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write_literal breaks raw strings #13959

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ChrisJefferson opened this issue Jan 7, 2025 · 1 comment · Fixed by #13990
Closed

write_literal breaks raw strings #13959

ChrisJefferson opened this issue Jan 7, 2025 · 1 comment · Fixed by #13990
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C-bug Category: Clippy is not doing the correct thing

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@ChrisJefferson
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ChrisJefferson commented Jan 7, 2025 •
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Summary

write_literal doesn't correctly handle raw strings.

Reproducer

I tried this code:

writeln!(
                pre,
                "{}",
                r#"
$#CON colcheck "Use the sum of col {{index[0]}} for {{index[1]}}"
find colcheck: matrix indexed by [int(1..width), ALLRANGE] of bool"#
                "
            )?;

I expected write_literal to rewrite this to valid Rust. Instead, this happened:

writeln!(
                pre,
                "
$#CON colcheck \\"Use the sum of col {{{{index[0]}}}} for {{{{index[1]}}}}\\"
find colcheck: matrix indexed by [int(1..width), ALLRANGE] of bool"
            )?;

My preference would be to just leave the raw string as is, I can't see why that wouldn't be the easist, and least-suprising option.

Version

rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 19.1.1

Additional Labels

No response
@ChrisJefferson ChrisJefferson added the C-bug Category: Clippy is not doing the correct thing label Jan 7, 2025
@t-webber
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t-webber commented Jan 8, 2025

This problem appears to happen even for non-raw strings, like in this example:

writeln!(pre, "{}", "x with braces {x}")?;

Clippy suggests replacing it with

writeln!(pre, "{}", "x with braces {{x}}")?;

@lapla-cogito lapla-cogito mentioned this issue Jan 12, 2025
Merged
github-merge-queue bot pushed a commit that referenced this issue Jan 28, 2025
@Centri3
Fix escaping problem in write_literal and print_literal lint sugg…
6a209cd 
…estion (#13990)

fix #13959

The current implementation of the `write_literal` and `print_literal`
lint performs escaping for the second argument of `write!` ,`writeln!`,
`print!` and `println!` of the suggestion by first replacing `"` with
`\"`, and then replacing `\` with `\\`. Performing these replacements in
this order may lead to unnecessary backslashes being added if the
original code contains `"` (e.g. `"` -> `\\"`), potentially resulting in
a suggestion that causes the code to fail to compile.
In the issue mentioned above, it’s suggested to use raw strings as raw
strings, but implementing this would require an ad-hoc change to the
current implementation, so it has been deferred. (I'll implement this in
another PR)

changelog: [`write_literal`]: fix incorrect escaping of suggestions
changelog: [`print_literal`]: fix incorrect escaping of suggestions
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Fix escaping problem in write_literal and print_literal lint suggestion lapla-cogito/rust-clippy
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@ChrisJefferson @t-webber