[ruby-core:83687] [Ruby trunk Bug#14086] Interpreter seems to sneak in a nil value when a comma is missing on a nested array wrapped in parenthesis

Issue #14086 has been updated by zverok (Victor Shepelev).


> is this the expected behaviour?

Yes.

Try this:

```ruby
[2, 2][3, 3] # => nil
```
Why?
Because it is read as "Array of `[2,2]`, call operator [] with arguments `3, 3` (which means fetch 3 elements starting from 3rd)". As this array doesn't have a 3rd element, the result of the operation is `nil`. So the first item of your larger array is the result of this calculation, e.g. `nil`.

----------------------------------------
Bug #14086: Interpreter seems to sneak in a nil value when a comma is missing on a nested array wrapped in parenthesis
https://bugs.ruby-lang.org/issues/14086#change-67713

* Author: mariogintili (Mario Gintili)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
I believe the title is self explanatory. But code is always louder than words:

~~~ ruby
$ ruby --version
ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin16]
$ irb
2.2.4 :001 > ([[2,2], [3,3], [4,4], [5,5], [6,6]])
 => [[2, 2], [3, 3], [4, 4], [5, 5], [6, 6]] 
2.2.4 :002 > ([[2,2] [3,3], [4,4], [5,5], [6,6]])
 => [nil, [4, 4], [5, 5], [6, 6]] 
~~~

the only difference between lines 1 and 2 in my REPL is a coma right after the first nested array. is this the expected behaviour? 




-- 
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