support pep-563 -- Postponed Evaluation of Annotations

05-annotations.py

@@ -1,4 +1,5 @@
 from math import pi
+import typing
 
 
 class TypeChecker:
@@ -17,7 +18,7 @@ def __set__(self, instance, value):
 
 
 def type_check(cls):
-    for var_name, var_type in cls.__annotations__.items():
+    for var_name, var_type in typing.get_type_hints(cls).items():
         class Checker(TypeChecker):
             required_type = var_type
 

07-metaclasses.py

@@ -1,4 +1,5 @@
 from math import pi
+import typing
 
 
 class TypeChecker:
@@ -17,7 +18,7 @@ def __set__(self, instance, value):
 
 
 def type_check(cls):
-    for var_name, var_type in cls.__annotations__.items():
+    for var_name, var_type in typing.get_type_hints(cls).items():
         class Checker(TypeChecker):
             required_type = var_type
 
@@ -32,7 +33,7 @@ def __new__(meta, name, bases, dct):
 
 
 class Base(metaclass=TypeCheckMeta):
-    __annotations__ = {}
+    pass
 
 
 class Point(Base):

08-interlude_dataclasses.py

@@ -1,9 +1,11 @@
+import typing
+
 def dataclass(cls):
     def __init__(self, *args, **kwargs):
-        for k, v in zip(cls.__annotations__.keys(), args):
+        for k, v in zip(typing.get_type_hints(cls).keys(), args):
             setattr(self, k, v)
         for k, v in kwargs.items():
-            if k not in cls.__annotations__:
+            if k not in typing.get_type_hints(cls):
                 raise TypeError(
                     f"__init__() got an unexpected keyword argument '{k}'"
                 )
@@ -14,7 +16,7 @@ def __init__(self, *args, **kwargs):
             post_init()
 
     def __repr__(self):
-        kwargs = {k: getattr(self, k) for k in cls.__annotations__}
+        kwargs = {k: getattr(self, k) for k in typing.get_type_hints(cls)}
         kwstr = ', '.join([f'{k}={v}' for k, v in kwargs.items()])
         return f'{cls.__name__}({kwstr})'
 

09-meta_dataclasses.py

@@ -1,5 +1,6 @@
 from dataclasses import dataclass
 from math import pi
+import typing
 
 
 class TypeChecker:
@@ -20,7 +21,7 @@ def __set__(self, instance, value):
 def typed_dataclass(cls):
     cls = dataclass(cls)
 
-    for var_name, var_type in cls.__annotations__.items():
+    for var_name, var_type in typing.get_type_hints(cls).items():
         class Checker(TypeChecker):
             required_type = var_type
 
@@ -35,7 +36,7 @@ def __new__(meta, name, bases, dct):
 
 
 class Base(metaclass=TypeCheckMeta):
-    __annotations__ = {}
+    pass
 
 
 class Point(Base):

11-ast.py

@@ -1,4 +1,5 @@
 import ast
+import typing
 
 # This could come from a variety of sources: not just text. For instance, we
 # could use inspect.get_source()
@@ -22,7 +23,7 @@ def __set__(self, instance, value):
 
 
 def type_check(cls):
-    for var_name, var_type in cls.__annotations__.items():
+    for var_name, var_type in typing.get_type_hints(cls).items():
         class Checker(TypeChecker):
             required_type = var_type
         setattr(cls, var_name, Checker(var_name))