#33157 fix issue in SR → CBF conversion from #32871

src/sage/symbolic/expression.pyx

@@ -384,6 +384,7 @@ from cpython.object cimport Py_EQ, Py_NE, Py_LE, Py_GE, Py_LT, Py_GT
 
 from sage.cpython.string cimport str_to_bytes, char_to_str
 
+from sage.structure.element cimport parent
 from sage.structure.element cimport RingElement, Element, Matrix
 from sage.structure.element cimport Expression as Expression_abc
 from sage.symbolic.complexity_measures import string_length
@@ -1804,6 +1805,9 @@ cdef class Expression(Expression_abc):
             Traceback (most recent call last):
             ...
             TypeError: unable to convert bogus_builtin_function(1) to a ComplexBall
+
+            sage: CBF(acos(float(1/4) * sqrt(int(5))))
+            [0.97759655064526...]
         """
         cdef bint progress = False
         cdef int i
@@ -1841,7 +1845,7 @@ cdef class Expression(Expression_abc):
             # not bother trying to stay in the real field.
             try:
                 for i in range(len(args)):
-                    if args[i].parent() is not C:
+                    if parent(args[i]) is not C:
                         progress = True
                         args[i] = C(args[i])
             except (TypeError, ValueError):