rust-lang / rust-lang/rust-analyzer
[bug] Incorrect inference from `-> _` for `Fn() -> Fn()`
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C-bug
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- Rust
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Description
rust-analyzer version: 2023-12-18
rustc version: 1.76
fn infer() -> _ {
|| || 42
}
turns into
fn infer() -> impl Fn() -> impl Fn() -> i32 {
|| || 42
}
Which does not compile on stable.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the minimal example from the issue and inspect rust-analyzer's type inference handling for nested closures and inferred return types. Done means the inferred result for || || 42 no longer produces a stable-incompatible nested impl Fn signature.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100