Don't call this method more than once, and only after you've generated all docs for the Package.
Source
void verifyLinks(Package package, String origin) { assert(_hrefs == null); _hrefs = package.allHrefs; final Set<String> visited = new Set(); final String start = 'index.html'; stdout.write('\nvalidating docs...'); _doCheck(package, origin, visited, start); _doOrphanCheck(package, origin, visited); _doSearchIndexCheck(package, origin, visited); }