sclass LASScope {

  // do we use FixedVarContext instead of FlexibleVarContext

  settable bool useFixedVars;

  // 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 (resolved)

  S[] names;

  *() {}

  *(LASScope *parentScope) {}

  bool resolved() { ret names != null; }

  void addDeclaredVar(S name, LASValueDescriptor type) {

    if (resolved())

      fail("Can't add variables to resolved scope");

    declaredVars.put(name, type);

  }

  int resolveVar(S name) {

    resolve();

    int idx = indexOfInSortedArray(names, name);

    if (idx < 0)

      fail("Variable not found in scope: " + name);

    ret idx;

  }

  void resolve {

    if (names != null) ret;

    names = empty(declaredVars) ? null

      : toStringArray(sortedKeys(declaredVars));

  }

}