From 342845e644ab2c09d7ddf5c2d15f2dd16d453c81 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C5=BEenan=20Zuki=C4=87?= <dzenan.zukic@kitware.com>
Date: Fri, 10 Sep 2021 11:16:43 -0400
Subject: [PATCH] ENH: deprecate itk::IsSame and the header which implements it

It should be replaced by std::is_same from STL.
---
 Documentation/ITK5MigrationGuide.md      |  1 +
 Modules/Core/Common/include/itkIsSame.h  | 10 +++++++++-
 Utilities/Maintenance/BuildHeaderTest.py |  1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/ITK5MigrationGuide.md b/Documentation/ITK5MigrationGuide.md
index a5b06b04d9b..4f6f1a01957 100644
--- a/Documentation/ITK5MigrationGuide.md
+++ b/Documentation/ITK5MigrationGuide.md
@@ -80,6 +80,7 @@ To modernize your code base, replace:
   * `FastMutexLock` with `std::mutex`, and `#include "itkFastMutexLock.h"`  with `#include <mutex>`.
   * `MutexLock` with `std::mutex`, and `#include "itkMutexLock.h"`  with `#include <mutex>`.
   * `mpl::EnableIf<X>::Type` with `std::enable_if_t<X>`, and `#include "itkEnableIf.h"` with `#include <type_traits>`.
+  * `mpl::IsSame<X, Y>::Value` with `std::is_same<X, Y>::value`, and `#include "itkIsSame.h"` with `#include <type_traits>`.
 
 
 Modern CMake requirement
diff --git a/Modules/Core/Common/include/itkIsSame.h b/Modules/Core/Common/include/itkIsSame.h
index 2cb976e5263..3a7019851e9 100644
--- a/Modules/Core/Common/include/itkIsSame.h
+++ b/Modules/Core/Common/include/itkIsSame.h
@@ -18,7 +18,11 @@
 #ifndef itkIsSame_h
 #define itkIsSame_h
 
-#include "itkMetaProgrammingLibrary.h"
+#include "itkMacro.h"
+
+#if !defined(ITK_LEGACY_REMOVE)
+
+#  include "itkMetaProgrammingLibrary.h"
 
 namespace itk
 {
@@ -50,4 +54,8 @@ using mpl::IsSame;
 
 } // end namespace itk
 
+#else // ITK_LEGACY_REMOVE
+#  error Use C++ 11 std::is_same directly
+#endif
+
 #endif // itkIsSame_h
diff --git a/Utilities/Maintenance/BuildHeaderTest.py b/Utilities/Maintenance/BuildHeaderTest.py
index a7280bfca2b..7cd755db63d 100755
--- a/Utilities/Maintenance/BuildHeaderTest.py
+++ b/Utilities/Maintenance/BuildHeaderTest.py
@@ -49,6 +49,7 @@
         "vtkCaptureScreen.h",  # these includes require VTK
         "itkMultiThreader.h",  # Compatibility file, it should not be used
         "itkEnableIf.h", # Compatibility file, it should not be used
+        "itkIsSame.h", # Compatibility file, it should not be used
         "itkViewImage.h",  # Depends on VTK_RENDERING_BACKEND
         "QuickView.h",  # Depends on VTK_RENDERING_BACKEND
         "itkBSplineDeformableTransformInitializer.h",