rust-lang / rust-lang/rustfmt

rustfmt duplicates Trait identifier causing syntax error

Open
#7,053 1 comment 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

C-bug
Dominant language
Rust
Stars
7k
Forks
1.1k
Avg merge
2d 13h
Merged PRs (30d)
24

Description

it turns out that after formatting weird_exprs from #7052 with comments, it no longer compiles.

The problem is that given a code like
trait /* 1 */ Trait /* 2 */ {}
rustfmt will turn this into trait Trait Trait which is invalid code

rustfmt --check output.rs
Diff in /tmp/fmt/2/output.rs:1:
-trait /* 1 */ Trait /* 2 */ {}
+trait Trait /* 1 */ Trait /* 2 */ {}

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the weird_exprs case from #7052 using the trait example and run rustfmt --check output.rs to observe the duplicated Trait identifier. Trace the formatting behavior for comments around the trait name; done means formatting preserves valid Rust with one Trait identifier and the resulting output compiles.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
68/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.