From b00e9be03aa6f95887d0591c88d177f388118534 Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <aoliva@redhat.com>
Date: Thu, 17 Jan 2019 07:32:29 +0000
Subject: [PATCH] [PR87768] reset location wrapper suppression when reentering
 top level

Concepts-checking and other kinds of early tsubsting may often take
place while location wrappers are suppressed, e.g. because we've
triggered template instantiation within template parameter lists.

With that, exprs that are usually wrapped by VIEW_CONVERT_EXPRs
location wrappers may end up wrapped by NON_LVALUE_EXPRs that are not
marked as location wrappers.  If such NON_LVALUE_EXPRs tsubsted exprs
undergo another round of tsubsting, say for constraint checking, or
even for another round of specialization, they will be rejected by
tsubst_copy_and_build.

This patch arranges for suppress_location_wrappers to be saved and
reset when pushing to the top level, and restored when popping from
it.


for  gcc/cp/ChangeLog

	PR c++/87768
	* cp-tree.h (saved_scope): Add suppress_location_wrappers.
	* name-lookup.c (do_push_to_top_level): Save and reset it.
	(do_pop_from_top_level): Restore it.

for  gcc/testsuite/ChangeLog

	PR c++/87768
	* g++.dg/concepts/pr87768.C: New.

From-SVN: r268006
---
 gcc/cp/ChangeLog                        |  5 +++++
 gcc/cp/cp-tree.h                        |  1 +
 gcc/cp/name-lookup.c                    |  3 +++
 gcc/testsuite/ChangeLog                 |  3 +++
 gcc/testsuite/g++.dg/concepts/pr87768.C | 14 ++++++++++++++
 5 files changed, 26 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/concepts/pr87768.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 73f1b76e5ff..524fbd366c0 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,10 @@
 2019-01-17  Alexandre Oliva <aoliva@redhat.com>
 
+	PR c++/87768
+	* cp-tree.h (saved_scope): Add suppress_location_wrappers.
+	* name-lookup.c (do_push_to_top_level): Save and reset it.
+	(do_pop_from_top_level): Restore it.
+
 	PR c++/86648
 	* pt.c (make_template_placeholder): Use auto_identifier.
 	(is_auto): Drop CLASS_PLACEHOLDER_TEMPLATE test.
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 1c85b37ba7f..5cc8f88d522 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1626,6 +1626,7 @@ struct GTY(()) saved_scope {
 
   int x_processing_template_decl;
   int x_processing_specialization;
+  int suppress_location_wrappers;
   BOOL_BITFIELD x_processing_explicit_instantiation : 1;
   BOOL_BITFIELD need_pop_function_context : 1;
 
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index b65fd5f463a..d7b9029b0a3 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -7133,6 +7133,7 @@ do_push_to_top_level (void)
   s->function_decl = current_function_decl;
   s->unevaluated_operand = cp_unevaluated_operand;
   s->inhibit_evaluation_warnings = c_inhibit_evaluation_warnings;
+  s->suppress_location_wrappers = suppress_location_wrappers;
   s->x_stmt_tree.stmts_are_full_exprs_p = true;
 
   scope_chain = s;
@@ -7143,6 +7144,7 @@ do_push_to_top_level (void)
   push_class_stack ();
   cp_unevaluated_operand = 0;
   c_inhibit_evaluation_warnings = 0;
+  suppress_location_wrappers = 0;
 }
 
 static void
@@ -7175,6 +7177,7 @@ do_pop_from_top_level (void)
   current_function_decl = s->function_decl;
   cp_unevaluated_operand = s->unevaluated_operand;
   c_inhibit_evaluation_warnings = s->inhibit_evaluation_warnings;
+  suppress_location_wrappers = s->suppress_location_wrappers;
 
   /* Make this saved_scope structure available for reuse by
      push_to_top_level.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3ce3da7940d..15cdb1ed432 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2019-01-17  Alexandre Oliva <aoliva@redhat.com>
 
+	PR c++/87768
+	* g++.dg/concepts/pr87768.C: New.
+
 	PR c++/86648
 	* gcc.dg/cpp1z/pr86648.C: New.
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr87768.C b/gcc/testsuite/g++.dg/concepts/pr87768.C
new file mode 100644
index 00000000000..de436e5d9ed
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/pr87768.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++17 } }
+// { dg-options "-fconcepts" }
+
+struct a {};
+template <bool> using b = a;
+
+template <typename> struct c;
+template <typename d>
+  requires requires(d e) { e[0]; }
+struct c<d> {
+  static constexpr bool f = [] { return false; }();
+};
+
+struct g : b<c<unsigned[]>::f> {};
-- 
2.30.2