Issue #14475 has been updated by sam.saffron (Sam Saffron).


sam.saffron (Sam Saffron) wrote:
> "If the string is frozen, then return the string itself."
> 
> Yeah I do not agree with this documentation, I think it should be changed. 
> 
> Trouble is that there is no simple way to de-duplicate unconditionally without inefficiency:
> 
> Say `x` is an arbitrary string (either frozen or unfrozen) :
> 
> ```
> x = -x # may return a non fstring
> 
> x = -+x # will return fstring, but makes an unneeded copy
> 
> x = -x.dup # fstring again, uneeded copy 
> 
> x = x.frozen? ? -+x : -x # too verbose
> ```
> 
> Instead why not change it so `-` dedupes unconditionally?



----------------------------------------
Bug #14475: String de-duplication is broken in files with frozen_string_literal: true
https://bugs.ruby-lang.org/issues/14475#change-70353

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.5.0, 2.6.0
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
Create 2 files:

test.rb

```
$LOAD_PATH.unshift(File.dirname(__FILE__))
require 'frozen'

puts frozen.object_id
puts frozen.object_id
```

frozen.rb

```
# frozen_string_literal: true

A = "a"
def frozen
  -"#{A}"
end
```

Run `test.rb` 

```
% ruby test.rb
70189973179400
70189973179260
```

Change to `# frozen_string_literal: false` 

And you get 

```
70189973181360
70189973181360
```

So something is over-optimising here, fix should be backported to 2.5.0 imo. 




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