Validation of `@mustCallSuper` overrides.

pkg/analyzer/lib/src/dart/element/element.dart

Index: pkg/analyzer/lib/src/dart/element/element.dart
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index 584f797d755272a2b1e32f74654d3cb8030a1b83..310e4e9625c9f97b6ef57718a46df0fc12f55c1c 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -1601,6 +1601,12 @@ class ElementAnnotationImpl implements ElementAnnotation {
   static String _META_LIB_NAME = "meta";
 
   /**
+   * The name of the top-level variable used to mark a method as requiring
+   * overriders to call super.
+   */
+  static String _MUST_CALL_SUPER_VARIABLE_NAME = "mustCallSuper";
+
+  /**
    * The name of the top-level variable used to mark a method as being expected
    * to override an inherited method.
    */
@@ -1667,6 +1673,12 @@ class ElementAnnotationImpl implements ElementAnnotation {
   }
 
   @override
+  bool get isMustCallSuper =>
+      element is PropertyAccessorElement &&
+      element.name == _MUST_CALL_SUPER_VARIABLE_NAME &&
+      element.library?.name == _META_LIB_NAME;
+
+  @override
   bool get isOverride =>
       element is PropertyAccessorElement &&
       element.name == _OVERRIDE_VARIABLE_NAME &&