commit 5334edd3fcf1834c514be08bda2f8f7c82ab1148
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 31 08:39:43 2019 +0000

    Check precondition for std::ssize(const Container&)
    
    This precondition is the subject of a national body comment on the C++20
    CD. This just adds a test to ensure we enforce the precondition.
    
    Also move existing 24_iterator/range_access*.cc tests to a dedicated
    directory for the [iterator.range] subclause.
    
            * testsuite/24_iterators/range_access*.cc: Move to ...
            * testsuite/24_iterators/range_access/range_access*.cc: ... here.
            * testsuite/24_iterators/range_access/range_access_cpp20_neg.cc: New
            test.

diff --git a/libstdc++-v3/testsuite/24_iterators/range_access.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access.cc
similarity index 100%
rename from libstdc++-v3/testsuite/24_iterators/range_access.cc
rename to libstdc++-v3/testsuite/24_iterators/range_access/range_access.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp14.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp14.cc
similarity index 100%
rename from libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc
rename to libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp14.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17.cc
similarity index 100%
rename from libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc
rename to libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17_neg.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17_neg.cc
similarity index 100%
rename from libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc
rename to libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp17_neg.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp20.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp20.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20.cc
similarity index 100%
rename from libstdc++-v3/testsuite/24_iterators/range_access_cpp20.cc
rename to libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc
diff --git a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc
new file mode 100644
index 00000000000..8caa941e161
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc
@@ -0,0 +1,49 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <iterator>
+
+void
+test01()
+{
+  struct C { unsigned size() { return 0u; } };
+  C c;
+  std::ssize(c); // { dg-error "no matching function" }
+}
+// { dg-error "discards qualifiers" "" { target *-*-* } 0 }
+
+void
+test02()
+{
+  struct C { bool size() { return false; } };
+  C c;
+  std::ssize(c);  // { dg-error "no matching function" }
+}
+// { dg-error "incomplete type .*make_signed.*bool" "" { target *-*-* } 0 }
+
+void
+test03()
+{
+  struct S { };
+  struct C { S size() { return {}; } };
+  C c;
+  std::ssize(c);  // { dg-error "no matching function" }
+}
+// { dg-error "incomplete type .*make_signed.*S" "" { target *-*-* } 0 }