is_NumberFieldElement: Deprecate, replace uses by isinstance

Author: Matthias Koeppe

src/sage/rings/finite_rings/residue_field.pyx

@@ -160,9 +160,8 @@ from sage.rings.finite_rings.finite_field_ntl_gf2e import FiniteField_ntl_gf2e
 from sage.rings.finite_rings.finite_field_prime_modn import FiniteField_prime_modn
 from sage.rings.finite_rings.finite_field_pari_ffelt import FiniteField_pari_ffelt
 from sage.rings.ideal import is_Ideal
-from sage.structure.element cimport Element
+from sage.structure.element cimport Element, NumberFieldElement
 
-from sage.rings.number_field.number_field_element import is_NumberFieldElement
 from sage.rings.number_field.number_field_ideal import is_NumberFieldIdeal
 
 from sage.modules.free_module_element import FreeModuleElement
@@ -295,7 +294,7 @@ class ResidueFieldFactory(UniqueFactory):
             if not is_Ideal(p):
                 if isinstance(p, (int, Integer, Rational)):
                     p = ZZ.ideal(p)
-                elif is_NumberFieldElement(p):
+                elif isinstance(p, NumberFieldElement):
                     if p.parent().is_field():
                         p = p.parent().ring_of_integers().ideal(p)
                     else:

src/sage/rings/number_field/number_field_element.pyx

@@ -113,6 +113,10 @@ def is_NumberFieldElement(x):
         sage: is_NumberFieldElement(a+1)
         True
     """
+    from sage.misc.superseded import deprecation
+    deprecation(34931,
+                'is_NumberFieldElement is deprecated; '
+                'use isinstance(..., sage.structure.element.NumberFieldElement) instead')
     return isinstance(x, NumberFieldElement)
 
 
@@ -3855,7 +3859,7 @@ cdef class NumberFieldElement(NumberFieldElement_base):
         """
         from .number_field_ideal import is_NumberFieldIdeal
         if not is_NumberFieldIdeal(P):
-            if is_NumberFieldElement(P):
+            if isinstance(P, NumberFieldElement):
                 P = self.number_field().fractional_ideal(P)
             else:
                 raise TypeError("P must be an ideal")

src/sage/schemes/elliptic_curves/heegner.py

@@ -97,6 +97,7 @@
 from sage.misc.verbose import verbose
 from sage.misc.cachefunc import cached_method
 
+from sage.structure.element import NumberFieldElement
 from sage.structure.sage_object import SageObject
 from sage.structure.richcmp import (richcmp_method, richcmp,
                                     richcmp_not_equal, rich_to_bool)
@@ -2679,7 +2680,7 @@ def __init__(self, N, D, c=ZZ(1), f=None, check=True):
                 elif isinstance(f, BinaryQF):
                     # convert from BinaryQF
                     f = tuple(f)
-                elif sage.rings.number_field.number_field_element.is_NumberFieldElement(f):
+                elif isinstance(f, NumberFieldElement):
                     # tau = number field element
                     g = f.minpoly()
                     if g.degree() != 2: