Apply suggestions from code review

Co-authored-by: bjorn3 <[email protected]>

Author: osiewicz

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -331,10 +331,7 @@ fn exported_symbols_provider_local(
                 rustc_middle::ty::Coroutine(def_id, _) => *def_id,
                 rustc_middle::ty::CoroutineClosure(def_id, _) => *def_id,
                 rustc_middle::ty::CoroutineWitness(def_id, _) => *def_id,
-                rustc_middle::ty::Foreign(def_id) => *def_id,
-                _ => {
-                    return false;
-                }
+                _ => return false,
             };
             let Some(root_def_id) = root_def_id.as_local() else {
                 return false;
@@ -346,12 +343,7 @@ fn exported_symbols_provider_local(
 
         let is_instantiable_downstream = |did, type_args| {
             std::iter::once(tcx.type_of(did).skip_binder()).chain(type_args).all(|arg| {
-                arg.walk().all(|ty| {
-                    let Some(ty) = ty.as_type() else {
-                        return true;
-                    };
-                    !is_local_to_current_crate(ty)
-                })
+                arg.walk().all(|ty| ty.as_type().map_or(true, |ty| !is_local_to_current_crate(ty)))
             })
         };
         // The symbols created in this loop are sorted below it
@@ -400,20 +392,17 @@ fn exported_symbols_provider_local(
                     }
                 }
                 MonoItem::Fn(Instance { def: InstanceKind::DropGlue(_, Some(ty)), args }) => {
-                    let Some(GenericArgKind::Type(typ)) = args.non_erasable_generics().next()
-                    else {
-                        bug!("Expected a type argument for drop glue");
-                    };
-                    let should_export = {
-                        let root_identifier = match typ.kind() {
-                            rustc_middle::ty::Adt(def, args) => Some((def.did(), args)),
-                            rustc_middle::ty::Closure(id, args) => Some((*id, args)),
-                            _ => None,
-                        };
-                        root_identifier.map_or(true, |(did, args)| {
-                            is_instantiable_downstream(did, args.types())
-                        })
+                    // A little sanity-check
+                    assert_eq!(args.non_erasable_generics().next(), Some(GenericArgKind::Type(ty)));
+
+                    let root_identifier = match ty.kind() {
+                        rustc_middle::ty::Adt(def, args) => Some((def.did(), args)),
+                        rustc_middle::ty::Closure(id, args) => Some((*id, args)),
+                        _ => None,
                     };
+                    let should_export = root_identifier
+                        .map_or(true, |(did, args)| is_instantiable_downstream(did, args.types()));
+
                     if should_export {
                         symbols.push((
                             ExportedSymbol::DropGlue(ty),