From 47304c6a0b365ca21d95be5e532e8d5925ed04f3 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 29 Jun 2017 17:13:43 -0400
Subject: [PATCH] PR c++/81180 - ICE with C++17 deduction of member class
 template.

	* pt.c (build_deduction_guide): Correct member template handling.

From-SVN: r249816
---
 gcc/cp/ChangeLog                              |  3 +++
 gcc/cp/pt.c                                   | 20 +++++++++----------
 .../g++.dg/cpp1z/class-deduction40.C          | 19 ++++++++++++++++++
 3 files changed, 31 insertions(+), 11 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction40.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0fae3cd6684..5549f720141 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2017-06-29  Jason Merrill  <jason@redhat.com>
 
+	PR c++/81180 - ICE with C++17 deduction of member class template.
+	* pt.c (build_deduction_guide): Correct member template handling.
+
 	PR c++/81188 - matching decltype of member function call.
 	* tree.c (cp_tree_equal): Remove COMPONENT_REF special case.
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 047d3baabbf..3ecacbd62de 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -25216,17 +25216,16 @@ build_deduction_guide (tree ctor, tree outer_args, tsubst_flags_t complain)
     }
   else
     {
+      ++processing_template_decl;
+
+      tree fn_tmpl
+	= (TREE_CODE (ctor) == TEMPLATE_DECL ? ctor
+	   : DECL_TI_TEMPLATE (ctor));
       if (outer_args)
-	ctor = tsubst (ctor, outer_args, complain, ctor);
+	fn_tmpl = tsubst (fn_tmpl, outer_args, complain, ctor);
+      ctor = DECL_TEMPLATE_RESULT (fn_tmpl);
+
       type = DECL_CONTEXT (ctor);
-      tree fn_tmpl;
-      if (TREE_CODE (ctor) == TEMPLATE_DECL)
-	{
-	  fn_tmpl = ctor;
-	  ctor = DECL_TEMPLATE_RESULT (fn_tmpl);
-	}
-      else
-	fn_tmpl = DECL_TI_TEMPLATE (ctor);
 
       tparms = DECL_TEMPLATE_PARMS (fn_tmpl);
       /* If type is a member class template, DECL_TI_ARGS (ctor) will have
@@ -25248,7 +25247,6 @@ build_deduction_guide (tree ctor, tree outer_args, tsubst_flags_t complain)
 	  /* For a member template constructor, we need to flatten the two
 	     template parameter lists into one, and then adjust the function
 	     signature accordingly.  This gets...complicated.  */
-	  ++processing_template_decl;
 	  tree save_parms = current_template_parms;
 
 	  /* For a member template we should have two levels of parms/args, one
@@ -25309,8 +25307,8 @@ build_deduction_guide (tree ctor, tree outer_args, tsubst_flags_t complain)
 	    ci = tsubst_constraint_info (ci, tsubst_args, complain, ctor);
 
 	  current_template_parms = save_parms;
-	  --processing_template_decl;
 	}
+      --processing_template_decl;
     }
 
   if (!memtmpl)
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction40.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction40.C
new file mode 100644
index 00000000000..eeffa69adf5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction40.C
@@ -0,0 +1,19 @@
+// PR c++/81180
+// { dg-options -std=c++1z }
+
+template < int I > struct int_{};
+
+template < typename T >
+struct A{
+    template < typename U, int I >
+    struct B{
+        B(U u, int_< I >){}
+    };
+};
+
+
+int main(){
+    A< int >::B v(0, int_< 0 >());
+    (void)v;
+}
+
-- 
2.30.2