PR c++/27952
        * cp-tree.h (xref_basetypes): Return bool instead of void.
        * decl.c (xref_basetypes): Adjust definition. Return false
        if the class bases are invalid.
        * parser.c (cp_parser_class_head): Check the return value
        from xref_basetypes.

        * g++.dg/inherit/virtual1.C: New test.

From-SVN: r117839