From e99d77c97fbee5c17594374b978a0c4f9cd125f4 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 5 Apr 2018 10:20:53 -0400
Subject: [PATCH] PR c++/85200 - ICE with constexpr if in generic lambda.

	* pt.c (extract_locals_r): Don't record the local specs of variables
	declared within the pattern.

From-SVN: r259127
---
 gcc/cp/ChangeLog                            |  6 ++++++
 gcc/cp/pt.c                                 | 13 +++++++++++--
 gcc/testsuite/g++.dg/cpp1z/constexpr-if19.C | 17 +++++++++++++++++
 3 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if19.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 4ae78f73b2b..99ec3ea171e 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2018-04-05  Jason Merrill  <jason@redhat.com>
+
+	PR c++/85200 - ICE with constexpr if in generic lambda.
+	* pt.c (extract_locals_r): Don't record the local specs of variables
+	declared within the pattern.
+
 2018-04-05  Alexandre Oliva <aoliva@redhat.com>
 
 	PR c++/84979
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 741c578b65b..ed6e62c2364 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11597,8 +11597,12 @@ tsubst_binary_right_fold (tree t, tree args, tsubst_flags_t complain,
 
 struct el_data
 {
+  hash_set<tree> internal;
   tree extra;
   tsubst_flags_t complain;
+
+  el_data (tsubst_flags_t c)
+    : extra (NULL_TREE), complain (c) {}
 };
 static tree
 extract_locals_r (tree *tp, int */*walk_subtrees*/, void *data_)
@@ -11606,8 +11610,13 @@ extract_locals_r (tree *tp, int */*walk_subtrees*/, void *data_)
   el_data &data = *reinterpret_cast<el_data*>(data_);
   tree *extra = &data.extra;
   tsubst_flags_t complain = data.complain;
-  if (tree spec = retrieve_local_specialization (*tp))
+  if (TREE_CODE (*tp) == DECL_EXPR)
+    data.internal.add (DECL_EXPR_DECL (*tp));
+  else if (tree spec = retrieve_local_specialization (*tp))
     {
+      if (data.internal.contains (*tp))
+	/* Don't mess with variables declared within the pattern.  */
+	return NULL_TREE;
       if (TREE_CODE (spec) == NONTYPE_ARGUMENT_PACK)
 	{
 	  /* Maybe pull out the PARM_DECL for a partial instantiation.  */
@@ -11658,7 +11667,7 @@ extract_locals_r (tree *tp, int */*walk_subtrees*/, void *data_)
 static tree
 extract_local_specs (tree pattern, tsubst_flags_t complain)
 {
-  el_data data = { NULL_TREE, complain };
+  el_data data (complain);
   cp_walk_tree_without_duplicates (&pattern, extract_locals_r, &data);
   return data.extra;
 }
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if19.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if19.C
new file mode 100644
index 00000000000..40016a5b7e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if19.C
@@ -0,0 +1,17 @@
+// PR c++/85200
+// { dg-additional-options -std=c++17 }
+
+struct A{
+    constexpr operator int(){ return 0; }
+};
+
+template < typename >
+void f(){
+    [](auto known){
+        if constexpr(constexpr int k = known);
+    }(A{});
+}
+
+int main(){
+    f<int>();
+}
-- 
2.30.2