Restore Result.isSuccess and isFailure, there are quite a few ext…

…ernal dependencies left.

lib/src/core/result.dart

@@ -6,6 +6,14 @@ import 'exception.dart';
 sealed class Result<R> extends Context {
   const Result(super.buffer, super.position);
 
+  /// Returns `true` if this result indicates a parse success.
+  @Deprecated('Use `is Success` operator instead')
+  bool get isSuccess => false;
+
+  /// Returns `true` if this result indicates a parse failure.
+  @Deprecated('Use `is Failure` operator instead')
+  bool get isFailure => false;
+
   /// Returns the parsed value of this result, or throws a [ParserException]
   /// if this is a parse failure.
   @inlineVm
@@ -21,6 +29,10 @@ sealed class Result<R> extends Context {
 class Success<R> extends Result<R> {
   const Success(super.buffer, super.position, this.value);
 
+  @override
+  @Deprecated('Use `is Success` operator instead')
+  bool get isSuccess => true;
+
   @override
   final R value;
 
@@ -36,6 +48,10 @@ class Success<R> extends Result<R> {
 class Failure extends Result<Never> {
   const Failure(super.buffer, super.position, this.message);
 
+  @override
+  @Deprecated('Use `is Failure` operator instead')
+  bool get isFailure => true;
+
   @override
   Never get value => throw ParserException(this);
 

test/context_test.dart

@@ -19,6 +19,8 @@ void main() {
       final success = context.success('result');
       expect(success.buffer, buffer);
       expect(success.position, 0);
+      expect(success.isSuccess, isTrue);
+      expect(success.isFailure, isFalse);
       expect(success.value, 'result');
       expect(() => success.message, throwsA(isUnsupportedError));
       expect(success.toString(), isNot(startsWith('Instance of')));
@@ -29,6 +31,8 @@ void main() {
       final success = context.success('result', 2);
       expect(success.buffer, buffer);
       expect(success.position, 2);
+      expect(success.isSuccess, isTrue);
+      expect(success.isFailure, isFalse);
       expect(success.value, 'result');
       expect(() => success.message, throwsA(isUnsupportedError));
       expect(success.toString(), isNot(startsWith('Instance of')));
@@ -41,6 +45,8 @@ void main() {
       final failure = context.failure('error');
       expect(failure.buffer, buffer);
       expect(failure.position, 0);
+      expect(failure.isSuccess, isFalse);
+      expect(failure.isFailure, isTrue);
       expect(
           () => failure.value,
           throwsA(isParserException
@@ -59,6 +65,8 @@ void main() {
       final failure = context.failure('problem', 2);
       expect(failure.buffer, buffer);
       expect(failure.position, 2);
+      expect(failure.isSuccess, isFalse);
+      expect(failure.isFailure, isTrue);
       expect(
           () => failure.value,
           throwsA(isParserException