Issue #12835 has been updated by Kazuhiro NISHIYAMA.


I created [pull request](https://github.com/rurema/doctree/pull/339) for Japanese Reference Manual.

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Misc #12835: RDoc comment of String#casecmp
https://bugs.ruby-lang.org/issues/12835#change-60883

* Author: Toshihiko Ichida
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
String#casecmp dose not return nil but raise TypError for incomparable argument.

So 

~~~
 *     str.casecmp(other_str)   -> -1, 0, +1 or nil
~~~
should be like

~~~
 *     str.casecmp(other_str)   -> -1, 0, +1
~~~
or

~~~
 *     str.casecmp(other_str)   -> -1, 0, +1 or raise TypeError if other_str is not comparable
~~~


Here is a example.

~~~
irb(main):001:0> "a" <=> 1                               
=> nil                                                   
irb(main):002:0> "a".casecmp(1)                          
TypeError: no implicit conversion of Fixnum into String  

~~~

Japanese Reference Manual has same issue.




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