make typeguard work on python3.9

.travis.yml

@@ -35,6 +35,11 @@ jobs:
       python: "3.8"
       after_success: *after_success
 
+    - stage: test
+      env: TOXENV=py39
+      python: "3.9-dev"
+      after_success: *after_success
+
     - stage: deploy to pypi
       install: skip
       script: skip

tests/test_typeguard.py

@@ -10,7 +10,17 @@
     Container, Generic, BinaryIO, TextIO, Generator, Iterator, AbstractSet, AnyStr, Type)
 
 import pytest
-from typing_extensions import NoReturn, Protocol, Literal, TypedDict, runtime_checkable
+try:
+    from typing_extensions import NoReturn, Protocol, Literal, TypedDict, runtime_checkable
+except ImportError:
+    try:
+        from typing import NoReturn, Protocol, Literal, TypedDict, runtime_checkable
+    except ImportError:
+        NoReturn = None
+        Protocol = None
+        Literal = None
+        TypedDict = None
+        runtime_checkable = None
 
 from typeguard import (
     typechecked, check_argument_types, qualified_name, TypeChecker, TypeWarning, function_name,

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.3.0
-envlist = pypy3, py35, py36, py37, py38, flake8
+envlist = pypy3, py35, py36, py37, py38, py39, flake8
 skip_missing_interpreters = true
 isolated_build = true
 

typeguard/__init__.py

@@ -173,7 +173,11 @@ def __init__(self, func: Callable, frame_locals: Optional[Dict[str, Any]] = None
 
 def resolve_forwardref(maybe_ref, memo: _TypeCheckMemo):
     if isinstance(maybe_ref, ForwardRef):
-        return evaluate_forwardref(maybe_ref, memo.globals, memo.locals)
+        if sys.version_info < (3, 9, 0):
+            return evaluate_forwardref(maybe_ref, memo.globals, memo.locals)
+        else:
+            return evaluate_forwardref(maybe_ref, memo.globals, memo.locals, frozenset())
+
     else:
         return maybe_ref
 
@@ -247,7 +251,7 @@ def check_callable(argname: str, value, expected_type, memo: _TypeCheckMemo) ->
     if not callable(value):
         raise TypeError('{} must be a callable'.format(argname))
 
-    if expected_type.__args__:
+    if hasattr(expected_type, "__args__") and expected_type.__args__:
         try:
             signature = inspect.signature(value)
         except (TypeError, ValueError):
@@ -297,7 +301,8 @@ def check_dict(argname: str, value, expected_type, memo: _TypeCheckMemo) -> None
                         format(argname, qualified_name(value)))
 
     if expected_type is not dict:
-        if expected_type.__args__ not in (None, expected_type.__parameters__):
+        if hasattr(expected_type, "__args__") and expected_type.__args__ not in \
+                (None, expected_type.__parameters__):
             key_type, value_type = expected_type.__args__
             if key_type is not Any or value_type is not Any:
                 for k, v in value.items():
@@ -332,7 +337,8 @@ def check_list(argname: str, value, expected_type, memo: _TypeCheckMemo) -> None
                         format(argname, qualified_name(value)))
 
     if expected_type is not list:
-        if expected_type.__args__ not in (None, expected_type.__parameters__):
+        if hasattr(expected_type, "__args__") and expected_type.__args__ not in \
+                (None, expected_type.__parameters__):
             value_type = expected_type.__args__[0]
             if value_type is not Any:
                 for i, v in enumerate(value):
@@ -344,7 +350,8 @@ def check_sequence(argname: str, value, expected_type, memo: _TypeCheckMemo) ->
         raise TypeError('type of {} must be a sequence; got {} instead'.
                         format(argname, qualified_name(value)))
 
-    if expected_type.__args__ not in (None, expected_type.__parameters__):
+    if hasattr(expected_type, "__args__") and expected_type.__args__ not in \
+            (None, expected_type.__parameters__):
         value_type = expected_type.__args__[0]
         if value_type is not Any:
             for i, v in enumerate(value):
@@ -357,7 +364,8 @@ def check_set(argname: str, value, expected_type, memo: _TypeCheckMemo) -> None:
                         format(argname, qualified_name(value)))
 
     if expected_type is not set:
-        if expected_type.__args__ not in (None, expected_type.__parameters__):
+        if hasattr(expected_type, "__args__") and expected_type.__args__ not in \
+                (None, expected_type.__parameters__):
             value_type = expected_type.__args__[0]
             if value_type is not Any:
                 for v in value:
@@ -366,12 +374,22 @@ def check_set(argname: str, value, expected_type, memo: _TypeCheckMemo) -> None:
 
 def check_tuple(argname: str, value, expected_type, memo: _TypeCheckMemo) -> None:
     # Specialized check for NamedTuples
-    if hasattr(expected_type, '_field_types'):
+    is_named_tuple = False
+    if sys.version_info < (3, 8, 0):
+        is_named_tuple = hasattr(expected_type, '_field_types')  # deprecated since python 3.8
+    else:
+        is_named_tuple = hasattr(expected_type, '__annotations__')
+
+    if is_named_tuple:
         if not isinstance(value, expected_type):
             raise TypeError('type of {} must be a named tuple of type {}; got {} instead'.
                             format(argname, qualified_name(expected_type), qualified_name(value)))
+        if sys.version_info < (3, 8, 0):
+            field_types = expected_type._field_types
+        else:
+            field_types = expected_type.__annotations__
 
-        for name, field_type in expected_type._field_types.items():
+        for name, field_type in field_types.items():
             check_type('{}.{}'.format(argname, name), getattr(value, name), field_type, memo)
 
         return
@@ -436,7 +454,8 @@ def check_class(argname: str, value, expected_type, memo: _TypeCheckMemo) -> Non
     if expected_type is Type:
         return
 
-    expected_class = expected_type.__args__[0] if expected_type.__args__ else None
+    expected_class = expected_type.__args__[0] if hasattr(
+        expected_type, "__args__") and expected_type.__args__ else None
     if expected_class:
         if expected_class is Any:
             return
@@ -728,10 +747,11 @@ def check_argument_types(memo: Optional[_CallMemo] = None) -> bool:
 
 class TypeCheckedGenerator:
     def __init__(self, wrapped: Generator, memo: _CallMemo):
-        rtype_args = memo.type_hints['return'].__args__
+        rtype_args = memo.type_hints['return'].__args__ if hasattr(
+            memo.type_hints['return'], "__args__") else []
         self.__wrapped = wrapped
         self.__memo = memo
-        self.__yield_type = rtype_args[0]
+        self.__yield_type = rtype_args[0] if rtype_args else Any
         self.__send_type = rtype_args[1] if len(rtype_args) > 1 else Any
         self.__return_type = rtype_args[2] if len(rtype_args) > 2 else Any
         self.__initialized = False