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/Bases/ResumeParser.cs

@@ -0,0 +1,24 @@
+using CanonSharp.Combinator.Abstractions;
+
+namespace CanonSharp.Combinator.Parsers.Bases;
+
+/// <summary>
+/// 恢复解析器
+/// 在上游解析器失败的情况下调用指定恢复函数返回的解析器
+/// </summary>
+/// <param name="parser">上游解析器</param>
+/// <param name="failedHandler">返回新解析器的恢复函数</param>
+/// <typeparam name="TToken">输入令牌类型</typeparam>
+/// <typeparam name="T">解析结果类型</typeparam>
+internal sealed class ResumeParser<TToken, T>(
+    Parser<TToken, T> parser,
+    Func<FailedResult<TToken, T>, Parser<TToken, T>> failedHandler) : Parser<TToken, T>
+{
+    internal override ParseResult<TToken, TResult> Run<TState, TResult>(TState state,
+        Func<ParseResult<TToken, T>, ParseResult<TToken, TResult>> continuation)
+    {
+        return parser.Run(state,
+            result => result.CaseOf(continuation,
+                failedResult => failedHandler(failedResult).Run(state, continuation)));
+    }
+}