[Bug c++/54055] spurious(?) "invalid use of incomplete type" warning in template definition

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54055

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-21 14:11:11 UTC ---
Yes, it was intentional, based on the discussion mentioned in the other
comments.  I made it a pedwarn rather than a hard error so that affected code
would continue to compile.