moveonly: add mp/type-exception.h

Author: ryanofsky

CMakeLists.txt

@@ -47,6 +47,7 @@ set(MP_PUBLIC_HEADERS
   include/mp/proxy.h
   include/mp/type-char.h
   include/mp/type-context.h
+  include/mp/type-exception.h
   include/mp/type-function.h
   include/mp/type-interface.h
   include/mp/type-map.h

include/mp/proxy-types.h

@@ -205,15 +205,6 @@ struct ListOutput<::capnp::List<T, kind>>
     // clang-format on
 };
 
-template <typename Output>
-void CustomBuildField(TypeList<std::exception>,
-    Priority<1>,
-    InvokeContext& invoke_context,
-    const std::exception& value,
-    Output&& output)
-{
-    BuildField(TypeList<std::string>(), invoke_context, output, std::string(value.what()));
-}
 template <typename LocalType, typename Value, typename Output>
 void CustomBuildField(TypeList<const LocalType>,
     Priority<0>,

include/mp/type-exception.h

@@ -0,0 +1,22 @@
+// Copyright (c) 2025 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef MP_PROXY_TYPE_EXCEPTION_H
+#define MP_PROXY_TYPE_EXCEPTION_H
+
+#include <mp/util.h>
+
+namespace mp {
+template <typename Output>
+void CustomBuildField(TypeList<std::exception>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    const std::exception& value,
+    Output&& output)
+{
+    BuildField(TypeList<std::string>(), invoke_context, output, std::string(value.what()));
+}
+} // namespace mp
+
+#endif // MP_PROXY_TYPE_EXCEPTION_H