feat: propagate generics to generated function

Author: haenoe

compiler/rustc_builtin_macros/src/autodiff.rs

@@ -73,10 +73,10 @@ mod llvm_enzyme {
     }
 
     // Get information about the function the macro is applied to
-    fn extract_item_info(iitem: &P<ast::Item>) -> Option<(Visibility, FnSig, Ident)> {
+    fn extract_item_info(iitem: &P<ast::Item>) -> Option<(Visibility, FnSig, Ident, Generics)> {
         match &iitem.kind {
-            ItemKind::Fn(box ast::Fn { sig, ident, .. }) => {
-                Some((iitem.vis.clone(), sig.clone(), ident.clone()))
+            ItemKind::Fn(box ast::Fn { sig, ident, generics, .. }) => {
+                Some((iitem.vis.clone(), sig.clone(), ident.clone(), generics.clone()))
             }
             _ => None,
         }
@@ -210,16 +210,18 @@ mod llvm_enzyme {
         }
         let dcx = ecx.sess.dcx();
 
-        // first get information about the annotable item:
-        let Some((vis, sig, primal)) = (match &item {
+        // first get information about the annotable item: visibility, signature, name and generic
+        // parameters.
+        // these will be used to generate the differentiated version of the function
+        let Some((vis, sig, primal, generics)) = (match &item {
             Annotatable::Item(iitem) => extract_item_info(iitem),
             Annotatable::Stmt(stmt) => match &stmt.kind {
                 ast::StmtKind::Item(iitem) => extract_item_info(iitem),
                 _ => None,
             },
             Annotatable::AssocItem(assoc_item, Impl { .. }) => match &assoc_item.kind {
-                ast::AssocItemKind::Fn(box ast::Fn { sig, ident, .. }) => {
-                    Some((assoc_item.vis.clone(), sig.clone(), ident.clone()))
+                ast::AssocItemKind::Fn(box ast::Fn { sig, ident, generics, .. }) => {
+                    Some((assoc_item.vis.clone(), sig.clone(), ident.clone(), generics.clone()))
                 }
                 _ => None,
             },
@@ -310,7 +312,7 @@ mod llvm_enzyme {
             defaultness: ast::Defaultness::Final,
             sig: d_sig,
             ident: first_ident(&meta_item_vec[0]),
-            generics: Generics::default(),
+            generics,
             contract: None,
             body: Some(d_body),
             define_opaque: None,