Add ASL_FWD_LIKE

2 files changed, 81 insertions, 0 deletions

diff --git a/asl/base/utility.hpp b/asl/base/utility.hpp
index b3fb36b..b8e13ae 100644
--- a/asl/base/utility.hpp
+++ b/asl/base/utility.hpp
@@ -7,6 +7,8 @@
 
 #define ASL_FWD(expr_) (static_cast<decltype(expr_)&&>(expr_))
 
+#define ASL_FWD_LIKE(ref_, expr_) (static_cast<::asl::copy_cref_t<ref_, decltype(expr_)&&>>(expr_))
+
 namespace asl
 {
 
diff --git a/asl/base/utility_tests.cpp b/asl/base/utility_tests.cpp
index 4b8e3d1..d959369 100644
--- a/asl/base/utility_tests.cpp
+++ b/asl/base/utility_tests.cpp
@@ -1 +1,80 @@
 #include "asl/base/utility.hpp"
+#include "asl/testing/testing.hpp"
+
+template<typename T> static constexpr int identify(const T&)  { return 1; }
+template<typename T> static constexpr int identify(const T&&) { return 2; }
+template<typename T> static constexpr int identify(T&)        { return 3; }
+template<typename T> static constexpr int identify(T&&)       { return 4; }
+
+struct IdentifySelf
+{
+    template<typename Self>
+    constexpr int get(this Self&& self) { return identify(ASL_FWD(self)); }
+};
+
+static int get_const_lref(const IdentifySelf& i)  { return ASL_FWD(i).get(); }
+static int get_const_rref(const IdentifySelf&& i) { return ASL_FWD(i).get(); }
+static int get_lref(IdentifySelf& i)              { return ASL_FWD(i).get(); }
+static int get_rref(IdentifySelf&& i)             { return ASL_FWD(i).get(); }
+
+ASL_TEST(forward)
+{
+    IdentifySelf id;
+    ASL_TEST_EXPECT(get_const_lref(id) == 1);
+    ASL_TEST_EXPECT(get_lref(id) == 3);
+    ASL_TEST_EXPECT(get_const_rref(ASL_MOVE(id)) == 2);
+    ASL_TEST_EXPECT(get_rref(ASL_MOVE(id)) == 4);
+}
+
+ASL_TEST(move)
+{
+    IdentifySelf id;
+    ASL_TEST_EXPECT(id.get() == 3);
+    ASL_TEST_EXPECT(ASL_MOVE(id).get() == 4);
+}
+
+struct Level1
+{
+    IdentifySelf id;
+};
+
+struct Level2
+{
+    Level1 deeper;
+};
+
+struct Level3
+{
+    Level2 deeper;
+};
+
+static int get_const_lref(const Level3& i)  { return ASL_FWD(i).deeper.deeper.id.get(); }
+static int get_const_rref(const Level3&& i) { return ASL_FWD(i).deeper.deeper.id.get(); }
+static int get_lref(Level3& i)              { return ASL_FWD(i).deeper.deeper.id.get(); }
+static int get_rref(Level3&& i)             { return ASL_FWD(i).deeper.deeper.id.get(); }
+
+ASL_TEST(forward2)
+{
+    Level3 id{};
+    ASL_TEST_EXPECT(get_const_lref(id) == 1);
+    ASL_TEST_EXPECT(get_lref(id) == 3);
+    ASL_TEST_EXPECT(get_const_rref(ASL_MOVE(id)) == 2);
+    ASL_TEST_EXPECT(get_rref(ASL_MOVE(id)) == 4);
+}
+
+template<typename T>
+static int test_fwd_like(T&& t)
+{
+    IdentifySelf id;
+    return ASL_FWD_LIKE(decltype(t), id).get();
+}
+
+ASL_TEST(forward_like)
+{
+    int x{};
+    ASL_TEST_EXPECT(test_fwd_like<const int&>(x) == 1);
+    ASL_TEST_EXPECT(test_fwd_like<int&>(x) == 3);
+    ASL_TEST_EXPECT(test_fwd_like<const int&&>(ASL_MOVE(x)) == 2);
+    ASL_TEST_EXPECT(test_fwd_like<int&&>(ASL_MOVE(x)) == 4);
+}
+