anchor.diff:  class LibraryScope extends EnclosedScope {
     /**
      * Initialize a newly created scope representing the names defined in the
  -   * [definingLibrary]. The error listener is no longer used and should be
  -   * omitted.
  +   * [definingLibrary].
      */
     LibraryScope(LibraryElement definingLibrary)
         : super(new LibraryImportScope(definingLibrary)) {
  
positive.code: class BlockScope extends EnclosedScope {
    /**
     * Initialize a newly created scope, enclosed within the [enclosingScope],
     * based on the given [classElement].
     */
    BlockScope(Scope enclosingScope, Block block) : super(enclosingScope) {
      if (block == null) {
  
negative.code: 
    /**
     * Initialize a newly created scope representing the names imported into the
     * [_definingLibrary].
     */
    LibraryImportScope(this._definingLibrary) {
      _createImportedNamespaces();
  