Function resolve_share 

pub fn resolve_share<'a, S: BuildHasher>(
    artifacts: &'a HashMap<ArtifactId, ArtifactValue, S>,
    artifact_id: &ArtifactId,
    property: Option<&str>,
) -> Result<&'a Share, ExecutionError>

Resolve a reference to one share.

shares.share_N names the share evaluated at N in a set a split made. A set holding exactly one share, as a typed-back share arrives, is named without a property. Borrowed, like every read.