I'm an engineer on Mapbox's search (geocoding) team, and our geocoding engine is actually open source: https://github.com/mapbox/carmen
Our data isn't, but as other commenters here have said, it's not currently possible to build a good geocoder with the open data available. We're constantly working to support open data efforts, but it's not there yet.
Our data isn't, but as other commenters here have said, it's not currently possible to build a good geocoder with the open data available. We're constantly working to support open data efforts, but it's not there yet.