Issue #22013 has been updated by byroot (Jean Boussier).
It would help to add a note similar to Object#eql? docs
Yes that is what I said. https://github.com/ruby/ruby/pull/16786 ---------------------------------------- Bug #22013: Array#| deduplication via eql? breaks when total element count exceeds ~16 https://bugs.ruby-lang.org/issues/22013#change-117113 * Author: andreyruby (Andrey Glushkov) * Status: Open * ruby -v: ruby 3.4.4 (2025-05-14 revision a38531fd3f) +PRISM [arm64-darwin24] * Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Problem description The documentation for `Array#|` states:
Returns the union of self and other_array; duplicates are removed; order is preserved; items are compared using `eql?`
However, when the total number of elements across both arrays exceeds ~16, deduplication via `eql?` stops working and duplicates are included in the result. ## Reproducible script ```ruby class Item attr_reader :id, :pos def initialize(id, pos:) @id = id @pos = pos end def inspect "item-#{id}-#{pos}" end def eql?(other) id == other.id end end items1 = [Item.new(1, pos: 1)] items2 = [Item.new(1, pos: 2)] # same id — should be treated as duplicate by eql? puts (items1 | items2 ).inspect # 2 total elements puts (items1 * 8 | items2 * 8 ).inspect # 16 total elements puts (items1 * 15 | items2 * 1 ).inspect # 16 total elements puts (items1 * 9 | items2 * 8 ).inspect # 17 total elements ``` ## Actual result ``` [item-1-1] [item-1-1] [item-1-1] [item-1-1, item-1-2] ``` ## Expected result All four lines should return `[item-1-1]`, since `eql?` returns `true` for both items and the documentation makes no mention of any size-dependent behavior. The last line incorrectly returns two elements. The only change is the total element count crossing ~16 — the objects and `eql?` implementation are identical. -- https://bugs.ruby-lang.org/