So, the suggestion is to replace the notes in [cmp.alg] about immediate context with the phrasing from [ranges.access]: "Ill-formed cases above result in substitution failure when strong_order(E) appears in the immediate context of a template instantiation." so that the note covers both ill-formed cases, not just the last one.

Also, it feels that "performed in a context that does not include a declaration of" should be replaced by the more precise "performed in a context in which unqualified lookup for strong_order finds nothing".

@jwakely, are these changes (in particular the first one) net improvements, and sufficiently editorial?

which implies that only one of the two ill-formed cases results in substitution failure.

It might imply it, but it's not normative, so I don't think the presence or absence of such notes can override anything normative. But I'm not sure whether [customization.point.object] p4 applies to the first bullet; is "If the decayed types of E and F differ, strong_­order(E, F) is ill-formed." a "requirement specified in the customization point's definition"? It's not stated as a requirement.

When I implemented std::strong_order I used a static_assert to check the decayed types are the same, which means it doesn't result in substitution failure. I'd like to hear from @brevzin whether the intention is that all the ill-formed cases in [cmp.alg] are supposed to result in substitution failures rather than hard errors.

@jwakely the intent was that all the ill-formed cases result in substitution failure, yeah.

Thanks, Barry. Then I like the suggestion. It's clarifying the original intent, so I'm happy for it to be done editorially.