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Feature #16037

Updated by sawa (Tsuyoshi Sawada) over 4 years ago

Pattern matching in `in` argument seems to prohibit multiple occurrences of single/double-splatted variables. 

 ```ruby 
 case ""; in *foo, Integer, bar; end # >> NoMatchingPatternError (Not SyntaxError) 
 case ""; in *foo, Integer, *bar; end # >> SyntaxError: unexpected * 
 ``` 

 However, unlike conventional constant/variable assignment, it makes sense to have multiple occurrences of single/double-splatted variables in a single pattern matching provided that we have a definite rule regarding whether the splats are greedy or not. 

 I propose the following. 

 1. Relax the syntax for pattern matching in `in` argument to allow multiple occurrences of single/double-splatted variables, and set up a rule regarding whether the splats are greedy or not; preferably greedy. 
 2. Further, introduce new syntax for non-greedy splats `*?foo`, `**?foo`. Currently, they are syntactically invalid, so I don't think they would conflict with existing code.

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