Re: [PATCH] c++: alias template of non-template class [PR112633]

[Jason Merrill]

On 11/22/23 12:26, Patrick Palka wrote:

Bootstrapped and regtested on x86-64-pc-linux-gnu, does this look OK for
trunk/13?

OK.

-- >8 --

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.

        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.
---
  gcc/cp/pt.cc                               |  1 +
  gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C | 13 +++++++++++++
  2 files changed, 14 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-75.C

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();