[gcc r14-5763] c++: alias template of non-template class [PR112633]

[gcc r14-5763] c++: alias template of non-template class [PR112633]

[Patrick Palka]

https://gcc.gnu.org/g:3f266c84a15d63e42bfad46397fea9aff92b0720

commit r14-5763-g3f266c84a15d63e42bfad46397fea9aff92b0720
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Nov 22 13:54:29 2023 -0500

    c++: alias template of non-template class [PR112633]
    
    The entering_scope adjustment in tsubst_aggr_type assumes if an alias is
    dependent, then so is the aliased type (and therefore it has template info)
    but that's not true for the dependent alias template specialization ty1<T>
    below which aliases the non-template class A.  In this case no adjustment
    is needed anyway, so we can just punt.
    
            PR c++/112633
    
    gcc/cp/ChangeLog:
    
            * pt.cc (tsubst_aggr_type): Handle empty TYPE_TEMPLATE_INFO
            in the entering_scope adjustment.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/alias-decl-75.C: New test.

Diff:
---
 gcc/cp/pt.cc                               |  1 +
 gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index ed681afb5d4..68ce4a87372 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -13976,6 +13976,7 @@ tsubst_aggr_type (tree t,
       if (entering_scope
 	  && CLASS_TYPE_P (t)
 	  && dependent_type_p (t)
+	  && TYPE_TEMPLATE_INFO (t)
 	  && TYPE_CANONICAL (t) == TREE_TYPE (TYPE_TI_TEMPLATE (t)))
 	t = TYPE_CANONICAL (t);
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C
new file mode 100644
index 00000000000..1a73a99856e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C
@@ -0,0 +1,13 @@
+// PR c++/112633
+// { dg-do compile { target c++11 } }
+
+struct A { using type = void; };
+
+template<class>
+using ty1 = A;
+
+template<class T>
+using ty2 = typename ty1<T>::type;
+
+template<class T>
+ty2<T> f();