Fix clippy::empty_enum triggering on nightly with feature(never_type) enabled (#234)

Author: Veetaha

.github/workflows/ci.yml

@@ -166,6 +166,10 @@ jobs:
             --allow edition-2024-expr-fragment-specifier \
             --allow if_let_rescope \
             --allow impl-trait-overcaptures
+        env:
+          RUSTFLAGS: >-
+            --deny warnings
+            --cfg ${{ matrix.toolchain }}
 
   cargo-miri:
     runs-on: ubuntu-latest

Cargo.toml

@@ -148,6 +148,8 @@ missing_crate_level_docs = "warn"
 unescaped_backticks      = "warn"
 
 [workspace.lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(nightly)'] }
+
 # This lint is used only to warn about the changes in drop order during the
 # transition from Rust 2021 to Rust 2024. There are too many instances of this
 # lint in our code base and some of them may be false positives. So we just allow

bon-macros/src/builder/builder_gen/state_mod.rs

@@ -271,7 +271,7 @@ impl<'a> StateModGenCtx<'a> {
             #[allow(non_camel_case_types)]
             mod members {
                 #(
-                    #vis_child_child enum #stateful_members_snake {}
+                    #vis_child_child struct #stateful_members_snake(());
                 )*
             }
         }

bon/tests/integration/main.rs

@@ -10,6 +10,9 @@
     missing_docs,
     impl_trait_overcaptures,
 )]
+// This catches the problem of `clippy::empty_enum` lint triggering.
+// This lint is enabled only when `feature(never_type)` is enabled.
+#![cfg_attr(nightly, allow(unstable_features), feature(never_type))]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;