gleam-lang/gleam

LSP fails to suggest completion for locally defined `use`d argument

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#5,258 opened on Jan 3, 2026

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help wanted

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Description

LSP fails to suggest completion for locally defined used argument. For example, if I use Lustre and want to create a custom effect I may write something like this:

fn load_data(msg: fn(String) -> msg) -> Effect(msg) {
  use dispatch <- effect.from
  let data = "Example data"
  dispatch(msg(data))
}

If I partially type disp in the last line expecting a suggestion — I wouldn't get it:

Note: suggestion works fine if I convert use to the callback-style call.

Versions:

  • Gleam: 1.14.0
  • VSCodium: 1.107.18627
  • Lustre: 5.4.0
  • macOS: 15.7.3

Contributor guide

Research direction
Investigate the LSP completion handler for identifiers, specifically how variables introduced by the `use` expression are registered in the completion context. Look at the `completion` module in the `gleam lsp` crate and trace the logic for variable completions around `use` expressions.
Tech stack
rust
Domain
developer experiencetooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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
RustGleam
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45