feat[lang]: introduce mana as an alias for gas (#3713)

per EIP-6789 (https://eips.ethereum.org/EIPS/eip-6789), add `msg.mana`
as an alias for `msg.gas`

---------

Signed-off-by: Pascal Marco Caversaccio <pascal.caversaccio@hotmail.ch>
Co-authored-by: Charles Cooper <cooper.charles.m@gmail.com>

docs/constants-and-vars.rst

@@ -26,6 +26,7 @@ Name                  Type             Value
 ``chain.id``          ``uint256``      Chain ID
 ``msg.data``          ``Bytes``        Message data
 ``msg.gas``           ``uint256``      Remaining gas
+``msg.mana``          ``uint256``      Remaining gas (alias for ``msg.gas``)
 ``msg.sender``        ``address``      Sender of the message (current call)
 ``msg.value``         ``uint256``      Number of wei sent with the message
 ``tx.origin``         ``address``      Sender of the transaction (full call chain)

tests/functional/codegen/features/test_mana.py

@@ -0,0 +1,11 @@
+def test_mana_call(get_contract):
+    mana_call = """
+@external
+def foo() -> uint256:
+    return msg.mana
+    """
+
+    c = get_contract(mana_call)
+
+    assert c.foo(gas=50000) < 50000
+    assert c.foo(gas=50000) > 25000

vyper/codegen/expr.py

@@ -269,7 +269,8 @@ def parse_Attribute(self):
                 return IRnode.from_list(["~calldata"], typ=BytesT(0))
             elif key == "msg.value" and self.context.is_payable:
                 return IRnode.from_list(["callvalue"], typ=UINT256_T)
-            elif key == "msg.gas":
+            elif key in ("msg.gas", "msg.mana"):
+                # NOTE: `msg.mana` is an alias for `msg.gas`
                 return IRnode.from_list(["gas"], typ=UINT256_T)
             elif key == "block.prevrandao":
                 if not version_check(begin="paris"):

vyper/semantics/environment.py

@@ -36,7 +36,13 @@ class _Chain(_EnvType):
 
 class _Msg(_EnvType):
     _id = "msg"
-    _type_members = {"data": BytesT(), "gas": UINT256_T, "sender": AddressT(), "value": UINT256_T}
+    _type_members = {
+        "data": BytesT(),
+        "gas": UINT256_T,
+        "mana": UINT256_T,
+        "sender": AddressT(),
+        "value": UINT256_T,
+    }
 
 
 class _Tx(_EnvType):