llvm-project/clang/test/SemaCXX/virtual-override.cpp

// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++0x
namespace T1 {

class A {
  virtual int f(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual void f(); // expected-error{{virtual function 'f' has a different return type ('void') than the function it overrides (which has return type 'int')}}
};

}

namespace T2 {

struct a { };
struct b { };
  
class A {
  virtual a* f(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual b* f(); // expected-error{{return type of virtual function 'f' is not covariant with the return type of the function it overrides ('T2::b *' is not derived from 'T2::a *')}}
};

}

namespace T3 {

struct a { };
struct b : private a { }; // expected-note{{declared private here}}
  
class A {
  virtual a* f(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual b* f(); // expected-error{{invalid covariant return for virtual function: 'T3::a' is a private base class of 'T3::b'}}
};

}

namespace T4 {

struct a { };
struct a1 : a { };
struct b : a, a1 { };
  
class A {
  virtual a* f(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual b* f(); // expected-error{{return type of virtual function 'f' is not covariant with the return type of the function it overrides (ambiguous conversion from derived class 'T4::b' to base class 'T4::a':\n\
    struct T4::b -> struct T4::a\n\
    struct T4::b -> struct T4::a1 -> struct T4::a)}}
};

}

namespace T5 {
  
struct a { };

class A {
  virtual a* const f(); 
  virtual a* const g(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual a* const f(); 
  virtual a* g(); // expected-error{{return type of virtual function 'g' is not covariant with the return type of the function it overrides ('T5::a *' has different qualifiers than 'T5::a *const')}}
};

}

namespace T6 {
  
struct a { };

class A {
  virtual const a* f(); 
  virtual a* g(); // expected-note{{overridden virtual function is here}}
};

class B : A {
  virtual a* f(); 
  virtual const a* g(); // expected-error{{return type of virtual function 'g' is not covariant with the return type of the function it overrides (class type 'const T6::a *' is more qualified than class type 'T6::a *'}}
};

}

namespace T7 {
  struct a { };
  struct b { };

  class A {
    a* f();
  };

  class B : A {
    virtual b* f();
  };
}

namespace T8 {
  struct a { };
  struct b; // expected-note {{forward declaration of 'T8::b'}}
  
  class A {
    virtual a *f();
  };
  
  class B : A {
    b* f(); // expected-error {{return type of virtual function 'f' is not covariant with the return type of the function it overrides ('T8::b' is incomplete)}}
  };
}

namespace T9 {
  struct a { };
  
  template<typename T> struct b : a {
    int a[sizeof(T) ? -1 : -1]; // expected-error {{array with a negative size}}
  };
  
  class A {
    virtual a *f();
  };
  
  class B : A {
    virtual b<int> *f(); // expected-note {{in instantiation of template class 'T9::b<int>' requested here}}
  };
}

// PR5656
class X0 {
  virtual void f0();
};
class X1 : public X0 {
  void f0() = 0;
};

template <typename Base>
struct Foo : Base { 
  void f(int) = 0; // expected-error{{not virtual and cannot be declared pure}}
};

struct Base1 { virtual void f(int); };
struct Base2 { };

void test() {
  (void)sizeof(Foo<Base1>);
  (void)sizeof(Foo<Base2>); // expected-note{{instantiation}}
}

template<typename Base>
struct Foo2 : Base {
  template<typename T> int f(T);
};

void test2() {
  Foo2<Base1> f1;
  Foo2<Base2> f2;
  f1.f(17);
  f2.f(17);
};

struct Foo3 {
  virtual void f(int) = 0; // expected-note{{pure virtual function}}
};

template<typename T>
struct Bar3 : Foo3 {
  void f(T);
};

void test3() {
  Bar3<int> b3i; // okay
  Bar3<float> b3f; // expected-error{{is an abstract class}}
}

// 5920
namespace PR5920 {
  class Base {};

  template <typename T>
  class Derived : public Base {};

  class Foo {
   public:
    virtual Base* Method();
  };

  class Bar : public Foo {
   public:
    virtual Derived<int>* Method();
  };
}

// Look through template types and typedefs to see whether return types are
// pointers or references.
namespace PR6110 {
  class Base {};
  class Derived : public Base {};

  typedef Base* BaseP;
  typedef Derived* DerivedP;

  class X { virtual BaseP f(); };
  class X1 : public X { virtual DerivedP f(); };

  template <typename T> class Y { virtual T f(); };
  template <typename T1, typename T> class Y1 : public Y<T> { virtual T1 f(); };
  Y1<Derived*, Base*> y;
}

// Defer checking for covariance if either return type is dependent.
namespace type_dependent_covariance {
  struct B {};
  template <int N> struct TD : public B {};
  template <> struct TD<1> {};

  template <int N> struct TB {};
  struct D : public TB<0> {};

  template <int N> struct X {
    virtual B* f1(); // expected-note{{overridden virtual function is here}}
    virtual TB<N>* f2(); // expected-note{{overridden virtual function is here}}
  };
  template <int N, int M> struct X1 : X<N> {
    virtual TD<M>* f1(); // expected-error{{return type of virtual function 'f1' is not covariant with the return type of the function it overrides ('TD<1> *'}}
    virtual D* f2(); // expected-error{{return type of virtual function 'f2' is not covariant with the return type of the function it overrides ('type_dependent_covariance::D *' is not derived from 'TB<1> *')}}
  };

  X1<0, 0> good;
  X1<0, 1> bad_derived; // expected-note{{instantiation}}
  X1<1, 0> bad_base; // expected-note{{instantiation}}
}

namespace T10 {
  struct A { };
  struct B : A { };

  struct C { 
    virtual A&& f();
  };

  struct D : C {
    virtual B&& f();
  };
};

namespace T11 {
  struct A { };
  struct B : A { };

  struct C { 
    virtual A& f(); // expected-note {{overridden virtual function is here}}
  };

  struct D : C {
    virtual B&& f(); // expected-error {{virtual function 'f' has a different return type ('T11::B &&') than the function it overrides (which has return type 'T11::A &')}}
  };
};

namespace T12 {
  struct A { };
  struct B : A { };

  struct C { 
    virtual A&& f(); // expected-note {{overridden virtual function is here}}
  };

  struct D : C {
    virtual B& f(); // expected-error {{virtual function 'f' has a different return type ('T12::B &') than the function it overrides (which has return type 'T12::A &&')}}
  };
};

namespace PR8168 {
  class A {
  public:
    virtual void foo() {} // expected-note{{overridden virtual function is here}}
  };

  class B : public A {
  public:
    static void foo() {} // expected-error{{'static' member function 'foo' overrides a virtual function}}
  };
}