c++: structural equality and partially inst typedef [PR119379]HEADtrunkmaster

Complex alias templates (and their dependent specializations) always use
structural equality because we need to treat them as transparent in some
contexts but not others.  Structural-ness however wasn't being preserved
during partial instantiation, which for the below testcase leads to the
checking ICE

  same canonical type node for different types 'S<int>::P<U>' and 'pair<int, U>'

when comparing those two types with comparing_dependent_aliases set
(from alias_ctad_tweaks).

This patch fixes this by making us preserve structural-ness for
partially instantiated typedefs in general.

	PR c++/119379

gcc/cp/ChangeLog:

	* pt.cc (tsubst_decl) <case TYPE_DECL>: Preserve structural-ness
	of a partially instantiated typedef.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/class-deduction-alias24.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

0 files changed, 0 insertions, 0 deletions