} // namespace function
} // namespace detail
-FOLLY_PUSH_WARNING
-FOLLY_MSVC_DISABLE_WARNING(4521) // Multiple copy constructors
-FOLLY_MSVC_DISABLE_WARNING(4522) // Multiple assignment operators
template <typename FunctionType>
class Function final : private detail::function::FunctionTraits<FunctionType> {
// These utility types are defined outside of the template to reduce
/**
* Move assignment operator
+ *
+ * \note Leaves `that` in a valid but unspecified state. If `&that == this`
+ * then `*this` is left in a valid but unspecified state.
*/
Function& operator=(Function&& that) noexcept {
- if (&that != this) {
- // Q: Why is is safe to destroy and reconstruct this object in place?
- // A: Two reasons: First, `Function` is a final class, so in doing this
- // we aren't slicing off any derived parts. And second, the move
- // operation is guaranteed not to throw so we always leave the object
- // in a valid state.
- this->~Function();
- ::new (this) Function(std::move(that));
- }
+ // Q: Why is is safe to destroy and reconstruct this object in place?
+ // A: Two reasons: First, `Function` is a final class, so in doing this
+ // we aren't slicing off any derived parts. And second, the move
+ // operation is guaranteed not to throw so we always leave the object
+ // in a valid state.
+ // In the case of self-move (this == &that), this leaves the object in
+ // a default-constructed state. First the object is destroyed, then we
+ // pass the destroyed object to the move constructor. The first thing the
+ // move constructor does is default-construct the object. That object is
+ // "moved" into itself, which is a no-op for a default-constructed Function.
+ this->~Function();
+ ::new (this) Function(std::move(that));
return *this;
}
return std::move(*this).asSharedProxy();
}
};
-FOLLY_POP_WARNING
template <typename FunctionType>
void swap(Function<FunctionType>& lhs, Function<FunctionType>& rhs) noexcept {
/**
* Construct a FunctionRef from a reference to a callable object.
*/
- template <typename Fun>
+ template <
+ typename Fun,
+ typename std::enable_if<
+ !std::is_same<FunctionRef, typename std::decay<Fun>::type>::value,
+ int>::type = 0>
/* implicit */ FunctionRef(Fun&& fun) noexcept {
using ReferencedType = typename std::remove_reference<Fun>::type;