Merge branch 'public/16203-1' of trac.sagemath.org:sage into tmp06

* 'public/16203-1' of trac.sagemath.org:sage:
  16203: fixes
  16203: sync with 17659
  16203: conversion from SR.series to PowerSeries

src/sage/rings/power_series_ring.py

@@ -703,6 +703,19 @@ def _element_constructor_(self, f, prec=infinity, check=True):
             1 - x + x^2 - x^3 + x^4 + O(x^5)
             sage: PowerSeriesRing(PowerSeriesRing(QQ,'x'),'x')(x).coefficients()
             [x]
+            
+        Conversion from symbolic series::
+        
+            sage: x,y = var('x,y')
+            sage: s=(1/(1-x)).series(x,3); s
+            1 + 1*x + 1*x^2 + Order(x^3)
+            sage: R.<x> = PowerSeriesRing(QQ)
+            sage: R(s)
+            1 + x + x^2 + O(x^3)
+            sage: ex=(gamma(1-y)).series(y,3)
+            sage: R.<y> = PowerSeriesRing(SR)
+            sage: R(ex)
+            1 + euler_gamma*y + (1/2*euler_gamma^2 + 1/12*pi^2)*y^2 + O(y^3)
 
         Laurent series with non-negative valuation are accepted (see
         :trac:`6431`)::
@@ -729,6 +742,7 @@ def _element_constructor_(self, f, prec=infinity, check=True):
             prec = integer.Integer(prec)
             if prec < 0:
                 raise ValueError("prec (= %s) must be non-negative" % prec)
+        from sage.symbolic.series import SymbolicSeries
         if isinstance(f, power_series_ring_element.PowerSeries) and f.parent() is self:
             if prec >= f.prec():
                 return f
@@ -745,6 +759,12 @@ def _element_constructor_(self, f, prec=infinity, check=True):
                 num = self.element_class(self, f.numerator(), prec, check=check)
                 den = self.element_class(self, f.denominator(), prec, check=check)
                 return self.coerce(num/den)
+        elif isinstance(f, SymbolicSeries):
+            if str(f.default_variable()) is self.variable_name():
+                return self.element_class(self, f.list(),
+                                      f.degree(f.default_variable()), check=check)
+            else:
+                raise TypeError("Can only convert series into ring with same variable name.")            
         return self.element_class(self, f, prec, check=check)
 
     def construction(self):

src/sage/symbolic/ring.pyx

@@ -26,7 +26,10 @@ from sage.structure.element cimport RingElement, Element, Matrix
 from sage.categories.morphism cimport Morphism
 from sage.structure.coerce cimport is_numpy_type
 
-from sage.rings.all import RR, CC, ZZ
+from sage.rings.integer_ring import ZZ
+from sage.rings.real_mpfr import RR
+from sage.rings.complex_field import ComplexField
+CC = ComplexField()
 
 
 cdef class SymbolicRing(CommutativeRing):