A missing enum case in a switch is a warning, not a compile-time error.

pkg/analyzer/lib/src/generated/error.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.
 
 library analyzer.src.generated.error;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart' show AstNode;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/source/error_processor.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/scanner.dart'
     show ScannerErrorCode, Token;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/model.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:source_span/source_span.dart';
 
-import 'generated/shared_messages.dart' as shared_messages;
-
 /**
  * The descriptor used to associate error processors with analysis contexts in
  * configuration data.
  */
 final ListResultDescriptor<List<ErrorProcessor>> CONFIGURED_ERROR_PROCESSORS =
     new ListResultDescriptorImpl('configured.errors', const <ErrorProcessor>[]);
 
 /**
  * An error discovered during the analysis of some Dart code.
  *
@@ skipping 1619 matching lines @@
           "List literals must be prefixed with 'const' when used as a constant expression");
 
   /**
    * 12.1 Constants: A constant expression is ... a constant map literal.
    */
   static const CompileTimeErrorCode MISSING_CONST_IN_MAP_LITERAL =
       const CompileTimeErrorCode('MISSING_CONST_IN_MAP_LITERAL',
           "Map literals must be prefixed with 'const' when used as a constant expression");
 
   /**
-   * Enum proposal: It is a static warning if all of the following conditions
-   * hold:
-   * * The switch statement does not have a 'default' clause.
-   * * The static type of <i>e</i> is an enumerated typed with elements
-   *   <i>id<sub>1</sub></i>, &hellip;, <i>id<sub>n</sub></i>.
-   * * The sets {<i>e<sub>1</sub></i>, &hellip;, <i>e<sub>k</sub></i>} and
-   *   {<i>id<sub>1</sub></i>, &hellip;, <i>id<sub>n</sub></i>} are not the
-   *   same.
-   *
-   * Parameters:
-   * 0: the name of the constant that is missing
-   */
-  static const CompileTimeErrorCode MISSING_ENUM_CONSTANT_IN_SWITCH =
-      const CompileTimeErrorCode(
-          'MISSING_ENUM_CONSTANT_IN_SWITCH',
-          "Missing case clause for '{0}'",
-          "Add a case clause for the missing constant or add a default clause.");
-
-  /**
    * 9 Mixins: It is a compile-time error if a declared or derived mixin
    * explicitly declares a constructor.
    *
    * Parameters:
    * 0: the name of the mixin that is invalid
    */
   static const CompileTimeErrorCode MIXIN_DECLARES_CONSTRUCTOR =
       const CompileTimeErrorCode('MIXIN_DECLARES_CONSTRUCTOR',
           "The class '{0}' cannot be used as a mixin because it declares a constructor");
 
