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feat(core): Add From<[T; N]> for LimitedVec #3647

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feat(core): Add From<[T; N]> for LimitedVec #3647

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39566f6
Added trait
mqxf Jan 9, 2024
1d45eb9
Merge branch 'master' into ms/issue-3641
mqxf Jan 9, 2024
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7 changes: 7 additions & 0 deletions core/src/buffer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,13 @@ use scale_info::{
#[derive(Clone, Default, Eq, Hash, Ord, PartialEq, PartialOrd, Decode, Encode, TypeInfo)]
pub struct LimitedVec<T, E, const N: usize>(Vec<T>, PhantomData<E>);

impl<T, E, const M: usize, const N: usize> From<[T; M]> for LimitedVec<T, E, N> {
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I'm against of assertions in runtime for such a type, that's mainly used in non-test code. It's not worth adding potentially not checked to be unreachable by tests panic in the trait impl that's needed only for tests.
If there's no other stable solution, then it seems better to close the PR and wait for stable.

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+1

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There is no way to use static assertions without unstable features. static_assert!() doesnt work with const generics and everything else is gated behind unstable features. Unless it is fine to use them, which you have specified it isn't, then I'm going to close this PR until some feature becomes stable.

fn from(value: [T; M]) -> Self {
assert!(M <= N);
Self(value.into(), Default::default())
}
}

Comment on lines +40 to +46
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Suggested change
impl<T, E, const M: usize, const N: usize> From<[T; M]> for LimitedVec<T, E, N> {
fn from(value: [T; M]) -> Self {
assert!(M <= N);
Self(value.into(), Default::default())
}
}
struct LessThenOrEqual<const M: usize, const N: usize> {}
impl<const M: usize, const N: usize> LessThenOrEqual<M, N> {
const ASSERTION: () = assert!(M <= N);
}
impl<T, E, const M: usize, const N: usize> From<[T; M]> for LimitedVec<T, E, N> {
fn from(value: [T; M]) -> Self {
let _ = LessThenOrEqual::<M, N>::ASSERTION;
Self(value.into(), Default::default())
}
}

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please also replace places where ::from can be used

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this is still runtime assertion isnt it?

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this is still runtime assertion isnt it?

No

/// Formatter for [`LimitedVec`] will print to precision of 8 by default, to print the whole data, use `{:+}`.
impl<T: Clone + Default, E: Default, const N: usize> Display for LimitedVec<T, E, N>
where
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