rust-lang / rust-lang/rust-analyzer

rust-analyzer incorrectly expands derives on bevy's `LoadedUntypedAsset`

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C-bug
Dominant language
Rust
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Description

rust-analyzer version: 0.3.1722-standalone

rustc version: rustc 1.73.0 (cc66ad468 2023-10-03)

relevant settings:

"rust-analyzer.diagnostics.disabled": [
    "unresolved-method",
    "E0616"
],
"rust-analyzer.hover.documentation.keywords.enable": false,
"rust-analyzer.cargo.buildScripts.useRustcWrapper": false,

Bevy 0.12 has this LoadedUntypedAsset type:

#[derive(Asset, TypePath)]
pub struct LoadedUntypedAsset {
    #[dependency]
    pub handle: UntypedHandle,
}

This type does not work correctly in rust-analyzer when wrapped in the Assets collection, which requires T: Asset. This is caused by rust-analyzer incorrectly expanding the derives on the type: running "expand macro recursively" on the Asset derive gives the output of the TypePath derive instead, and running it on the TypePath token says "not available".

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

Start by reproducing the Bevy 0.12 LoadedUntypedAsset example and inspecting rust-analyzer's "expand macro recursively" entry point; the issue names no repository file or test. Compare the Asset and TypePath derive expansions, and consider the issue done when each derive expands to its own output and the type works where T: Asset is required.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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