Unable to match non_exhaustive enum tuple variants with rest pattern
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Description
Tuple enum variants Tuple(i32) from external crates marked with #[non_exhaustive] should be able to be matched by the RestPattern Tuple(val, ..). But it fails to compile.
I tried this code:
// In an external lib crate
#[non_exhaustive]
pub enum ExtNonExhaustiveVariant {
ExhaustiveUnit,
#[non_exhaustive]
Unit,
#[non_exhaustive]
Tuple(i32),
#[non_exhaustive]
StructNoField {},
#[non_exhaustive]
Struct {
field: i32,
},
}
// In the bin crate
fn main() {
match ExtNonExhaustiveVariant::ExhaustiveUnit {
ExtNonExhaustiveVariant::ExhaustiveUnit => 0, // OK
ExtNonExhaustiveVariant::Unit { .. } => 0, // OK
ExtNonExhaustiveVariant::Tuple(val, ..) => val, // FAIL
ExtNonExhaustiveVariant::StructNoField { .. } => 0, // OK
ExtNonExhaustiveVariant::Struct { field, .. } => field, // OK
_ => 0,
};
}
I expected to see this happen: No compile error.
Instead, this happened:
error[E0603]: tuple variant `Tuple` is private
--> src/main.rs:9:34
|
9 | ExtNonExhaustiveVariant::Tuple(val, ..) => val,
| ^^^^^ private tuple variant
|
note: the tuple variant `Tuple` is defined here
--> /repro/lib/src/lib.rs:14:5
|
13 | #[non_exhaustive]
| ----------------- cannot be constructed because it is `#[non_exhaustive]`
14 | Tuple(i32),
| ^^^^^
For more information about this error, try `rustc --explain E0603`.
error: could not compile `bin` (bin "bin") due to 1 previous error
Meta
rustc --version --verbose:
rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7
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 error from the external library and binary examples in /repro/lib/src/lib.rs and src/main.rs with the reported rustc version. Trace how the compiler handles matching the non_exhaustive Tuple variant with Tuple(val, ..). Done means the example compiles without the E0603 error and the behavior is covered by a regression test.
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
- 45/100