Implementation: fixed module and forward declarations

Author: H-G-Hristov

libcxx/include/libcxx.imp

@@ -434,7 +434,7 @@
   { include: [ "<__fwd/ostream.h>", "private", "<iosfwd>", "public" ] },
   { include: [ "<__fwd/pair.h>", "private", "<utility>", "public" ] },
   { include: [ "<__fwd/span.h>", "private", "<span>", "public" ] },
-  { include: [ "<__fwd/spanstream.h>", "private", "<spanstream>", "public" ] },
+  { include: [ "<__fwd/spanstream.h>", "private", "<iosfwd>", "public" ] },
   { include: [ "<__fwd/sstream.h>", "private", "<iosfwd>", "public" ] },
   { include: [ "<__fwd/streambuf.h>", "private", "<iosfwd>", "public" ] },
   { include: [ "<__fwd/string.h>", "private", "<string>", "public" ] },

libcxx/modules/std/spanstream.inc

@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
-#if 0
+#if _LIBCPP_STD_VER >= 23
   using std::basic_spanbuf;
 
   using std::swap;
@@ -38,5 +38,5 @@ export namespace std {
 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
   using std::wspanstream;
 #  endif
-#endif
+#endif // _LIBCPP_STD_VER >= 23
 } // namespace std

libcxx/utils/generate_iwyu_mapping.py

@@ -40,7 +40,7 @@ def IWYU_mapping(header: str) -> typing.Optional[typing.List[str]]:
         return ["utility"]
     elif header == "__fwd/subrange.h":
         return ["ranges"]
-    elif re.match("__fwd/(fstream|ios|istream|ostream|sstream|streambuf)[.]h", header):
+    elif re.match("__fwd/(fstream|ios|istream|ostream|spanstream|sstream|streambuf)[.]h", header):
         return ["iosfwd"]
     # Handle remaining forward declaration headers
     elif re.match("__fwd/(.+)[.]h", header):