For JS: Moving all usages of Proxy from class constructor to getters helped me.

  const inspect = Symbol.for('nodejs.util.inspect.custom');
  // ...
  toString() {
    return "321";
  }
  get [Symbol.toStringTag]() {
    return 'Validator';
  }
  [inspect]() {
    return "123";
  }

doesn't solve the problem

If the grammar was different, such cases would be handled! But you're right, I could have added \b.

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)

Symbol.toStringTag is passed into an object when Object.prototype.toString of that object is called:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag

So you'll need to handle this case as well.

Edit: In addition, Node itself uses util.inspect.custom symbol when inspecting objects:

https://nodejs.org/api/util.html#util_util_inspect_custom

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

I didn't do the JS translation but I can tell you that Symbol is not used anywhere in the reference solution.

It would be good to know whether or not this is a chai incompatibility error, or whether it is a requirement for the task that Thing not have anything using Symbols...:hmm?

Yup, I too am at this point.

I'm facing with error something like your. In Browser everything working good. Sad that I spent many time for all tests are passed, and can't finish this kata :(

jane = new Thing("Jane") creates a new object

• TypeError: value.lookupGetter is not a function
• at formatProperty
• at /runner/node_modules/chai/lib/chai/utils/inspect.js:174:14
• at Array.map
• at formatValue
• at formatProperty
• at /runner/node_modules/chai/lib/chai/utils/inspect.js:174:14
• at Array.map
• at formatValue
• at inspect
• at module.exports
• at /runner/node_modules/chai/lib/chai/utils/getMessage.js:46:49
• at RegExp.[Symbol.replace]
• at RegExp.[Symbol.replace]
• at String.replace
• at Object.module.exports [as getMessage]
• at Assertion.chai.Assertion.assert

I'm experiencing the same issue.

jane = new Thing("Jane") creates a new object

TypeError: Cannot convert a Symbol value to a string
at Object.get
at objectToString
at isRegExp
at formatValue
at formatProperty
at /runner/node_modules/chai/lib/chai/utils/inspect.js:174:14
at Array.map
at formatValue
at inspect
at module.exports
at /runner/node_modules/chai/lib/chai/utils/getMessage.js:46:49
at RegExp.[Symbol.replace]
at RegExp.[Symbol.replace]
at String.replace
at Object.module.exports [as getMessage]
at Assertion.chai.Assertion.assert

I'm going to keep working on the rest of the kata, but unless this is resolved I won't be able to submit it - so I hope I'm not setting myself up for disappointment!

I'm facing the same issue. This assertion has some trouble on codewars, but it passes on my machine with node v6.10.3 and chai v3.5.0.
I have also translated the tests to run them with should (v11.1.2) instead of chai, and again, everything is ok.
Maybe a problem with an old chai version?

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!