Issue #17104 has been updated by Eregon (Benoit Daloze).


mame (Yusuke Endoh) wrote in #note-18:
> I found `"foo#{ "foo" }"` frozen because it is optimized to `"foofoo"` at the parser.  What do you think?

I guess that's semantically correct (besides the frozen status), since interpolation does not need to call `#to_s` for a String.
Since such code is very unlikely to appear in real code, I think it ultimately does not matter too much.

But if we can easily remove that optimization in the parser, I think it would be better, because this is an inconsistency (it makes it harder to reason about Ruby semantics & it breaks referential transparency) and optimizing `"foo#{ "foo" }"` seems to have no use in practice.
Could you point me to where the optimization is done in the parser if you found it? :)

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Feature #17104: Do not freeze interpolated strings when using frozen-string-literal
https://bugs.ruby-lang.org/issues/17104#change-87347

* Author: bughit (bug hit)
* Status: Open
* Priority: Normal
* Assignee: Eregon (Benoit Daloze)
----------------------------------------
I think the point of frozen string literals is to avoid needless allocations. Interpolated strings are allocated each time, so freezing them appears pointless. 

```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'
```




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