AK: Add Optional::lazy_emplace(Callable)

This makes it possible to emplace using a given function instead of
passing constructor arguments.

1 files changed, 8 insertions, 0 deletions

diff --git a/AK/Optional.h b/AK/Optional.h
index 08f659dce4..6acf64f384 100644
--- a/AK/Optional.h
+++ b/AK/Optional.h
@@ -200,6 +200,14 @@ public:
         new (&m_storage) T(forward<Parameters>(parameters)...);
     }
 
+    template<typename Callable>
+    ALWAYS_INLINE void lazy_emplace(Callable callable)
+    {
+        clear();
+        m_has_value = true;
+        new (&m_storage) T { callable() };
+    }
+
     [[nodiscard]] ALWAYS_INLINE bool has_value() const { return m_has_value; }
 
     [[nodiscard]] ALWAYS_INLINE T& value() &