Very nice, lazy evaluation. One thing to improve though:
keywords get mixed with identifiers - for input buffer 'ifonly' the lexer will output 2 tokens Keyword(if) Identifier(only), where it should only one Keyword(ifonly)

My implementation doesn't use Symbol either (at least not explicitly).

I'm having some trouble with the first assertion. Every other passes.
In the browser I'm getting:

const jane = new Thing('Jane');
typeof jane //object

But chai fails with
TypeError: Cannot convert a Symbol value to a string

Can it be something with my code, or an error in chai?

This is a compiler, not an interpreter :D

Love it!

As mentioned, fix the 'report' function description.

Kata description is a bit misleading. It should be mentioned, that the main object object's properties may also be objects (nesting!). At first I thought there would be no nesting. Moreover you should add an example.