use CPython's behaviour in floatNew

Author: Boxiang Sun

src/runtime/float.cpp

@@ -868,27 +868,15 @@ template <ExceptionStyle S> static BoxedFloat* _floatNew(Box* a) noexcept(S == C
 
         return res;
     } else {
-        static BoxedString* float_str = internStringImmortal("__float__");
-        Box* r = callattrInternal<S, NOT_REWRITABLE>(a, float_str, CLASS_ONLY, NULL, ArgPassSpec(0), NULL, NULL, NULL,
-                                                     NULL, NULL);
-
+        Box* r = PyNumber_Float(a);
         if (!r) {
             if (S == CAPI) {
-                if (!PyErr_Occurred())
-                    PyErr_SetString(PyExc_TypeError, "float() argument must be a string or a number");
                 return NULL;
             } else {
-                raiseExcHelper(TypeError, "float() argument must be a string or a number");
+                throwCAPIException();
             }
         }
 
-        if (!PyFloat_Check(r)) {
-            if (S == CAPI) {
-                PyErr_Format(TypeError, "__float__ returned non-float (type %s)", r->cls->tp_name);
-                return NULL;
-            } else
-                raiseExcHelper(TypeError, "__float__ returned non-float (type %s)", r->cls->tp_name);
-        }
         return static_cast<BoxedFloat*>(r);
     }
 }