feat: Parser Combinator库和词法分析器 (#2)

Reviewed-on: https://git.bupt-hpc.cn/jackfiled/CanonSharp/pulls/2
Co-authored-by: jackfiled <xcrenchangjun@outlook.com>
Co-committed-by: jackfiled <xcrenchangjun@outlook.com>

CanonSharp.Combinator/Parsers/Modifiers/ReverseParser.cs

@@ -0,0 +1,26 @@
+using CanonSharp.Combinator.Abstractions;
+
+namespace CanonSharp.Combinator.Parsers.Modifiers;
+
+/// <summary>
+/// 翻转结果的解析器
+/// 当成功时失败
+/// 当失败时返回指定的成功结果
+/// </summary>
+/// <param name="parser">上游解析器</param>
+/// <param name="result">期望中的结果</param>
+/// <typeparam name="TToken">输入流的类型</typeparam>
+/// <typeparam name="TIntermediate">上游解析器结果类型</typeparam>
+/// <typeparam name="T">最终的返回结果</typeparam>
+internal sealed class ReverseParser<TToken, TIntermediate, T>(Parser<TToken, TIntermediate> parser, T result)
+    : ModifiedParser<TToken, TIntermediate, T>(parser)
+{
+    protected override ParseResult<TToken, T> Succeed<TState>(TState state,
+        SuccessfulResult<TToken, TIntermediate> successfulResult)
+        => ParseResultBuilder.Fail<TToken, TState, T>($"Unexpected successful result: {successfulResult.Value}",
+            state);
+
+    protected override ParseResult<TToken, T> Fail<TState>(TState state,
+        FailedResult<TToken, TIntermediate> failedResult)
+        => ParseResultBuilder.Succeed<TToken, TState, T>(result, state);
+}