Confusing error with missing dependencies

[alexcrichton]

If .cargo/config is missing, or if the dependency has an ill-formatted Cargo.toml, one is met with this error message:

task '<main>' failed at 'invalid num of results 0', src/cargo/core/resolver.rs:31

A simple Cargo.toml with one dependency is enough to trigger the error. If the dependency is added via .cargo/config's path option, then if the dependency's Cargo.toml project name and lib name are not equal you are met with the same error.