etl/test/test_invoke.cpp

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com

Copyright(c) 2025 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
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******************************************************************************/

#include "unit_test_framework.h"

#include <string>
#include <type_traits>

#include "etl/invoke.h"
#include "etl/type_traits.h"

namespace
{
  //*************************************************************************
  // Callable subjects
  int free_add(int a, int b)
  {
    return a + b;
  }
  int free_noexcept(int v) noexcept
  {
    return v;
  }
  int free_throw(int v)
  {
    throw v;
    return v;
  }

  // C-style variadic function
  int varfn(int first, ...)
  {
    return first;
  }

  //*********************************************
  struct Base
  {
    int data;
    Base(int d = 10)
      : data(d)
    {
    }

    int add(int v)
    {
      return data + v;
    }
    int add_const(int v) const
    {
      return data + v + 1;
    }

    int ref_only(int v) &
    {
      return data + v + 2;
    }
    int rref_only(int v) &&
    {
      return data + v + 3;
    }

    static int static_function(int v)
    {
      return v + 1;
    }
    int noexcept_member(int v) noexcept
    {
      return data + v;
    }
  };

  //*********************************************
  struct Derived : Base
  {
    Derived(int d = 20)
      : Base(d)
    {
    }
  };

  //*********************************************
  struct VolatileBase
  {
    int x;
    VolatileBase(int v = 0)
      : x(v)
    {
    }
    int read() const volatile
    {
      return x;
    }
  };

  //*********************************************
  struct Functor
  {
    int x;
    explicit Functor(int x_)
      : x(x_)
    {
    }
    int operator()(int i)
    {
      return i + x;
    }
  };

  //*********************************************
  struct ConstFunctor
  {
    int x;
    explicit ConstFunctor(int x_)
      : x(x_)
    {
    }
    int operator()(int i) const
    {
      return i + x;
    }
  };

  //*********************************************
  struct OverloadedFunctor
  {
    int operator()(int i) &
    {
      return i + 1;
    }
    int operator()(int i) &&
    {
      return i + 2;
    }
  };

  //*********************************************
  struct MoveOnlyFunctor
  {
    MoveOnlyFunctor()                       = default;
    MoveOnlyFunctor(const MoveOnlyFunctor&) = delete;
    MoveOnlyFunctor(MoveOnlyFunctor&&)      = default;
    int operator()(int i)
    {
      return i + 1;
    }
  };

  //*********************************************
  struct NoThrowFunctor
  {
    int operator()(int i) const noexcept
    {
      return i + 2;
    }
  };

  //*********************************************
  struct ThrowingFunctor
  {
    int operator()(int)
    {
      throw 42;
    }
  };

  //*********************************************
  struct MemberObj
  {
    MemberObj(int v)
      : i(v)
    {
    }

    int i;
  };

  //*********************************************
  template <typename T>
  struct IntegralOnly
  {
    template <typename U, typename = typename etl::enable_if< etl::is_integral<U>::value>::type>
    int operator()(U u)
    {
      return static_cast<int>(u) + 1;
    }

    template < typename U, typename = typename etl::enable_if<!etl::is_integral<U>::value>::type, typename = void>
    int operator()(U) = delete;
  };

  //*********************************************
  // Non-capturing lambda (convertible to function pointer)
  static auto lambda_nc = [](int a, int b)
  {
    return a + b;
  };

#if ETL_USING_CPP14
  //*********************************************
  // Generic lambda (C++14+)
  static auto lambda_generic = [](auto x, auto y)
  {
    return x + y;
  };
#endif

  //*********************************************
  // Overload set (not directly a single callable type for traits)
  int overload(int i)
  {
    return i + 10;
  }
  long overload(long l)
  {
    return l + 20;
  }

  int takes_ptr(const int* p)
  {
    return *(p + 1);
  }

  //*********************************************
  struct Selective
  {
    template <typename T, etl::enable_if_t<etl::is_same<int, T>::value, int> = 0>
    int operator()(T)
    {
      return 1;
    }

    template <typename T, etl::enable_if_t<etl::is_same<char, T>::value, int> = 0>
    char operator()(T)
    {
      return 2;
    }

    template <typename T, etl::enable_if_t<!etl::is_integral<T>::value, int> = 0>
    int operator()(T) = delete;
  };
} // namespace

//*************************************************************************
// Unit tests for etl::is_invocable / etl::is_invocable_r
//*************************************************************************
SUITE(test_invoke)
{
  //*************************************************************************
  TEST(test_invoke_result)
  {
    int  capture_value = 5;
    auto lambda_cap    = [capture_value](int a)
    {
      return a + capture_value;
    };

