Partial fix for Angular Annotations viewed in Docgen.

pkg/docgen/lib/src/models/annotation.dart

Index: pkg/docgen/lib/src/models/annotation.dart
diff --git a/pkg/docgen/lib/src/models/annotation.dart b/pkg/docgen/lib/src/models/annotation.dart
index 0cc97c6e20f37077e667136ab2648cdd5097020a..ac4791f311f892810973bf3ed1fff24807d91644 100644
--- a/pkg/docgen/lib/src/models/annotation.dart
+++ b/pkg/docgen/lib/src/models/annotation.dart
@@ -21,8 +21,26 @@ class Annotation extends MirrorBased {
 
   Annotation(InstanceMirror originalMirror, this.owningLibrary)
       : mirror = originalMirror.type {
-    parameters = dart2js_util.variablesOf(originalMirror.type.declarations)
-        .where((e) => e.isFinal)
+    var curMirror = originalMirror.type;
+    Map<Symbol, DeclarationMirror> allDeclarations =
+        new Map.from(curMirror.declarations);
+    // This method assumes that our users aren't creating deep inheritance
+    // chains of custom annotation inheritance. If this is not the case,
+    // re-write this section for performance.
+    while (curMirror.superclass !=  null &&
+        curMirror.superclass.simpleName.toString() != 'Object') {
+      allDeclarations.addAll(curMirror.superclass.declarations);
+      curMirror = curMirror.superclass;
+    }
+
+    // TODO(efortuna): Some originalMirrors, such as the
+    // Dart2JsMapConstantMirror and Dart2JsListConstantMirror don't have a
+    // reflectee field, but we want the value of the parameter from them.
+    // Gross workaround is to assemble the object manually.
+    // See issue 18346.
+    parameters = dart2js_util.variablesOf(allDeclarations)
+        .where((e) => e.isFinal &&
+            originalMirror.getField(e.simpleName).hasReflectee)
         .map((e) => originalMirror.getField(e.simpleName).reflectee)
         .where((e) => e != null)
         .toList();