CWG2804 Lookup for determining rewrite targets

[jensmaurer]

Some cases for synthesized equality operator candidates yield possibly surprising outcomes, owing to the details of the "rewrite target" rules.

CWG seeks the advice of EWG to possible improve or change these rules.

See CWG2804 for details.

[erichkeane]

EWG discussed CWG2804 during the Tuesday Morning session in Kona. The following poll was taken.

CWG2804 "Lookup for determining rewrite targets", the intent is to check for the existence of a declaration that differs only in the operator name (ie, bx should work, by should be ill-formed).

SF	F	N	A	SA
4	11	3	0	0

Result: Consensus

[jfbastien]

@jensmaurer does this also resolve #1645 ?

[jensmaurer]

@jfbastien : Yes, but this for sure makes the example in #1645 ill-formed. But we intentionally made this example well-formed very recently. So, EWG seems to have reversed direction as far as the example in #1645 is concerned.

[jensmaurer]

The EWG decision partially reverts P2468R2 (The Equality Operator You Are Looking For), applied in July 2022. In particular, the line bool c1 = B() == C(); from the example added thereby is no longer well-formed.

Back to EWG for confirmation of the intent.

[erichkeane]

EWG discussed this on Thursday PM in Kona, and request that the authors of P2468 (#1127 @brevzin et-al) review the original CWG2804 as well as the break that was caused by the fix to it, and come back with a more all-encompassing solution/set of questions as an omnibus as a revision to P2468.