paritytech / paritytech/parity-scale-codec
Derive encode for variants can result in having multiple variants having same index.
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- Dominant language
- Rust
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- 287
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- 103
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Description
for instance this example does compile without warning:
#[test]
fn discriminant_variant_counted_in_default_index() {
#[derive(Encode)]
enum T {
A = 1,
B,
}
assert_eq!(T::A.encode(), vec![1]);
assert_eq!(T::B.encode(), vec![1]);
}
We should make this a compile_error or try to give some warning in some way
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Research direction
Start with the provided discriminant_variant_counted_in_default_index reproducer and trace the #[derive(Encode)] handling for enum discriminants. Add a regression test showing that duplicate encoded indices are rejected or warned about, then verify the chosen diagnostic with the test suite.
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Assessment
- Tech stack
- rust
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100