lib: clean up types for RepoCheckoutFilter

rust-bindings/rust/src/repo_checkout_at_options/repo_checkout_filter.rs

@@ -5,20 +5,29 @@ use libc::c_char;
 use ostree_sys::{OstreeRepo, OstreeRepoCheckoutFilterResult};
 use std::path::{Path, PathBuf};
 
-pub type RepoCheckoutFilter =
-    Option<Box<dyn Fn(&Repo, &Path, &libc::stat) -> RepoCheckoutFilterResult>>;
+pub type RepoCheckoutFilter = Box<dyn Fn(&Repo, &Path, &libc::stat) -> RepoCheckoutFilterResult>;
 
-pub(super) unsafe extern "C" fn filter_trampoline(
+unsafe extern "C" fn filter_trampoline(
     repo: *mut OstreeRepo,
     path: *const c_char,
     stat: *mut libc::stat,
     user_data: gpointer,
 ) -> OstreeRepoCheckoutFilterResult {
     // TODO: handle unwinding
-    let closure =
-        user_data as *const Box<dyn Fn(&Repo, &Path, &libc::stat) -> RepoCheckoutFilterResult>;
+    let closure = user_data as *const RepoCheckoutFilter;
     let repo = FromGlibPtrNone::from_glib_none(repo);
     let path: PathBuf = FromGlibPtrNone::from_glib_none(path);
     let result = (*closure)(&repo, &path, &*stat);
     result.to_glib()
 }
+
+pub(super) fn trampoline() -> Option<
+    unsafe extern "C" fn(
+        *mut OstreeRepo,
+        *const c_char,
+        *mut libc::stat,
+        gpointer,
+    ) -> OstreeRepoCheckoutFilterResult,
+> {
+    Some(filter_trampoline)
+}