test/SemaCXX/conversion-function.cpp

// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected                -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected                -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx98_11,cxx11 -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify=expected,cxx98_11,cxx98 -triple %itanium_abi_triple -Wbind-to-temporary-copy %s

class X {
public:
  operator bool();
  operator int() const;

  bool f() {
    return operator bool();
  }

  float g() {
    return operator float(); // expected-error{{use of undeclared 'operator float'}}
  }

  static operator short(); // expected-error{{conversion function must be a non-static member function}}
};

operator int(); // expected-error{{conversion function must be a non-static member function}}

operator int; // expected-error{{'operator int' cannot be the name of a variable or data member}}

typedef int func_type(int);
typedef int array_type[10];

class Y {
public:
  void operator bool(int, ...) const; // expected-error{{conversion function cannot have a return type}} \
  // expected-error{{conversion function cannot have any parameters}}

  operator bool(int a = 4, int b = 6) const; // expected-error{{conversion function cannot have any parameters}}


  operator float(...) const;  // expected-error{{conversion function cannot be variadic}}


  operator func_type(); // expected-error{{conversion function cannot convert to a function type}}
  operator array_type(); // expected-error{{conversion function cannot convert to an array type}}
};


typedef int INT;
typedef INT* INT_PTR;

class Z {
  operator int(); // expected-note {{previous declaration is here}}
  operator int**(); // expected-note {{previous declaration is here}}

  operator INT();  // expected-error{{conversion function cannot be redeclared}}
  operator INT_PTR*(); // expected-error{{conversion function cannot be redeclared}}
};


class A { };

class B : public A {
public:
  operator A&() const; // expected-warning{{conversion function converting 'B' to its base class 'A' will never be used}}
  operator const void() const; // expected-warning{{conversion function converting 'B' to 'const void' will never be used}}
  operator const B(); // expected-warning{{conversion function converting 'B' to itself will never be used}}
};

class BaseA {};
class DerivedA;

class BaseB {
  virtual operator BaseA &() = 0;
  virtual operator DerivedA &() = 0;
};

class DerivedA : public BaseA, BaseB {
  virtual operator BaseA &();    // OK. Overrides BaseB::operatorBaseA&()
  virtual operator DerivedA &(); // OK. Overrides BaseB::operatorDerivedA&()
};

class DerivedB : public BaseA {
  virtual operator DerivedB &(); // expected-warning{{conversion function converting 'DerivedB' to itself will never be used}}
  virtual operator BaseA &();    // expected-warning{{conversion function converting 'DerivedB' to its base class 'BaseA' will never be used}}
};

// This used to crash Clang.
struct Flip;
struct Flop {
  Flop();
  Flop(const Flip&); // expected-note{{candidate constructor}}
};
struct Flip {
  operator Flop() const; // expected-note{{candidate function}}
};
Flop flop = Flip(); // expected-error {{conversion from 'Flip' to 'Flop' is ambiguous}}

// This tests that we don't add the second conversion declaration to the list of user conversions
struct C {
  operator const char *() const;
};

C::operator const char*() const { return 0; }

void f(const C& c) {
  const char* v = c;
}

// Test. Conversion in base class is visible in derived class.
class XB {
public:
  operator int(); // expected-note {{candidate function}}
};

class Yb : public XB {
public:
  operator char(); // expected-note {{candidate function}}
};

void f(Yb& a) {
  if (a) { } // expected-error {{conversion from 'Yb' to 'bool' is ambiguous}}
  int i = a; // OK. calls XB::operator int();
  char ch = a;  // OK. calls Yb::operator char();
}

// Test conversion + copy construction. This is a pure C++98 test.
// However we may extend implicit moves into C++98, we must make sure the
// result here is not changed.
class AutoPtrRef { };

class AutoPtr {
  AutoPtr(AutoPtr &); // cxx98-note {{declared private here}}

public:
  AutoPtr();
  AutoPtr(AutoPtrRef);

  operator AutoPtrRef();
};

AutoPtr make_auto_ptr();

AutoPtr test_auto_ptr(bool Cond) {
  AutoPtr p1( make_auto_ptr() );

  AutoPtr p;
  if (Cond)
    return p; // cxx98-error {{calling a private constructor}}

  return AutoPtr();
}

struct A1 {
  A1(const char *);
  ~A1();

private:
  A1(const A1 &); // cxx98_11-note 2 {{declared private here}}
};

