alamb commented on code in PR #8564:
URL: https://github.com/apache/arrow-rs/pull/8564#discussion_r2411859592
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arrow-array/src/array/primitive_array.rs:
##########
@@ -1458,14 +1458,21 @@ impl<T: ArrowPrimitiveType, Ptr:
Into<NativeAdapter<T>>> FromIterator<Ptr> for P
impl<T: ArrowPrimitiveType> PrimitiveArray<T> {
/// Creates a [`PrimitiveArray`] from an iterator of trusted length.
+ ///
/// # Safety
+ ///
/// The iterator must be
[`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
- /// I.e. that `size_hint().1` correctly reports its length.
+ /// I.e. that `size_hint().1` correctly reports its length. Note that this
is a stronger
+ /// guarantee than `ExactSizeIterator` provides, which could still report
a wrong length.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the iterator does not report an upper bound on `size_hint()`.
#[inline]
pub unsafe fn from_trusted_len_iter<I, P>(iter: I) -> Self
where
P: std::borrow::Borrow<Option<<T as ArrowPrimitiveType>::Native>>,
- I: IntoIterator<Item = P>,
+ I: ExactSizeIterator<Item = P>,
Review Comment:
what is the rationale for this change? I am thinking that maybe someone who
had an iterator that knew its length but did not implement `ExactSizeIterator`
would have to change their code
Maybe that is ok, but the implementation doesn't even seem to use any of the
methods on `ExactSizeIterator`
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