lowest_layer is removed (API Change):

The nested function lowest_layer and nested type lowest_layer_type
are removed from all stream layers.

Actions Required:

* Remove lowest_layer and lowest_layer_type from user-defined streams.
* Use the get_lowest_layer free function and the lowest_layer_type trait
  as needed.

include/boost/beast/_experimental/core/flat_stream.hpp

@@ -102,9 +102,6 @@ public:
     using next_layer_type =
         typename std::remove_reference<NextLayer>::type;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type = boost::beast::get_lowest_layer<next_layer_type>;
-
     /// The type of the executor associated with the object.
     using executor_type = typename next_layer_type::executor_type;
 
@@ -171,34 +168,6 @@ public:
         return stream_;
     }
 
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers.
-    */
-    lowest_layer_type&
-    lowest_layer() noexcept
-    {
-        return stream_.lowest_layer();
-    }
-
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers. Ownership is not transferred to the caller.
-    */
-    lowest_layer_type const&
-    lowest_layer() const noexcept
-    {
-        return stream_.lowest_layer();
-    }
-
     //--------------------------------------------------------------------------
 
     /** Read some data from the stream.

include/boost/beast/_experimental/core/ssl_stream.hpp

@@ -84,9 +84,6 @@ public:
     /// The type of the next layer.
     using next_layer_type = typename ssl_stream_type::next_layer_type;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type = typename ssl_stream_type::lowest_layer_type;
-
     /// The type of the executor associated with the object.
     using executor_type = typename stream_type::executor_type;
 
@@ -185,35 +182,7 @@ public:
         return p_->next_layer().next_layer();
     }
 
-    /** Get a reference to the lowest layer.
-
-        This function returns a reference to the lowest layer in a stack of stream
-        layers.
-
-        @return A reference to the lowest layer in the stack of stream layers.
-        Ownership is not transferred to the caller.
-    */
-    lowest_layer_type&
-    lowest_layer() noexcept
-    {
-        return p_->lowest_layer();
-    }
-
-    /** Get a reference to the lowest layer.
-
-        This function returns a reference to the lowest layer in a stack of stream
-        layers.
-
-        @return A reference to the lowest layer in the stack of stream layers.
-        Ownership is not transferred to the caller.
-    */
-    lowest_layer_type const&
-    lowest_layer() const noexcept
-    {
-        return p_->lowest_layer();
-    }
-
-      /** Set the peer verification mode.
+    /** Set the peer verification mode.
 
         This function may be used to configure the peer verification mode used by
         the stream. The new mode will override the mode inherited from the context.

include/boost/beast/_experimental/http/icy_stream.hpp

@@ -87,10 +87,6 @@ public:
     using next_layer_type =
         typename std::remove_reference<NextLayer>::type;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type =
-        get_lowest_layer<next_layer_type>;
-
     /// The type of the executor associated with the object.
     using executor_type = typename next_layer_type::executor_type;
 
@@ -157,34 +153,6 @@ public:
         return stream_;
     }
 
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers.
-    */
-    lowest_layer_type&
-    lowest_layer()
-    {
-        return stream_.lowest_layer();
-    }
-
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers. Ownership is not transferred to the caller.
-    */
-    lowest_layer_type const&
-    lowest_layer() const
-    {
-        return stream_.lowest_layer();
-    }
-
     //--------------------------------------------------------------------------
 
     /** Read some data from the stream.

include/boost/beast/_experimental/test/stream.hpp

@@ -165,9 +165,6 @@ class stream
 public:
     using buffer_type = flat_buffer;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type = stream;
-
     /** Destructor
 
         If an asynchronous read operation is pending, it will
@@ -278,34 +275,6 @@ public:
         return in_->ioc.get_executor();
     };
 
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers.
-    */
-    lowest_layer_type&
-    lowest_layer() noexcept
-    {
-        return *this;
-    }
-
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers. Ownership is not transferred to the caller.
-    */
-    lowest_layer_type const&
-    lowest_layer() const noexcept
-    {
-        return *this;
-    }
-
     /// Set the maximum number of bytes returned by read_some
     void
     read_size(std::size_t n) noexcept

include/boost/beast/core/buffered_read_stream.hpp

@@ -111,9 +111,6 @@ public:
     using next_layer_type =
         typename std::remove_reference<Stream>::type;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type = get_lowest_layer<next_layer_type>;
-
     /** Move constructor.
 
