Flesh out type annotations

Closes #281

Author: Tinche

HISTORY.rst

@@ -16,6 +16,8 @@ History
 * Fix ``typing.Set`` applying too broadly when used with the ``GenConverter.unstruct_collection_overrides`` parameter on Python versions below 3.9. Switch to ``typing.AbstractSet`` on those versions to restore the old behavior.
   (`#264 <https://github.com/python-attrs/cattrs/issues/264>`_)
 * Uncap the required Python version, to avoid problems detailed in https://iscinumpy.dev/post/bound-version-constraints/#pinning-the-python-version-is-special (`#275 <https://github.com/python-attrs/cattrs/issues/275>`_)
+* Fix `Converter.register_structure_hook_factory` and `cattrs.gen.make_dict_unstructure_fn` type annotations.
+  (`#281 <https://github.com/python-attrs/cattrs/issues/281>`_)
 
 22.1.0 (2022-04-03)
 -------------------

src/cattrs/converters.py

@@ -264,7 +264,7 @@ def register_structure_hook_func(
     def register_structure_hook_factory(
         self,
         predicate: Callable[[Any], bool],
-        factory: Callable[[Any], Callable[[Any], Any]],
+        factory: Callable[[Any], Callable[[Any, Any], Any]],
     ) -> None:
         """
         Register a hook factory for a given predicate.
@@ -750,7 +750,9 @@ def gen_structure_annotated(self, type):
         h = self._structure_func.dispatch(origin)
         return h
 
-    def gen_unstructure_attrs_fromdict(self, cl: Type[T]) -> Dict[str, Any]:
+    def gen_unstructure_attrs_fromdict(
+        self, cl: Type[T]
+    ) -> Callable[[T], Dict[str, Any]]:
         origin = get_origin(cl)
         attribs = fields(origin or cl)
         if attrs_has(cl) and any(isinstance(a.type, str) for a in attribs):
@@ -767,7 +769,9 @@ def gen_unstructure_attrs_fromdict(self, cl: Type[T]) -> Dict[str, Any]:
         )
         return h
 
-    def gen_structure_attrs_fromdict(self, cl: Type[T]) -> T:
+    def gen_structure_attrs_fromdict(
+        self, cl: Type[T]
+    ) -> Callable[[Mapping[str, Any], Any], T]:
         attribs = fields(get_origin(cl) if is_generic(cl) else cl)
         if attrs_has(cl) and any(isinstance(a.type, str) for a in attribs):
             # PEP 563 annotations - need to be resolved.

src/cattrs/gen.py

@@ -46,12 +46,12 @@ def override(omit_if_default=None, rename=None, omit: bool = False):
 
 
 def make_dict_unstructure_fn(
-    cl,
-    converter,
+    cl: Type[T],
+    converter: "BaseConverter",
     _cattrs_omit_if_default: bool = False,
     _cattrs_use_linecache: bool = True,
     **kwargs,
-) -> Callable[[Any], Dict]:
+) -> Callable[[T], Dict[str, Any]]:
     """
     Generate a specialized dict unstructuring function for an attrs class or a
     dataclass.