Ticket #14058: testcoercion.py

from sage.categories.pushout import ConstructionFunctor
from sage.structure.element import RingElement

class FunctorA(ConstructionFunctor):
    rank = 1
    def _apply_functor(self, R):
        if R is ZZ:
            return A()
        return C()

FA = FunctorA(Rings(),Rings())

class MyRingElement(RingElement):
    def _mul_(self,other):
        return self.parent()(1)

class FunctorB(ConstructionFunctor):
    rank = 2
    def _apply_functor(self, R):
        if R is ZZ:
            return B()
        return C()

FB = FunctorB(Rings(),Rings())

class A(UniqueRepresentation,Parent):
    Element = MyRingElement
    def __init__(self):
        Parent.__init__(self, category=Rings())
    def _element_constructor_(self, *data):
        return self.element_class(parent=self)
    def _repr_(self):
        return "A"
    def construction(self):
        return FA, ZZ
   
class B(UniqueRepresentation,Parent):
    Element = MyRingElement
    def __init__(self):
        Parent.__init__(self, category=Rings())
    def _element_constructor_(self, *data):
        return self.element_class(parent=self)
    def _repr_(self):
        return "B"
    def construction(self):
        return FB, ZZ

class C(UniqueRepresentation,Parent):
    Element = MyRingElement
    def __init__(self):
        Parent.__init__(self, category=Rings())
    def _element_constructor_(self, *data):
        return self.element_class(parent=self)
    def _repr_(self):
        return "C"
    def _coerce_map_from_(self,R):
        return isinstance(R,(A,B,C))