From e4837e9b4f2e9edff62ae0bb192a406c44cba561 Mon Sep 17 00:00:00 2001
From: Daniel Krenn <git@danielkrenn.at>
Date: Mon, 19 Oct 2015 15:04:19 +0200
Subject: [PATCH] correct parent of result of an_element

---
 src/sage/symbolic/ring.pyx   |  1 -
 src/sage/symbolic/subring.py | 23 +++++++++++++++++++----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/sage/symbolic/ring.pyx b/src/sage/symbolic/ring.pyx
index e48091b2942..c199f80d231 100644
--- a/src/sage/symbolic/ring.pyx
+++ b/src/sage/symbolic/ring.pyx
@@ -266,7 +266,6 @@ cdef class SymbolicRing(CommutativeRing):
 
         """
         cdef GEx exp
-
         if is_Expression(x):
             if (<Expression>x)._parent is self:
                 return x
diff --git a/src/sage/symbolic/subring.py b/src/sage/symbolic/subring.py
index 978e1c5127a..1f7f5b0004f 100644
--- a/src/sage/symbolic/subring.py
+++ b/src/sage/symbolic/subring.py
@@ -342,12 +342,15 @@ def _element_constructor_(self, x):
             sage: S = SymbolicSubring(accepting_variables=('a',))
             sage: S('a')  # indirect doctest
             a
+            sage: _.parent()
+            Symbolic Subring accepting the variable a
             sage: S('x')  # indirect doctest
             Traceback (most recent call last):
             ...
             TypeError: x is not contained in Symbolic Subring accepting the variable a
         """
-        expression = SR(x)
+        expression = super(GenericSymbolicSubring, self)._element_constructor_(x)
+        assert(expression.parent() is self)
         if not all(self.is_variable_valid(var)
                    for var in expression.variables()):
             raise TypeError('%s is not contained in %s' % (x, self))
@@ -707,8 +710,10 @@ def _an_element_(self):
             sage: from sage.symbolic.subring import SymbolicSubring
             sage: SymbolicSubring(accepting_variables=('a',)).an_element()
             a
+            sage: _.parent()
+            Symbolic Subring accepting the variable a
         """
-        return sorted(self._vars_, key=str)[0]
+        return self(sorted(self._vars_, key=str)[0])
 
 
 class SymbolicSubringAcceptingVarsFunctor(GenericSymbolicSubringFunctor):
@@ -897,17 +902,25 @@ def _an_element_(self):
             sage: from sage.symbolic.subring import SymbolicSubring
             sage: SymbolicSubring(rejecting_variables=('r',)).an_element()
             some_variable
+            sage: _.parent()
+            Symbolic Subring rejecting the variable r
             sage: SymbolicSubring(rejecting_variables=('some_variable',)).an_element()
             some_some_variable
+            sage: _.parent()
+            Symbolic Subring rejecting the variable some_variable
             sage: SymbolicSubring(rejecting_variables=('some_some_variable',)).an_element()
             some_variable
+            sage: _.parent()
+            Symbolic Subring rejecting the variable some_some_variable
             sage: SymbolicSubring(rejecting_variables=('some_variable','some_some_variable')).an_element()
             some_some_some_variable
+            sage: _.parent()
+            Symbolic Subring rejecting the variables some_some_variable, some_variable
         """
         v = SR.an_element()
         while not self.is_variable_valid(v):
             v = SR('some_' + str(v))
-        return v
+        return self(v)
 
 
 class SymbolicSubringRejectingVarsFunctor(GenericSymbolicSubringFunctor):
@@ -1042,5 +1055,7 @@ def _an_element_(self):
             sage: from sage.symbolic.subring import SymbolicSubring
             sage: SymbolicSubring(no_variables=True).an_element()
             I*pi*e
+            sage: _.parent()
+            Symbolic Constants Subring
         """
-        return SR('I') * SR('pi') * SR('e')
+        return self(SR('I') * SR('pi') * SR('e'))