anchor.diff:      //
       // Prepare inputs.
       //
  -    // Note: UNIT_INPUT is not needed.  It is merely a bookkeeping dependency
  -    // to ensure that resolution has occurred before we attempt to determine
  -    // constant dependencies.
  -    //
       ConstantEvaluationTarget constant = target;
       TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
       //
  
positive.code:     //
      // Record outputs.
      //
      outputs[RESOLVE_UNIT_ERRORS] = errorListener.errors;
      outputs[RESOLVED_UNIT9] = unit;
    }
  
negative.code:    * given [target].
     */
    static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
      //
      // We need to force the computation of the RESOLVED_UNIT9 for each unit
      // reachable from the target's library so that all of the AST's for the
      // contructor initializers that we might encounter have been copied into
      // the element model.
      //
      // TODO(brianwilkerson) This could be improved by computing a more accurate
      // list of the sources containing constructors that are actually referenced.
      //
      if (target is Element) {
        CompilationUnitElementImpl unit = target
            .getAncestor((Element element) => element is CompilationUnitElement);
        Source librarySource = unit.librarySource;
        return <String, TaskInput>{
          'resolvedUnits': IMPORT_EXPORT_SOURCE_CLOSURE.of(librarySource).toList(
              (Source library) => UNITS.of(library).toList((Source source) =>
                  RESOLVED_UNIT9.of(new LibrarySpecificUnit(library, source)))),
          TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
        };
      } else if (target is ConstantEvaluationTarget_Annotation) {
        Source librarySource = target.librarySource;
        return <String, TaskInput>{
          'resolvedUnits': IMPORT_EXPORT_SOURCE_CLOSURE.of(librarySource).toList(
              (Source library) => UNITS.of(library).toList((Source source) =>
                  RESOLVED_UNIT9.of(new LibrarySpecificUnit(library, source)))),
          TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
        };
      }
  