fix: 区分字符和字符串 (#74)

Co-authored-by: Huaps <1183155719@qq.com>
Reviewed-on: PostGuard/Canon#74

Canon.Core/LexicalParser/LexemeFactory.cs

@@ -16,6 +16,13 @@ public static class LexemeFactory
                 };
                 token = characterSemanticToken;
                 break;
+            case SemanticTokenType.String:
+                StringSemanticToken stringSemanticToken = new()
+                {
+                    LinePos = line, CharacterPos = chPos, LiteralValue = literal,
+                };
+                token = stringSemanticToken;
+                break;
             case SemanticTokenType.Identifier:
                 IdentifierSemanticToken identifierSemanticToken = new()
                 {

Canon.Core/LexicalParser/Lexer.cs

@@ -80,6 +80,7 @@ public class Lexer : ILexer
         }
 
         _tokens.Add(SemanticToken.End);
+
         return _tokens;
     }
 
@@ -447,7 +448,6 @@ public class Lexer : ILexer
                 }
                 break;
             case '\'':
-            case '\"':
                 {
                     // 重置_token，准备收集字符串内容
                     ResetTokenBuilder();
@@ -464,8 +464,18 @@ public class Lexer : ILexer
                         }
                     }
 
-                    _semanticToken = LexemeFactory.MakeToken(SemanticTokenType.Character,
-                        GetCurrentTokenString(), _line, _chPos);
+                    string currentString = GetCurrentTokenString();
+                    if (currentString.Length > 1)
+                    {
+                        _semanticToken = LexemeFactory.MakeToken(SemanticTokenType.String,
+                            currentString, _line, _chPos);
+                    }
+                    else
+                    {
+                        _semanticToken = LexemeFactory.MakeToken(SemanticTokenType.Character,
+                            currentString, _line, _chPos);
+                    }
+
 
                     ResetTokenBuilder();
 

Canon.Core/LexicalParser/SemanticToken.cs

@@ -104,6 +104,32 @@ public abstract class SemanticToken : IEquatable<SemanticToken>
 public class CharacterSemanticToken : SemanticToken
 {
     public override SemanticTokenType TokenType => SemanticTokenType.Character;
+
+    /// <summary>
+    /// 获得令牌代表的字符
+    /// </summary>
+    /// <returns>字符</returns>
+    public char ParseAsCharacter()
+    {
+        return char.Parse(LiteralValue);
+    }
+}
+
+/// <summary>
+/// 字符串类型记号
+/// </summary>
+public class StringSemanticToken : SemanticToken
+{
+    public override SemanticTokenType TokenType => SemanticTokenType.String;
+
+    /// <summary>
+    /// 获得令牌代表的字符串
+    /// </summary>
+    /// <returns>字符串</returns>
+    public string ParseAsString()
+    {
+        return LiteralValue;
+    }
 }
 
 /// <summary>