I'm not sure why, but CI seems to fail both for this PR and master. This is a bit out of my paygrade, its only like my first week using Rust, so I don't know where to start debugging the issue.
Thanks you for your PR.
But lalrpop dependency is already up to date (0.16.1, 0.16.2, ... versions are compatible with 0.16).
See here to be sure.
And Travis build fails because of OOM I guess.
See https://github.com/bluss/petgraph/issues/153 for more details