fix a couple of analyzer warnings.

lib/src/internal/async_utils.dart

@@ -7,7 +7,7 @@ mixin StreamSubscriberBase {
       <StreamSubscription<dynamic>>[];
 
   /// Listens to a stream and saves it to the list of subscriptions.
-  void listen(Stream<dynamic> stream, void onData(dynamic data),
+  void listen(Stream<dynamic> stream, void Function(dynamic data) onData,
       {Function onError}) {
     if (stream != null) {
       _subscriptions.add(stream.listen(onData, onError: onError));

lib/src/internal/byte_utils.dart

@@ -13,7 +13,7 @@ class ByteUtils {
     if (a.length != b.length) {
       return false;
     }
-    for (int i = a.length - 1; i >= 0; i--) {
+    for (var i = a.length - 1; i >= 0; i--) {
       if (a[i] != b[i]) {
         return false;
       }

lib/src/internal/crypto_utils.dart

@@ -2,6 +2,8 @@ import 'dart:typed_data';
 
 import 'package:pointycastle/export.dart';
 
+// ignore_for_file: omit_local_variable_types
+
 /// https://gist.github.com/proteye/e54eef1713e1fe9123d1eb04c0a5cf9b
 class AesHelper {
   static const CBC_MODE = 'CBC';

lib/src/kdbx_dao.dart

@@ -1,10 +1,7 @@
 import 'package:kdbx/kdbx.dart';
 import 'package:kdbx/src/kdbx_file.dart';
-import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 
-final _logger = Logger('kdbx_dao');
-
 /// Helper object for accessing and modifing data inside
 /// a kdbx file.
 extension KdbxDao on KdbxFile {

lib/src/kdbx_times.dart

@@ -17,6 +17,7 @@ class KdbxTimes extends KdbxNode implements KdbxNodeContext {
   }
   KdbxTimes.read(XmlElement node, this.ctx) : super.read(node);
 
+  @override
   final KdbxReadWriteContext ctx;
 
   DateTimeUtcNode get creationTime => DateTimeUtcNode(this, 'CreationTime');

lib/src/utils/scope_functions.dart

@@ -1,16 +1,16 @@
 /// https://github.com/YusukeIwaki/dart-kotlin_flavor/blob/74593dada94bdd8ca78946ad005d3a2624dc833f/lib/scope_functions.dart
 /// MIT license: https://github.com/YusukeIwaki/dart-kotlin_flavor/blob/74593dada94bdd8ca78946ad005d3a2624dc833f/LICENSE
 
-ReturnType run<ReturnType>(ReturnType operation()) {
+ReturnType run<ReturnType>(ReturnType Function() operation) {
   return operation();
 }
 
 extension ScopeFunctionsForObject<T extends Object> on T {
-  ReturnType let<ReturnType>(ReturnType operationFor(T self)) {
+  ReturnType let<ReturnType>(ReturnType Function(T self) operationFor) {
     return operationFor(this);
   }
 
-  T also(void operationFor(T self)) {
+  T also(void Function(T self) operationFor) {
     operationFor(this);
     return this;
   }

test/internal/test_utils.dart

@@ -6,6 +6,8 @@ import 'dart:typed_data';
 import 'package:ffi/ffi.dart';
 import 'package:kdbx/kdbx.dart';
 
+// ignore_for_file: non_constant_identifier_names
+
 typedef Argon2HashNative = Pointer<Utf8> Function(
   Pointer<Uint8> key,
   IntPtr keyLen,