Create ParameterMirror.type lazily.

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.
 
 // These values are allowed to be passed directly over the wire.
 bool _isSimpleValue(var value) {
   return (value == null || value is num || value is String || value is bool);
 }
@@ skipping 1033 matching lines @@
   }
 
   final bool isStatic;
   final bool isFinal;
 
   String toString() => "VariableMirror on '${_n(simpleName)}'";
 }
 
 class _LocalParameterMirrorImpl extends _LocalVariableMirrorImpl
     implements ParameterMirror {
-  _LocalParameterMirrorImpl(type, this.isOptional)
-      : super(null, '<TODO:unnamed>', null, type, false, false) {}
+  _LocalParameterMirrorImpl(this._reflectee,
+                            this._position,
+                            this.isOptional)
+      : super(null, '<TODO:unnamed>', null, null, false, false);
 
+  final _MirrorReference _reflectee;
+  final int _position;
   final bool isOptional;
 
   String get defaultValue {
     throw new UnimplementedError(
         'ParameterMirror.defaultValue is not implemented');
   }
 
   bool get hasDefaultValue {
     throw new UnimplementedError(
         'ParameterMirror.hasDefaultValue is not implemented');
   }
 
   // TODO(11418): Implement.
   List<InstanceMirror> get metadata {
     throw new UnimplementedError(
         'ParameterMirror.metadata is not implemented');
   }
+
+  TypeMirror _type = null;
+  TypeMirror get type {
+    if (_type == null) {
+      _type = _ParameterMirror_type(_reflectee, _position);
+    }
+    return _type;
+  }
+
+  static TypeMirror _ParameterMirror_type(_reflectee, _position)
+      native "ParameterMirror_type";
 }
 
 class _SpecialTypeMirrorImpl extends _LocalMirrorImpl
     implements TypeMirror, DeclarationMirror {
   _SpecialTypeMirrorImpl(String name) : simpleName = _s(name);
 
   final bool isPrivate = false;
   final bool isTopLevel = true;
 
   // Fixed length 0, therefore immutable.
@@ skipping 63 matching lines @@
   static Expando<ClassMirror> _classMirrorCache = new Expando("ClassMirror");
   static ClassMirror reflectClass(Type key) {
     var classMirror = _classMirrorCache[key];
     if (classMirror == null) {
       classMirror = makeLocalClassMirror(key);
       _classMirrorCache[key] = classMirror;
     }
     return classMirror;
   }
 }