From 2dd86ce358b1409d18d70ac1c564422ef604a493 Mon Sep 17 00:00:00 2001
From: chenruibiao <chenruibiao@baidu.com>
Date: Mon, 23 May 2022 21:08:16 +0800
Subject: [PATCH] Add type() interface for variant

---
 paddle/utils/CMakeLists.txt  |  4 +++-
 paddle/utils/variant.h       | 21 +++++++++++++++++
 paddle/utils/variant_test.cc | 44 ++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 paddle/utils/variant_test.cc

diff --git a/paddle/utils/CMakeLists.txt b/paddle/utils/CMakeLists.txt
index 64c88a47b4393..7669c06b2c2b7 100644
--- a/paddle/utils/CMakeLists.txt
+++ b/paddle/utils/CMakeLists.txt
@@ -1,3 +1,5 @@
 add_subdirectory(string)
-cc_test(small_vector_test SRCS small_vector_test.cc DEPS gtest gflags)
+
 cc_test(array_ref_test SRCS array_ref_test.cc DEPS gtest gflags)
+cc_test(small_vector_test SRCS small_vector_test.cc DEPS gtest gflags)
+cc_test(variant_test SRCS variant_test.cc DEPS gtest)
diff --git a/paddle/utils/variant.h b/paddle/utils/variant.h
index 50bdc4287e21a..4348abc9cbff0 100644
--- a/paddle/utils/variant.h
+++ b/paddle/utils/variant.h
@@ -2199,6 +2199,18 @@ class impl : public copy_assignment<traits<Ts...>> {
     }
   }
 
+  inline const std::type_info &type() const {
+    return visitation::alt::visit_alt_at(
+        this->index(),
+#ifdef MPARK_GENERIC_LAMBDAS
+        [](auto &alt) -> const std::type_info & { return typeid(alt.value); }
+#else
+        typer {}
+#endif
+        ,
+        *this);
+  }
+
  private:
 #ifndef MPARK_GENERIC_LAMBDAS
   struct swapper {
@@ -2208,6 +2220,13 @@ class impl : public copy_assignment<traits<Ts...>> {
       swap(this_alt.value, that_alt.value);
     }
   };
+
+  struct typer {
+    template <typename Alt>
+    inline const std::type_info &operator()(Alt &alt) const {
+      return typeid(alt.value);
+    }
+  };
 #endif
 
   inline constexpr bool move_nothrow() const {
@@ -2432,6 +2451,8 @@ class variant {
     impl_.swap(that.impl_);
   }
 
+  inline const std::type_info &type() noexcept { return impl_.type(); }
+
  private:
   detail::impl<Ts...> impl_;
 
diff --git a/paddle/utils/variant_test.cc b/paddle/utils/variant_test.cc
new file mode 100644
index 0000000000000..7358274e8b7bf
--- /dev/null
+++ b/paddle/utils/variant_test.cc
@@ -0,0 +1,44 @@
+// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+//
+// 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 "paddle/utils/variant.h"
+
+#include <string>
+#include <vector>
+#include "gtest/gtest.h"
+#include "paddle/phi/core/enforce.h"
+
+TEST(interface_test, type) {
+  using phi::enforce::demangle;
+
+  paddle::variant<bool, int, float, std::string, std::vector<int>> var;
+
+  var = true;
+  EXPECT_EQ(demangle(var.type().name()), "bool");
+
+  var = 0;
+  EXPECT_EQ(demangle(var.type().name()), "int");
+
+  var = 0.f;
+  EXPECT_EQ(demangle(var.type().name()), "float");
+
+  var = std::string();
+  EXPECT_EQ(demangle(var.type().name()),
+            "std::__cxx11::basic_string<char, std::char_traits<char>, "
+            "std::allocator<char> >");
+
+  var = std::vector<int>();
+  EXPECT_EQ(demangle(var.type().name()),
+            "std::vector<int, std::allocator<int> >");
+}