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

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#include "unit_test_framework.h"

#include <type_traits>
#include <string>

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

//*************************************************************************
// 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));
  }
}