refactor: bring utf8 patch for std::ostream back.

testbench/yycc/string/stream.cpp

@@ -0,0 +1,31 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/string/stream.hpp>
+#include <yycc/string/reinterpret.hpp>
+#include <sstream>
+
+#define REINTERPRET ::yycc::string::reinterpret
+using namespace std::literals::string_view_literals;
+using namespace ::yycc::string::stream;
+
+namespace yycctest::string::stream {
+    
+    TEST(StringStream, StringView) {
+        std::stringstream ss;
+        ss << u8"hello"sv;
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"hello"sv);
+    }
+
+    TEST(StringStream, CStrPtr) {
+        std::stringstream ss;
+        ss << u8"hello";
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"hello");
+    }
+
+    TEST(StringStream, Character) {
+        std::stringstream ss;
+        ss << u8'y';
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"y");
+    }
+
+}