1 files changed, 57 insertions, 0 deletions
diff --git a/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp b/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp
new file mode 100644
index 00000000000..0030afa5df8
--- /dev/null
+++ b/libcxx/test/std/experimental/string.view/string.view.access/at.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// NOTE: Older versions of clang have a bug where they fail to evalute
+// string_view::at as a constant expression.
+// XFAIL: apple-clang-6.0, clang-3.4, clang-3.3
+
+// <string_view>
+
+// constexpr const _CharT& at(size_type _pos) const;
+
+#include <experimental/string_view>
+#include <cassert>
+
+template <typename CharT>
+void test ( const CharT *s, size_t len ) {
+    std::experimental::basic_string_view<CharT> sv ( s, len );
+    assert ( sv.length() == len );
+    for ( size_t i = 0; i < len; ++i ) {
+        assert (  sv.at(i) == s[i] );
+        assert ( &sv.at(i) == s + i );
+        }
+
+    try { sv.at(len); } catch ( const std::out_of_range & ) { return ; }
+    assert ( false );
+    }
+    
+int main () {
+    test ( "ABCDE", 5 );
+    test ( "a", 1 );
+
+    test ( L"ABCDE", 5 );
+    test ( L"a", 1 );
+
+#if __cplusplus >= 201103L
+    test ( u"ABCDE", 5 );
+    test ( u"a", 1 );
+
+    test ( U"ABCDE", 5 );
+    test ( U"a", 1 );
+#endif
+
+#if __cplusplus >= 201103L
+    {
+    constexpr std::experimental::basic_string_view<char> sv ( "ABC", 2 );
+    static_assert ( sv.length() ==  2,  "" );
+    static_assert ( sv.at(0) == 'A', "" );
+    static_assert ( sv.at(1) == 'B', "" );
+    }
+#endif
+}