[pushed] c++: template template parm pack expansion [PR100372]

[Jason Merrill via Gcc-patches]

Here we have a pack expansion of a template template parameter pack, of
which the pattern is a TEMPLATE_DECL, which strip_typedefs doesn't want to
see.

Tested x86_64-pc-linux-gnu, applying to trunk.

        PR c++/100372

gcc/cp/ChangeLog:

        * tree.c (strip_typedefs): Only look at the pattern of a
        TYPE_PACK_EXPANSION if it's a type.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/alias-decl-ttp1.C: New test.
---
 gcc/cp/tree.c                                | 19 ++++++++++++-------
 gcc/testsuite/g++.dg/cpp0x/alias-decl-ttp1.C |  6 ++++++
 2 files changed, 18 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-ttp1.C

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 35faeff065a..72f498f4b3b 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1741,13 +1741,18 @@ strip_typedefs (tree t, bool *remove_attributes, 
unsigned int flags)
       result = finish_underlying_type (type);
       break;
     case TYPE_PACK_EXPANSION:
-      type = strip_typedefs (PACK_EXPANSION_PATTERN (t),
-                            remove_attributes, flags);
-      if (type != PACK_EXPANSION_PATTERN (t))
-       {
-         result = copy_node (t);
-         PACK_EXPANSION_PATTERN (result) = type;
-       }
+      {
+       tree pat = PACK_EXPANSION_PATTERN (t);
+       if (TYPE_P (pat))
+         {
+           type = strip_typedefs (pat, remove_attributes, flags);
+           if (type != pat)
+             {
+               result = copy_node (t);
+               PACK_EXPANSION_PATTERN (result) = type;
+             }
+         }
+      }
       break;
     default:
       break;
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-ttp1.C 
b/gcc/testsuite/g++.dg/cpp0x/alias-decl-ttp1.C
new file mode 100644
index 00000000000..d1af8d1bbb2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-ttp1.C
@@ -0,0 +1,6 @@
+// PR c++/100372
+// { dg-do compile { target c++14 } }
+
+template <bool> using enable_if_t = int;
+template <class> bool has_P_match_v;
+template <template <class> class... List> enable_if_t<has_P_match_v<List...>> 
a;

base-commit: a8daf9a19a5eae6b98acede14bb6c27b2e0038e0
-- 
2.27.0