[libcxx-commits] [libcxx] [libc++] Do not forward-declare syncstream outside experimental (PR #82511)

[Mark de Wever via libcxx-commits]

================
@@ -18,18 +18,22 @@ export namespace std {
   using std::u8streampos;
 #endif
 
+#ifndef _LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM
   using std::basic_osyncstream;
   using std::basic_syncbuf;
+#endif
 
   using std::istreambuf_iterator;
   using std::ostreambuf_iterator;
 
+#ifndef _LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM
   using std::osyncstream;
   using std::syncbuf;
 
-#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
   using std::wosyncstream;
   using std::wsyncbuf;
+#  endif
----------------
mordante wrote:

```suggestion
#  endif // _LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM
```

https://github.com/llvm/llvm-project/pull/82511