Specialize IsMoveOnlyType<T> for vectors.

base/callback_internal.h

Index: base/callback_internal.h
diff --git a/base/callback_internal.h b/base/callback_internal.h
index e4e538ff15c2d0dfe239bc5d8b17fe411c59926e..56bf58fecbc48eb038e9f5a0e6e8aa0cb180c958 100644
--- a/base/callback_internal.h
+++ b/base/callback_internal.h
@@ -11,6 +11,7 @@
 #include <stddef.h>
 #include <memory>
 #include <type_traits>
+#include <vector>
 
 #include "base/atomic_ref_count.h"
 #include "base/base_export.h"
@@ -116,7 +117,13 @@ template <typename T> struct IsMoveOnlyType {
 // Specialization of IsMoveOnlyType so that std::unique_ptr is still considered
 // move-only, even without the sentinel member.
 template <typename T, typename D>
-struct IsMoveOnlyType<std::unique_ptr<T, D>> : std::true_type {};
+struct IsMoveOnlyType<std::unique_ptr<T, D>> : public std::true_type {};

[danakj, 2016/02/02 01:38:34]

nit: let's leave out redundant public here and below

[dcheng, 2016/02/02 01:52:11]

Done.

+
+// Specialization of std::vector, so that it's considered move-only if the
+// element type is move-only.

[danakj, 2016/02/02 01:38:33]

Leave a note that it ignores the Allocator?

[dcheng, 2016/02/02 01:52:11]

Done.

+template <typename T, typename Allocator>
+struct IsMoveOnlyType<std::vector<T, Allocator>>
+    : public IsMoveOnlyType<typename std::vector<T, Allocator>::value_type> {};

[danakj, 2016/02/02 01:39:21]

vlad's right though that this is the same as

: IsMoveOnlyType<T> {}

which is way easier to read, tho less copy-paste friendly. I think I like that
better.

[dcheng, 2016/02/02 01:52:11]

OK, sure. I had imagined that we could use some generic programming to enable
this for most STL containers without having to explicitly specify each one, but
that might be a bit too clever.

 
 template <typename>
 struct CallbackParamTraitsForMoveOnlyType;