delegate_cpp11.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2019 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions :
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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******************************************************************************/
 
/******************************************************************************
 
Copyright (C) 2017 by Sergey A Kryukov: derived work
http://www.SAKryukov.org
http://www.codeproject.com/Members/SAKryukov
 
Based on original work by Sergey Ryazanov:
"The Impossibly Fast C++ Delegates", 18 Jul 2005
https://www.codeproject.com/articles/11015/the-impossibly-fast-c-delegates
 
MIT license:
http://en.wikipedia.org/wiki/MIT_License
 
Original publication: https://www.codeproject.com/Articles/1170503/The-Impossibly-Fast-Cplusplus-Delegates-Fixed
 
******************************************************************************/
 
#ifndef ETL_DELEGATE_CPP11_INCLUDED
#define ETL_DELEGATE_CPP11_INCLUDED
 
#include "../platform.h"
#include "../error_handler.h"
#include "../exception.h"
#include "../type_traits.h"
#include "../function_traits.h"
#include "../utility.h"
#include "../optional.h"
#include "../type_list.h"
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class delegate_exception : public exception
  {
  public:
 
    delegate_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class delegate_uninitialised : public delegate_exception
  {
  public:
 
    delegate_uninitialised(string_type file_name_, numeric_type line_number_)
      : delegate_exception(ETL_ERROR_TEXT("delegate:uninitialised", ETL_DELEGATE_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //*****************************************************************
  //*****************************************************************
  struct delegate_tag
  {
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename T>
  struct is_delegate : etl::bool_constant<etl::is_base_of<delegate_tag, T>::value>
  {
  };
 
#if ETL_USING_CPP17
  template <typename T>
  inline constexpr bool is_delegate_v = is_delegate<T>::value;
#endif
 
  //*************************************************************************
  //*************************************************************************
  template <typename T>
  class delegate;
 
  //*************************************************************************
  //*************************************************************************
  template <typename TReturn, typename... TArgs>
  class delegate<TReturn(TArgs...)> final : public delegate_tag
  {
  public:
 
    using return_type    = TReturn;
    using argument_types = etl::type_list<TArgs...>;
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 delegate() ETL_NOEXCEPT
    {
    }
 
    //*************************************************************************
    // Copy constructor.
    //*************************************************************************
    ETL_CONSTEXPR14 delegate(const delegate& other) = default;
 
    //*************************************************************************
    // Construct from lambda or functor.
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 delegate(TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    // Construct from const lambda or functor.
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 delegate(const TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), const_lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    // Delete construction from rvalue reference lambda or functor.
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !etl::is_same<etl::delegate<TReturn(TArgs...)>, TLambda>::value, void>>
    ETL_CONSTEXPR14 delegate(TLambda&& instance) = delete;
 
    //*************************************************************************
    //*************************************************************************
    template <TReturn(*Method)(TArgs...)>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(ETL_NULLPTR, function_stub<Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create(TLambda& instance) ETL_NOEXCEPT
    {
      return delegate((void*)(&instance), lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create(const TLambda& instance) ETL_NOEXCEPT
    {
      return delegate((void*)(&instance), const_lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...)>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create(T& instance) ETL_NOEXCEPT
    {
      return delegate((void*)(&instance), method_stub<T, Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...)>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create(T&& instance) = delete;
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...) const>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create(const T& instance) ETL_NOEXCEPT
    {
      return delegate((void*)(&instance), const_method_stub<T, Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...) const>
    static ETL_CONSTEXPR14 delegate create(T&& instance) = delete;
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, T& Instance, TReturn(T::*Method)(TArgs...)>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...), T& Instance>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, T const& Instance, TReturn(T::*Method)(TArgs...) const>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(const_method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...) const, T const& Instance>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(const_method_instance_stub<T, Method, Instance>);
    }
 
