Minor improvements for _cwiring.DependencyResolver code generation

* Remove KWPair
* Avoid type checks around _is_injectable

src/dependency_injector/_cwiring.pyx

@@ -5,24 +5,11 @@ from collections.abc import Awaitable
 from inspect import CO_ITERABLE_COROUTINE
 from types import CoroutineType, GeneratorType
 
-from .providers cimport Provider, Resource, NULL_AWAITABLE
+from .providers cimport Provider, Resource
 from .wiring import _Marker
 
-cimport cython
 
-
-@cython.internal
-@cython.no_gc
-cdef class KWPair:
-    cdef str name
-    cdef object value
-
-    def __cinit__(self, str name, object value, /):
-        self.name = name
-        self.value = value
-
-
-cdef inline bint _is_injectable(dict kwargs, str name):
+cdef inline bint _is_injectable(dict kwargs, object name):
     return name not in kwargs or isinstance(kwargs[name], _Marker)
 
 
@@ -38,11 +25,8 @@ cdef class DependencyResolver:
         self.injections = injections
         self.closings = closings
 
-    async def _await_injection(self, kw_pair: KWPair, /) -> None:
-        self.to_inject[kw_pair.name] = await kw_pair.value
-
-    cdef object _await_injections(self, to_await: list):
-        return gather(*map(self._await_injection, to_await))
+    async def _await_injection(self, name: str, value: object, /) -> None:
+        self.to_inject[name] = await value
 
     cdef void _handle_injections_sync(self):
         cdef Provider provider
@@ -60,7 +44,7 @@ cdef class DependencyResolver:
                 provide = provider()
 
                 if provider.is_async_mode_enabled() or _isawaitable(provide):
-                    to_await.append(KWPair(name, provide))
+                    to_await.append(self._await_injection(name, provide))
                 else:
                     self.to_inject[name] = provide
 
@@ -93,13 +77,12 @@ cdef class DependencyResolver:
 
     async def __aenter__(self):
         if to_await := self._handle_injections_async():
-            await self._await_injections(to_await)
+            await gather(*to_await)
         return self.to_inject
 
-    def __aexit__(self, *_):
+    async def __aexit__(self, *_):
         if to_await := self._handle_closings_async():
-            return gather(*to_await)
-        return NULL_AWAITABLE
+            await gather(*to_await)
 
 
 cdef bint _isawaitable(object instance):