Implement correct move constructor and assignment for absl::strings_internal::OStringStream, and mark that class final.

This should be explicit per https://google.github.io/styleguide/cppguide.html#Copyable_Movable_Types, and is currently hard to infer due to multiple inheritance.

PiperOrigin-RevId: 474311032
Change-Id: I72d7adcb9f7a991c19c26bc7083a4df31de5da49

1 files changed, 14 insertions, 7 deletions

diff --git a/absl/strings/internal/ostringstream.cc b/absl/strings/internal/ostringstream.cc
index dc6cfe16..a0e5ec08 100644
--- a/absl/strings/internal/ostringstream.cc
+++ b/absl/strings/internal/ostringstream.cc
@@ -14,20 +14,27 @@
 
 #include "absl/strings/internal/ostringstream.h"
 
+#include <cassert>
+#include <cstddef>
+#include <ios>
+#include <streambuf>
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
-OStringStream::Buf::int_type OStringStream::overflow(int c) {
-  assert(s_);
-  if (!Buf::traits_type::eq_int_type(c, Buf::traits_type::eof()))
-    s_->push_back(static_cast<char>(c));
+OStringStream::Streambuf::int_type OStringStream::Streambuf::overflow(int c) {
+  assert(str_);
+  if (!std::streambuf::traits_type::eq_int_type(
+          c, std::streambuf::traits_type::eof()))
+    str_->push_back(static_cast<char>(c));
   return 1;
 }
 
-std::streamsize OStringStream::xsputn(const char* s, std::streamsize n) {
-  assert(s_);
-  s_->append(s, static_cast<size_t>(n));
+std::streamsize OStringStream::Streambuf::xsputn(const char* s,
+                                                 std::streamsize n) {
+  assert(str_);
+  str_->append(s, static_cast<size_t>(n));
   return n;
 }