only include CythonFunction utility code if it's really used, might be unused...

only include CythonFunction utility code if it's really used, might be unused if .pxd overrides all def functions to cdef

Cython/Compiler/ExprNodes.py

@@ -6781,14 +6781,7 @@ class PyCFunctionNode(ExprNode, ModuleNameMixin):
 
     def analyse_types(self, env):
         if self.binding:
-            if self.specialized_cpdefs or self.is_specialization:
-                env.use_utility_code(
-                    UtilityCode.load_cached("FusedFunction", "CythonFunction.c"))
-            else:
-                env.use_utility_code(
-                    UtilityCode.load_cached("CythonFunction", "CythonFunction.c"))
             self.analyse_default_args(env)
-
         #TODO(craig,haoyu) This should be moved to a better place
         self.set_qualified_name(env, self.def_node.name)
         return self
@@ -6888,14 +6881,18 @@ class PyCFunctionNode(ExprNode, ModuleNameMixin):
         code.put_gotref(self.py_result())
 
     def generate_cyfunction_code(self, code):
-        def_node = self.def_node
-
         if self.specialized_cpdefs:
-            constructor = "__pyx_FusedFunction_NewEx"
             def_node = self.specialized_cpdefs[0]
-        elif self.is_specialization:
+        else:
+            def_node = self.def_node
+
+        if self.specialized_cpdefs or self.is_specialization:
+            code.globalstate.use_utility_code(
+                UtilityCode.load_cached("FusedFunction", "CythonFunction.c"))
             constructor = "__pyx_FusedFunction_NewEx"
         else:
+            code.globalstate.use_utility_code(
+                UtilityCode.load_cached("CythonFunction", "CythonFunction.c"))
             constructor = "__Pyx_CyFunction_NewEx"
 
         if self.code_object: