Validation of @protected property accesses.

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index f0d926bef3e8039fc56d1600386f28dec6587aea..9faabbd122422a9d0e60380d2cad43dadd6ca191 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -238,6 +238,7 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
   @override
   Object visitSimpleIdentifier(SimpleIdentifier node) {
     _checkForDeprecatedMemberUseAtIdentifier(node);
+    _checkForInvalidProtectedPropertyAccess(node);
     return super.visitSimpleIdentifier(node);
   }
 
@@ -609,6 +610,41 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
   }
 
   /**
+   * Produces a hint if the given identifier is a protected field or getter
+   * accessed outside a subclass.
+   */
+  void _checkForInvalidProtectedPropertyAccess(SimpleIdentifier identifier) {
+    if (identifier.inDeclarationContext()) {
+      return;
+    }
+    Element element = identifier.bestElement;
+    if (element != null) {

[Brian Wilkerson, 2016/02/24 19:54:25]

The 'is' test below should negate the need to the null check.

[pquitslund, 2016/02/24 20:34:43]

Nice.  I missed that when I refactored.  Thanks!

+      if (element is PropertyAccessorElement &&
+          (element.isProtected || element.variable.isProtected)) {
+        ClassElement definingClass = element.enclosingElement;
+        if (definingClass == null) {
+          return;
+        }
+        ClassDeclaration accessingClass =
+            identifier.getAncestor((AstNode node) => node is ClassDeclaration);
+
+        if (accessingClass == null) {
+          _errorReporter.reportErrorForNode(
+              HintCode.INVALID_USE_OF_PROTECTED_MEMBER,
+              identifier,
+              [identifier.name.toString(), definingClass.name]);
+        } else if (!_hasSuperClassOrMixin(
+            accessingClass.element, definingClass.type)) {
+          _errorReporter.reportErrorForNode(
+              HintCode.INVALID_USE_OF_PROTECTED_MEMBER,
+              identifier,
+              [identifier.name.toString(), definingClass.name]);
+        }
+      }
+    }
+  }
+
+  /**
    * Produces a hint if the given invocation is of a protected method outside
    * a subclass instance method.
    */