Add error checking for the immutable annotation (issue 27750)

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 808 matching lines @@
    * deprecated.
    */
   bool get isDeprecated;
 
   /**
    * Return `true` if this annotation marks the associated member as a factory.
    */
   bool get isFactory;
 
   /**
+   * Return `true` if this annotation marks the associated class and its
+   * subclasses as being immutable.
+   */
+  bool get isImmutable;
+
+  /**
    * Return `true` if this annotation marks the associated element with the `JS`
    * annotation.
    */
   bool get isJS;
 
   /**
    * Return `true` if this annotation marks the associated member as requiring
    * overriding methods to call super.
    */
   bool get isMustCallSuper;
@@ skipping 431 matching lines @@
    * Return `true` if the function is an entry point, i.e. a top-level function
    * and has the name `main`.
    */
   bool get isEntryPoint;
 
   @override
   FunctionDeclaration computeNode();
 }
 
 /**
- * The pseudo-declaration that defines a generic function type.
- */
-abstract class GenericFunctionTypeElement implements FunctionTypedElement {}
-
-/**
  * A function type alias (`typedef`).
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class FunctionTypeAliasElement
     implements FunctionTypedElement, TypeDefiningElement {
   /**
    * An empty array of type alias elements.
    */
   static List<FunctionTypeAliasElement> EMPTY_LIST =
@@ skipping 25 matching lines @@
    * fully populated, then the [returnType] will not be `null`, even if no
    * return type was explicitly specified.
    */
   DartType get returnType;
 
   @override
   FunctionType get type;
 }
 
 /**
+ * The pseudo-declaration that defines a generic function type.
+ */
+abstract class GenericFunctionTypeElement implements FunctionTypedElement {}
+
+/**
  * A combinator that causes some of the names in a namespace to be hidden when
  * being imported.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class HideElementCombinator implements NamespaceCombinator {
   /**
    * Return a list containing the names that are not to be made visible in the
    * importing library even if they are defined in the imported library.
    */
@@ skipping 723 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();
 }