[ruby-core:120327] [Ruby master Bug#20970] `it /1/i` raises undefined method 'it' for main (NoMethodError) even if binding.local_variables includes `it`

Issue #20970 has been updated by zverok (Victor Shepelev).


Interesting. Before the change (on `3.4.0dev (2024-12-15T13:36:38Z master 366fd9642f)`) it was an error both with Prism and parse.y:

```bash
$ ruby -e "i = 2; [1, 2, 3].each { it /1/i }"
-e:1:in 'block in <main>': undefined method 'it' for main (NoMethodError)
$ ruby --parser=parse.y -e "i = 2; [1, 2, 3].each { it /1/i }"
-e:1:in 'block in <main>': undefined method 'it' for main (NoMethodError)
```

As far as I can guess (by IRB syntax highlighting), `it /1/i` parses at once as `it(/1/i)` (with `/1/i` treated as a regexp literal). Reproduced in other ambiguous cases (that are resolved by local name presence, for all I can understand), say:

```bash
ruby -e "[1, 2, 3].each { it + 1 }"
#=> OK
$ ruby -e "[1, 2, 3].each { it +1 }"
-e:1:in 'block in <main>': undefined method 'it' for main (NoMethodError)
$ ruby -e "[1, 2, 3].each { |it| it +1 }"
#=> OK
```

I.e., ambiguous operators parsing decisions are made based on whether `it` is known to be a local var (then it is `it.+(1)`), or not known (then it is tentatively considered `it(+1)`).

----------------------------------------
Bug #20970: `it /1/i` raises undefined method 'it' for main (NoMethodError) even if binding.local_variables includes `it`
https://bugs.ruby-lang.org/issues/20970#change-111099

* Author: tompng (tomoya ishida)
* Status: Open
* ruby -v: ruby 3.4.0dev (2024-12-19T07:16:12Z master 335bba0fde) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
`it` parameter became a local variable with #20965, but it does not behave like local variable with `--parser=prism`

~~~ruby
i=2
42.tap do
  p it # 42
  p local_variables # [:it, :i]
  p it /1/i # should be 21, got NoMethodError
end
~~~


It prints `42`, `[:it, :i], `21` with `--parser=parse.y`




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