[Bug c++/102305] intrinsic __is_constrctible is wrong for templated abstract classes

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102305

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51447
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51447&action=edit
gcc12-pr102305.patch

Untested fix.
is_xible_helper checks ABSTRACT_CLASS_TYPE_P (to) and returns error_mark_node
if it is true, but when to is yet uninstantiated class template, it is false
and the template is instantiated only later on when trying to make the dummy
object.
With this patch we instantiate it before checking for abstract classes, but
will keep rejecting it or dealing with arrays of unknown bound till the spots
that were checking for that before.