Add class method optional parameter tests

trans/stdlib/__init__.py

@@ -15,7 +15,8 @@ U = TypeVar("U")
 V = TypeVar("V")
 
 
-
+# TODO: really, these should work as interfaces, on a duck-typing basis. it's gonna be a hell of a ride to implement
+# unification for this
 class HasLen:
     def __len__(self) -> int: ...
 
@@ -110,3 +111,14 @@ assert __test_opt(5)
 assert __test_opt(5, 6)
 assert not __test_opt(5, 6, 7)
 assert not __test_opt()
+
+class __test_type:
+    def __init__(self) -> None: ...
+
+    def test_opt(self, x: int, y: int = 5) -> int:
+        ...
+
+assert __test_type().test_opt(5)
+assert __test_type().test_opt(5, 6)
+assert not __test_type().test_opt(5, 6, 7)
+assert not __test_type().test_opt()
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