#if !(defined(ETL_COMPILER_GCC) && (__GNUC__ <= 8))
    //*************************************************************************
    //*************************************************************************
    template <typename T, T& Instance>
    ETL_NODISCARD
    static ETL_CONSTEXPR14 delegate create() ETL_NOEXCEPT
    {
      return delegate(operator_instance_stub<T, Instance>);
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    template <TReturn(*Method)(TArgs...)>
    ETL_CONSTEXPR14 void set() ETL_NOEXCEPT
    {
      assign(ETL_NULLPTR, function_stub<Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 void set(TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 void set(const TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), const_lambda_stub<TLambda>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...)>
    ETL_CONSTEXPR14 void set(T& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), method_stub<T, Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...) const>
    ETL_CONSTEXPR14 void set(T& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), const_method_stub<T, Method>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, T& Instance, TReturn(T::* Method)(TArgs...)>
    ETL_CONSTEXPR14 void set() ETL_NOEXCEPT
    {
      assign(ETL_NULLPTR, method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...), T& Instance>
    ETL_CONSTEXPR14 void set() ETL_NOEXCEPT
    {
      assign(ETL_NULLPTR, method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, T const& Instance, TReturn(T::* Method)(TArgs...) const>
    ETL_CONSTEXPR14 void set() ETL_NOEXCEPT
    {
      assign(ETL_NULLPTR, const_method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::* Method)(TArgs...) const, T const& Instance>
    ETL_CONSTEXPR14 void set() ETL_NOEXCEPT
    {
      assign(ETL_NULLPTR, const_method_instance_stub<T, Method, Instance>);
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 void clear() ETL_NOEXCEPT
    {
      invocation.clear();
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename... TCallArgs>
    ETL_CONSTEXPR14
    return_type operator()(TCallArgs&&... args) const
    {
      ETL_STATIC_ASSERT((sizeof...(TCallArgs) == sizeof...(TArgs)), "Incorrect number of parameters passed to delegate");
      ETL_STATIC_ASSERT((etl::type_lists_are_convertible<etl::type_list<TCallArgs&&...>, argument_types>::value), "Incompatible parameter types passed to delegate");
 
      ETL_ASSERT(is_valid(), ETL_ERROR(delegate_uninitialised));
 
      return (*invocation.stub)(invocation.object, etl::forward<TCallArgs>(args)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TRet = TReturn, typename... TCallArgs>
    ETL_CONSTEXPR14
    typename etl::enable_if_t<etl::is_same<TRet, void>::value, bool>
      call_if(TCallArgs&&... args) const
    {
      ETL_STATIC_ASSERT((sizeof...(TCallArgs) == sizeof...(TArgs)), "Incorrect number of parameters passed to delegate");
      ETL_STATIC_ASSERT((etl::type_lists_are_convertible<etl::type_list<TCallArgs&&...>, argument_types>::value), "Incompatible parameter types passed to delegate");
 
      if (is_valid())
      {
        (*invocation.stub)(invocation.object, etl::forward<TCallArgs>(args)...);
        return true;
      }
      else
      {
        return false;
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TRet = TReturn, typename... TCallArgs>
    ETL_CONSTEXPR14
    typename etl::enable_if_t<!etl::is_same<TRet, void>::value, etl::optional<TReturn>>
      call_if(TCallArgs&&... args) const
    {
      ETL_STATIC_ASSERT((sizeof...(TCallArgs) == sizeof...(TArgs)), "Incorrect number of parameters passed to delegate");
      ETL_STATIC_ASSERT((etl::type_lists_are_convertible<etl::type_list<TCallArgs&&...>, argument_types>::value), "Incompatible parameter types passed to delegate");
 
      etl::optional<TReturn> result;
 
      if (is_valid())
      {
        result = (*invocation.stub)(invocation.object, etl::forward<TCallArgs>(args)...);
      }
 
      return result;
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TAlternative, typename... TCallArgs>
    ETL_CONSTEXPR14 TReturn call_or(TAlternative&& alternative, TCallArgs&&... args) const
    {
      ETL_STATIC_ASSERT((sizeof...(TCallArgs) == sizeof...(TArgs)), "Incorrect number of parameters passed to delegate");
      ETL_STATIC_ASSERT((etl::type_lists_are_convertible<etl::type_list<TCallArgs&&...>, argument_types>::value), "Incompatible parameter types passed to delegate");
 
      if (is_valid())
      {
        return (*invocation.stub)(invocation.object, etl::forward<TCallArgs>(args)...);
      }
      else
      {
        return etl::forward<TAlternative>(alternative)(etl::forward<TCallArgs>(args)...);
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    template <TReturn(*Method)(TArgs...), typename... TCallArgs>
    ETL_CONSTEXPR14 TReturn call_or(TCallArgs&&... args) const
    {
      ETL_STATIC_ASSERT((sizeof...(TCallArgs) == sizeof...(TArgs)), "Incorrect number of parameters passed to delegate");
      ETL_STATIC_ASSERT((etl::type_lists_are_convertible<etl::type_list<TCallArgs&&...>, argument_types>::value), "Incompatible parameter types passed to delegate");
 
      if (is_valid())
      {
        return (*invocation.stub)(invocation.object, etl::forward<TCallArgs>(args)...);
      }
      else
      {
        return (Method)(etl::forward<TCallArgs>(args)...);
      }
    }
 
