[libcxx][tests] span: Add failing tests for span::first and span::last

[miscco]

Summary

Both methods have compile time constraints that we should test against

[miscco]

Updating D71999: [libcxx][tests] span: Add failing tests for span::first and span::last

[miscco]

Updating D71999: [libcxx][tests] span: Add failing tests for span::first and span::last

[ldionne]

Thanks for the patch!

libcxx/test/std/containers/views/span.sub/first.fail.cpp

+// -*- C++ -*-
+//===------------------------------ span ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===---------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <span>
+
+// template<size_t Count>
+//  constexpr span<element_type, Count> first() const;
+//
+// constexpr span<element_type, dynamic_extent> first(size_type count) const;
+//
+//  Requires: Count <= size().
+
+#include <span>
+
+#include "test_macros.h"
+
+constexpr int carr[] = {1, 2, 3, 4};
+
+int main(int, char**) {
+  std::span<const int, 4> sp(carr);
+
+  //  Count too large
+  {
+    [[maybe_unused]] auto s1 = sp.first<5>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Count out of range in span::first()"}}
+  }
+
+  //  Count numeric_limits
+  {
+    [[maybe_unused]] auto s1 = sp.first<std::size_t(-1)>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Count out of range in span::first()"}}
+  }
+
+  return 0;
+}

libcxx/test/std/containers/views/span.sub/first.pass.cpp

 
 // <span>
 
 // template<size_t Count>
 //  constexpr span<element_type, Count> first() const;
 //
 // constexpr span<element_type, dynamic_extent> first(size_type count) const;
 //
-//  Requires: 0 <= Count && Count <= size().
+//  Requires: Count <= size().
 
 
 #include <span>
 #include <cassert>
 #include <algorithm>
 #include <string>
 
 #include "test_macros.h"

libcxx/test/std/containers/views/span.sub/last.fail.cpp

+// -*- C++ -*-
+//===------------------------------ span ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===---------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <span>
+
+// template<size_t Count>
+//  constexpr span<element_type, Count> last() const;
+//
+// constexpr span<element_type, dynamic_extent> last(size_type count) const;
+//
+//  Requires: Count <= size().
+
+#include <span>
+
+#include "test_macros.h"
+
+constexpr int carr[] = {1, 2, 3, 4};
+
+int main(int, char**) {
+  std::span<const int, 4> sp(carr);
+
+  //  Count too large
+  {
+    [[maybe_unused]] auto s1 = sp.last<5>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Count out of range in span::last()"}}
+  }
+
+  //  Count numeric_limits
+  {
+    [[maybe_unused]] auto s1 = sp.last<std::size_t(-1)>(); // expected-error-re@span:* {{static_assert failed{{( due to requirement '.*')?}} "Count out of range in span::last()"}}
+  }
+
+  return 0;
+}

libcxx/test/std/containers/views/span.sub/last.pass.cpp

 
 // <span>
 
 // template<size_t Count>
 //  constexpr span<element_type, Count> last() const;
 //
 // constexpr span<element_type, dynamic_extent> last(size_type count) const;
 //
-//  Requires: 0 <= Count && Count <= size().
+//  Requires: Count <= size().
 
 
 #include <span>
 #include <cassert>
 #include <algorithm>
 #include <string>
 
 #include "test_macros.h"