Edition <2021 uninlined_format_args fix causes non_fmt_panics

[alexheretic]

Summary

uninlined_format_args can be false positive for older edition, e.g. 2018, where some macros do not support such formatting.

Lint Name

uninlined_format_args

Reproducer

I tried this code:

// Cargo.toml edition = "2018"
let v = vec![1];
assert!(v.is_empty(), "v non-empty: {:?}", v);

I saw this happen:

warning: variables can be used directly in the `format!` string
  --> src/main.rs:11:5
   |
11 |     assert!(v.is_empty(), "v non-empty: {:?}", v);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
   = note: `#[warn(clippy::uninlined_format_args)]` on by default
help: change this to
   |
11 -     assert!(v.is_empty(), "v non-empty: {:?}", v);
11 +     assert!(v.is_empty(), "v non-empty: {v:?}");
   |

I expected to see this happen:

No such warning unless on at least edition 2021.

If the fix is applied to older editions it'll result in the rustc warning

warning: panic message contains an unused formatting placeholder
 --> src/main.rs:9:37
  |
9 | assert!(v.is_empty(), "v non-empty: {v:?}");
  |                                     ^^^^^
  |
  = note: this message is not used as a format string when given without arguments, but will be in Rust 2021

And indeed it will not work outputting thread 'main' panicked at 'v non-empty: {v:?}' (instead of thread 'main' panicked at 'v non-empty: [1]')

Version

rustc 1.67.0 (fc594f156 2023-01-24)
binary: rustc
commit-hash: fc594f15669680fa70d255faec3ca3fb507c3405
commit-date: 2023-01-24
host: x86_64-unknown-linux-gnu
release: 1.67.0
LLVM version: 15.0.6

Additional Labels

No response

[taiki-e]

This was fixed in rust-lang/rust@e5010c9 (#10055), but that patch is only included in 1.68 and later, not 1.67.

[taiki-e]

(Also this issue is duplicate of #10234)

[alexheretic]

thanks