Clarify a case optimisation.
Clarify a case optimisation.

Ignore-this: 619b56c41e2e94f05985a425a18c6381

darcs-hash:725b6280e1e6bfa0dc1a24e4e34b1b9c8984d7a2

dpwright/jhc,dpwright/jhc,dpwright/jhc,dpwright/jhc