Implement metadata as an internal native. Be honest about which mirrors don't yet support metadata …

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
===================================================================
--- runtime/lib/mirrors_impl.dart	(revision 25060)
+++ runtime/lib/mirrors_impl.dart	(working copy)
@@ -70,8 +70,8 @@
     return result;
 }
 
-List<InstanceMirror> _metadata(mirror) 

[rmacnak, 2013/07/16 21:11:15]

This annotation is incorrect. The native answered an array of plain instances,
which were later wrapped as instance mirrors.

-  native 'Mirrors_metadata';
+List _metadata(reflectee)
+  native 'DeclarationMirror_metadata';
 
 // This will verify the argument types, unwrap them, and ensure we have a fixed
 // array.
@@ -171,7 +171,7 @@
 
 abstract class _LocalVMObjectMirrorImpl extends _LocalMirrorImpl {
   _LocalVMObjectMirrorImpl(this._reference) {}
-
+  
   // For now, all VMObjects hold a VMReference.  We could consider
   // storing the Object reference itself here if the object is a Dart
   // language objects (except for objects of type VMReference, of
@@ -584,7 +584,7 @@
 
   // get the metadata objects, convert them into InstanceMirrors using
   // reflect() and then make them into a Dart list
-  List<InstanceMirror> get metadata => _metadata(this).map(reflect).toList();
+  List<InstanceMirror> get metadata => _metadata(_reflectee).map(reflect).toList();
 
 
   static _name(reflectee)
@@ -702,9 +702,10 @@
     return _upperBound;
   }
 
-  // get the metadata objects, convert them into InstanceMirrors using
-  // reflect() and then make them into a Dart list
-  List<InstanceMirror> get metadata => _metadata(this).map(reflect).toList();
+  List<InstanceMirror> get metadata {

[rmacnak, 2013/07/16 21:11:15]

Previously this would always answer an empty list, even if there was metadata.

+    throw new UnimplementedError(
+        'TypeVariableMirror.metadata is not implemented');
+  }
 
   String toString() => "TypeVariableMirror on '${_n(simpleName)}'";
 }
@@ -848,7 +849,7 @@
 
   // get the metadata objects, convert them into InstanceMirrors using
   // reflect() and then make them into a Dart list
-  List<InstanceMirror> get metadata => _metadata(this).map(reflect).toList();
+  List<InstanceMirror> get metadata => _metadata(_reflectee).map(reflect).toList();
 
   String toString() => "LibraryMirror on '${_n(simpleName)}'";
 
@@ -970,7 +971,7 @@
     owner; // ensure owner is computed
     // get the metadata objects, convert them into InstanceMirrors using
     // reflect() and then make them into a Dart list
-    return _metadata(this).map(reflect).toList();
+    return _metadata(_reflectee).map(reflect).toList();
   }
 
   String toString() => "MethodMirror on '${_n(simpleName)}'";
@@ -981,13 +982,15 @@
 
 class _LocalVariableMirrorImpl extends _LocalMirrorImpl
     implements VariableMirror {
-  _LocalVariableMirrorImpl(String simpleName,
+  _LocalVariableMirrorImpl(this._reflectee,
+                           String simpleName,
                            this._owner,
                            this._type,
                            this.isStatic,
                            this.isFinal)
       : this.simpleName = _s(simpleName);
 
+  final _MirrorReference _reflectee;
   final Symbol simpleName;
 
   Symbol _qualifiedName = null;
@@ -1031,10 +1034,9 @@
   final bool isFinal;
 
   List<InstanceMirror> get metadata {
-    owner; // ensure owner is computed
     // get the metadata objects, convert them into InstanceMirrors using
     // reflect() and then make them into a Dart list
-    return _metadata(this).map(reflect).toList();
+    return _metadata(_reflectee).map(reflect).toList();
   }
 
   String toString() => "VariableMirror on '${_n(simpleName)}'";
@@ -1043,7 +1045,7 @@
 class _LocalParameterMirrorImpl extends _LocalVariableMirrorImpl
     implements ParameterMirror {
   _LocalParameterMirrorImpl(type, this.isOptional)
-      : super('<TODO:unnamed>', null, type, false, false) {}
+      : super(null, '<TODO:unnamed>', null, type, false, false) {}
 
   final bool isOptional;
 
@@ -1056,6 +1058,12 @@
     throw new UnimplementedError(
         'ParameterMirror.hasDefaultValue is not implemented');
   }
+
+  // TODO(11418): Implement.
+  List<InstanceMirror> get metadata {

[rmacnak, 2013/07/16 21:11:15]

Previously this raised a fatal, non-meaningful error.

+    throw new UnimplementedError(
+        'ParameterMirror.metadata is not implemented');
+  }
 }
 
 class _SpecialTypeMirrorImpl extends _LocalMirrorImpl