Compiling --test with #[no_std] produces error span at first line

[nagisa]

#![crate_name="odd_span"]
#![no_std]

#[test]
fn t(){
}

will result in

test.rs:1:1: 1:4 error: unresolved import `std::slice::AsSlice`. Maybe a missing `extern crate std`?
test.rs:1 #![crate_name="odd_span"]
          ^~~
error: aborting due to previous error

Note the odd span and error location.

Since --test depends on libstd, maybe a following error message would be better?

test.rs:2:1: 1:4 error: Test harness binaries require std crate. Maybe a missing `extern crate std`?
test.rs:2 #![no_std]
          ^~~~~~~~~~
error: aborting due to previous error

[alexcrichton]

Closing as a dupe of #18843