Expand description
Constructs the dependency graph for compilation.
Rust code is typically organized as a set of Cargo packages. The
dependencies between the packages themselves are stored in the
Resolve struct. However, we can’t use that information as is for
compilation! A package typically contains several targets, or crates,
and these targets has inter-dependencies. For example, you need to
compile the lib target before the bin one, and you need to compile
build.rs before either of those.
So, we need to lower the Resolve, which specifies dependencies between
packages, to a graph of dependencies between their targets, and this
is exactly what this module is doing! Well, almost exactly: another
complication is that we might want to compile the same target several times
(for example, with and without tests), so we actually build a dependency
graph of Units, which capture these properties.