Differing uninlined_format_args behavior between stable/beta and nightly?

[smoelius]

Summary

Sorry, this is weird and I don't know the reason for it.

cargo clippy and cargo +beta clippy produce different warnings than cargo +nightly clippy on this code:

#![allow(clippy::all)]
#![warn(clippy::uninlined_format_args)]

fn main() {
    let path = "x";

    let _ = format!("Failed to open `{}`", path);

    let _ = || format!("Failed to open `{}`", path);
}

The difference does't seem to be a commit: if you checkout tag rust-1.72.0 and run it on the above code, you see the nightly behavior.

The only things I've found that make a difference are: being stable/beta or being a uitest.

Re the latter, if you create a uitest and put both of the expected warnings in the stderr file, the test passes.

I've performed the above experiment on two different OSes (Linux and Mac)---same results.

I've also tried debug vs. release. Again, no difference.

I am really at a loss.

What about being stable/beta or being a uitest could make a difference?

Lint Name

uninlined_format_args

Reproducer

I tried this code with cargo +nightly clippy:

#![allow(clippy::all)]
#![warn(clippy::uninlined_format_args)]

fn main() {
    let path = "x";

    let _ = format!("Failed to open `{}`", path);

    let _ = || format!("Failed to open `{}`", path);
}

I expected to see this happen (the same warnings produced by cargo clippy):

warning: variables can be used directly in the `format!` string
 --> src/main.rs:7:13
  |
7 |     let _ = format!("Failed to open `{}`", path);
  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
note: the lint level is defined here
 --> src/main.rs:2:9
  |
2 | #![warn(clippy::uninlined_format_args)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: change this to
  |
7 -     let _ = format!("Failed to open `{}`", path);
7 +     let _ = format!("Failed to open `{path}`");
  |

warning: variables can be used directly in the `format!` string
 --> src/main.rs:9:16
  |
9 |     let _ = || format!("Failed to open `{}`", path);
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
help: change this to
  |
9 -     let _ = || format!("Failed to open `{}`", path);
9 +     let _ = || format!("Failed to open `{path}`");
  |

warning: `a` (bin "a") generated 2 warnings (run `cargo clippy --fix --bin "a"` to apply 2 suggestions)
    Finished dev [unoptimized + debuginfo] target(s) in 0.08s

Instead, this happened (no warning for the format inside the closure)):

warning: variables can be used directly in the `format!` string
 --> src/main.rs:7:13
  |
7 |     let _ = format!("Failed to open `{}`", path);
  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
note: the lint level is defined here
 --> src/main.rs:2:9
  |
2 | #![warn(clippy::uninlined_format_args)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: change this to
  |
7 -     let _ = format!("Failed to open `{}`", path);
7 +     let _ = format!("Failed to open `{path}`");
  |

warning: `a` (bin "a") generated 1 warning (run `cargo clippy --fix --bin "a"` to apply 1 suggestion)
    Finished dev [unoptimized + debuginfo] target(s) in 0.09s

Version

rustc 1.74.0-nightly (e3abbd499 2023-09-06)
binary: rustc
commit-hash: e3abbd4994f72888f9e5e44dc89a4102e48c2a54
commit-date: 2023-09-06
host: x86_64-apple-darwin
release: 1.74.0-nightly
LLVM version: 17.0.0

[smoelius]

Could someone please try cargo clippy vs. cargo +nightly clippy on the above code, just to confirm I am not crazy?

[Alexendoo]

It's because -Zincremental-relative-spans is enabled by default on nightly only for now

The ui tests don't hit the issue because they don't use incremental compilation

[smoelius]

@Alexendoo 🙏 I thought I was losing my mind.