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
 
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of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
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copies or substantial portions of the Software.
 
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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