Add initial type hints

This is *super* early, but it add hints for the two most commonly used
entry points for wrapt.

Signed-off-by: Stephen Finucane <stephen@that.guru>

src/wrapt/decorators.py

@@ -6,6 +6,7 @@
 from functools import partial
 from inspect import isclass, signature
 from threading import Lock, RLock
+from typing import Any, Callable, Optional, Type, TypeVar, overload
 
 from .arguments import formatargspec
 
@@ -15,6 +16,10 @@
     CallableObjectProxy,
 )
 
+F = TypeVar('F', bound=Callable[..., Any])
+A = TypeVar('A', bound=Callable[..., Any])
+T = TypeVar('T', bound=Any)
+
 # Adapter wrapper for the wrapped function which will overlay certain
 # properties from the adapter function onto the wrapped function so that
 # functions such as inspect.getfullargspec(), inspect.signature() and
@@ -141,7 +146,30 @@ def __call__(self, wrapped):
 # original wrapped function.
 
 
-def decorator(wrapper=None, enabled=None, adapter=None, proxy=FunctionWrapper):
+@overload
+def decorator(
+    wrapper: None = None,
+    enabled: Optional[bool] = None,
+    adapter: Optional[A] = None,
+    proxy: Type[FunctionWrapper] = FunctionWrapper,
+) -> partial[F]: ...
+
+
+@overload
+def decorator(
+    wrapper: F,
+    enabled: Optional[bool] = None,
+    adapter: Optional[A] = None,
+    proxy: Type[FunctionWrapper] = FunctionWrapper,
+) -> F: ...
+
+
+def decorator(
+    wrapper: Optional[F] = None,
+    enabled: Optional[bool] = None,
+    adapter: Optional[A] = None,
+    proxy: Type[FunctionWrapper] = FunctionWrapper,
+) -> F | partial[F]:
     # The decorator should be supplied with a single positional argument
     # which is the wrapper function to be used to implement the
     # decorator. This may be preceded by a step whereby the keyword

src/wrapt/wrappers.py

@@ -1,6 +1,10 @@
-import sys
-import operator
 import inspect
+import operator
+import sys
+from typing import Any, Generic, TypeVar
+
+
+T = TypeVar("T", bound=Any)
 
 
 class _ObjectProxyMethods(object):
@@ -61,10 +65,11 @@ def __new__(cls, name, bases, dictionary):
 class _ObjectProxyBase(metaclass=_ObjectProxyMetaType): ...
 
 
-class ObjectProxy(_ObjectProxyBase):
+class ObjectProxy(_ObjectProxyBase, Generic[T]):
     __slots__ = '__wrapped__'
+    __wrapped__: T
 
-    def __init__(self, wrapped):
+    def __init__(self, wrapped: T):
         object.__setattr__(self, '__wrapped__', wrapped)
 
         # Python 3.2+ has the __qualname__ attribute, but it does not