[RaphaelFakhri]

get_expected_errors() in conformance/src/main.py is meant to reject a # E[tag] group that appears on only one line, as conformance/README.md documents ("must appear multiple times in a file with the same tag"). The check never runs, because each value in groups is a (linenos, multiplicity) tuple. len() of that tuple is always 2, so len(linenos) == 1 is never true.

As a result, a mistyped tag (for example # E[final] on one line and # E[fianl] on the other) silently turns one "error on exactly one of these lines" group into two single-line groups. Each of them then requires an error on its own line, and a type checker that behaves correctly is scored as failing.

This change unpacks the tuple so the check compares the number of lines. It also updates the docstring example, which still showed the old bool value instead of ErrorMultiplicity.SINGLE.

Testing

• With a file that contains # E[typo] on one line and # E[good] on two lines, get_expected_errors() now raises ValueError: Error group typo only appears on a single line in .... Before the change it returned without an error.
• Every file in conformance/tests still passes through get_expected_errors() without errors (156 files), so no existing test needs changes and no results change.

[srittau]

Thanks!