TL;DR Animats's errors were attempting to compile code from a more recent version of Rust on 1.2, or something similar. When I attempted to reproduce, I got the

TL;DR Animats's errors were attempting to compile code from a more recent version of Rust on 1.2, or something similar. When I attempted to reproduce, I got the same errors on 1.2, and no errors on 1.17. Rust does not guarantee forward compatibility, code that compiles on 1.17 will not necessarily compile on 1.2 (of course, that would mean no new features). I attempted to reproduce your report by downloading the 1.2 compiler and compiling this code in both versions. Here is what I got: --- First, the Vec.join report. I attempted to compile a crate with this body on both versions: fn main() { let v: Vec<&str> = vec!["hello, ", "world"]; v.join(""); } On 1.2 this failed to compile with exactly the error you stated. This isn't surprising to me since I recall us adding .join to Vec several months after the 1.2 release. So you certainly weren't compiling that code on 1.2. In contrast, on 1.17, this code compiled just fine. This is exactly what I expected, since I use vec.join all the time on vectors of string slices. In conclusion, I was unable to reproduce this bug. --- Second, the Cargo star dependencies report. Manishearth is wrong, we disallow those dependencies from being uploaded to crates.io, but end users are allowed to use them just fine (strongly recommended that you don't, though!). To attempt to reproduce, I built a crate with this dependencies section: [dependencies] chrono="*" On 1.2, I got exactly the error you stated. I don't know what the source of it is, but I know that star dependencies are risky because they imply indefinite forward compatibility, which is impossible to guarantee. On 1.17, this successfully resolved to the 0.3.0 version of chrono, which compiled just fine. Once again, I was unable to reproduce your bug report. --- If you have any more bug reports, please post them on https://github.com/rust-lang/rust https://github.com/rust-lang/rust . And you can check which version of the compiler you're using with `rustc --version` (supported since before 1.0).