From: "Dan0042 (Daniel DeLorme) via ruby-core" <ruby-core@...>
Date: 2024-03-03T15:17:37+00:00
Subject: [ruby-core:117043] [Ruby master Bug#20307] `Hash#update` from compare_by_identity hash can have unfrozen string keys

Issue #20307 has been updated by Dan0042 (Daniel DeLorme).


After the code above, we can do
```ruby
h.rehash
p h      #=> {"A"=>1}
```
When a key is clobbered like that due to a rehash, maybe there should be a warning or an error? It seems to me a pretty clear sign of a bug, either in the ruby code or in the interpreter itself.

----------------------------------------
Bug #20307: `Hash#update` from compare_by_identity hash can have unfrozen string keys
https://bugs.ruby-lang.org/issues/20307#change-107114

* Author: nobu (Nobuyoshi Nakada)
* Status: Open
* Backport: 3.0: REQUIRED, 3.1: REQUIRED, 3.2: REQUIRED, 3.3: REQUIRED
----------------------------------------
I don't think this behavior is expected.

```ruby
i = Hash.new.compare_by_identity
k = "a"
i[k] = 0
h = {}.update(i)
p h.compare_by_identity?  # => false
p h["a"]                  # => 0

k.upcase!
# `k` is still in `h`.
p h.keys.include?(k)      # => true

# but not found.
p((h.fetch(k) rescue $!)) # => #<KeyError: key not found: "A">
h["A"] = 1  
p h                       # => {"A"=>0, "A"=>1}
```

I expect `h` to still have `"a"=>0` entry.




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