ASTAddr.java

public class ASTAddr implements ASTNode {
    private final String id;  

    public ASTAddr(String id) {
        this.id = id;
    }

    @Override
    public IValue eval(Environment<IValue> e) throws InterpreterError {
        IValue v = e.find(id);
        if (!(v instanceof VMut mut))
            throw new InterpreterError("&: " + id + " is not a mut variable");
        return mut.getAddr();
    }

    @Override
    public ASTType typecheck(Environment<ASTType> e) throws TypeCheckError, InterpreterError {
        ASTType t = e.find(id);
        t = ASTTypeDef.unfold(t, e);

        if (!(t instanceof ASTTMut mut))
            throw new TypeCheckError("&: " + id + " is not a mut variable");

        int varDepth = e.getScopeDepth(id);
        return new ASTTAddr(mut.getInner(), varDepth);  
    }
}