Repair calls to fused staticmethods : we currently generate the wrong C...

Repair calls to fused staticmethods : we currently generate the wrong C signature for them (first arg becomes 'self' arg), so this change works around that by really passing the first argument as 'self'.
Eventually, ths signature should be fixed instead.

Cython/Compiler/FusedNode.py

@@ -655,6 +655,7 @@ class FusedCFuncDefNode(StatListNode):
         UtilityCode.declare_declarations_in_scope(
             decl_code.getvalue(), env.global_scope())
         ast.scope = env
+        # FIXME: for static methods of cdef classes, we build the wrong signature here: first arg becomes 'self'
         ast.analyse_declarations(env)
         py_func = ast.stats[-1]  # the DefNode
         self.fragment_scope = ast.scope

Cython/Utility/CythonFunction.c

@@ -1072,16 +1072,25 @@ __pyx_FusedFunction_call(PyObject *func, PyObject *args, PyObject *kw)
 #endif
 
     if (binding_func->__signatures__) {
-        PyObject *tup = PyTuple_Pack(4, binding_func->__signatures__, args,
-                                        kw == NULL ? Py_None : kw,
-                                        binding_func->func.defaults_tuple);
-        if (!tup)
-            goto bad;
-
-        new_func = (__pyx_FusedFunctionObject *) __pyx_FusedFunction_callfunction(func, tup, NULL);
+        PyObject *tup;
+        if (is_staticmethod && binding_func->func.flags & __Pyx_CYFUNCTION_CCLASS) {
+            // FIXME: this seems wrong, but we must currently pass the signatures dict as 'self' argument
+            tup = PyTuple_Pack(3, args,
+                               kw == NULL ? Py_None : kw,
+                               binding_func->func.defaults_tuple);
+            if (unlikely(!tup)) goto bad;
+            new_func = (__pyx_FusedFunctionObject *) __Pyx_CyFunction_CallMethod(
+                func, binding_func->__signatures__, tup, NULL);
+        } else {
+            tup = PyTuple_Pack(4, binding_func->__signatures__, args,
+                               kw == NULL ? Py_None : kw,
+                               binding_func->func.defaults_tuple);
+            if (unlikely(!tup)) goto bad;
+            new_func = (__pyx_FusedFunctionObject *) __pyx_FusedFunction_callfunction(func, tup, NULL);
+        }
         Py_DECREF(tup);
 
-        if (!new_func)
+        if (unlikely(!new_func))
             goto bad;
 
         Py_XINCREF(binding_func->func.func_classobj);