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.

From-SVN: r277658

libstdc++-v3/ChangeLog

+2019-10-31  Jonathan Wakely  <jwakely@redhat.com>
+
+	* 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.
+
 2019-10-30  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/std/concepts (std::ranges::swap): Use a single overload for

libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc

+// 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 }