@@ skipping 916 matching lines @@
     CompileTimeErrorCode.INVALID_REFERENCE_TO_THIS,
     CompileTimeErrorCode.INVALID_TYPE_ARGUMENT_IN_CONST_LIST,
     CompileTimeErrorCode.INVALID_TYPE_ARGUMENT_IN_CONST_MAP,
     CompileTimeErrorCode.INVALID_URI,
     CompileTimeErrorCode.LABEL_IN_OUTER_SCOPE,
     CompileTimeErrorCode.LABEL_UNDEFINED,
     CompileTimeErrorCode.MEMBER_WITH_CLASS_NAME,
     CompileTimeErrorCode.METHOD_AND_GETTER_WITH_SAME_NAME,
     CompileTimeErrorCode.MISSING_CONST_IN_LIST_LITERAL,
     CompileTimeErrorCode.MISSING_CONST_IN_MAP_LITERAL,
-    CompileTimeErrorCode.MISSING_ENUM_CONSTANT_IN_SWITCH,
     CompileTimeErrorCode.MIXIN_DECLARES_CONSTRUCTOR,
     CompileTimeErrorCode.MIXIN_DEFERRED_CLASS,
     CompileTimeErrorCode.MIXIN_HAS_NO_CONSTRUCTORS,
     CompileTimeErrorCode.MIXIN_INHERITS_FROM_NOT_OBJECT,
     CompileTimeErrorCode.MIXIN_OF_DISALLOWED_CLASS,
     CompileTimeErrorCode.MIXIN_OF_ENUM,
     CompileTimeErrorCode.MIXIN_OF_NON_CLASS,
     CompileTimeErrorCode.MIXIN_REFERENCES_SUPER,
     CompileTimeErrorCode.MIXIN_WITH_NON_CLASS_SUPERCLASS,
     CompileTimeErrorCode.MULTIPLE_REDIRECTING_CONSTRUCTOR_INVOCATIONS,
@@ skipping 214 matching lines @@
     StaticWarningCode.UNDEFINED_CLASS,
     StaticWarningCode.UNDEFINED_CLASS_BOOLEAN,
     StaticWarningCode.UNDEFINED_GETTER,
     StaticWarningCode.UNDEFINED_IDENTIFIER,
     StaticWarningCode.UNDEFINED_NAMED_PARAMETER,
     StaticWarningCode.UNDEFINED_SETTER,
     StaticWarningCode.UNDEFINED_STATIC_METHOD_OR_GETTER,
     StaticWarningCode.UNDEFINED_SUPER_GETTER,
     StaticWarningCode.UNDEFINED_SUPER_SETTER,
     StaticWarningCode.VOID_RETURN_FOR_GETTER,
+    StaticWarningCode.MISSING_ENUM_CONSTANT_IN_SWITCH,
     TodoCode.TODO,
 
     //
     // parser.dart:
     //
     ParserErrorCode.ABSTRACT_CLASS_MEMBER,
     ParserErrorCode.ABSTRACT_ENUM,
     ParserErrorCode.ABSTRACT_STATIC_METHOD,
     ParserErrorCode.ABSTRACT_TOP_LEVEL_FUNCTION,
     ParserErrorCode.ABSTRACT_TOP_LEVEL_VARIABLE,
@@ skipping 2778 matching lines @@
           "The setter '{0}' is not defined in a superclass of '{1}'");
 
   /**
    * 7.2 Getters: It is a static warning if the return type of a getter is void.
    */
   static const StaticWarningCode VOID_RETURN_FOR_GETTER =
       const StaticWarningCode('VOID_RETURN_FOR_GETTER',
           "The return type of the getter must not be 'void'");
 
   /**
+   * 17.9 Switch: It is a static warning if all of the following conditions
+   * hold:
+   * * The switch statement does not have a 'default' clause.
+   * * The static type of <i>e</i> is an enumerated typed with elements
+   *   <i>id<sub>1</sub></i>, &hellip;, <i>id<sub>n</sub></i>.
+   * * The sets {<i>e<sub>1</sub></i>, &hellip;, <i>e<sub>k</sub></i>} and
+   *   {<i>id<sub>1</sub></i>, &hellip;, <i>id<sub>n</sub></i>} are not the
+   *   same.
+   *
+   * Parameters:
+   * 0: the name of the constant that is missing
+   */
+  static const StaticWarningCode MISSING_ENUM_CONSTANT_IN_SWITCH =
+      const StaticWarningCode('MISSING_ENUM_CONSTANT_IN_SWITCH',
+          "Missing case clause for '{0}'",
+          "Add a case clause for the missing constant or add a default clause.");
+
+  /**
    * Initialize a newly created error code to have the given [name]. The message
    * associated with the error will be created from the given [message]
    * template. The correction associated with the error will be created from the
    * given [correction] template.
    */
   const StaticWarningCode(String name, String message, [String correction])
       : super(name, message, correction);
 
   @override
   ErrorSeverity get errorSeverity => ErrorType.STATIC_WARNING.severity;
@@ skipping 32 matching lines @@
    * Initialize a newly created error code to have the given [name].
    */
   const TodoCode(String name) : super(name, "{0}");
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.INFO;
 
   @override
   ErrorType get type => ErrorType.TODO;
 }