A1 f() {
  // FIXME: redundant diagnostics!
  return "Hello"; // cxx98_11-error {{calling a private constructor}}
  // cxx98-warning@-1 {{an accessible copy constructor}}
  // cxx11-warning@-2 {{copying parameter of type 'A1' when binding a reference to a temporary would invoke an inaccessible constructor in C++98}}
}

namespace source_locations {
  template<typename T>
  struct sneaky_int {
    typedef int type;
  };

  template<typename T, typename U>
  struct A { };

  template<typename T>
  struct A<T, T> : A<T, int> { };

  struct E {
    template<typename T>
    operator A<T, typename sneaky_int<T>::type>&() const; // expected-note{{candidate function}}
  };

  void f() {
    A<float, float> &af = E(); // expected-error{{no viable conversion}}
    A<float, int> &af2 = E();
    const A<float, int> &caf2 = E();
  }

  // Check
  template<typename T>
  struct E2 {
    operator T
    * // expected-error{{'operator type-parameter-0-0 *' declared as a pointer to a reference of type 'int &'}}
    () const;
  };

  E2<int&> e2i; // expected-note{{in instantiation}}
}

namespace crazy_declarators {
  struct A {
    (&operator bool())(); // expected-error {{use a typedef to declare a conversion to 'bool (&)()'}}
    *operator int();  // expected-error {{put the complete type after 'operator'}}
    // No suggestion of using a typedef here; that's not possible.
    template<typename T> (&operator T())();
#if __cplusplus <= 199711L
    // expected-error-re@-2 {{cannot specify any part of a return type in the declaration of a conversion function{{$}}}}
#else
    // expected-error-re@-4 {{cannot specify any part of a return type in the declaration of a conversion function; use an alias template to declare a conversion to 'T (&)()'{{$}}}}
#endif

  };
}

namespace smart_ptr {
  class Y {
    class YRef { };

    Y(Y&);

  public:
    Y();
    Y(YRef);

    operator YRef(); // expected-note{{candidate function}}
  };

  struct X { // expected-note{{candidate constructor (the implicit copy constructor) not}}
#if __cplusplus >= 201103L
  // expected-note@-2 {{candidate constructor (the implicit move constructor) not}}
#endif

    explicit X(Y); // expected-note {{not a candidate}}
  };

  Y make_Y();

  X f() {
    X x = make_Y(); // expected-error{{no viable conversion from 'Y' to 'X'}}
    X x2(make_Y());
    return X(Y());
  }
}

struct Any {
  Any(...);
};

struct Other {
  Other(const Other &);
  Other();
};

void test_any() {
  Any any = Other();
#if __cplusplus <= 199711L
  // expected-error@-2 {{cannot pass object of non-POD type 'Other' through variadic constructor; call will abort at runtime}}
#else
  // expected-error@-4 {{cannot pass object of non-trivial type 'Other' through variadic constructor; call will abort at runtime}}
#endif
}

namespace PR7055 {
  // Make sure that we don't allow too many conversions in an
  // auto_ptr-like template. In particular, we can't create multiple
  // temporary objects when binding to a reference.
  struct auto_ptr {
    struct auto_ptr_ref { };

    auto_ptr(auto_ptr&);
    auto_ptr(auto_ptr_ref);
    explicit auto_ptr(int *);

    operator auto_ptr_ref();
  };

  struct X {
    X(auto_ptr);
  };

  X f() {
    X x(auto_ptr(new int));
    return X(auto_ptr(new int));
  }

  auto_ptr foo();

  X e(foo());

  struct Y {
    Y(X);
  };

