Adds missing subscript operator to ArrayIteratorBase

[kennyweiss]

Summary

• This PR is a bugfix
• It adds a missing subscript operator to core's ArrayIteratorBase, which is necessary to satisfy the random access iterator contract
  • This missing function was responsible for the error triggered in a clang-22 build on Mac (Build with clang-22 #1961) due to an apparent library change from a dereference to a subscript operator in the implementation of std::__sift_down, called by std::sort
  • Note: I don't have access to the environment from Build with clang-22 #1961, but the new tests trigger an error for the missing operator[] without the changes to ArrayIteratorBase and are resolved with this fix
• Fixes Build with clang-22 #1961

[kennyweiss]

This is the bugfix

[publixsubfan]

Would it make sense to put this in IteratorBase?

[kennyweiss]

Good suggestion, but I don't think so since other iterators that are not random access iterators derive from IteratorBase.

E.g. ItemCollection is a forward iterator, and it's advance would give the wrong answer for operator[](-1)
See:

axom/src/axom/core/ItemCollection.hpp

Lines 207 to 214 in 97f1e49

	/// Implementation of advance() as required by IteratorBase
	void advance(IndexType n)
	{
	for(int i = 0; i < n; ++i)
	{
	BaseType::m_pos = m_collection->getNextValidIndex(BaseType::m_pos);
	}
	}

[Arlie-Capps]

Thanks, Kenny!

[rhornung67]

thank you @kennyweiss for the quick fix