box_value constructor: Replace param::hstring with hstring

strings/base_reference_produce.h

@@ -509,12 +509,13 @@ namespace winrt::impl
 
 WINRT_EXPORT namespace winrt
 {
-    inline Windows::Foundation::IInspectable box_value(param::hstring const& value)
+    template <typename T, std::enable_if_t<std::is_constructible_v<hstring, T>, int> = 0>
+    Windows::Foundation::IInspectable box_value(T&& value)
     {
-        return Windows::Foundation::IReference<hstring>(*(hstring*)(&value));
+        return Windows::Foundation::IReference<hstring>(hstring(std::forward<T>(value)));
     }
 
-    template <typename T, std::enable_if_t<!std::is_convertible_v<T, param::hstring>, int> = 0>
+    template <typename T, std::enable_if_t<!std::is_constructible_v<hstring, T>, int> = 0>
     Windows::Foundation::IInspectable box_value(T const& value)
     {
         if constexpr (std::is_base_of_v<Windows::Foundation::IInspectable, T>)

test/test/box_string.cpp

@@ -0,0 +1,53 @@
+#include "pch.h"
+
+TEST_CASE("box_string")
+{
+    // hstring
+    {
+        winrt::hstring value = L"hstring";
+        auto boxed = winrt::box_value(value);
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"hstring");
+    }
+
+    // wchar_t const* (string literal)
+    {
+        auto boxed = winrt::box_value(L"literal");
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"literal");
+    }
+
+    // std::wstring
+    {
+        std::wstring value = L"wstring";
+        auto boxed = winrt::box_value(value);
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"wstring");
+    }
+
+    // std::wstring_view (null-terminated)
+    {
+        std::wstring_view value = L"view";
+        auto boxed = winrt::box_value(value);
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"view");
+    }
+
+    // std::wstring_view (not null-terminated)
+    // Regression test for https://github.com/microsoft/cppwinrt/issues/1527
+    {
+        std::wstring source = L"ABCDE";
+        std::wstring_view value(source.data(), 3); // "ABC"
+        auto boxed = winrt::box_value(value);
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"ABC");
+    }
+
+    // Empty string
+    {
+        auto boxed = winrt::box_value(winrt::hstring{});
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"");
+    }
+
+    // Empty wstring_view
+    {
+        std::wstring_view value;
+        auto boxed = winrt::box_value(value);
+        REQUIRE(winrt::unbox_value<winrt::hstring>(boxed) == L"");
+    }
+}

test/test/test.vcxproj

@@ -233,6 +233,7 @@
     <ClCompile Include="box_array.cpp" />
     <ClCompile Include="box_delegate.cpp" />
     <ClCompile Include="box_guid.cpp" />
+    <ClCompile Include="box_string.cpp" />
     <ClCompile Include="capture.cpp" />
     <ClCompile Include="coro_foundation.cpp">
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">NotUsing</PrecompiledHeader>