  Y f2(foo());
}

namespace PR7934 {
  typedef unsigned char uint8;

  struct MutablePtr {
    MutablePtr() : ptr(0) {}
    void *ptr;

    operator void*() { return ptr; }

  private:
    operator uint8*() { return reinterpret_cast<uint8*>(ptr); }
    operator const char*() const { return reinterpret_cast<const char*>(ptr); }
  };

  void fake_memcpy(const void *);

  void use() {
    MutablePtr ptr;
    fake_memcpy(ptr);
  }
}

namespace rdar8018274 {
  struct X { };
  struct Y {
    operator const struct X *() const;
  };

  struct Z : Y {
    operator struct X * ();
  };

  void test() {
    Z x;
    (void) (x != __null);
  }


  struct Base {
    operator int();
  };

  struct Derived1 : Base { };

  struct Derived2 : Base { };

  struct SuperDerived : Derived1, Derived2 {
    using Derived1::operator int;
  };

  struct UeberDerived : SuperDerived {
    operator long();
  };

  void test2(UeberDerived ud) {
    int i = ud; // expected-error{{ambiguous conversion from derived class 'UeberDerived' to base class 'rdar8018274::Base'}}
  }

  struct Base2 {
    operator int();
  };

  struct Base3 {
    operator int();
  };

  struct Derived23 : Base2, Base3 {
    using Base2::operator int;
  };

  struct ExtraDerived23 : Derived23 { };

  void test3(ExtraDerived23 ed) {
    int i = ed;
  }
}

namespace PR8065 {
  template <typename T> struct Iterator;
  template <typename T> struct Container;

  template<>
  struct Iterator<int> {
    typedef Container<int> container_type;
  };

  template <typename T>
  struct Container {
    typedef typename Iterator<T>::container_type X;
    operator X(void) { return X(); }
  };

  Container<int> test;
}

namespace PR8034 {
  struct C {
    operator int();

  private:
    template <typename T> operator T();
  };
  int x = C().operator int();
}

namespace PR9336 {
  template<class T>
  struct generic_list
  {
    template<class Container>
    operator Container()
    {
      Container ar;
      T* i;
      ar[0]=*i;
      return ar;
    }
  };

  template<class T>
  struct array
  {
    T& operator[](int);
    const T& operator[](int)const;
  };

  generic_list<generic_list<int> > l;
  array<array<int> > a = l;
}

namespace PR8800 {
  struct A;
  struct C {
    operator A&();
  };
  void f() {
    C c;
    A& a1(c);
    A& a2 = c;
    A& a3 = static_cast<A&>(c);
    A& a4 = (A&)c;
  }
}

namespace PR12712 {
  struct A {};
  struct B {
    operator A();
    operator A() const;
  };
  struct C : B {};

  A f(const C c) { return c; }
}

namespace PR18234 {
  struct A {
    operator enum E { e } (); // expected-error {{'PR18234::A::E' cannot be defined in a type specifier}}
    operator struct S { int n; } (); // expected-error {{'PR18234::A::S' cannot be defined in a type specifier}}
    // expected-note@-1 {{candidate constructor (the implicit copy constructor) not viable: no known conversion from 'struct A' to 'const S &' for 1st argument}}
#if __cplusplus >= 201103L
  // expected-note@-3 {{candidate constructor (the implicit move constructor) not viable: no known conversion from 'struct A' to 'S &&' for 1st argument}}
#endif
  } a;
  A::S s = a; // expected-error {{no viable conversion from 'struct A' to 'A::S'}}
  A::E e = a;
  bool k1 = e == A::e; // expected-error {{no member named 'e'}}
  bool k2 = e.n == 0;
}

namespace PR30595 {
struct S {
  const operator int(); // expected-error {{cannot specify any part of a return type in the declaration of a conversion function; put the complete type after 'operator'}}
  const operator int() const; // expected-error {{cannot specify any part of a return type}}
  volatile const operator int(); // expected-error {{cannot specify any part of a return type}}

  operator const int() const;
};
}

#if __cplusplus >= 201103L
namespace dependent_conversion_function_id_lookup {
namespace gh77583 {
struct A1 {
  operator int();
};
template<class T> struct C {
  template <typename U> using Lookup = decltype(T{}.operator U());
};
C<A1> v{};
}
template<typename T> struct A2 {
  operator T();
};
template<typename T> struct B : A2<T> {
  template<typename U> using Lookup = decltype(&B::operator U);
};
using Result = B<int>::Lookup<int>;
using Result = int (A2<int>::*)();
}
#endif

namespace GH121706 {
struct S {
  *operator int();   // expected-error {{cannot specify any part of a return type in the declaration of a conversion function; put the complete type after 'operator'}}
  **operator char(); // expected-error {{cannot specify any part of a return type in the declaration of a conversion function; put the complete type after 'operator'}}
};
}