feat: implement visitor pattern (#1)

Signed-off-by: tison <wander4096@gmail.com>

Author: tisonkun

Cargo.lock

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 [workspace]
-members = ["visitor", "xtask"]
+members = ["visitor", "visitor-derive", "xtask"]
 resolver = "2"
 
 [workspace.package]
@@ -24,6 +24,9 @@ readme = "README.md"
 repository = "https://github.com/fast/visitor"
 rust-version = "1.85.0"
 
+[workspace.dependencies]
+visitor-derive = { version = "0.1.0", path = "visitor-derive" }
+
 [workspace.lints.rust]
 unknown_lints = "deny"
 

Cargo.toml

@@ -0,0 +1,35 @@
+# Copyright 2025 FastLabs Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+[package]
+name = "visitor-derive"
+version = "0.1.0"
+
+edition.workspace = true
+homepage.workspace = true
+license.workspace = true
+readme.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = { version = "1.0.101" }
+quote = { version = "1.0.41" }
+syn = { version = "2.0.106", features = ["extra-traits"] }
+
+[lints]
+workspace = true