From 38f693213b0b89b6fb80a8365ad7472fc1039807 Mon Sep 17 00:00:00 2001
From: Eric Niebler <eniebler@nvidia.com>
Date: Tue, 10 May 2022 15:49:11 -0700
Subject: [PATCH 1/2] partial fix for iterator traits and tags

---
 testing/regression/CMakeLists.txt             |  4 ++++
 ...or_category_to_system_returns_wrong_tag.cu | 22 +++++++++++++++++++
 .../detail/iterator_category_to_system.h      | 20 ++++++++---------
 .../detail/iterator_category_to_traversal.h   | 16 +++++++-------
 4 files changed, 44 insertions(+), 18 deletions(-)
 create mode 100644 testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu

diff --git a/testing/regression/CMakeLists.txt b/testing/regression/CMakeLists.txt
index eea8b3a45..6c180839c 100644
--- a/testing/regression/CMakeLists.txt
+++ b/testing/regression/CMakeLists.txt
@@ -1,3 +1,7 @@
+if ("thrust" IN_LIST THRUST_TARGETS)
+  thrust_add_test(test_target "regression.gh_902__iterator_category_to_system_returns_wrong_tag" "gh_902__iterator_category_to_system_returns_wrong_tag.cu" "thrust")
+endif()
+
 #
 # Disabled as these test names are too long for CMAKE_OBJECT_PATH_MAX.
 # We should integrate these with the other unit tests.
diff --git a/testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu b/testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu
new file mode 100644
index 000000000..7f4ad9f1b
--- /dev/null
+++ b/testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu
@@ -0,0 +1,22 @@
+#include <thrust/iterator/detail/iterator_category_with_system_and_traversal.h>
+#include <thrust/iterator/iterator_categories.h>
+#include <thrust/iterator/iterator_traits.h>
+
+template <class IteratorCategory>
+using _category_to_system_t =
+    typename thrust::detail::iterator_category_to_system<IteratorCategory>::type;
+
+static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::output_device_iterator_tag>>::value);
+static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::input_device_iterator_tag>>::value);
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::forward_device_iterator_tag>>::value);
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::bidirectional_device_iterator_tag>>::value);
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::random_access_device_iterator_tag>>::value);
+
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::output_host_iterator_tag>>::value);
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::input_host_iterator_tag>>::value);
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::forward_host_iterator_tag>>::value);
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::bidirectional_host_iterator_tag>>::value);
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::random_access_host_iterator_tag>>::value);
+
+// static_assert(!std::is_convertible<thrust::input_device_iterator_tag, thrust::input_host_iterator_tag>::value);
+static_assert(!std::is_convertible<thrust::input_host_iterator_tag, thrust::input_device_iterator_tag>::value);
diff --git a/thrust/iterator/detail/iterator_category_to_system.h b/thrust/iterator/detail/iterator_category_to_system.h
index e6103b539..f8f209396 100644
--- a/thrust/iterator/detail/iterator_category_to_system.h
+++ b/thrust/iterator/detail/iterator_category_to_system.h
@@ -38,24 +38,24 @@ template <typename> struct device_iterator_category_to_backend_system;
 // we should just specialize this metafunction for iterator_category_with_system_and_traversal
 template<typename Category>
   struct iterator_category_to_system
-    // convertible to host iterator?
+    // convertible to device iterator?
     : eval_if<
         or_<
-          is_convertible<Category, thrust::input_host_iterator_tag>,
-          is_convertible<Category, thrust::output_host_iterator_tag>
+          is_convertible<Category, thrust::input_device_iterator_tag>,
+          is_convertible<Category, thrust::output_device_iterator_tag>
         >::value,
 
-        detail::identity_<thrust::host_system_tag>,
-        
-        // convertible to device iterator?
+        detail::identity_<thrust::device_system_tag>,
+
+        // convertible to host iterator?
         eval_if<
           or_<
-            is_convertible<Category, thrust::input_device_iterator_tag>,
-            is_convertible<Category, thrust::output_device_iterator_tag>
+            is_convertible<Category, thrust::input_host_iterator_tag>,
+            is_convertible<Category, thrust::output_host_iterator_tag>
           >::value,
 
-          detail::identity_<thrust::device_system_tag>,
-
+          detail::identity_<thrust::host_system_tag>,
+        
           // unknown system
           detail::identity_<void>
         > // if device
diff --git a/thrust/iterator/detail/iterator_category_to_traversal.h b/thrust/iterator/detail/iterator_category_to_traversal.h
index d8c736c50..e3675163c 100644
--- a/thrust/iterator/detail/iterator_category_to_traversal.h
+++ b/thrust/iterator/detail/iterator_category_to_traversal.h
@@ -88,23 +88,23 @@ template <typename Category>
 
 template<typename Category>
   struct category_to_traversal
-      // check for host system
+      // check for device system
     : eval_if<
         or_<
-          is_convertible<Category, thrust::input_host_iterator_tag>,
-          is_convertible<Category, thrust::output_host_iterator_tag>
+          is_convertible<Category, thrust::input_device_iterator_tag>,
+          is_convertible<Category, thrust::output_device_iterator_tag>
         >::value,
 
