Clarify wording of [class.eq]

[leni536]

Background

[class.eq] currently reads:

The return value V of a defaulted == operator function with parameters x and y is determined by comparing corresponding elements $x_i$ and $y_i$ in the expanded lists of subobjects for x and y (in increasing index order) until the first index $i$ where $x_i == y_i$ yields a result value which, when contextually converted to bool, yields false.
If no such index exists, V is true.
Otherwise, V is false.

The first long sentence describes the side effects of calling a defaulted operator==, while the other two sentences describe the return value.

This is unambiguous, but I think the wording could be improved.

Problem

At first glance this might be interpreted in a way that describes three distinct cases. In that case it's hard to make sense of the "Otherwise, V is false." sentence, as seemingly the previous sentences cover all cases.

This came up on the std-discussion mailing list: https://lists.isocpp.org/std-discussion/2022/12/1927.php

Some proposals for rewording

1. Mirror the wording of [class.spaceship]:

...when contextually converted to bool, yields false;
V is false.
If no such index exists, V is true.

2. Switch around the last two sentences:

..when contextually converted to bool, yields false.
If such index exists, V is false.
Otherwise, V is true.

Some other considerations

Even though the first long sentence describes the side effects of calling a defaulted operator==, it leads in with "The return value V of a defaulted == operator function with parameters x and y is determined...". It might be better to reword the first sentence in a way that doesn't mention the return value yet. One such wording would be, combined with the second suggestion above:

When a defaulted == operator function is called with parameters x and y then the corresponding elemnts $x_i$ and $y_i$ in the expanded lists of subobjects for x and y (in increasing index order) are compared until the first index $i$ where $x_i == y_i$ yields a result value which, when contextually converted to bool, yields false.
If such index exists, the return value is false.
Otherwise, the return value is true.

[class.spaceship] can have similar treatment.

[jwakely]

See #6035

[leni536]

See #6035

Thank you! This does modify the wording of the paragraphs in question, but I don't think it fully addresses the issue outlined here.

The PR simply removes V. It is an improvement though.