2.1.32 [ECMA-262/9:2018] Section 19.2.4.1 length

V0074: The [[writable]] attribute of the length property cannot be set to true, regardless of the setting of [[configurable]]

The specification states:

 19.2.4.1 length
  
     The value of the length property is an integer that indicates the typical number of 
     arguments expected by the function. However, the language permits the function to be 
     invoked with some other number of arguments. The behaviour of a function when invoked 
     on a number of arguments other than the number specified by its length property 
     depends on the function. This property has the attributes { [[Writable]]: false, 
     [[Enumerable]]: false, [[Configurable]]: true }.

EdgeHTML Mode

The [[writable]] attribute of the length property cannot be set to true, regardless of the setting of [[configurable]]. No error is thrown on an attempt to set it true.