feat: add convert for enum

docs/types.rst

@@ -622,5 +622,6 @@ All type conversions in Vyper must be made explicitly using the built-in ``conve
 * Narrowing conversions (e.g., ``int256 -> int128``) check that the input is in bounds for the output type.
 * Converting between bytes and int types results in sign-extension if the output type is signed. For instance, converting ``0xff`` (``bytes1``) to ``int8`` returns ``-1``.
 * Converting between bytes and int types which have different sizes follows the rule of going through the closest integer type, first. For instance, ``bytes1 -> int16`` is like ``bytes1 -> int8 -> int16`` (signextend, then widen). ``uint8 -> bytes20`` is like ``uint8 -> uint160 -> bytes20`` (rotate left 12 bytes).
+* Enums can be converted to and from ``uint256`` only.
 
 A small Python reference implementation is maintained as part of Vyper's test suite, it can be found `here <https://github.com/vyperlang/vyper/blob/c4c6afd07801a0cc0038cdd4007cc43860c54193/tests/parser/functions/test_convert.py#L318>`_. The motivation and more detailed discussion of the rules can be found `here <https://github.com/vyperlang/vyper/issues/2507>`_.

tests/parser/functions/test_convert.py

@@ -22,6 +22,7 @@
     DECIMAL_DIVISOR,
     SizeLimits,
     checksum_encode,
+    int_bounds,
     is_checksum_encoded,
     round_towards_zero,
     unsigned_to_signed,
@@ -513,6 +514,56 @@ def test_memory_variable_convert(x: {i_typ}) -> {o_typ}:
     assert c4.test_memory_variable_convert(val) == expected_val
 
 
+@pytest.mark.parametrize("typ", ["uint8", "int128", "int256", "uint256"])
+@pytest.mark.parametrize("val", [1, 2, 2 ** 128, 2 ** 256 - 1, 2 ** 256 - 2])
+def test_enum_conversion(get_contract_with_gas_estimation, assert_compile_failed, val, typ):
+    roles = "\n    ".join([f"ROLE_{i}" for i in range(256)])
+    contract = f"""
+enum Roles:
+    {roles}
+
+@external
+def foo(a: Roles) -> {typ}:
+    return convert(a, {typ})
+
+@external
+def bar(a: uint256) -> Roles:
+    return convert(a, Roles)
+    """
+    if typ == "uint256":
+        c = get_contract_with_gas_estimation(contract)
+        assert c.foo(val) == val
+        assert c.bar(val) == val
+    else:
+        assert_compile_failed(lambda: get_contract_with_gas_estimation(contract), TypeMismatch)
+
+
+@pytest.mark.parametrize("typ", ["uint8", "int128", "int256", "uint256"])
+@pytest.mark.parametrize("val", [1, 2, 2 ** 128, 2 ** 256 - 1, 2 ** 256 - 2])
+def test_enum_conversion_2(
+    get_contract_with_gas_estimation, assert_compile_failed, assert_tx_failed, val, typ
+):
+    contract = f"""
+enum Status:
+    STARTED
+    PAUSED
+    STOPPED
+
+@external
+def foo(a: {typ}) -> Status:
+    return convert(a, Status)
+    """
+    if typ == "uint256":
+        c = get_contract_with_gas_estimation(contract)
+        lo, hi = int_bounds(signed=False, bits=3)
+        if lo <= val <= hi:
+            assert c.foo(val) == val
+        else:
+            assert_tx_failed(lambda: c.foo(val))
+    else:
+        assert_compile_failed(lambda: get_contract_with_gas_estimation(contract), TypeMismatch)
+
+
 # TODO CMC 2022-04-06 I think this test is somewhat unnecessary.
 @pytest.mark.parametrize(
     "builtin_constant,out_type,out_value",

vyper/builtin_functions/convert.py

@@ -22,10 +22,12 @@
     BaseType,
     ByteArrayLike,
     ByteArrayType,
+    EnumType,
     StringType,
     is_base_type,
     is_bytes_m_type,
     is_decimal_type,
+    is_enum_type,
     is_integer_type,
 )
 from vyper.exceptions import (
@@ -326,6 +328,11 @@ def to_int(expr, arg, out_typ):
     elif is_decimal_type(arg.typ):
         arg = _fixed_to_int(arg, out_typ)
 
+    elif is_enum_type(arg.typ):
+        if out_typ.typ != "uint256":
+            _FAIL(arg.typ, out_typ, expr)
+        arg = _int_to_int(arg, out_typ)
+
     elif is_integer_type(arg.typ):
         arg = _int_to_int(arg, out_typ)
 
@@ -455,6 +462,18 @@ def to_bytes(expr, arg, out_typ):
     return IRnode.from_list(arg, typ=out_typ)
 
 
+@_input_types("int")
+def to_enum(expr, arg, out_typ):
+    if not is_base_type(arg.typ, "uint256"):
+        _FAIL(arg.typ, out_typ, expr)
+
+    _check_bytes(expr, arg, out_typ, 32)
+    arg = _int_to_int(arg, out_typ)
+
+    clamped_arg = int_clamp(arg, len(out_typ.members), False)
+    return IRnode.from_list(clamped_arg, typ=out_typ)
+
+
 def convert(expr, context):
     if len(expr.args) != 2:
         raise StructureException("The convert function expects two parameters.", expr)
@@ -471,6 +490,8 @@ def convert(expr, context):
             ret = to_bool(arg_ast, arg, out_typ)
         elif is_base_type(out_typ, "address"):
             ret = to_address(arg_ast, arg, out_typ)
+        elif isinstance(out_typ, EnumType):
+            ret = to_enum(arg_ast, arg, out_typ)
         elif is_integer_type(out_typ):
             ret = to_int(arg_ast, arg, out_typ)
         elif is_bytes_m_type(out_typ):

vyper/codegen/types/types.py

@@ -159,6 +159,10 @@ def parse_decimal_info(typename: str) -> DecimalTypeInfo:
     return DecimalTypeInfo(bits=168, decimals=10, is_signed=True)
 
 
+def is_enum_type(t: "NodeType") -> bool:
+    return isinstance(t, EnumType)
+
+
 def _basetype_to_abi_type(t: "BaseType") -> ABIType:
     if is_integer_type(t):
         info = t._int_info
@@ -237,6 +241,8 @@ def __repr__(self):
         return f"enum {self.name}"
 
     def __eq__(self, other):
+        if type(self) is not type(other):
+            return False
         return self.name == other.name and self.members == other.members
 
     @property