-        host_system_category_to_traversal<Category>,
+        device_system_category_to_traversal<Category>,
 
-        // check for device system
+        // check for host system
         eval_if<
           or_<
-            is_convertible<Category, thrust::input_device_iterator_tag>,
-            is_convertible<Category, thrust::output_device_iterator_tag>
+            is_convertible<Category, thrust::input_host_iterator_tag>,
+            is_convertible<Category, thrust::output_host_iterator_tag>
           >::value,
 
-          device_system_category_to_traversal<Category>,
+          host_system_category_to_traversal<Category>,
 
           // unknown category
           detail::identity_<void>

From 5e1ef886008f9f0dfaaa627016e4c2ab784767c6 Mon Sep 17 00:00:00 2001
From: Eric Niebler <eniebler@nvidia.com>
Date: Fri, 13 May 2022 14:25:41 -0700
Subject: [PATCH 2/2] review feedback

---
 ...ns_wrong_tag.cu => iterator_categories.cu} | 24 +++++++++----------
 testing/regression/CMakeLists.txt             |  4 ----
 .../detail/iterator_category_to_system.h      |  2 +-
 3 files changed, 13 insertions(+), 17 deletions(-)
 rename testing/{regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu => iterator_categories.cu} (63%)

diff --git a/testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu b/testing/iterator_categories.cu
similarity index 63%
rename from testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu
rename to testing/iterator_categories.cu
index 7f4ad9f1b..2d249dba4 100644
--- a/testing/regression/gh_902__iterator_category_to_system_returns_wrong_tag.cu
+++ b/testing/iterator_categories.cu
@@ -6,17 +6,17 @@ template <class IteratorCategory>
 using _category_to_system_t =
     typename thrust::detail::iterator_category_to_system<IteratorCategory>::type;
 
-static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::output_device_iterator_tag>>::value);
-static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::input_device_iterator_tag>>::value);
-// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::forward_device_iterator_tag>>::value);
-// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::bidirectional_device_iterator_tag>>::value);
-// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::random_access_device_iterator_tag>>::value);
+static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::output_device_iterator_tag>>::value, "");
+static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::input_device_iterator_tag>>::value, "");
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::forward_device_iterator_tag>>::value, "");       // Still broken
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::bidirectional_device_iterator_tag>>::value, ""); // Still broken
+// static_assert(std::is_same<thrust::device_system_tag, _category_to_system_t<thrust::random_access_device_iterator_tag>>::value, ""); // Still broken
 
-static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::output_host_iterator_tag>>::value);
-static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::input_host_iterator_tag>>::value);
-static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::forward_host_iterator_tag>>::value);
-static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::bidirectional_host_iterator_tag>>::value);
-static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::random_access_host_iterator_tag>>::value);
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::output_host_iterator_tag>>::value, "");
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::input_host_iterator_tag>>::value, "");
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::forward_host_iterator_tag>>::value, "");
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::bidirectional_host_iterator_tag>>::value, "");
+static_assert(std::is_same<thrust::host_system_tag, _category_to_system_t<thrust::random_access_host_iterator_tag>>::value, "");
 
-// static_assert(!std::is_convertible<thrust::input_device_iterator_tag, thrust::input_host_iterator_tag>::value);
-static_assert(!std::is_convertible<thrust::input_host_iterator_tag, thrust::input_device_iterator_tag>::value);
+// static_assert(!std::is_convertible<thrust::input_device_iterator_tag, thrust::input_host_iterator_tag>::value, "");                  // Still broken
+static_assert(!std::is_convertible<thrust::input_host_iterator_tag, thrust::input_device_iterator_tag>::value, "");
diff --git a/testing/regression/CMakeLists.txt b/testing/regression/CMakeLists.txt
index 6c180839c..eea8b3a45 100644
--- a/testing/regression/CMakeLists.txt
+++ b/testing/regression/CMakeLists.txt
@@ -1,7 +1,3 @@
-if ("thrust" IN_LIST THRUST_TARGETS)
-  thrust_add_test(test_target "regression.gh_902__iterator_category_to_system_returns_wrong_tag" "gh_902__iterator_category_to_system_returns_wrong_tag.cu" "thrust")
-endif()
-
 #
 # Disabled as these test names are too long for CMAKE_OBJECT_PATH_MAX.
 # We should integrate these with the other unit tests.
diff --git a/thrust/iterator/detail/iterator_category_to_system.h b/thrust/iterator/detail/iterator_category_to_system.h
index f8f209396..cbb9b4380 100644
--- a/thrust/iterator/detail/iterator_category_to_system.h
+++ b/thrust/iterator/detail/iterator_category_to_system.h
@@ -55,7 +55,7 @@ template<typename Category>
           >::value,
 
           detail::identity_<thrust::host_system_tag>,
-        
+
           // unknown system
           detail::identity_<void>
         > // if device