[php-langspec][Issue #248] - primary-expression and assignment-expression not being used

You can view the Issue on github:
https://github.com/php/php-langspec/issues/248

Comment by dende:
I see, and i can follow that chain even to assignment-expression and simple-assignemnt-expression. Thank you!

But I don't seem to find a way to generate an `assignment` from an `expression-statement`. 

All of 
<pre>
   include-expression
   include-once-expression
   require-expression
   require-once-expression
</pre>
have their keywords "hardcoded" into them.

I see the chain from `expression` over `logical-inc-OR-expression-2` to `yield-expression`, but can not find a way to generate an `assignment-expression` without the keywords `yield` or `yield from` before it