refactor(ast): Improve error type, remove unnecessary eof judge

src/lexer/types.rs

@@ -81,7 +81,7 @@ impl std::fmt::Display for TokenValue {
             TokenValue::Return => write!(f, "return"),
             TokenValue::Break => write!(f, "break"),
             TokenValue::Continue => write!(f, "continue"),
-            TokenValue::Eof => write!(f, "<EOF>"),
+            TokenValue::Eof => write!(f, "end of input"),
             TokenValue::Unrecognized => write!(f, "unrecognized"),
         }
     }