[php-langspec][PR #229] - Change isset expression

[email protected] Fri, 21 Dec 2018 04:16:36 +0000

Newsgroups	php.standards
Message-ID	<[email protected]>

You can view the Pull Request on github:
https://github.com/php/php-langspec/pull/229

Comment by zhujinxuan:
@nikic I think using Constraints would harm a simplicity that a parser writer just need to read expressions for writing a parser.

How about:
```
list-intrinsic:
   list   (   list-expression-list   )

list-expression-list:
  commas? list-element
  commas? list-element , list-expression-list?
  commas? list-element commas

commas:
  ,
  , commas

list-element
   expression   =>   list-or-variable
   list-or-variable
```