Language: C++

#include <iostream>
using namespace std;

class angle{
  private:
  	bool hasval;
  	int16_t maxCtn;
  	int16_t val = 1;
  public:
  	inline angle(bool hasval,int16_t maxCtn,int16_t val){setAngle(hasval,maxCtn,val);}
  	
  	
  	inline explicit operator bool() const(return angle->hasval);
  	inline explicit operator int16_t() const(return angle->val);
  	
  	inline void setAngle(bool hasval, int16_t maxCtn, int16_t val) {
			this->hasval = hasval;
      		this->maxCtn = maxCtn;
			this->val = hasval ? val : 1;
	}
  
  	inline angle& operator+=(int16_t b){
      (*this) = angle(bool(*this),*this->maxCtn, (int16_t(*this) + b) %= maxCtn);
    }
}
inline const angle operator+(const angle& a,int16_t b){return angle(a)+=b}

//inline const angle operator+(const angle& a, const angle& b) { return angle(a) += b; }

int main(){
  angle a(true,12,1);
  a + 1;
  cout << int16_t(a) << endl;
  
}

Compiler output:
a.cc:13:47: error: expected identifier before 'return'
   13 |         inline explicit operator bool() const(return angle->hasval);
      |                                               ^~~~~~
a.cc:13:47: error: expected ',' or '...' before 'return'
a.cc:13:67: error: '<invalid operator>' declared as function returning a function
   13 |         inline explicit operator bool() const(return angle->hasval);
      |                                                                   ^
a.cc:14:50: error: expected identifier before 'return'
   14 |         inline explicit operator int16_t() const(return angle->val);
      |                                                  ^~~~~~
a.cc:14:50: error: expected ',' or '...' before 'return'
a.cc:14:67: error: '<invalid operator>' declared as function returning a function
   14 |         inline explicit operator int16_t() const(return angle->val);
      |                                                                   ^
a.cc: In member function 'angle& angle::operator+=(int16_t)':
a.cc:23:23: error: invalid cast from type 'angle' to type 'bool'
   23 |       (*this) = angle(bool(*this),*this->maxCtn, (int16_t(*this) + b) %= maxCtn);
      |                       ^~~~~~~~~~~
a.cc:23:35: error: invalid type argument of unary '*' (have 'int16_t' {aka 'short int'})
   23 |       (*this) = angle(bool(*this),*this->maxCtn, (int16_t(*this) + b) %= maxCtn);
      |                                   ^~~~~~~~~~~~~
a.cc:23:51: error: invalid cast from type 'angle' to type 'int16_t' {aka 'short int'}
   23 |       (*this) = angle(bool(*this),*this->maxCtn, (int16_t(*this) + b) %= maxCtn);
      |                                                   ^~~~~~~~~~~~~~
a.cc:24:5: warning: no return statement in function returning non-void [-Wreturn-type]
   24 |     }
      |     ^
      |     return *this;
a.cc: At global scope:
a.cc:26:20: error: expected initializer before 'operator'
   26 | inline const angle operator+(const angle& a,int16_t b){return angle(a)+=b}
      |                    ^~~~~~~~
a.cc: In function 'int main()':
a.cc:32:5: error: no match for 'operator+' (operand types are 'angle' and 'int')
   32 |   a + 1;
      |   ~ ^ ~
      |   |   |
      |   |   int
      |   angle
In file included from /usr/include/c++/14/string:48,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'int'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'int'
   32 |   a + 1;
      |       ^
In file included from /usr/include/c++/14/string:54:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'const _CharT*' and 'angle'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   'angle' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'const _CharT*' and 'angle'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:32:7: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
   32 |   a + 1;
      |       ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deductio