[gcc/devel/c++-modules] c++: Find parameter pack in typedef in lambda [92909].

[gcc/devel/c++-modules] c++: Find parameter pack in typedef in lambda [92909].

[Nathan Sidwell]

https://gcc.gnu.org/g:b3b0c671cc341fd04afc045a8d42d7a845d7f73c

commit b3b0c671cc341fd04afc045a8d42d7a845d7f73c
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Mar 14 17:10:39 2020 -0400

    c++: Find parameter pack in typedef in lambda [92909].
    
    find_parameter_packs_r doesn't look through typedefs, which is normally
    correct, but that means we need to handle their declarations specially.
    
    gcc/cp/ChangeLog
    2020-03-14  Jason Merrill  <jason@redhat.com>
    
            PR c++/92909
            * pt.c (find_parameter_packs_r): [DECL_EXPR]: Walk
            DECL_ORIGINAL_TYPE of a typedef.

Diff:
---
 gcc/cp/ChangeLog                                      |  6 ++++++
 gcc/cp/pt.c                                           | 16 ++++++++++++----
 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-variadic10.C | 12 ++++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b4fa15047b5..bb7f590ea0b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-14  Jason Merrill  <jason@redhat.com>
+
+	PR c++/92909
+	* pt.c (find_parameter_packs_r): [DECL_EXPR]: Walk
+	DECL_ORIGINAL_TYPE of a typedef.
+
 2020-03-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/93248
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0f3c2ad8fec..bd2f9be82ea 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -3916,10 +3916,18 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
       return NULL_TREE;
 
     case DECL_EXPR:
-      /* Ignore the declaration of a capture proxy for a parameter pack.  */
-      if (is_capture_proxy (DECL_EXPR_DECL (t)))
-	*walk_subtrees = 0;
-      return NULL_TREE;
+      {
+	tree decl = DECL_EXPR_DECL (t);
+	/* Ignore the declaration of a capture proxy for a parameter pack.  */
+	if (is_capture_proxy (decl))
+	  *walk_subtrees = 0;
+	if (is_typedef_decl (decl))
+	  /* Since we stop at typedefs above, we need to look through them at
+	     the point of the DECL_EXPR.  */
+	  cp_walk_tree (&DECL_ORIGINAL_TYPE (decl),
+			&find_parameter_packs_r, ppd, ppd->visited);
+	return NULL_TREE;
+      }
 
     case TEMPLATE_DECL:
       if (!DECL_TEMPLATE_TEMPLATE_PARM_P (t))
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-variadic10.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-variadic10.C
new file mode 100644
index 00000000000..052283e6caa
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-variadic10.C
@@ -0,0 +1,12 @@
+// PR c++/92909
+// { dg-do compile { target c++11 } }
+
+template <class ... Ts>
+void foo()
+{
+    []
+    {
+        using T = Ts;
+    }();			// { dg-error "not expanded" }
+}
+template void foo<>();