[flang-commits] [flang] [Flang] Fix handling of unlimited polymorphic arrays (PR #159624)

[Peter Klausler via flang-commits]

klausler wrote:

This case (assignment to polymorphic allocatable entity under one or more levels of `WHERE` or in `DO CONCURRENT` with a condition) can't change the type in a well-defined way, since the values of the elements that are masked out would become undefined.  The behavior of other compilers doesn't give a clear portable precedent.  I think that semantics should flag it as an error and we should document it in the section of Extensions.md about ambiguous and unclear semantics in the standard.  Feel free to reassign this bug to me if you want.  I don't advise asking J3 for an interpretation.

https://github.com/llvm/llvm-project/pull/159624