tracing::instrument breaks "type ... is more private than the item" warnings

[grahamc]

Bug Report

Version

tracing 0.1.41

Platform

Darwin Grahams-MacBook-Pro.local 24.2.0 Darwin Kernel Version 24.2.0: Fri Dec 6 19:02:12 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T6031 arm64 arm Darwin

but also play.rust-lang.org.

Crates

• tracing

Description

Marking a function with tracing::instrument obscures type visibility errors.

The following code has a warning that the pub function hi returns Foo, which is not pub:

struct Foo {}

pub fn hi() -> Foo {
    Foo {}
}

and the error:

warning: type `Foo` is more private than the item `hi`
 --> src/lib.rs:5:1
  |
5 | pub fn hi() -> Foo {
  | ^^^^^^^^^^^^^^^^^^ function `hi` is reachable at visibility `pub`
  |
note: but type `Foo` is only usable at visibility `pub(crate)`
 --> src/lib.rs:3:1
  |
3 | struct Foo {}
  | ^^^^^^^^^^
  = note: `#[warn(private_interfaces)]` on by default

However, if I mark hi with tracing::instrument...:

use tracing; // 0.1.41;

struct Foo {}

#[tracing::instrument]
pub fn hi() -> Foo {
    Foo {}
}

The warning goes away:

   Compiling playground v0.0.1 (/playground)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.41s

I would expect Rust to continue issuing warnings about these types.