[Voted into WP at March, 2010 meeting.]

Proposed resolution (February, 2010):

Change 11.7.3 [class.virtual] bullet 5.1 as follows:

...If a function D::f overrides a function B::f, the return types of the functions are covariant if they satisfy the following criteria:

• both are pointers to classes, both are lvalue references to classes, or both are rvalue references to classes¹⁰⁶

• ...

11.7.3 [class.virtual] paragraph 5 requires that covariant return types be either both pointers or both references, but it does not specify that references must be both lvalue references or both rvalue references. Presumably this is an oversight.