[ruby-core:112485] [Ruby master Bug#19448] [Hash] Using Set as default value

Issue #19448 has been updated by sawa (Tsuyoshi Sawada).


@byroot (Jean Boussier), I think your comment is misleading if not irrelevant.

The issue's point is that, a key-value pair is not stored in the hash just by calling it. The only relevant part in the example you cited is:

```ruby
synonyms.keys # => [], oops
```

which is indeed not a bug.

> To use a mutable object as default, it is recommended to use a default proc

is irrelevant/incomplete as a response to this issue because:

```ruby
h = Hash.new{Set.new}
```

will not help. You have to explicitly store the key-value pair as in:

```ruby
h = Hash.new{|hash, key| hash[key] = Set.new}
```

----------------------------------------
Bug #19448: [Hash] Using Set as default value 
https://bugs.ruby-lang.org/issues/19448#change-101928

* Author: bobanj (Boban Jovanoski)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
When using a hash and set is used as a default value, the keys method for the hash does not return expected values.
A workaround for this is provided in the attachment. 

---Files--------------------------------
bug.rb (382 Bytes)


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