Immutable objects

[giann]

Either declare an object as immutable:

immut object Point {
    int x,
    int y,
}

And/Or declare an instance as immutable:

immut Point point = Point{
    x = 10,
    y = 10,
}

point.x = 20; | -> fails

Both would allow:

• object instances to be enum value
• interning of object instances and potentially speed up a lot of buzz code

And/Or declare fields as immutable #13

If we do https://github.com/buzz-language/buzz/issues/139 the keyword would need to specify mutability instead:

mut object Point {
    int x,
    int y,
}

| If we do it per instance + immutability by default we would have to say here that
| the variable is mutable and that the instance it contains is itself mutable.
| Not really elegant.
var mut Point point = Point{
    x = 10,
    y = 10,
}