fromListN documentation: clarify (or remove?) "It's expected that the supplied list will be exactly n elements long"

[jwaldmann]

This is about the wording in the haddock comment
https://hackage-content.haskell.org/package/vector-0.13.2.0/docs/Data-Vector.html#v:fromListN

Convert the first n elements of a list to a vector. It's expected that the supplied list will be exactly n elements long.

What is the meaning of "expected"? What happens when the expectation is not met?

• list longer than n: seems to work fine: builds vector from the n-element prefix, as stated in first sentence V.fromListN 4 "foobar" => "foob"
• list shorter than n: builds vector from full list, consistent with behaviour of Data.List.take V.fromListN 8 "foobar" => "foobar"

[Shimuuar]

fromList n will produce same vector as V.fromList . take n. Difference lies in allocation strategy fromListuse unbounded doubling and fromListN uses doubling up to maximum n. See #301 for why buffer of size n is not allocated immediately.

Yes documentation is confusing in this case.