From c33f2f63603ecd39c8e1b7fd1becac0e03e9b4da Mon Sep 17 00:00:00 2001
From: Steve Gerbino <steve@gerbino.co>
Date: Thu, 23 Jul 2026 15:31:09 +0200
Subject: [PATCH] fix(any_write_sink): accept mutable buffer sequences in write

ConstBufferSequence admits mutable sequences, but write windowed them
through buffer_param, whose span<mutable_buffer> cannot convert to
the type-erased write_(span<const_buffer const>), so calls such as
write(make_buffer(some_string)) failed to instantiate. Use
const_buffer_param, as write_eof already does.
---
 include/boost/capy/io/any_write_sink.hpp |  2 +-
 test/unit/io/any_write_sink.cpp          | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/boost/capy/io/any_write_sink.hpp b/include/boost/capy/io/any_write_sink.hpp
index 2047bc99d..39900c6bd 100644
--- a/include/boost/capy/io/any_write_sink.hpp
+++ b/include/boost/capy/io/any_write_sink.hpp
@@ -854,7 +854,7 @@ template<ConstBufferSequence CB>
 io_task<std::size_t>
 any_write_sink::write(CB buffers)
 {
-    buffer_param<CB> bp(buffers);
+    const_buffer_param<CB> bp(buffers);
     std::size_t total = 0;
 
     for(;;)
diff --git a/test/unit/io/any_write_sink.cpp b/test/unit/io/any_write_sink.cpp
index 1b0f09034..a57cac86f 100644
--- a/test/unit/io/any_write_sink.cpp
+++ b/test/unit/io/any_write_sink.cpp
@@ -302,6 +302,27 @@ class any_write_sink_test
         BOOST_TEST(r.success);
     }
 
+    void
+    testWriteMutableSequence()
+    {
+        test::fuse f;
+        auto r = f.armed([&](test::fuse&) -> task<> {
+            test::write_sink ws(f);
+
+            any_write_sink aws(&ws);
+
+            std::string body = "hello world";
+            auto [ec, n] = co_await aws.write(make_buffer(body));
+            if(ec)
+                co_return;
+
+            BOOST_TEST_EQ(n, 11u);
+            BOOST_TEST_EQ(ws.data(), "hello world");
+            BOOST_TEST(!ws.eof_called());
+        });
+        BOOST_TEST(r.success);
+    }
+
     void
     testWriteMultiple()
     {
@@ -775,6 +796,7 @@ class any_write_sink_test
         testWriteSomeEmptyBuffer();
         testWriteEmptyBuffer();
         testWrite();
+        testWriteMutableSequence();
         testWriteMultiple();
         testWriteBufferSequence();
         testWriteSingleBuffer();