gleam-lang/gleam

Formatter unnecessarily wraps expressions inside bit array size segments in a block.

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#5606 opened on Apr 11, 2026

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 (3 comments) (0 reactions) (1 assignee)Rust (21,417 stars) (960 forks)batch import
help wanted

Description

Given this like:

  let slice = <<bits:bits-size(count * marshal_zone_size)-unit(8)>>

The formatter will modify it to:

  let slice = <<bits:bits-size({ count * marshal_zone_size })-unit(8)>>

Even though the original is less than 80 characters wide.

Contributor guide

Tech stack
rust
Domain
developer experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Gleam syntax basicsRust programmingAST manipulation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Start by looking at the formatter code in the `compiler core/src/format.rs` file (or similar). Identify where bit array size expressions are handled. The issue shows that when the expression is under 80 characters, it should not be wrapped in braces. Check the condition that triggers the wrapping, and modify it to account for line length. Review the test suite for formatting to ensure no regressions. There are 3 comments on the issue, so read those for any additional context.