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(free_add), int, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(free_noexcept), int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(free_throw), int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(varfn), int>, int>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Base::add), Base, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Base::add_const), Base, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Base::ref_only), Base&, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Base::rref_only), Base, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Base::noexcept_member), Base, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Base::static_function), int>, int>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&Derived::add), Derived, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Derived::add_const), Derived, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Derived::ref_only), Derived&, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Derived::rref_only), Derived, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Derived::noexcept_member), Derived, int>, int>::value));
    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&Derived::static_function), int>, int>::value));

    CHECK_TRUE((etl::is_same< etl::invoke_result_t<decltype(&VolatileBase::read), VolatileBase>, int>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<Functor, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<ConstFunctor, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<OverloadedFunctor&, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<OverloadedFunctor&&, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<MoveOnlyFunctor, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<NoThrowFunctor, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<ThrowingFunctor, int>, int>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(&MemberObj::i), MemberObj&>, int&>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<IntegralOnly<int>, int>, int>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(lambda_nc), int, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(lambda_cap), int>, int>::value));
#if ETL_USING_CPP14
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(lambda_generic), int, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(lambda_generic), long, short>, long>::value));
#endif

    int (*ov_int)(int) = &overload;
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(ov_int), int>, int>::value));

    long (*ov_long)(long) = &overload;
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(ov_long), long>, long>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<Selective, int>, int>::value));
    CHECK_TRUE((etl::is_same<etl::invoke_result_t<Selective, char>, char>::value));

    CHECK_TRUE((etl::is_same<etl::invoke_result_t<decltype(takes_ptr), const int* >, int>::value));
  }

  //*************************************************************************
  TEST(test_free_function)
  {
    CHECK_EQUAL(3, etl::invoke(free_add, 1, 2));
  }

  //*************************************************************************
  TEST(test_free_function_pointer_variable)
  {
    int (*fp)(int, int) = &free_add;

    CHECK_EQUAL(3, etl::invoke(fp, 1, 2));
  }

  //*************************************************************************
  TEST(test_function_pointer_const_qualification)
  {
    int (*const cfp)(int, int) = &free_add;

    CHECK_EQUAL(3, etl::invoke(cfp, 1, 2));
  }

  //*************************************************************************
  TEST(test_free_function_noexcept)
  {
    CHECK_EQUAL(1, etl::invoke(free_noexcept, 1));
  }

  //*************************************************************************
  TEST(test_free_function_throw)
  {
    CHECK_THROW(etl::invoke(free_throw, 1), int);
  }

  //*************************************************************************
  TEST(test_static_member_function)
  {
    CHECK_EQUAL(2, etl::invoke(&Base::static_function, 1));
  }

  //*************************************************************************
  TEST(test_member_function)
  {
    Base       base(10);
    const Base const_base(20);

    Base*       p_base       = &base;
    const Base* p_const_base = &const_base;

    CHECK_EQUAL(11, etl::invoke(&Base::add, base, 1));
    CHECK_EQUAL(12, etl::invoke(&Base::add, p_base, 2));
    CHECK_EQUAL(14, etl::invoke(&Base::add_const, base, 3));
    CHECK_EQUAL(15, etl::invoke(&Base::add_const, p_base, 4));
    CHECK_EQUAL(26, etl::invoke(&Base::add_const, const_base, 5));
    CHECK_EQUAL(27, etl::invoke(&Base::add_const, p_const_base, 6));
  }

  //*************************************************************************
  TEST(test_member_function_noexcept)
  {
    Base base(10);

    CHECK_EQUAL(11, etl::invoke(&Base::noexcept_member, base, 1));
  }

  //*************************************************************************
  TEST(test_member_functions_ref_qualification)
  {
    Base  base(10);
    Base& base_ref = base;

    Base&& base_rref = Base(10);

    CHECK_EQUAL(13, etl::invoke(&Base::ref_only, base_ref, 1));
    CHECK_EQUAL(15, etl::invoke(&Base::rref_only, std::move(base_rref), 2));
  }

  //*************************************************************************
  TEST(test_inheritance_member_function)
  {
    Derived  derived(10);
    Derived* p_derived = &derived;

    CHECK_EQUAL(11, etl::invoke(&Base::add, derived, 1));
    CHECK_EQUAL(12, etl::invoke(&Base::add, p_derived, 2));
  }

  //*************************************************************************
  TEST(test_member_function_volatile)
  {
    VolatileBase volatile_base(10);

