Restrict the 1-argument ArrayView constructor to types with .size() and .data()

webrtc/base/array_view_unittest.cc

 /*
  *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
 #include "webrtc/base/array_view.h"
 #include "webrtc/base/buffer.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/gunit.h"
 
 namespace rtc {
 
 namespace {
+
+namespace test_has_data_and_size {
+
+template <typename C, typename T>
+using DS = internal::HasDataAndSize<C, T>;
+
+template <typename DR, typename SR>
+struct Test1 {
+  DR data();
+  SR size();
+};
+static_assert(DS<Test1<int*, int>, int>::value, "");
+static_assert(DS<Test1<int*, int>, const int>::value, "");
+static_assert(DS<Test1<const int*, int>, const int>::value, "");
+static_assert(!DS<Test1<const int*, int>, int>::value, "");
+static_assert(!DS<Test1<char*, size_t>, int>::value, "");
+
+struct Test2 {
+  int* data;
+  size_t size;
+};
+static_assert(!DS<Test2, int>::value, "");
+
+struct Test3 {
+  int* data();
+};
+static_assert(!DS<Test3, int>::value, "");
+
+class Test4 {
+  int* data();
+  size_t size();
+};
+static_assert(!DS<Test3, int>::value, "");

[ossu, 2016/09/05 09:32:27]

Surely, this should be DS<Test4, int>::value!

[kwiberg-webrtc, 2016/09/05 09:40:18]

Yes...

[ossu, 2016/09/05 09:50:44]

Ah, so it's supposed to be false because data and size are private? Right. It's
a bit unclear that that's what's going on. I expected it to be true. Maybe just
highlight the intent with a comment. Explicitly putting private: in the class
could also work, but since it's not practically needed, it might look weird as
well.

[kwiberg-webrtc, 2016/09/05 10:11:16]

Added comments.

+
+}  // namespace test_has_data_and_size
+
 template <typename T>
 void Call(ArrayView<T>) {}
+
 }  // namespace
 
 TEST(ArrayViewTest, TestConstructFromPtrAndArray) {
   char arr[] = "Arrr!";
   const char carr[] = "Carrr!";
   Call<const char>(arr);
   Call<const char>(carr);
   Call<char>(arr);
   // Call<char>(carr);  // Compile error, because can't drop const.
   // Call<int>(arr);  // Compile error, because incompatible types.
@@ skipping 189 matching lines @@
   int a[] = {1, 2, 3};
   int b[] = {1, 2, 3};
   EXPECT_EQ(ArrayView<int>(a), ArrayView<int>(a));
   EXPECT_EQ(ArrayView<int>(), ArrayView<int>());
   EXPECT_NE(ArrayView<int>(a), ArrayView<int>(b));
   EXPECT_NE(ArrayView<int>(a), ArrayView<int>());
   EXPECT_NE(ArrayView<int>(a), ArrayView<int>(a, 2));
 }
 
 }  // namespace rtc