rustc should warn when a (library) crate's name doesn't match its filename

[wthrowe]

Staring at libfoo.rlib while having rustc insist that it can't find crate foo is really confusing.

$ cat lib.rs 
#![crate_type = "rlib"]

pub fn foo() {}
$ cat main.rs 
extern crate foo;

fn main() { foo::foo(); }
$ rustc lib.rs -o libfoo.rlib
$ rustc -L. main.rs
main.rs:1:1: 1:18 error: can't find crate for `foo` [E0463]
main.rs:1 extern crate foo;
          ^~~~~~~~~~~~~~~~~
error: aborting due to previous error
$ ls
lib.rs  libfoo.rlib  main.rs
$ 

[steveklabnik]

Triage: still reproduces today.

[steveklabnik]

Triage: there's been no other comments in over three years; given that people use cargo 99% of the time, and are not very likely to invoke rustc in this particular way, I'm not sure this is going to be implemented.

[jieyouxu]

Triage: I don't think it's worth the implementation complexity and potential for false positives, and users are unlikely to invoke rustc directly in this form. I'm going to close as not super actionable.