c++: stream PACK_EXPANSION_EXTRA_ARGS [PR106761]

It looks like after the libstdc++ commit r13-2158-g02f6b405f0e9dc
some xtreme-header-* tests are failing with "conflicting global module
declaration" errors ultimately because we're neglecting to stream
PACK_EXPANSION_EXTRA_ARGS, which leads to wrong equivalences of
different partial instantiations of _TupleConstraints::__constructible.

	PR c++/106761

gcc/cp/ChangeLog:

	* module.cc (trees_out::type_node) <case TYPE_PACK_EXPANSION>:
	Stream PACK_EXPANSION_EXTRA_ARGS.
	(trees_in::tree_node) <case TYPE_PACK_EXPANSION>: Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr106761.h: New test.
	* g++.dg/modules/pr106761_a.H: New test.
	* g++.dg/modules/pr106761_b.C: New test.

4 files changed, 37 insertions, 0 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 1a1ff5b..9a9ef4e 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -8922,6 +8922,7 @@ trees_out::type_node (tree type)
       if (streaming_p ())
 	u (PACK_EXPANSION_LOCAL_P (type));
       tree_node (PACK_EXPANSION_PARAMETER_PACKS (type));
+      tree_node (PACK_EXPANSION_EXTRA_ARGS (type));
       break;
 
     case TYPENAME_TYPE:
@@ -9455,12 +9456,14 @@ trees_in::tree_node (bool is_use)
 	    {
 	      bool local = u ();
 	      tree param_packs = tree_node ();
+	      tree extra_args = tree_node ();
 	      if (!get_overrun ())
 		{
 		  tree expn = cxx_make_type (TYPE_PACK_EXPANSION);
 		  SET_TYPE_STRUCTURAL_EQUALITY (expn);
 		  PACK_EXPANSION_PATTERN (expn) = res;
 		  PACK_EXPANSION_PARAMETER_PACKS (expn) = param_packs;
+		  PACK_EXPANSION_EXTRA_ARGS (expn) = extra_args;
 		  PACK_EXPANSION_LOCAL_P (expn) = local;
 		  res = expn;
 		}
diff --git a/gcc/testsuite/g++.dg/modules/pr106761.h b/gcc/testsuite/g++.dg/modules/pr106761.h
new file mode 100644
index 0000000..9f22a22
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr106761.h
@@ -0,0 +1,22 @@
+// PR c++/106761
+
+template<class...>
+struct __and_;
+
+template<class, class>
+struct is_convertible;
+
+template<class... Ts>
+struct _TupleConstraints {
+  template<class... Us>
+  using __constructible = __and_<is_convertible<Ts, Us>...>;
+};
+
+template<class... Ts>
+struct tuple {
+  template<class... Us>
+  using __constructible
+    = typename _TupleConstraints<Ts...>::template __constructible<Us...>;
+};
+
+tuple<int, int> t;
diff --git a/gcc/testsuite/g++.dg/modules/pr106761_a.H b/gcc/testsuite/g++.dg/modules/pr106761_a.H
new file mode 100644
index 0000000..8ad1164
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr106761_a.H
@@ -0,0 +1,5 @@
+// PR c++/106761
+// { dg-additional-options -fmodule-header }
+
+// { dg-module-cmi {} }
+#include "pr106761.h"
diff --git a/gcc/testsuite/g++.dg/modules/pr106761_b.C b/gcc/testsuite/g++.dg/modules/pr106761_b.C
new file mode 100644
index 0000000..418991b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr106761_b.C
@@ -0,0 +1,7 @@
+// PR c++/106761
+// { dg-additional-options -fmodules-ts }
+
+#include "pr106761.h"
+import "pr106761_a.H";
+
+tuple<int, int> u = t;