[ruby-core:74466] [Ruby trunk Bug#12198] Hash#== sometimes returns false incorrectly

Issue #12198 has been updated by Tsuyoshi Sawada.


Sebastian Skalacki wrote:
> Actually it has nothing to do with sets:
> 
> ~~~
> b = []
> h1 = {b => true}
> b << 42
> 
> h2 = {[42] => true}
> 
> p h2 #=> {[42]=>true}
> p h1 #=> {[42]=>true}
> p h2 == h1 #=> false
> ~~~

You have to apply `Hash#rehash`.

~~~RUBY
h1.rehash
h2 == h1 # => true
~~~

----------------------------------------
Bug #12198: Hash#== sometimes returns false incorrectly
https://bugs.ruby-lang.org/issues/12198#change-57590

* Author: Sebastian Skalacki
* Status: Assigned
* Priority: Normal
* Assignee: Akinori MUSHA
* ruby -v: ruby 2.4.0dev (2016-03-11 trunk 54086) [x86_64-darwin14]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
Hi!

Sorry for lack of the accuracy in the bug title. I have some trouble with pinpointing the issue.

According to documentation, "two hashes are equal if they each contain the same number of keys and if each key-value pair is equal to (according to Object#==) the corresponding elements in the other hash." I was able to produce two hashes which satisfy this condition, however the method returns false. In other words, following happens:

~~~
e.class #=> Hash
r.class #=> Hash
e.size == r.size #=> true
e.each_pair.to_a == r.each_pair.to_a #=> true
e == r #=> false
~~~

That happens in Ruby 1.9.3, 2.3, 2.4 and probably in other versions as well. Pure Ruby, no gem could interfere.

Happy Easter ]:->

---Files--------------------------------
problem.rb (1.69 KB)


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