Issue #14478 has been updated by shevegen (Robert A. Heiler).


I don't have any pro or con opinion here but I wanted to comment on
one statement:

> maybe only another like 5 people know about the uminus change in 2.5 :)

Actually I noticed it first when nobu was using it, several months ago. :)

Noticed it in some of the ruby changelog and the method was new to me.

I have not used uminus myself, mostly because I do not like the syntax,
even though I understand that it is easier than adding checks for 
frozen strings and using dup (which I actually am doing nowadays a
lot; I use more frozen strings these days, mostly because I have noticed
a significant speed improvement in general; and for ruby scripts that
do a lot of work, I actually try to "optimize" these simply because it
can make a big difference between e. g. 30 seconds and 20 seconds
execution run, for larger ruby scripts/ruby projects).

----------------------------------------
Feature #14478: String #uminus should de-dupe unconditionally
https://bugs.ruby-lang.org/issues/14478#change-70383

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
continuing: https://bugs.ruby-lang.org/issues/14475

Current documentation for String uminus says: "If the string is frozen, then return the string itself."

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, uneeded copy
```

Instead why not change it so `-` is deduped unconditionally? 

I would argue this is worth backporting, cause if we are making fstring optimisations now, we are going to be stuck with legacy inefficient code going forward.

An alternative may be a c-extension gem that adds #fstring to String but that just feel wrong. 

I think the documentation should say:

String uminus says: "If the string is de-duplicated, then return the string itself."

Happy to make the change it is quite simple:`(FL_TEST(str, RSTRING_FSTR)` 






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