Add a (public) utility method to clean-up code

pkg/analyzer/lib/dart/ast/ast.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Defines the AST model. The AST (Abstract Syntax Tree) model describes the
  * syntactic (as opposed to semantic) structure of Dart code. The semantic
  * structure of the code is modeled by the
  * [element model](../element/element.dart).
  *
@@ skipping 3020 matching lines @@
   /**
    * Return the static type of this expression, or `null` if the AST structure
    * has not been resolved.
    */
   DartType get staticType;
 
   /**
    * Set the static type of this expression to the given [type].
    */
   void set staticType(DartType type);
+
+  /**
+   * If this expression is a parenthesized expression, return the result of
+   * unwrapping the expression inside the parentheses. Otherwise, return this
+   * expression.
+   */
+  Expression get unParenthesized;
 }
 
 /**
  * A function body consisting of a single expression.
  *
  *    expressionFunctionBody ::=
  *        'async'? '=>' [Expression] ';'
  *
  * Clients may not extend, implement or mix-in this class.
  */
@@ skipping 5047 matching lines @@
   /**
    * Return the 'yield' keyword.
    */
   Token get yieldKeyword;
 
   /**
    * Return the 'yield' keyword to the given [token].
    */
   void set yieldKeyword(Token token);
 }