Line 895 in eieio.el, were it not commented out, would fix this by
having edebug print using the object-print generic, not prin1. I eval'ed
the line and tried it, and it seemed to work fine.
How come it's currently commented out? Can I open a bug for this?
`defalias' is clearly not right, since it hijacks the function. But if
we change it to advice-add, I think it'd be OK to enable this
edebug help.
I think it would also be good to add hooks to the native printing system
so that such tweaks can be done more reliably. Ideally, these same
hooks could be used for things like desktop and savehist to replace
markers or other "non-printable" objects with alternative output.