Bug 21603 – Provide deprecation warning or error for placement new syntax

Class allocators are deprecated. 'new(address) TYPE' syntax (placement new) complains that a class allocator is needed but does not trigger a deprecation notice itself. Disregard if 'new(address) TYPE' syntax is not actually deprecated. https://forum.dlang.org/thread/[email protected]

DMD 2.098.0 removes class allocators from the language - https://dlang.org/changelog/2.098.0.html#remove_alloc Placement new syntax still triggers a "no allocator for 'CLASSNAME'" error. As far as I know there's no way to use placement new syntax without an allocator, so this should also be removed. I think it's worth noting that Andrei's book tells people they can use this syntax so a deprecation notice would be helpful.

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