Replace boost::optional with our own implementation

1 files changed, 77 insertions, 0 deletions

diff --git a/src/optional.hh b/src/optional.hh
new file mode 100644
index 00000000..61dc9618
--- /dev/null
+++ b/src/optional.hh
@@ -0,0 +1,77 @@
+#ifndef optional_hh_INCLUDED
+#define optional_hh_INCLUDED
+
+namespace Kakoune
+{
+
+template<typename T>
+struct Optional
+{
+public:
+    constexpr Optional() : m_valid(false) {}
+    Optional(const T& other) : m_valid(true) { new (&m_value) T(other); }
+    Optional(T&& other) : m_valid(true) { new (&m_value) T(std::move(other)); }
+
+    Optional(const Optional& other)
+        : m_valid(other.m_valid)
+    {
+        if (m_valid)
+            new (&m_value) T(other.m_value);
+    }
+
+    Optional(Optional&& other)
+        : m_valid(other.m_valid)
+    {
+        if (m_valid)
+            new (&m_value) T(std::move(other.m_value));
+    }
+
+    Optional& operator=(const Optional& other)
+    {
+        if (m_valid)
+            m_value.~T();
+        if ((m_valid = other.m_valid))
+            new (&m_value) T(other.m_value);
+        return *this;
+    }
+
+    Optional& operator=(Optional&& other)
+    {
+        if (m_valid)
+            m_value.~T();
+        if ((m_valid = other.m_valid))
+            new (&m_value) T(std::move(other.m_value));
+        return *this;
+    }
+
+    ~Optional()
+    {
+        if (m_valid)
+            m_value.~T();
+    }
+
+    constexpr explicit operator bool() const noexcept { return m_valid; }
+
+    T& operator*()
+    {
+        kak_assert(m_valid);
+        return m_value;
+    }
+    const T& operator*() const { return *const_cast<Optional&>(*this); }
+
+    T* operator->()
+    {
+        kak_assert(m_valid);
+        return &m_value;
+    }
+    const T* operator->() const { return const_cast<Optional&>(*this).operator->(); }
+
+private:
+    bool m_valid;
+    union { T m_value; };
+};
+
+}
+
+#endif // optional_hh_INCLUDED
+