Issue #5328 has been updated by Akira Tanaka.


I can remember several documents.

* The document of Proc#lambda?.
* The thread from ruby-core:47453 "yield plus splat unwraps too much"
  (I don't recommend reading it in bugs.ruby-lang.org because messages are unintentionally formatted as markdown.) 
* ruby-dev:38795 (in Japanese)

Note that "always expands single array" was mistake.
The expantion also depends on the form of block arguments.

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Bug #5328: Splat args are treated wrongly in instance_exec and class_exec
https://bugs.ruby-lang.org/issues/5328#change-46580

* Author: Myron Marston
* Status: Rejected
* Priority: Normal
* Assignee: Akira Tanaka
* Category: 
* Target version: 
* ruby -v: ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
* Backport: 
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This gist demonstrates the issue:

https://gist.github.com/1218664

On 1.8.7, instance_exec and class_exec treat splat block args the same as method splat args.  On 1.9, it is treated differently and this is very unexpected.



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