sclass LASScope {
  // variables declared in this scope, with type/value description
  gettable new Map<S, LASValueDescriptor> declaredVars;
  
  // optional parent scope
  // (we can see the parent's variables in this scope too, unless they
  // are redeclared)
  settable LASScope parentScope;
  
  // true = we may outlive the parent scope
  // (e.g. when we're a lambda)
  settable bool parentIsDetached;
  
  // sorted names when scope is finalized
  S[] names;
  
  *() {}
  *(LASScope *parentScope) {}
  
  int resolveVar(S name) {
    resolve();
    ret indexOfInSortedArray(names, name);
  }
  
  void resolve {
    if (names != null) ret;
    names = empty(declaredVars) ? null
      : toStringArray(sortedKeys(declaredVars));
  }
}