[pushed] c++: ICE with alias in pack expansion [PR103769]

[Jason Merrill via Gcc-patches]

This was breaking because when we stripped the 't' typedef in s<t<Args>...>
to be s<Args...>, the TYPE_MAIN_VARIANT of "Args..." was still
"t<Args>...", because type pack expansions are treated as types.  Fixed by
using the right function to copy a "type".

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

        PR c++/99445
        PR c++/103769

gcc/cp/ChangeLog:

        * tree.cc (strip_typedefs): Use build_distinct_type_copy.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/variadic-alias5.C: New test.
---
 gcc/cp/tree.cc                               | 2 +-
 gcc/testsuite/g++.dg/cpp0x/variadic-alias5.C | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-alias5.C

diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index eb59e56610b..492921721f2 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -1791,7 +1791,7 @@ strip_typedefs (tree t, bool *remove_attributes, unsigned 
int flags)
              Ts pack, resulting in an error.  */
            if (type != pat && uses_parameter_packs (type))
              {
-               result = copy_node (t);
+               result = build_distinct_type_copy (t);
                PACK_EXPANSION_PATTERN (result) = type;
              }
          }
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-alias5.C 
b/gcc/testsuite/g++.dg/cpp0x/variadic-alias5.C
new file mode 100644
index 00000000000..70956c91838
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-alias5.C
@@ -0,0 +1,9 @@
+// PR c++/103769
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "--param=hash-table-verification-limit=1000" }
+
+template <typename T> using t = T;
+template <typename...> struct s {};
+template <typename...Args> s<t<Args>...> f() { return {};}
+
+int main() { f<void>(); }

base-commit: bc86a86a4f2c057bc0e0be94dcbb8c128ae7f717
-- 
2.27.0