Javascript and automatic semicolon insertion

Question

test262 test suite has test containing source:

var x=0, y=0;
var z=
x
++
++
y

The annotation says:

Since LineTerminato

Answer 1

This code will become:

var z = x;
++ ++ y;

The ++ ++ y is the root of the problem. Let’s look at why...

++ ++ y gets evaluated as ++(++y). The first step is to evaluate (++y). The ++ operator increments the value referenced by the variable it is next to, and returns the incremented value. The important part here is that it does not return a reference, just a value. So the second step would be ++(1), (or whatever ++y yielded), which is an error, since only references can be incremented.