Implement <= between two OneOf instances (Fix for issue #15)

runtype/__init__.py

@@ -1,6 +1,6 @@
 from .dataclass import dataclass
 from .dispatch import DispatchError, MultiDispatch
-from .validation import PythonTyping, TypeSystem, TypeMismatchError, assert_isa, isa, issubclass, validate_func
+from .validation import PythonTyping, TypeSystem, TypeMismatchError, assert_isa, isa, issubclass, validate_func, is_subtype
 from .pytypes import Constraint, String, Int
 
 __version__ = "0.3.1"

runtype/pytypes.py

@@ -166,6 +166,8 @@ def __init__(self, values):
         self.values = values
 
     def __le__(self, other):
+        if isinstance(other, OneOf):
+            return set(self.values) <= set(other.values)
         return NotImplemented
 
     def validate_instance(self, obj, sampler=None):

tests/test_basic.py

@@ -11,7 +11,7 @@
 import logging
 logging.basicConfig(level=logging.INFO)
 
-from runtype import Dispatch, DispatchError, dataclass, isa, issubclass, assert_isa, String, Int, validate_func
+from runtype import Dispatch, DispatchError, dataclass, isa, is_subtype, issubclass, assert_isa, String, Int, validate_func
 from runtype.dataclass import Configuration
 
 
@@ -106,6 +106,8 @@ def test_py38(self):
         assert isa('a', typing.Literal['a', 'b'])
         assert not isa('c', typing.Literal['a', 'b'])
 
+        assert is_subtype(typing.Literal[1], typing.Literal[1,2])
+
     def test_validate_func(self):
         @validate_func
         def f(a: int, b: str, c: List[int] = []):