rust-lang / rust-lang/rust

Imports of legacy modules with numeric constants do not get flagged as unused when the corresponding type is used in the code

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A-diagnostics T-compiler
Dominant language
Rust
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Description

Code
use std::usize;

fn main() {
    let x: usize = 1;
    println!("{}", x);
}
Current output

Desired output
warning: unused import: `std::usize`
 --> src/main.rs:1:5
  |
1 | use std::usize;
  |     ^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default
Rationale and extra context

No response

Other cases

No response

Rust Version
$ rustc --version --verbose
rustc 1.79.0-beta.1 (6b544f5ff 2024-04-28)
binary: rustc
commit-hash: 6b544f5ff8d45221d61962651a5f5ab9fe535e16
commit-date: 2024-04-28
host: x86_64-unknown-linux-gnu
release: 1.79.0-beta.1
LLVM version: 18.1.4
Anything else?

No response

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Research direction

Reproduce the report with the Rust code shown in src/main.rs and the listed rustc version, then compare the current diagnostics with the desired unused_imports warning. Done means the legacy std::usize import is reported as unused even when the usize type is used.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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