[ruby-core:107034] [Ruby master Bug#18470] Union of two identical sets produces a set with duplicate members

Issue #18470 has been updated by ufuk (Ufuk Kayserilioglu).


Doesn't the following from https://bugs.ruby-lang.org/issues/16996 address this issue?
> ...
> Today, it is official that sets with elements that are later mutated must be `Set#reset`, so it is official that this should not be relied upon.
> ...

It seems like this is not a bug and the outcome is expected without a call to `Set#reset`:

```ruby
C = Struct.new :id
a = Set.new
b = Set.new
f = C.new
a << f
f.id = 1
b << f

a.reset

# => #<Set: {#<struct C id=1>}>
a + b
# => #<Set: {#<struct C id=1>}>
b + a
# => #<Set: {#<struct C id=1>}>
```

----------------------------------------
Bug #18470: Union of two identical sets produces a set with duplicate members
https://bugs.ruby-lang.org/issues/18470#change-95865

* Author: smokinggun (John Weir)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-linux]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
We came across an issue where the union of two identical sets produced a non uniq Set.

We noticed this when upgrading from 2.7.1 to 3.1

See the attached test, the last assertion fails

``` ruby
C = Struct.new :id
a = Set.new
b = Set.new
f = C.new
a << f
f.id = 1
b << f
a + b
# => #<Set: {#<struct C id=1>, #<struct C id=1>}>
b + a
# => #<Set: {#<struct C id=1>}>

(a + b).uniq
=> [#<struct C id=1>]
```


---Files--------------------------------
set_test.rb (348 Bytes)


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