         @note The behavior of move assignment on or from streams
@@ -150,20 +147,6 @@ public:
         return next_layer_;
     }
     
-    /// Get a reference to the lowest layer.
-    lowest_layer_type&
-    lowest_layer() noexcept
-    {
-        return next_layer_.lowest_layer();
-    }
-
-    /// Get a const reference to the lowest layer.
-    lowest_layer_type const&
-    lowest_layer() const noexcept
-    {
-        return next_layer_.lowest_layer();
-    }
-
     using executor_type =
         detail::get_executor_type<next_layer_type>;
 

include/boost/beast/core/detail/type_traits.hpp

@@ -161,21 +161,6 @@ struct is_contiguous_container<T, E, void_t<
 
 //------------------------------------------------------------------------------
 
-template<class T, class = void>
-struct get_lowest_layer_helper
-{
-    using type = T;
-};
-
-template<class T>
-struct get_lowest_layer_helper<T,
-    void_t<typename T::lowest_layer_type>>
-{
-    using type = typename T::lowest_layer_type;
-};
-
-//------------------------------------------------------------------------------
-
 //
 // buffer concepts
 //

include/boost/beast/core/type_traits.hpp

@@ -121,41 +121,6 @@ struct has_get_executor<T, beast::detail::void_t<decltype(
         std::declval<T&>().get_executor())>> : std::true_type {};
 #endif
 
-/** Alias for `T::lowest_layer_type` if it exists, else `T`
-
-    This will be a type alias for `T::lowest_layer_type`
-    if it exists, else it will be an alias for `T`.
-
-    @par Example
-
-    Declaring a wrapper:
-
-    @code
-    template<class Stream>
-    struct stream_wrapper
-    {
-        using next_layer_type = typename std::remove_reference<Stream>::type;
-        using lowest_layer_type = get_lowest_layer<stream_type>;
-    };
-    @endcode
-
-    Defining a metafunction:
-
-    @code
-    /// Alias for `std::true_type` if `T` wraps another stream
-    template<class T>
-    using is_stream_wrapper : std::integral_constant<bool,
-        ! std::is_same<T, get_lowest_layer<T>>::value> {};
-    @endcode
-*/
-#if BOOST_BEAST_DOXYGEN
-template<class T>
-struct get_lowest_layer;
-#else
-template<class T>
-using get_lowest_layer = typename detail::get_lowest_layer_helper<T>::type;
-#endif
-
 /** Determine if `T` meets the requirements of @b AsyncReadStream.
 
     Metafunctions are used to perform compile time checking of template

include/boost/beast/websocket/impl/stream.hpp

@@ -79,24 +79,6 @@ next_layer() const noexcept ->
     return impl_->stream;
 }
 
-template<class NextLayer, bool deflateSupported>
-auto
-stream<NextLayer, deflateSupported>::
-lowest_layer() noexcept ->
-    lowest_layer_type&
-{
-    return impl_->stream.lowest_layer();
-}
-
-template<class NextLayer, bool deflateSupported>
-auto
-stream<NextLayer, deflateSupported>::
-lowest_layer() const noexcept ->
-    lowest_layer_type const&
-{
-    return impl_->stream.lowest_layer();
-}
-
 template<class NextLayer, bool deflateSupported>
 bool
 stream<NextLayer, deflateSupported>::

include/boost/beast/websocket/stream.hpp

@@ -161,9 +161,6 @@ public:
     using next_layer_type =
         typename std::remove_reference<NextLayer>::type;
 
-    /// The type of the lowest layer.
-    using lowest_layer_type = get_lowest_layer<next_layer_type>;
-
     /// The type of the executor associated with the object.
     using executor_type = typename next_layer_type::executor_type;
 
@@ -245,30 +242,6 @@ public:
     next_layer_type const&
     next_layer() const noexcept;
 
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers.
-    */
-    // DEPRECATED
-    lowest_layer_type&
-    lowest_layer() noexcept;
-
-    /** Get a reference to the lowest layer
-
-        This function returns a reference to the lowest layer
-        in a stack of stream layers.
-
-        @return A reference to the lowest layer in the stack of
-        stream layers. Ownership is not transferred to the caller.
-    */
-    // DEPRECATED
-    lowest_layer_type const&
-    lowest_layer() const noexcept;
-
     //--------------------------------------------------------------------------
     //
     // Observers