    //*************************************************************************
    //*************************************************************************
    delegate& operator =(const delegate& rhs) = default;
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 delegate& operator =(TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), lambda_stub<TLambda>);
      return *this;
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value && !is_delegate<TLambda>::value, void>>
    ETL_CONSTEXPR14 delegate& operator =(const TLambda& instance) ETL_NOEXCEPT
    {
      assign((void*)(&instance), const_lambda_stub<TLambda>);
      return *this;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14 bool operator == (const delegate& rhs) const ETL_NOEXCEPT
    {
      return invocation == rhs.invocation;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 bool operator != (const delegate& rhs) const ETL_NOEXCEPT
    {
      return invocation != rhs.invocation;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14 bool is_valid() const ETL_NOEXCEPT
    {
      return invocation.stub != ETL_NULLPTR;
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14 operator bool() const ETL_NOEXCEPT
    {
      return is_valid();
    }
 
  private:
 
    using stub_type = TReturn(*)(void* object, TArgs...);
 
    //*************************************************************************
    // Callable compatibility: detects if C (or const C) is invocable with (TArgs...) and returns a type
    // convertible to TReturn. Works with generic lambdas and functors.
    template <typename TCallableType, typename = void>
    struct is_invocable_with 
      : etl::false_type {};
 
    template <typename TCallableType>
    struct is_invocable_with<TCallableType, etl::void_t<decltype(etl::declval<TCallableType&>()(etl::declval<TArgs>()...))>>
      : etl::bool_constant<etl::is_convertible<decltype(etl::declval<TCallableType&>()(etl::declval<TArgs>()...)), TReturn>::value>
    {};
 
    template <typename TCallableType, typename = void>
    struct is_invocable_with_const : etl::false_type {};
 
    template <typename TCallableType>
    struct is_invocable_with_const<TCallableType, etl::void_t<decltype(etl::declval<const TCallableType&>()(etl::declval<TArgs>()...))>>
      : etl::bool_constant<etl::is_convertible<decltype(etl::declval<const TCallableType&>()(etl::declval<TArgs>()...)), TReturn>::value>
    {};
 
    template <typename TCallableType>
    struct is_compatible_callable
      : etl::bool_constant<is_invocable_with<TCallableType>::value || is_invocable_with_const<TCallableType>::value>
    {};
 
    //*************************************************************************
    //*************************************************************************
    struct invocation_element
    {
      invocation_element() = default;
 
      //***********************************************************************
      ETL_CONSTEXPR14 invocation_element(void* object_, stub_type stub_) ETL_NOEXCEPT
        : object(object_)
        , stub(stub_)
      {
      }
 
      //***********************************************************************
      ETL_CONSTEXPR14 bool operator ==(const invocation_element& rhs) const ETL_NOEXCEPT
      {
        return (rhs.stub == stub) && (rhs.object == object);
      }
 
      //***********************************************************************
      ETL_CONSTEXPR14 bool operator !=(const invocation_element& rhs) const ETL_NOEXCEPT
      {
        return (rhs.stub != stub) || (rhs.object != object);
      }
 
      //***********************************************************************
      ETL_CONSTEXPR14 void clear() ETL_NOEXCEPT
      {
        object = ETL_NULLPTR;
        stub   = ETL_NULLPTR;
      }
 
