nl_tokens: https : // tc39 . github . io / ecmascript_sharedmem / shmem . html#Atomics . ValidateAtomicAccess
pl_tokens: function ValidateIndex ( index , <mask> ) { var numberIndex = TO_NUMBER ( index ) ; var accessIndex = TO_INTEGER ( numberIndex ) ; if ( numberIndex !== accessIndex ) { throw MakeRangeError ( kInvalidAtomicAccessIndex ) ; } if ( accessIndex < 0 || accessIndex >= length ) { throw MakeRangeError ( kInvalidAtomicAccessIndex ) ; } return accessIndex ; }