Cargo check regression report

This is a bug report originally found here and reported to cargo team here.

Steps to reproduce

Make sure to install these versions of cargo:

• cargo 1.42.0-nightly (9d32b7b01 2020-01-26) - referred as nightly

• cargo 1.41.0 (626f0f40e 2019-12-03) - referred as stable

rustup default nightly
cargo check --message-format json > check-1.42.json

rustup default stable
cargo check --message-format json > check-1.41.json

You can see the difference in spans for an empty main.rs error message. Stable version returns no error spans, but nightly one returns an array of one span where line_start and line_end are set to 0, though they are guaranteed to be 1-based.