enable lint prefer_generic_function_type_aliases (#21680)

packages/flutter_tools/lib/src/vmservice.dart

diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index a99c278..599940d 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -22,7 +22,7 @@
 import 'vmservice_record_replay.dart';
 
 /// A function that opens a two-way communication channel to the specified [uri].
-typedef Future<StreamChannel<String>> _OpenChannel(Uri uri);
+typedef _OpenChannel = Future<StreamChannel<String>> Function(Uri uri);
 
 _OpenChannel _openChannel = _defaultOpenChannel;
 
@@ -37,13 +37,13 @@
 /// hot mode.
 ///
 /// See: https://github.com/dart-lang/sdk/issues/30023
-typedef Future<Null> ReloadSources(
+typedef ReloadSources = Future<Null> Function(
   String isolateId, {
   bool force,
   bool pause,
 });
 
-typedef Future<String> CompileExpression(
+typedef CompileExpression = Future<String> Function(
   String isolateId,
   String expression,
   List<String> definitions,