
    i3 : QQ[x]

    o3 = QQ [x]

    o3 : PolynomialRing

    i4 : x 

    o4 = x

    o4 : QQ [x]

    i5 : dismiss o3
    stdio:5:1:(1):[0]: no method found for applying dismiss to:
	 argument   :  QQ [x] (of class PolynomialRing)

This could unassign x, releasing it for other uses...
