P3503 R2 Make type-erased allocator use in promise and packaged_task consistent

[wg21bot]

P3503R0 Make type-erased allocator use in promise and packaged_task consistent (Nicolas Morales, Jonathan Wakely)

[inbal2l]

Mailing list review for forwarding, with the motion:
POLL: Send P3503R0 directly to LWG as the resolution to LWG2095 and LWG3003

Was started on Jan 8th, 2025.

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15 votes no objection.
Sending to LWG with the following fix

- where f is the task stored in *this.
+ where f is the task stored in *this and a is the allocator stored in the shared state.

in the specification of packaged_task::reset

[cor3ntin]

@jwakely @JeffGarland