Add toSource() to ElementAnnotation, ElementAnnotationImpl (issue 28631)

pkg/analyzer/lib/dart/element/element.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 element model. The element model describes the semantic (as
  * opposed to syntactic) structure of Dart code. The syntactic structure of the
  * code is modeled by the [AST structure](../ast/ast.dart).
  *
  * The element model consists of two closely related kinds of objects: elements
@@ skipping 849 matching lines @@
    * required.
    */
   bool get isRequired;
 
   /**
    * Return a representation of the value of this annotation, forcing the value
    * to be computed if it had not previously been computed, or `null` if the
    * value of this annotation could not be computed because of errors.
    */
   DartObject computeConstantValue();
+
+  /**
+   * Return a textual description of this annotation in a form approximating
+   * valid source. The returned string will not be valid source primarily in the
+   * case where the annotation itself is not well-formed.
+   */
+  String toSource();
 }
 
 /**
  * The kind of elements in the element model.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 class ElementKind implements Comparable<ElementKind> {
   static const ElementKind CLASS = const ElementKind('CLASS', 0, "class");
 
@@ skipping 1170 matching lines @@
   DartType get type;
 
   /**
    * Return a representation of the value of this variable, forcing the value
    * to be computed if it had not previously been computed, or `null` if either
    * this variable was not declared with the 'const' modifier or if the value of
    * this variable could not be computed because of errors.
    */
   DartObject computeConstantValue();
 }