LazyScope.java

package jetbrains.mps.lang.scopes.runtime;

/*Generated by MPS */

import jetbrains.mps.baseLanguage.closures.runtime._FunctionTypes;
import jetbrains.mps.scope.Scope;
import jetbrains.mps.scope.EmptyScope;

public class LazyScope extends DelegatingScope {
  private final _FunctionTypes._return_P0_E0<? extends Scope> scopePromise;
  private Scope scope;
  private boolean isCalculated = false;
  public LazyScope(_FunctionTypes._return_P0_E0<? extends Scope> scopePromise) {
    this.scopePromise = scopePromise;
  }
  @Override
  protected Scope getScope() {
    if (!(isCalculated)) {
      scope = scopePromise.invoke();
      // todo: think about this case... 
      if (scope == null) {
        scope = new EmptyScope();
      }
      isCalculated = true;
    }
    return scope;
  }
}