Function resolve_graph 

pub fn resolve_graph(
    project_root: &Path,
    overlay: &HashMap<PathBuf, String>,
) -> (Option<PackageGraph>, Vec<GraphProblem>)

Resolve the path-dependency graph of the project at project_root. None with no problems when the project declares no dependencies.

A path dependency in the project’s own manifest is the author’s own file and is honoured wherever it points. One declared by a dependency is honoured only inside the workspace the project belongs to (track §6.3, decision F): outside a workspace it is refused, so no dependency can make the build read a directory the author never named.