    CHECK_EQUAL(10, etl::invoke(&VolatileBase::read, volatile_base));
  }

  //*************************************************************************
  TEST(test_member_object_pointer)
  {
    MemberObj obj(10);

    CHECK_EQUAL(10, etl::invoke(&MemberObj::i, obj));
    CHECK_EQUAL(20, etl::invoke(&MemberObj::i, obj) = 20);
  }

  //*************************************************************************
  TEST(test_functor_non_const)
  {
    Functor functor(10);

    CHECK_EQUAL(12, etl::invoke(functor, 2));
  }

  //*************************************************************************
  TEST(test_functor_const)
  {
    const ConstFunctor functor(10);

    CHECK_EQUAL(12, etl::invoke(functor, 2));
  }

  //*************************************************************************
  TEST(test_move_only_functor)
  {
    MoveOnlyFunctor functor;

    CHECK_EQUAL(11, etl::invoke(etl::move(functor), 10));
  }

  //*************************************************************************
  TEST(test_overloaded_functor_ref_qualifier)
  {
    OverloadedFunctor   functor;
    OverloadedFunctor&  functor_ref  = functor;
    OverloadedFunctor&& functor_rref = OverloadedFunctor();

    CHECK_EQUAL(11, etl::invoke(functor_ref, 10));
    CHECK_EQUAL(12, etl::invoke(etl::move(functor_rref), 10));
  }

  //*************************************************************************
  TEST(test_nothrow_and_throwing_functors)
  {
    NoThrowFunctor  nothrow_functor;
    ThrowingFunctor throwing_functor;

    CHECK_EQUAL(12, etl::invoke(nothrow_functor, 10));
    CHECK_THROW(etl::invoke(throwing_functor, 10), int);
  }

  //*************************************************************************
  TEST(test_lambda_non_capturing)
  {
    CHECK_EQUAL(3, etl::invoke(lambda_nc, 1, 2));
  }

  //*************************************************************************
  TEST(test_lambda_capturing)
  {
    int  capture_value = 5;
    auto lambda_cap    = [capture_value](int a)
    {
      return a + capture_value;
    };

    CHECK_EQUAL(6, etl::invoke(lambda_cap, 1));
  }

#if ETL_USING_CPP14
  //*************************************************************************
  TEST(test_lambda_generic)
  {
    CHECK_EQUAL(3, etl::invoke(lambda_generic, 1, 2));
    CHECK_EQUAL(3L, etl::invoke(lambda_generic, 1L, 2L));
    CHECK_CLOSE(3.5, etl::invoke(lambda_generic, 1.5, 2.0), 0.001);
  }
#endif

  //*************************************************************************
  TEST(test_template_functor_integral_only)
  {
    CHECK_EQUAL(2, etl::invoke(IntegralOnly<int>(), 1));
  }

  //*************************************************************************
  TEST(test_additional_user_defined_conversion)
  {
    struct Converter
    {
      operator int() const
      {
        return 11;
      }
    };

    CHECK_EQUAL(22, etl::invoke(free_add, Converter(), 11)); // Converter -> int
  }

  //*************************************************************************
  TEST(test_overload_set)
  {
    // Selecting explicit overload
    int (*ov_i)(int)   = &overload;
    long (*ov_l)(long) = &overload;

    CHECK_EQUAL(11, etl::invoke(ov_i, 1));
    CHECK_EQUAL(21L, etl::invoke(ov_l, 1L));
  }

  //*************************************************************************
  TEST(test_deleted_overload)
  {
    struct DeletedOverload
    {
      int operator()(double d)
      {
        return static_cast<int>(2 * d);
      }
      int operator()(int) = delete;
    };

    CHECK_CLOSE(6, etl::invoke(DeletedOverload(), 3.14), 0.001);
  }

  //*************************************************************************
  TEST(test_variadic_free_function)
  {
    CHECK_EQUAL(1, etl::invoke(varfn, 1));
    CHECK_EQUAL(2, etl::invoke(varfn, 2, 3.14, "test"));
  }

  //*************************************************************************
  TEST(test_array_decay_argument)
  {
    int arr[] = {1, 2, 3};

    CHECK_EQUAL(2, etl::invoke(takes_ptr, arr));
  }

  //*************************************************************************
  TEST(test_template_functor_multiple_enable_if)
  {
    CHECK_EQUAL(1, etl::invoke(Selective(), int(0)));
    CHECK_EQUAL(2, etl::invoke(Selective(), char(0)));
  }

  //*************************************************************************
  TEST(test_rvalue_ref_member_on_temporary)
  {
    struct RR
    {
      int f() &&
      {
        return 1;
      }
      int g() &
      {
        return 2;
      }
    };

