Issue #10543 has been updated by Nobuyoshi Nakada.

Related to Bug #10437: ruby -c and ripper inconsistency: /*/ added

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Bug #10543: ruby -c and ripper inconsistency: /(?<n>a(b|\g<n>))/
https://bugs.ruby-lang.org/issues/10543#change-50213

* Author: Akira Tanaka
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.2.0dev (2014-11-26 trunk 48577) [x86_64-linux]
* Backport: 2.0.0: DONTNEED, 2.1: DONTNEED
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以下のように、/(?<n>a(b|\g<n>))/ というだけのソースは
ruby -c では問題無しとなりますが、
Ripper.sexp では構文木でなく nil が返ってきてしまいます。

```
% cat z.rb                   
/(?<n>a(b|\g<n>))/
% ./ruby -c z.rb
Syntax OK
% ./ruby -rripper -e 'p Ripper.sexp(STDIN.read)' < z.rb  
nil
% ./ruby -v                                                
ruby 2.2.0dev (2014-11-26 trunk 48577) [x86_64-linux]
```




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