public void enterVar(Expression.Var var) {
// If this is a let variable in the counts map increment the reference count.
String varName = var.getName().getUnqualifiedName();
LetDefn letDef = varNamToDef.get(varName);
if (letDef != null) {
letDef.incrementUseCount();
}
}
@Override
public void enterLetNonRec(Expression.LetNonRec let) {
// Add the let variable to the counts map with a reference count of zero.