refactor: improve definition of MaybeStatic

1 files changed, 27 insertions, 2 deletions

diff --git a/src/util.rs b/src/util.rs
index 5c9ffb8..d96c4f4 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,13 +1,38 @@
 macro_rules! trait_alias {
     (
         $(#[$attr: meta])*
-        $visibility: vis $name: ident$(<$($type_param: ident),*>)?$(: $first_bound: tt $(+ $bound: tt)*)?;
+        $visibility: vis $name: ident$(<$($type_param: ident),*>)?
+            $(: $first_bound: tt $(+ $bound: tt)*)?;
     ) => {
         $(#[$attr])*
         $visibility trait $name $(<$($type_param),*>)? $(: $first_bound $(+ $bound)*)? {}
 
-        impl<T: $($first_bound $(+ $bound)*)?, $($($type_param),*)?> $name$(<$($type_param),*>)? for T {}
+        impl<
+            T: $($first_bound $(+ $bound)*)?,
+            $($($type_param),*)?
+        > $name$(<$($type_param),*>)? for T {}
     };
+
+    // Rule where the trait bounds will only be applied if the specified feature is enabled
+    (
+        bounds_when_feature = $bounds_feature: literal,
+        $(#[$attr: meta])*
+        $visibility: vis $name: ident$(<$($type_param: ident),*>)?
+            $(: $first_bound: tt $(+ $bound: tt)*)?;
+    ) => {
+        #[cfg(feature = $bounds_feature)]
+        trait_alias! {
+            $(#[$attr])*
+            $visibility $name$(<$($type_param),*>)?
+                $(: $first_bound $(+ $bound)*)?;
+        }
+
+        #[cfg(not(feature = $bounds_feature))]
+        trait_alias! {
+            $(#[$attr])*
+            $visibility $name$(<$($type_param),*>)?;
+        }
+    }
 }
 
 macro_rules! feature_alternate {