In the current scenario, where the definition of 'Rust' changes on a daily basis, that's a major pain-point, but once Rust hits 1.0 then all future changes will

In the current scenario, where the definition of 'Rust' changes on a daily basis, that's a major pain-point, but once Rust hits 1.0 then all future changes will be backwards-compatible (until version 2.0, in the distant future if ever), so it should be much less of an issue. That said, it's definitely a thing the Cargo devs are thinking about: https://github.com/rust-lang/cargo/issues/1044 https://github.com/rust-lang/cargo/issues/1044 https://github.com/rust-lang/cargo/issues/837 https://github.com/rust-lang/cargo/issues/837