STYLE: Remove 6 no-op dynamic_casts (casting T* to T*) from Modules/Core

[N-Dekker]

Removed six "no-op" dynamic_casts that just cast pointers to their own compile-time type from Modules/Core.

[dzenanz]

How did you identify these instances?

[N-Dekker]

How did you identify these instances?

@dzenanz Thanks for asking! And thanks to you both for approving the pull request! We're hunting dynamic_casts as they do occasionally appear to cause troubles (segfaults) for ITKElastix on MacOS. I found these particular "no-op" cases by doing a #define dynamic_cast MyDynamicCast, with the following definition of MyDynamicCast:

#include <type_traits>

template<class TPointer, class U>
TPointer
MyDynamicCast(U* source)
{
  using T = typename std::remove_pointer<TPointer>::type;
  static_assert(!std::is_same<typename std::remove_cv<T>::type, typename std::remove_cv<U>::type>::value,
      "no-op dynamic_cast<T*>!");
  return dynamic_cast<T*>(source);
}

template <class T, class U>
T &
MyDynamicCast(U& source)
{
  static_assert(!std::is_same<typename std::remove_cv<T>::type, typename std::remove_cv<U>::type>::value,
      "no-op dynamic_cast<T&>!");
  return dynamic_cast<T &>(source);
}

This redefinition of dynamic_cast triggers a compilation error whenever trying to cast to its own compile-time type. Disclaimer: #define dynamic_cast is non-Standard, as far as I know. So it could do anything. 😸

I must say I'm not against all uses of dynamic_cast, but in cases where they can be avoided easily, I would rather have them removed.