3 files changed, 30 insertions, 9 deletions
diff --git a/asl/log/log.cpp b/asl/log/log.cpp
index cd5d287..af31a84 100644
--- a/asl/log/log.cpp
+++ b/asl/log/log.cpp
@@ -4,7 +4,7 @@
 
 // @Todo Don't use internal get_stdout_writer, make console module
 
-static asl::log::DefaultLogger g_default_logger{asl::print_internals::get_stdout_writer()};
+static asl::log::DefaultLogger<asl::Writer*> g_default_logger{asl::print_internals::get_stdout_writer()};
 static asl::log::Logger* g_head = &g_default_logger;
 
 static constexpr asl::string_view kLevelName[] = {
@@ -20,9 +20,9 @@ void asl::log::register_logger(box<Logger> logger_box)
     logger->m_next = exchange(g_head, logger);
 }
 
-void asl::log::DefaultLogger::log(const message& msg)
+void asl::log::DefaultLoggerBase::log_inner(Writer& writer, const message& msg)
 {
-    asl::format(m_writer, "[{}] {}:{}: {}\n",
+    asl::format(&writer, "[{}] {}:{}: {}\n",
         kLevelName[msg.level], // NOLINT
         msg.location.file,
         msg.location.line,
diff --git a/asl/log/log.hpp b/asl/log/log.hpp
index f2e3a47..7445cf6 100644
--- a/asl/log/log.hpp
+++ b/asl/log/log.hpp
@@ -39,16 +39,24 @@ public:
     constexpr Logger* next_logger() const { return m_next; }
 };
 
-// @Todo Make a deref_as trait & deref utility
-// @Todo Accept writer as box, pointer, reference, or value
-class DefaultLogger : public Logger
+class DefaultLoggerBase : public Logger
 {
-    Writer* m_writer;
+protected:
+    static void log_inner(Writer&, const message&);
+};
+
+template<derefs_as<Writer> W>
+class DefaultLogger : public DefaultLoggerBase
+{
+    W m_writer;
 
 public:
-    explicit constexpr DefaultLogger(Writer* writer) : m_writer{writer} {}
+    explicit constexpr DefaultLogger(W&& writer) : m_writer{ASL_FWD(writer)} {}
 
-    void log(const message&) override;
+    constexpr void log(const message& m) override
+    {
+        log_inner(deref<Writer>(m_writer), m);
+    }
 };
 
 void register_logger(box<Logger>);
diff --git a/asl/log/log_tests.cpp b/asl/log/log_tests.cpp
index 01e8fd7..4ab83e8 100644
--- a/asl/log/log_tests.cpp
+++ b/asl/log/log_tests.cpp
@@ -1,5 +1,6 @@
 #include <asl/log/log.hpp>
 #include <asl/testing/testing.hpp>
+#include <asl/string_builder.hpp>
 
 ASL_TEST(log)
 {
@@ -8,3 +9,15 @@ ASL_TEST(log)
     ASL_LOG_ERROR("Oh no! {}", 42);
 }
 
+static asl::StringWriter g_string_writer{};
+
+ASL_TEST(custom_writer)
+{
+    asl::log::register_logger<asl::log::DefaultLogger<asl::StringWriter<>&>>(g_string_writer);
+
+    ASL_LOG_INFO("Hello");
+    auto sv = g_string_writer.as_string_view();
+
+    ASL_TEST_EXPECT(sv == "[  INFO   ] asl/log/log_tests.cpp:18: Hello\n");
+}
+