[Issue 23090] Allocators should not use NullAllocator as a sentinel type

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23090

--- Comment #1 from Dlang Bot <dlang-bot at dlang.rocks> ---
@pbackus updated dlang/phobos pull request #8574 "[allocator/region] Issue
23090 - Don't use NullAllocator as a sentinel type" mentioning this issue:

- Region: don't use NullAllocator as a sentinel

  Region will now always assume that its ParentAllocator is a real
  allocator, and attempt to use its 'allocate' and 'deallocate' methods
  accordingly.

  The behavior previously provided by Region!(NullAllocator, ...) remains
  available via BorrowedRegion!(...).

  See issue 23090 for detailed rationale.

- SharedRegion: don't use NullAllocator as sentinel

  SharedRegion will now always assume that its ParentAllocator is a real
  allocator, and attempt to use its 'allocate' and 'deallocate' methods
  accordingly.

  The behavior previously provided by SharedRegion!(NullAllocator, ...)
  remains available via shared(BorrowedRegion!(...)).

  See issue 23090 for detailed rationale.

https://github.com/dlang/phobos/pull/8574

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