There once was a long disscusion going on whether closure types should be considered as structural types or not (essentially determining whether they would be eligible as NTTPs). An interesting post about this, made by user dfrib, can be found here.

The initial concern about this seemed to be raised by Zhihao Yuan, back in March 2022. This ended up becoming defect report CWG 2542, which was accepted by a working group meeting in June 2023. The proposed resolution of that defect report was approved and it very clearly stated that closure types are not structural types.

This change was reflected in many versions of the C++ Working Draft, at least all the way up to N4971. The passage of interested being listed under [expr.prim.lambda.closure]/3. This is also what people will find when looking up the cppreference entry about lambdas, which references defect report CWG 2542 at the bottom of the page.

However, in the more recent C++ Working Draft version N4981, passage [expr.prim.lambda.closure]/3 now reads:

The closure type is not an aggregate type (9.4.2); it is a structural
type (13.2) if and only if the lambda has no lambda-capture.

Which seems to revert the approved resolution of defect report CWG 2542. Should this defect report now be considered obsolete? And, by which meeting/decision/paper did closure types now become structural types?