Using `let` pattern with `ref` results in 'mismatched types' when combined with 'panic!()'
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Nobody has claimed this yet.
A-coercions
C-bug
T-compiler
T-lang
- Dominant language
- Rust
- Stars
- 119k
- Forks
- 16.1k
- PR merge metrics
- PR metrics pending
Description
I tried this code:
struct Foo {
bar: u8
}
fn main() {
let Foo { ref bar } = panic!();
}
I expected to see this happen: The code should compile successfully by coercing the ! from panic!() to Foo.
Instead, this happened: rustc produces the following error:
error[E0308]: mismatched types
--> src/main.rs:6:9
|
6 | let Foo { ref bar } = panic!();
| ^^^^^^^^^^^^^^^ -------- this expression has type `!`
| |
| expected `!`, found `Foo`
|
= note: expected type `!`
found struct `Foo`
For more information about this error, try `rustc --explain E0308`.
error: could not compile `playground` (bin "playground") due to previous error
The code compiles successfully if the ref keyword is removed.
Meta
rustc --version --verbose:
rustc 1.76.0-nightly (2b603f95a 2023-11-12)
binary: rustc
commit-hash: 2b603f95a48f10f931a61dd208fe3e5ffd64e491
commit-date: 2023-11-12
host: x86_64-unknown-linux-gnu
release: 1.76.0-nightly
LLVM version: 17.0.4
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
Reproduce the example in src/main.rs with the reported rustc --version --verbose details, and review rustc --explain E0308 for context on the diagnostic. Trace the compiler handling of the let pattern, ref binding, and panic!() expression; done means the example compiles without the mismatched-types error.
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