      //***********************************************************************
      void*     object = ETL_NULLPTR;
      stub_type stub   = ETL_NULLPTR;
    };
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 delegate(void* object, stub_type stub) ETL_NOEXCEPT
      : invocation(object, stub)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 delegate(stub_type stub) ETL_NOEXCEPT
      : invocation(ETL_NULLPTR, stub)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    ETL_CONSTEXPR14 void assign(void* object, stub_type stub) ETL_NOEXCEPT
    {
      invocation.object = object;
      invocation.stub   = stub;
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...)>
    static ETL_CONSTEXPR14 TReturn method_stub(void* object, TArgs... args)
    {
      T* p = static_cast<T*>(object);
      return (p->*Method)(etl::forward<TArgs>(args)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...) const>
    static ETL_CONSTEXPR14 TReturn const_method_stub(void* object, TArgs... args)
    {
      T* const p = static_cast<T*>(object);
      return (p->*Method)(etl::forward<TArgs>(args)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...), T& Instance>
    static ETL_CONSTEXPR14 TReturn method_instance_stub(void*, TArgs... args)
    {
      return (Instance.*Method)(etl::forward<TArgs>(args)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename T, TReturn(T::*Method)(TArgs...) const, const T& Instance>
    static ETL_CONSTEXPR14 TReturn const_method_instance_stub(void*, TArgs... args)
    {
      return (Instance.*Method)(etl::forward<TArgs>(args)...);
    }
 
#if !(defined(ETL_COMPILER_GCC) && (__GNUC__ <= 8))
    //*************************************************************************
    //*************************************************************************
    template <typename T, T& Instance>
    static ETL_CONSTEXPR14 TReturn operator_instance_stub(void*, TArgs... args)
    {
      return Instance.operator()(etl::forward<TArgs>(args)...);
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    template <TReturn(*Method)(TArgs...)>
    static ETL_CONSTEXPR14 TReturn function_stub(void*, TArgs... args)
    {
      return (Method)(etl::forward<TArgs>(args)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda>
    static ETL_CONSTEXPR14 TReturn lambda_stub(void* object, TArgs... arg)
    {
      ETL_STATIC_ASSERT(is_compatible_callable<TLambda>::value, "etl::delegate: bound lambda/functor is not compatible with the delegate signature");
      
      TLambda* p = static_cast<TLambda*>(object);
      return (p->operator())(etl::forward<TArgs>(arg)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    template <typename TLambda>
    static ETL_CONSTEXPR14 TReturn const_lambda_stub(void* object, TArgs... arg)
    {
      ETL_STATIC_ASSERT(is_compatible_callable<TLambda>::value, "etl::delegate: bound lambda/functor is not compatible with the delegate signature");
      
      const TLambda* p = static_cast<const TLambda*>(object);
      return (p->operator())(etl::forward<TArgs>(arg)...);
    }
 
    //*************************************************************************
    //*************************************************************************
    invocation_element invocation;
  };
 
#if ETL_USING_CPP17
  //*************************************************************************
  //*************************************************************************
  template <auto Function>
  ETL_NODISCARD
  constexpr auto make_delegate() ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(Function)>::function_type;
 
    return etl::delegate<function_type>::template create<Function>();
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename TLambda, typename = etl::enable_if_t<etl::is_class<TLambda>::value, void>>
  ETL_NODISCARD
  constexpr auto make_delegate(TLambda& instance) ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(&TLambda::operator())>::function_type;
 
    return etl::delegate<function_type>(instance);
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, T& Instance>
  ETL_NODISCARD
  constexpr auto make_delegate() ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(&T::operator())>::function_type;
 
    return etl::delegate<function_type>::template create<T, Instance>();
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, auto Method, T& Instance, typename = etl::enable_if_t<!etl::function_traits<decltype(Method)>::is_const>>
  ETL_NODISCARD
  constexpr auto make_delegate() ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(Method)>::function_type;
 
    return etl::delegate<function_type>::template create<T, Method, Instance>();
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, auto Method, const T& Instance, typename = etl::enable_if_t<etl::function_traits<decltype(Method)>::is_const>>
  ETL_NODISCARD
  constexpr auto make_delegate() ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(Method)>::function_type;
 
    return etl::delegate<function_type>::template create<T, Method, Instance>();
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, auto Method>
  ETL_NODISCARD
  constexpr auto make_delegate(T& instance) ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(Method)>::function_type;
 
    return etl::delegate<function_type>::template create<T, Method>(instance);
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename T, auto Method>
  ETL_NODISCARD
  constexpr auto make_delegate(const T& instance) ETL_NOEXCEPT
  {
    using function_type = typename etl::function_traits<decltype(Method)>::function_type;
 
    return etl::delegate<function_type>::template create<T, Method>(instance);
  }
#endif
}
 
#endif