anchor.diff:          if (target.isConst) {
             if (target.isInExternalLibrary && target.initializer == null) {
               // The variable is unavailable due to separate compilation.
  -            return new UnevaluatedConstant(node);
  +            return unevaluated(node);
             }
             return runInsideContext(target, () {
               return _evaluateSubexpression(target.initializer);
  
positive.code:       // Ensure the "identical()" function comes from dart:core.
        final parent = target.parent;
        if (parent is Library && parent == coreTypes.coreLibrary) {
          final positionalArguments = evaluatePositionalArguments(arguments);
          final Constant left = positionalArguments[0];
          final Constant right = positionalArguments[1];
          // Since we canonicalize constants during the evaluation, we can use
          // identical here.
          return identical(left, right) ? trueConstant : falseConstant;
  
negative.code:     }
    }
  
    Constant unevaluated(Expression expression) {
      return new UnevaluatedConstant(expression);
    }
  
    /// Evaluates [node] and possibly cache the evaluation result.
    /// @throws _AbortCurrentEvaluation if expression can't be evaluated.
    Constant _evaluateSubexpression(Expression node) {
  