Optimize getField by caching a closure generated from a specialized function kind.

runtime/lib/mirrors_impl.dart

 // Copyright (c) 2012, 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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection";
 
 final emptyList = new UnmodifiableListView([]);
 final emptyMap = new _UnmodifiableMapView({});
@@ skipping 337 matching lines @@
     if (numNamedArguments > 0) {
       namedArguments.forEach((name, value) {
         arguments[argumentIndex++] = value;
         names[nameIndex++] = _n(name);
       });
     }
 
     return reflect(this._invoke(_reflectee, _n(memberName), arguments, names));
   }
 
+  static Map _getFieldClosures = new Map.identity();
+  static Map _setFieldClosures = new Map.identity();
+
+  InstanceMirror getField(Symbol memberName) {
+    var f = _getFieldClosures[memberName];
+    if (f == null) {
+      f = _makeGetter(_n(memberName), _ScratchClass);
+      _getFieldClosures[memberName] = f;
+    }
+    return reflect(f(_reflectee));
+  }
+
+  InstanceMirror setField(Symbol memberName, value) {
+    var f = _setFieldClosures[memberName];
+    if (f == null) {
+      f = _makeSetter(_n(memberName), _ScratchClass);
+      _setFieldClosures[memberName] = f;
+    }
+    return reflect(f(_reflectee, value));
+  }
+
+  static _makeGetter(selector, scratchClass)
+      native "Mirrors_makeGetter";
+
+  static _makeSetter(selector, scratchClass)
+      native "Mirrors_makeSetter";
+
   _invoke(reflectee, functionName, arguments, argumentNames)
       native 'InstanceMirror_invoke';
 
   _invokeGetter(reflectee, getterName)
       native 'InstanceMirror_invokeGetter';
 
   _invokeSetter(reflectee, setterName, value)
       native 'InstanceMirror_invokeSetter';
 
   static _computeType(reflectee)
       native 'InstanceMirror_computeType';
 }
 
+class _ScratchClass {}
+
 class _LocalClosureMirror extends _LocalInstanceMirror
     implements ClosureMirror {
   _LocalClosureMirror(reflectee) : super(reflectee);
 
   MethodMirror _function;
   MethodMirror get function {
     if (_function == null) {
       _function = _computeFunction(reflectee);
     }
     return _function;
@@ skipping 1111 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }