IndexOutOfRangeException' in Fabulous.XamarinForms.Collections.deleteAt

[marklam]

Description

The upper bound at
https://github.com/fsprojects/Fabulous/blob/c442b48c9e30bad413948298b5bee1be2a455291/Fabulous.XamarinForms/src/Fabulous.XamarinForms/Collections.fs#L41-L42
is too high, and the arr.[i + 1] will attempt to read outside the array.

Steps to Reproduce

Happens from Collections.diff at https://github.com/fsprojects/Fabulous/blob/c442b48c9e30bad413948298b5bee1be2a455291/Fabulous.XamarinForms/src/Fabulous.XamarinForms/Collections.fs#L140 with a 16-element array, reusableIndex = 0 reusableElementsCount = 16, discardedElementsCount = 0, identicalElements is empty.

Expected Behavior

Item is removed

Actual Behavior

Exception is thrown, and swallowed by WPF

Basic Information

• Version with issue: 0.60
• Platform Target Frameworks: netcoreapp3.1, WPF

[TimLariviere]

@marklam Thanks for the precise report
It helped me find the real reason why we did not see it before, and write a unit test to catch this specific case.
I will release a new version with this fix.