rust-lang / rust-lang/rust-analyzer
FP `expected fn foo(), found unsafe fn bar()`: match arms that returns different kinds of functions
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C-bug
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Description
const fn foo() {}
unsafe fn bar() {}
fn baz() {}
fn main() {
let x = match 2 {
2 => foo,
3 => bar,
_ => baz
};
}
this compiles with rustc but shows error in ra diag:
at crate ra, file /tmp/ra/src/main.rs: Error RustcHardError("E0308") from LineCol { line: 7, col: 7 } to LineCol { line: 7, col: 10 }: expected fn foo(), found unsafe fn bar()
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 with the Rust reproduction in the issue and compare rustc's result with rust-analyzer's diagnostic for the match expression in main.rs. Trace the type-checking or diagnostic path that reports E0308, then verify that this valid match no longer reports an error while preserving diagnostics for genuinely incompatible arms.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 52/100