[ruby-core:94029] [Ruby master Bug#16008] Ripper hshptn node drops information

Issue #16008 has been updated by ko1 (Koichi Sasada).

Assignee set to nobu (Nobuyoshi Nakada)

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Bug #16008: Ripper hshptn node drops information
https://bugs.ruby-lang.org/issues/16008#change-80254

* Author: kddeisz (Kevin Deisz)
* Status: Open
* Priority: Normal
* Assignee: nobu (Nobuyoshi Nakada)
* Target version: 
* ruby -v: 2.7.0-preview1
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Hi - I'm the author of the prettier plugin for ruby. I'm trying to get it to support 2.7 pattern matching. It works well for everything to do with the array pattern. However, for hash patterns, it drops certain information if you touch the `on_label` method (which I do to add metadata about the location of the token). For example,


``` ruby
require 'ripper'

class Parser < Ripper::SexpBuilder
  private

  def on_label(token)
    [:@label, token]
  end
end

content = <<~EORUBY
  case foo
  in { a: 1 }
    bar
  else
    baz
  end
EORUBY

pp Ripper::SexpBuilder.new(content).parse
pp Parser.new(content).parse
```

This script results in:

```ruby
[:program,
 [:stmts_add,
  [:stmts_new],
  [:case,
   [:vcall, [:@ident, "foo", [1, 5]]],
   [:in,
    [:hshptn, nil, [[[:@label, "a:", [2, 5]], [:@int, "1", [2, 8]]]], nil],
    [:stmts_add, [:stmts_new], [:vcall, [:@ident, "bar", [3, 2]]]],
    [:else, [:stmts_add, [:stmts_new], [:vcall, [:@ident, "baz", [5, 2]]]]]]]]]
[:program,
 [:stmts_add,
  [:stmts_new],
  [:case,
   [:vcall, [:@ident, "foo", [1, 5]]],
   [:in,
    [:hshptn, nil, nil, nil],
    [:stmts_add, [:stmts_new], [:vcall, [:@ident, "bar", [3, 2]]]],
    [:else, [:stmts_add, [:stmts_new], [:vcall, [:@ident, "baz", [5, 2]]]]]]]]]
```

As you can see, in the second example the `hashptn` node has no label on it. I'm not entirely sure what's going on there. Any insight would be appreciated.




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