nl_tokens: If target is non - extensible and setPrototypeOf trap returns true check whether the trap result corresponds to the target s [[ Prototype ]]
pl_tokens: function ( newProto ) { var trap = this . getTrap ( "setPrototypeOf" ) ; if ( trap === undefined ) { // default forwarding behavior return Reflect . setPrototypeOf ( this . target , newProto ) ; } var success = trap . call ( this . handler , this . target , newProto ) ; success = ! ! success ; if ( <mask> && ! Object_isExtensible ( this . target ) ) { var actualProto = Object_getPrototypeOf ( this . target ) ; if ( ! sameValue ( newProto , actualProto ) ) { throw new TypeError ( "prototype value does not match: " + this . target ) ; } } return success ; }