Move struct attribute regex behind unstable feature flag

I'm still working on the interface for this, so things could break.

Author: 2kai2kai2

.github/workflows/cargo-test.yml

@@ -8,3 +8,4 @@ jobs:
       - uses: actions/checkout@v4
       - run: cargo build
       - run: cargo test
+      - run: cargo test -F unstable-attr-regex

Cargo.toml

@@ -16,3 +16,9 @@ repository = "https://github.com/2kai2kai2/ere"
 [dependencies]
 ere-core = { version = "0.2.0", path = "./ere-core" }
 ere-macros = { version = "0.2.0", path = "./ere-macros" }
+
+[features]
+unstable-attr-regex = [
+    "ere-core/unstable-attr-regex",
+    "ere-macros/unstable-attr-regex",
+]

ere-core/Cargo.toml

@@ -12,3 +12,6 @@ proc-macro2 = "1.0.95"
 quote = "1.0.38"
 syn = { version = "2.0.96", features = ["parsing"] }
 thiserror = "2.0.11"
+
+[features]
+unstable-attr-regex = []

ere-core/src/lib.rs

@@ -94,6 +94,7 @@ pub fn __compile_regex(stream: TokenStream) -> TokenStream {
     };
 }
 
+#[cfg(feature = "unstable-attr-regex")]
 pub fn __compile_regex_attr(attr: TokenStream, input: TokenStream) -> TokenStream {
     let ere: parse_tree::ERE = syn::parse_macro_input!(attr);
     let tree = simplified_tree::SimplifiedTreeNode::from(ere);

ere-macros/Cargo.toml

@@ -14,3 +14,6 @@ proc-macro = true
 ere-core = { version = "0.2.0", path = "../ere-core" }
 quote = "1.0.38"
 syn = { version = "2.0.96", features = ["parsing"] }
+
+[features]
+unstable-attr-regex = ["ere-core/unstable-attr-regex"]

ere-macros/src/lib.rs

@@ -26,6 +26,7 @@ pub fn compile_regex(stream: TokenStream) -> TokenStream {
     return ere_core::__compile_regex(stream);
 }
 
+#[cfg(feature = "unstable-attr-regex")]
 #[proc_macro_attribute]
 pub fn regex(attr: TokenStream, input: TokenStream) -> TokenStream {
     return ere_core::__compile_regex_attr(attr, input);

src/lib.rs

@@ -16,5 +16,6 @@ pub use ::ere_macros::*;
 pub mod prelude {
     pub use ::ere_core::Regex;
     pub use ::ere_macros::compile_regex;
+    #[cfg(feature = "unstable-attr-regex")]
     pub use ::ere_macros::regex;
 }

tests/pure_regex.rs

@@ -16,6 +16,7 @@ fn phone_number() {
     assert!(!PHONE_REGEX.test("1 555-555-5555"));
 }
 
+#[cfg(feature = "unstable-attr-regex")]
 #[test]
 fn phone_number_struct() {
     #[derive(PartialEq, Eq, Debug)]