Fix property_set_insert_t metafunction in pushmi

Summary: The property_set_insert_t<PS1, PS2> template metafunction had a bug that meant that it would fail to replace elements in the base set that had the same category as elements from the set being inserted.

Reviewed By: ericniebler, kirkshoop

Differential Revision: D14268145

fbshipit-source-id: ccc64e455bc6ff2073229e028a19d64dc7050092

folly/experimental/pushmi/properties.h

@@ -120,7 +120,7 @@ POut __property_set_index_fn(
     property_set_element<POut, property_category_t<PIn>>);
 
 template <class PIn, class POut, class... Ps>
-property_set<std::conditional_t<PUSHMI_PP_IS_SAME(Ps, PIn), POut, Ps>...>
+property_set<std::conditional_t<PUSHMI_PP_IS_SAME(Ps, POut), PIn, Ps>...>
 __property_set_insert_fn(
     property_set<Ps...>,
     property_set_element<POut, property_category_t<PIn>>);

folly/experimental/pushmi/test/PropertyTest.cpp

+/*
+ * Copyright 2019-present Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <folly/experimental/pushmi/properties.h>
+
+namespace {
+
+struct foo_category;
+struct bar_category;
+
+struct big_foo_property {
+  using property_category = foo_category;
+};
+
+struct small_foo_property {
+  using property_category = foo_category;
+};
+
+struct fast_bar_property {
+  using property_category = bar_category;
+};
+
+struct slow_bar_property {
+  using property_category = bar_category;
+};
+
+} // namespace
+
+using namespace folly::pushmi;
+
+////////////////
+// Tests for property_set_insert_t<PS1, PS2>
+
+static_assert(
+    std::is_same<
+        property_set<big_foo_property>,
+        property_set_insert_t<property_set<>, property_set<big_foo_property>>>::
+        value, "");
+static_assert(std::is_same<
+              property_set<big_foo_property>,
+              property_set_insert_t<
+                  property_set<big_foo_property>,
+                  property_set<big_foo_property>>>::value, "");
+static_assert(
+    std::is_same<
+        property_set<big_foo_property>,
+        property_set_insert_t<property_set<big_foo_property>, property_set<>>>::
+        value, "");
+static_assert(std::is_same<
+              property_set<big_foo_property>,
+              property_set_insert_t<
+                  property_set<small_foo_property>,
+                  property_set<big_foo_property>>>::value, "");
+static_assert(std::is_same<
+              property_set<big_foo_property, slow_bar_property>,
+              property_set_insert_t<
+                  property_set<big_foo_property, slow_bar_property>,
+                  property_set<big_foo_property>>>::value, "");
+static_assert(std::is_same<
+              property_set<big_foo_property, slow_bar_property>,
+              property_set_insert_t<
+                  property_set<small_foo_property, slow_bar_property>,
+                  property_set<big_foo_property>>>::value, "");
+static_assert(std::is_same<
+              property_set<slow_bar_property, big_foo_property>,
+              property_set_insert_t<
+                  property_set<slow_bar_property>,
+                  property_set<big_foo_property>>>::value, "");
+
+int main() {
+  return 0;
+}