[ruby-core:99551] [Ruby master Feature#17104] Do not freeze interpolated strings when using frozen-string-literal

[duerst@it.aoyama.ac.jp]

Issue #17104 has been updated by duerst (Martin Dürst).


bughit (bug hit) wrote in #note-11:
> > However in my view what defines a literal, is the use of a specific syntax, so ""
> 
> There is only one reason for freezing literals, to be able to intern them and reduce allocation. In fact the feature is poorly named, after the consequence(freezing), not the cause (interning).

My understanding is that another reason is avoidance of alias effects. It's easy to write code that when cut down to the essential, does this:
```
a = b = "My string"
a.gsub!(/My/, 'Your')
```
and expects `b` to still be "My string". Freezing makes sure this throws an error.

(This is not an argument for or againts freezing interpolated strings.)


----------------------------------------
Feature #17104: Do not freeze interpolated strings when using frozen-string-literal
https://bugs.ruby-lang.org/issues/17104#change-87013

* Author: bughit (bug hit)
* Status: Open
* Priority: Normal
----------------------------------------
```rb
#frozen_string_literal: true

def foo(str)
  "#{str}"
end

fr1 = 'a'
fr2 = 'a'
fr1_1 = foo(fr1)
fr2_1 = foo(fr2)

puts fr1.__id__, fr2.__id__, fr1_1.__id__, fr2_1.__id__

puts fr1_1 << 'b'
```

Isn't the point of frozen literals to avoid needless allocations? But interpolated strings are allocated each time, so freezing appears pointless. 




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