Comment 10 for bug 1676169

Same issue is happening to me. Here are minimal steps to reproduce:

Create an empty directory containing a single file "main.rs", containing the following single line:

extern crate arena;

Then, with that directory as the current directory, run:

rustc main.rs

The error is "error[E0523]: found two different crates with name `std` that are not distinguished by differing `-C metadata`. This will result in symbol conflicts between the two.". The use of "arena" here is not critical; any stable, public crate that's part of the standard library will do (e.g. for the original reporter, it happened with "proc_macro").