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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
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I want to add new node types to the parser translator, for example `itblock`. The bulk of the work is already done by prism itself. In the `parser`
builder, this would be a 5-line change at most but we don't control that here.
Instead, we can add our own builder and either overwrite the few methods we need,
or just inline the complete builder. I'm not sure yet which would be better.
`rubocop-ast` uses its own builder for `parser`. For this to correctly work, it must explicitly choose to extend the
prism builder and use it, same as it currently chooses to use a different parser when prism is used.
I'd like to enforce that the builder for prism extends its custom one since it will lead to
some pretty weird issues otherwise. But first, I'd like to change `rubocop-ast` to make use of this.
https://github.com/ruby/prism/commit/b080e608a8
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