Function report_ids 

pub fn report_ids(
    files: &[InputFile<'_>],
    contexts: &[FileContext<'_>],
    variant: &BuildVariant,
    report: &EngineReport,
    literals: LiteralNorm,
) -> Vec<GroupIds>

Compute stable identifiers for every group of an engine report.

contexts runs parallel to files. Type-1 groups hash their members raw; Type-2 groups hash them under scope-local normalization with literals (the strategy the detection ran with), so the fingerprint captures exactly the identity that made the members a group. The engine this reads reports no gapped clones, so only those two classes occur; gapped groups are identified by structural_clone_group_fingerprint instead, which anchors on a canonical instance rather than on one shared content.