Class with constructor got issue

I got error with these lines of code:

```
class Animal {
    function constructor(breed = "bear") {
        this.breed = breed
    }
    function speak() {
        print(this.breed)
    }
}

animal = Animal.new()
animal.speak()

```

The detail error is:

`
panic: interface conversion: ast.ExpressionNode is *ast.Identifier, not *ast.Number
`