shared_ptr Derived types cannot be implicitly cast to the share_ptr Base types with gsl::not_null #1187
Description
Describe the bug
When I try to change function A to return a gsl::not_null<std::shared_ptr> instead of std::shared_ptr, it causes problems in function B that returns the result of function A as a std::shared_ptr
To Reproduce
#include <gsl>
#include <memory>
class Base
{
};
class Derived : public Base
{
};
gsl::not_null<std::shared_ptr<Derived>> A()
{
return std::make_shared<Derived>();
}
std::shared_ptr<Base> B()
{
// this fails to compile after the result of A was changed to a not_null
return A();
}
// your repro here: ...Expected behavior
I expect the code above to compile and work exactly the same with or without the gsl::not_null
Spec (please complete the following information):
- OS: Windows
Microsoft (R) C/C++ Optimizing Compiler Version 19.28.29335 for x64
All C++ versions
Additional context
Changing the implicit conversion operator:
constexpr operator T() const { return get(); }To a templatized version seems to fix this issue:
template <typename RESULT_TYPE,
typename = std::enable_if_t<
std::is_convertible<T, RESULT_TYPE>::value>>
operator RESULT_TYPE() const
{
return get();
}