gh-38277: Deprecate is_ChowCycle, is_CohomologyClass, `is_Divisor…

…`, `is_ToricDivisor`

    
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- Part of #32414

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### ⌛ Dependencies

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URL: #38277
Reported by: Matthias Köppe
Reviewer(s): Travis Scrimshaw

src/sage/schemes/generic/divisor.py

@@ -111,10 +111,18 @@ def is_Divisor(x):
         sage: x,y = AffineSpace(2, GF(5), names='xy').gens()
         sage: C = Curve(y^2 - x^9 - x)
         sage: is_Divisor(C.divisor([]))
+        doctest:warning...
+        DeprecationWarning: The function is_Divisor is deprecated;
+        use 'isinstance(..., Divisor_generic)' instead.
+        See https://github.com/sagemath/sage/issues/38277 for details.
         True
         sage: is_Divisor("Ceci n'est pas un diviseur")
         False
     """
+    from sage.misc.superseded import deprecation
+    deprecation(38277,
+                "The function is_Divisor is deprecated; "
+                "use 'isinstance(..., Divisor_generic)' instead.")
     return isinstance(x, Divisor_generic)
 
 

src/sage/schemes/toric/chow_group.py

@@ -132,7 +132,7 @@
 
 import sage.geometry.abc
 from sage.schemes.toric.variety import ToricVariety_field
-from sage.schemes.toric.divisor import is_ToricDivisor
+from sage.schemes.toric.divisor import ToricDivisor_generic
 
 
 class ChowCycle(FGP_Element):
@@ -408,7 +408,7 @@ def intersection_with_divisor(self, divisor):
              (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
              (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)]
         """
-        assert is_ToricDivisor(divisor), f'{divisor} is not a toric divisor'
+        assert isinstance(divisor, ToricDivisor_generic), f'{divisor} is not a toric divisor'
 
         A = self.parent()  # the Chow group
         X = A._variety  # the toric variety
@@ -610,7 +610,7 @@ def __init__(self, toric_variety, base_ring, check):
             Chow group of 2-d CPR-Fano toric variety covered by 3 affine patches
             sage: isinstance(A, ChowGroup_class)
             True
-            sage: is_ChowCycle(A.an_element())
+            sage: isinstance(A.an_element(), ChowCycle)
             True
 
         TESTS::
@@ -701,7 +701,7 @@ def _element_constructor_(self, x, check=True):
         if isinstance(x, sage.geometry.abc.ConvexRationalPolyhedralCone):
             cone = fan.embed(x)
             return self.element_class(self, self._cone_to_V(cone), False)
-        if is_ToricDivisor(x):
+        if isinstance(x, ToricDivisor_generic):
             v = sum(x.coefficient(i) * self._cone_to_V(onecone)
                     for i, onecone in enumerate(fan(1)))
             return self.element_class(self, v, False)
@@ -1244,10 +1244,18 @@ def is_ChowCycle(x) -> bool:
         sage: A = P2.Chow_group()
         sage: from sage.schemes.toric.chow_group import *
         sage: is_ChowCycle(A)
+        doctest:warning...
+        DeprecationWarning: The function is_ChowCycle is deprecated;
+        use 'isinstance(..., ChowCycle)' instead.
+        See https://github.com/sagemath/sage/issues/38277 for details.
         False
         sage: is_ChowCycle(A.an_element())
         True
         sage: is_ChowCycle('Victoria')
         False
     """
+    from sage.misc.superseded import deprecation
+    deprecation(38277,
+                "The function is_ChowCycle is deprecated; "
+                "use 'isinstance(..., ChowCycle)' instead.")
     return isinstance(x, ChowCycle)

src/sage/schemes/toric/divisor.py

@@ -209,13 +209,21 @@ def is_ToricDivisor(x):
 
         sage: from sage.schemes.toric.divisor import is_ToricDivisor
         sage: is_ToricDivisor(1)
+        doctest:warning...
+        DeprecationWarning: The function is_ToricDivisor is deprecated;
+        use 'isinstance(..., ToricDivisor_generic)' instead.
+        See https://github.com/sagemath/sage/issues/38277 for details.
         False
         sage: P2 = toric_varieties.P2()
         sage: D = P2.divisor(0); D
         V(x)
         sage: is_ToricDivisor(D)
         True
     """
+    from sage.misc.superseded import deprecation
+    deprecation(38277,
+                "The function is_ToricDivisor is deprecated; "
+                "use 'isinstance(..., ToricDivisor_generic)' instead.")
     return isinstance(x, ToricDivisor_generic)
 
