Use entry API instead of a match
Use entry API instead of a match

This makes the code easier to read and also avoids looking up the
position in the map twice. The clone of `unit` is very cheap since it is
an Rc.

nipunn1313/cargo,rustyhorde/cargo,nipunn1313/cargo,tsurai/cargo,eminence/cargo,rustyhorde/cargo,rustyhorde/cargo,rust-lang/cargo,tsurai/cargo,eminence/cargo,tshepang/cargo,nipunn1313/cargo,tshepang/cargo,tsurai/cargo,tshepang/cargo,nipunn1313/cargo,tsurai/cargo,tshepang/cargo,eminence/cargo,rust-lang/cargo,rustyhorde/cargo,eminence/cargo,tsurai/cargo,rust-lang/cargo,rust-lang/cargo