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## Summary
`itblock` node is added to support the `it` block parameter syntax introduced in Ruby 3.4.
```console
$ ruby -Ilib -rprism -rprism/translation/parser34 -e 'buffer = Parser::Source::Buffer.new("path"); buffer.source = "proc { it }"; \
p Prism::Translation::Parser34.new.tokenize(buffer)[0]'
s(:itblock,
s(:send, nil, :proc), :it,
s(:lvar, :it))
```
This node design is similar to the `numblock` node, which was introduced for the numbered parameter syntax in Ruby 2.7.
```
$ ruby -Ilib -rprism -rprism/translation/parser34 -e 'buffer = Parser::Source::Buffer.new("path"); buffer.source = "proc { _1 }"; \
p Prism::Translation::Parser34.new.tokenize(buffer)[0]'
s(:numblock,
s(:send, nil, :proc), 1,
s(:lvar, :_1))
```
The difference is that while numbered parameters can have multiple parameters, the `it` block parameter syntax allows only a single parameter.
In Ruby 3.3, the conventional node prior to the `it` block parameter syntax is returned.
```console
$ ruby -Ilib -rprism -rprism/translation/parser33 -e 'buffer = Parser::Source::Buffer.new("path"); buffer.source = "proc { it }"; \
p Prism::Translation::Parser33.new.tokenize(buffer)[0]'
s(:block,
s(:send, nil, :proc),
s(:args),
s(:send, nil, :it))
```
## Development Note
The Parser gem does not yet support the `it` block parameter syntax. This is the first case where Prism's node design precedes that of the Parser gem.
When implementing https://github.com/whitequark/parser/issues/962, this node design will need to be taken into consideration.
https://github.com/ruby/prism/commit/c141e1420a