Update __init__.py

src/pyoload/__init__.py

@@ -1,4 +1,5 @@
 from typing import Any, GenericAlias, Union
+from types import UnionType
 from functools import wraps, partial
 from inspect import isclass
 
@@ -62,32 +63,36 @@ def __call__(self, val):
 class Cast:
     @staticmethod
     def cast(val, type):
-        if issubclass(type, Union):
+        if isinstance(type, UnionType):
             type = type.__args__
         if isinstance(type, tuple):
+            e = None
             for x in type:
                 try:
-                    return Cast.cast(val, x)
-                except Exception:
+                    return Cast.cast(val, type)
+                except Exception as e:
                     pass
             else:
-                raise CastingError()
-        return type(val) if not isinstance(val, type) else val
+                raise e
+        else:
+            print(f"casting {val!r} to {type!r}")
+            return type(val) if not isinstance(val, type) else val
 
     def __init__(self, type):
         self.type = type
 
     def __call__(self, val):
         try:
-            return Cast.cast(self.type, val)
+            return Cast.cast(val, self.type)
         except Exception as e:
+            raise e from e
             raise CastingError(
-                f'Exception while casting: {val!r} to {self.type}',
+                f'Exception({e}) while casting: {val!r} to {self.type}',
             ) from e
 
 
 def typeMatch(val, spec):
-    if spec == Any or spec is None:
+    if spec == Any or spec is None or val is None:
         return True
     if isinstance(val, tuple):
         return isinstance(val, tuple)
@@ -124,6 +129,8 @@ def annotate(func, oload=False):
     if isclass(func):
         return annotateClass(func)
     anno = func.__annotations__
+    if len(anno) == 0:
+        return func
 
     @wraps(func)
     def wrapper(*args, **kw):
@@ -225,14 +232,15 @@ def new_setter(self, name, value):
             resolveAnnotations(anno, globals(), get_name(cls))
 
         if name not in anno:
-            anno[name] = type(value)
-        if not typeMatch(value, anno[name]):
+            if value is not None:
+                anno[name] = type(value)
+        elif not typeMatch(value, anno[name]):
             raise AnnotationError(
                 f'value {value!r} does not match annotation' +
-                'of attribute: {name!r}:{anno[name]!r} of object of class {get_name(cls)}',
+                f'of attribute: {name!r}:{anno[name]!r} of object of class {get_name(cls)}',
             )
-        else:
-            return setter(self, name, value)
+
+        return setter(self, name, value)
     cls.__setattr__ = new_setter
     return cls