Scala Bound checking - scala

Question

I am confused about this sentence "If the identifier is bound to a thunk or a text". How can I check that? I have code where identifier is an extension of expression, while thunk and text are of type values. I have this code here but when I run it, I get a stackoverflow error.
package expression
import context._
import value._
case class Identifier(val name: String) extends Expression{
override def toString = name
/*def execute(env: Environment): Value = {
env(this)
}*/
def execute(env:Environment): Value =
{
val envThis = env(this)//wrong here
println(this.getClass)
if(envThis.isInstanceOf[Text])
{
//println(envThis.asInstanceOf[Text].body.getClass) identifier class type
envThis.asInstanceOf[Text].body.execute(env) //wrong here
}
else if(envThis.isInstanceOf[Thunk])
{
envThis.asInstanceOf[Thunk].apply()
}
else
{
env(this)
}
}
}

Answer 1

It is hard to tell without knowing more about the context, but perhaps you should be looking up the name of the identifier in the environment, rather than the Identifier instance?
It would certainly be much clearer to use a match statement, something like this:
def execute(env: Environment): Value =
{
val envThis = env(name)
println(this.getClass)
envThis match {
case text: Text =>
text.body.execute(env)
case thunk: Thunk =>
thunk()
case other =>
other
}
}