coinbase": AddressDefinition,
         "difficulty": Uint256Definition,
+        "prevrandao": Uint256Definition,
         "number": Uint256Definition,
         "gaslimit": Uint256Definition,
         "basefee": Uint256Definition,