`unused_imports` redundant import `is already defined here` points to self

[correabuscar]

is already defined here doesn't point to the proper place:
playground link
in this output:

   Compiling playground v0.0.1 (/playground)
warning: the item `libc` is imported redundantly
 --> src/main.rs:3:5
  |
3 | use libc;
  |     ^^^^ the item `libc` is already defined here
  |
  = note: `#[warn(unused_imports)]` on by default

warning: `playground` (bin "playground") generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.58s
     Running `target/debug/playground`

for this code:

use std::ffi::{CStr, CString};

use libc;

fn main() {
    let lib_name = CString::new("libEGL.so").unwrap();
    let lib_ptr = unsafe { libc::dlopen(lib_name.as_ptr(), libc::RTLD_NOW) };

    if lib_ptr.is_null() {
        let error_msg = unsafe { CStr::from_ptr(libc::dlerror()) }.to_str().unwrap();
        println!("Error loading library: {}", error_msg);
        return;
    }

    // Access functions from the library
    // ...

    unsafe { libc::dlclose(lib_ptr) };
}

Meta

rustc --version --verbose:

rustc 1.78.0-nightly (ef324565d 2024-02-27)
binary: rustc
commit-hash: ef324565d071c6d7e2477a195648549e33d6a465
commit-date: 2024-02-27
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

initially mentioned it here, on the pull request: #117772 (comment)

[ehuss]

I believe it is pointing at the correct place (the use libc; is redundant and should be removed). What I think is missing is an explanation of why the redundancy exists (it is because libc already exists in the extern prelude).

[correabuscar]

Normally you see something like:

   Compiling playground v0.0.1 (/playground)
warning: the item `TryFrom` is imported redundantly
   --> src/main.rs:3:5
    |
3   | use std::convert::TryFrom;//~ WARNING the item `TryFrom` is imported redundantly
    |     ^^^^^^^^^^^^^^^^^^^^^
    |
   ::: /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/prelude/mod.rs:129:13
    |
129 |     pub use core::prelude::rust_2021::*;
    |             ------------------------ the item `TryFrom` is already defined here
    |
note: the lint level is defined here
   --> src/main.rs:1:9

Here it says where is already defined here is, correctly.
playground link

#![warn(unused_imports)]

use std::convert::TryFrom;//~ WARNING the item `TryFrom` is imported redundantly
use std::convert::TryInto;//~ WARNING the item `TryInto` is imported redundantly

fn main() {
    let _e: Result<i32, _> = 8u8.try_into();
    let _f: Result<i32, _> = i32::try_from(8u8);
}

[fmease]

I believe it is pointing at the correct place (the use libc; is redundant and should be removed). What I think is missing is an explanation of why the redundancy exists (it is because libc already exists in the extern prelude).

Yes, exactly! We just need to adjust the contents of the label in this situation.

[fmease]

Minimized:

// --- dep.rs ---    rustc dep.rs --crate-type=lib
pub fn item() {}

// --- usr.rs ---    rustc usr.rs --extern=dep -L. --edition=2021
fn main() {
    use dep;
    dep::item();
}

warning: the item `dep` is imported redundantly
 --> usr.rs:2:9
  |
2 |     use dep;
  |         ^^^ the item `dep` is already defined here
  |
  = note: `#[warn(unused_imports)]` on by default

warning: 1 warning emitted