nl_tokens: Internal smash call . Performance abstraction to bypass all the argument shenanigans as we know we will only be smashing two items at a time internally .
pl_tokens: function _smash ( a , b ) { this . forEach ( b , ( val , <mask> ) => { if ( this . isSmashable ( a [ key ] , b [ key ] ) ) // find a way to move isSmashable internal
   this . _smash ( a [ key ] , b [ key ] ) ; else a [ key ] = this . deepCopy ( b [ key ] ) ; } ) ; return a ; }