 
@@ -1819,7 +1827,7 @@ def _element_constructor_(self, x, check=True, reduce=True):
             sage: TDiv(TDiv.gen(0), check=True)
             V(x)
         """
-        if is_ToricDivisor(x):
+        if isinstance(x, ToricDivisor_generic):
             if x.parent() is self:
                 return x
             else:
@@ -2014,7 +2022,7 @@ def _element_constructor_(self, x):
             sage: Cl(D)
             Divisor class [0, 0, 1, 0]
         """
-        if is_ToricDivisor(x):
+        if isinstance(x, ToricDivisor_generic):
             x = self._projection_matrix * vector(x)
         if isinstance(x, Vector):
             x = list(x)

src/sage/schemes/toric/morphism.py

@@ -755,8 +755,8 @@ def pullback_divisor(self, divisor):
             sage: f.pullback_divisor(D)
             4*V(z0) + 2*V(z1)
         """
-        from sage.schemes.toric.divisor import is_ToricDivisor
-        if not (is_ToricDivisor(divisor) and divisor.is_QQ_Cartier()):
+        from sage.schemes.toric.divisor import ToricDivisor_generic
+        if not (isinstance(divisor, ToricDivisor_generic) and divisor.is_QQ_Cartier()):
             raise ValueError('the divisor must be torus-invariant and QQ-Cartier')
         m = divisor.m(self._defining_cone)
         values = []
@@ -1300,8 +1300,8 @@ def pullback_divisor(self, divisor):
             sage: square.pullback_divisor(D)
             2*V(z)
         """
-        from sage.schemes.toric.divisor import is_ToricDivisor
-        if not (is_ToricDivisor(divisor) and divisor.is_QQ_Cartier()):
+        from sage.schemes.toric.divisor import ToricDivisor_generic
+        if not (isinstance(divisor, ToricDivisor_generic) and divisor.is_QQ_Cartier()):
             raise ValueError('the divisor must be torus-invariant and QQ-Cartier')
         fm = self.fan_morphism()
         values = []
@@ -1978,8 +1978,8 @@ def pullback_divisor(self, divisor):
             sage: fc.embedding_morphism().pullback_divisor(D)
             -V(z0) - 3*V(z1) - 3*V(z2)
         """
-        from sage.schemes.toric.divisor import is_ToricDivisor
-        if not (is_ToricDivisor(divisor) and divisor.is_QQ_Cartier()):
+        from sage.schemes.toric.divisor import ToricDivisor_generic
+        if not (isinstance(divisor, ToricDivisor_generic) and divisor.is_QQ_Cartier()):
             raise ValueError('the divisor must be torus-invariant and QQ-Cartier')
         m = divisor.m(self.defining_cone())
         values = []

src/sage/schemes/toric/variety.py

@@ -3313,12 +3313,20 @@ def is_CohomologyClass(x):
         sage: HH = P2.cohomology_ring()
         sage: from sage.schemes.toric.variety import is_CohomologyClass
         sage: is_CohomologyClass( HH.one() )                                            # needs sage.libs.singular
+        doctest:warning...
+        DeprecationWarning: The function is_CohomologyClass is deprecated;
+        use 'isinstance(..., CohomologyClass)' instead.
+        See https://github.com/sagemath/sage/issues/38277 for details.
         True
         sage: is_CohomologyClass( HH(P2.fan(1)[0]) )                                    # needs sage.libs.singular
         True
         sage: is_CohomologyClass('z')
         False
     """
+    from sage.misc.superseded import deprecation
+    deprecation(38277,
+                "The function is_CohomologyClass is deprecated; "
+                "use 'isinstance(..., CohomologyClass)' instead.")
     return isinstance(x, CohomologyClass)