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4278. Consider changing how get-domain-early(sndr) works

Section: 33.9.2 [exec.snd.expos] Status: New Submitter: Jonathan Wakely Opened: 2025-06-16 Last modified: 2026-01-16

Priority: 2

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Discussion:

During LWG review of P3481R3 it was noted that we need to say "except that sndr is only evaluated once" because it's used in get-domain-early(sndr), but that exposition-only-function doesn't actually use its argument, it only cares about the type, and it default constructs a Domain of a type determined by using the type of sndr.

If we had something like:

template<class Sender>
using get-domain-early-t = decltype(get-domain-early(declval<const Sender&>()));

then we wouldn't need to use sndr twice in expressions that currently use get-domain-early(sndr).

[2026-01-16; Reflector poll.]

Set priority to 2 after reflector poll.

A re-design, but we're already doing it for get-domain-late.

Proposed resolution: