Avoid extra indirection for storing FifoWatcher

By improving the Value interface we can avoid storing a unique_ptr
to a FifoWatcher and directly store the FifoWatcher.

src/buffer_utils.cc

@@ -264,7 +264,7 @@ Buffer* create_fifo_buffer(String name, int fd, Buffer::Flags flags, bool scroll
         bool m_scroll;
     };
 
-    buffer->values()[fifo_watcher_id] = Value(std::make_unique<FifoWatcher>(fd, *buffer, scroll));
+    buffer->values()[fifo_watcher_id] = Value(Meta::Type<FifoWatcher>{}, fd, *buffer, scroll);
     buffer->flags() = flags | Buffer::Flags::Fifo | Buffer::Flags::NoUndo;
     buffer->run_hook_in_own_context(Hook::BufOpenFifo, buffer->name());
 

src/value.hh

@@ -3,6 +3,7 @@
 
 #include "hash_map.hh"
 #include "units.hh"
+#include "meta.hh"
 
 #include <type_traits>
 #include <memory>
@@ -20,6 +21,10 @@ struct Value
     Value(T&& val)
         : m_value{new Model<std::remove_cvref_t<T>>{std::forward<T>(val)}} {}
 
+    template<typename T>
+    Value(Meta::Type<T>, auto&&... args) :
+        m_value(new Model<T>(std::forward<decltype(args)>(args)...)) {}
+
     Value(const Value& val) = delete;
     Value(Value&&) = default;
 
@@ -58,7 +63,7 @@ private:
     template<typename T>
     struct Model : public Concept, public UseMemoryDomain<MemoryDomain::Values>
     {
-        Model(T&& val) : m_content(std::move(val)) {}
+        Model(auto&&... args) : m_content(std::forward<decltype(args)>(args)...) {}
         const std::type_info& type() const override { return typeid(T); }
 
         T m_content;