src/sage/schemes/elliptic_curves/constructor.py: Remove use of SR, is…

…_SymbolicEquation; add test for symbolic input

src/sage/schemes/elliptic_curves/constructor.py

@@ -36,10 +36,8 @@
 _Fields = Fields()
 
 from sage.structure.sequence import Sequence
-from sage.structure.element import parent
+from sage.structure.element import parent, Expression
 from sage.structure.factory import UniqueFactory
-from sage.symbolic.ring import SR
-from sage.symbolic.expression import is_SymbolicEquation
 
 
 class EllipticCurveFactory(UniqueFactory):
@@ -385,6 +383,20 @@ def create_key_and_extra_args(self, x=None, y=None, j=None, minimal_twist=True,
             incorrect data may lead to wrong results of computations
             instead of errors or warnings.
 
+        TESTS::
+
+            sage: var('x', 'y', 'v', 'w')
+            (x, y, v, w)
+            sage: EllipticCurve(y^2 + y > x^3 + x - 9)
+            Traceback (most recent call last):
+            ...
+            ValueError: no symbolic relations other than equalities are allowed
+            sage: E = EllipticCurve(y^2 + y == x^3 + x - 9)
+            sage: E is EllipticCurve(y^2 + y - ( x^3 + x - 9 ))
+            True
+            sage: R.<x,y> = QQ[]
+            sage: E is EllipticCurve(y^2 + y - ( x^3 + x - 9 ))
+            True
         """
         R = None
         if is_Ring(x):
@@ -400,10 +412,13 @@ def create_key_and_extra_args(self, x=None, y=None, j=None, minimal_twist=True,
                 raise ValueError("First parameter (if present) must be a ring when j is specified")
             x = coefficients_from_j(j, minimal_twist)
 
-        if is_SymbolicEquation(x):
+        if isinstance(x, Expression) and x.is_relational():
+            import operator
+            if x.operator() != operator.eq:
+                raise ValueError("no symbolic relations other than equalities are allowed")
             x = x.lhs() - x.rhs()
 
-        if parent(x) is SR:
+        if isinstance(parent(x), sage.rings.abc.SymbolicRing):
             x = x._polynomial_(rings.QQ['x', 'y'])
 
         if is_MPolynomial(x):