    RR rr;

    CHECK_EQUAL(1, etl::invoke(&RR::f, etl::move(rr)));
    CHECK_EQUAL(2, etl::invoke(&RR::g, rr));
  }

  //*************************************************************************
  // Tests for reference_wrapper as callable (first argument)
  //*************************************************************************

  //*************************************************************************
  TEST(test_reference_wrapper_free_function)
  {
    // reference_wrapper wrapping a function (decays to function pointer)
    auto ref_fn = etl::ref(free_add);

    CHECK_EQUAL(3, etl::invoke(ref_fn, 1, 2));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_functor)
  {
    Functor functor(10);
    auto    ref_functor = etl::ref(functor);

    CHECK_EQUAL(12, etl::invoke(ref_functor, 2));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_const_functor)
  {
    const ConstFunctor functor(10);
    auto               ref_functor = etl::cref(functor);

    CHECK_EQUAL(12, etl::invoke(ref_functor, 2));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_lambda)
  {
    int  capture_value = 5;
    auto lambda        = [capture_value](int a)
    {
      return a + capture_value;
    };
    auto ref_lambda = etl::ref(lambda);

    CHECK_EQUAL(6, etl::invoke(ref_lambda, 1));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_nothrow_functor)
  {
    NoThrowFunctor nothrow_functor;
    auto           ref_functor = etl::ref(nothrow_functor);

    CHECK_EQUAL(12, etl::invoke(ref_functor, 10));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_throwing_functor)
  {
    ThrowingFunctor throwing_functor;
    auto            ref_functor = etl::ref(throwing_functor);

    CHECK_THROW(etl::invoke(ref_functor, 10), int);
  }

  //*************************************************************************
  TEST(test_reference_wrapper_member_function_pointer)
  {
    // reference_wrapper wrapping a pointer-to-member-function
    auto pmf     = &Base::add;
    auto ref_pmf = etl::ref(pmf);

    Base base(10);

    CHECK_EQUAL(11, etl::invoke(ref_pmf, base, 1));
    CHECK_EQUAL(12, etl::invoke(ref_pmf, &base, 2));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_const_member_function_pointer)
  {
    auto pmf     = &Base::add_const;
    auto ref_pmf = etl::ref(pmf);

    const Base const_base(20);

    CHECK_EQUAL(24, etl::invoke(ref_pmf, const_base, 3));
    CHECK_EQUAL(25, etl::invoke(ref_pmf, &const_base, 4));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_member_object_pointer)
  {
    // reference_wrapper wrapping a pointer-to-member-data
    auto pmd     = &MemberObj::i;
    auto ref_pmd = etl::ref(pmd);

    MemberObj obj(42);

    CHECK_EQUAL(42, etl::invoke(ref_pmd, obj));
    CHECK_EQUAL(42, etl::invoke(ref_pmd, &obj));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_derived_member_function)
  {
    // reference_wrapper wrapping member pointer, invoked on derived class
    auto pmf     = &Base::add;
    auto ref_pmf = etl::ref(pmf);

    Derived derived(10);

    CHECK_EQUAL(11, etl::invoke(ref_pmf, derived, 1));
    CHECK_EQUAL(12, etl::invoke(ref_pmf, &derived, 2));
  }

#if ETL_USING_CPP14
  //*************************************************************************
  TEST(test_reference_wrapper_identity)
  {
    // This is the case that triggered the original compile error:
    // reference_wrapper<etl::identity> as a callable
    etl::identity id;
    auto          ref_id = etl::ref(id);

    CHECK_EQUAL(42, etl::invoke(ref_id, 42));
    CHECK_EQUAL(7, etl::invoke(ref_id, 7));
  }
#endif

  //*************************************************************************
  TEST(test_reference_wrapper_with_reference_wrapper_arg)
  {
    // reference_wrapper as both callable and second argument (member pointer
    // case)
    auto pmf     = &Base::add;
    auto ref_pmf = etl::ref(pmf);

    Base base(10);
    auto ref_base = etl::ref(base);

    CHECK_EQUAL(11, etl::invoke(ref_pmf, ref_base, 1));
  }

  //*************************************************************************
  TEST(test_reference_wrapper_member_object_with_reference_wrapper_arg)
  {
    auto pmd     = &MemberObj::i;
    auto ref_pmd = etl::ref(pmd);

    MemberObj obj(99);
    auto      ref_obj = etl::ref(obj);

    CHECK_EQUAL(99, etl::invoke(ref_pmd, ref_obj));
  }
}