Fix an uncoming Clippy lint (#267)

This lint isn't an issue on our pinned nightly, but it is on more
recent nightlies as of this writing. Might as well fix it now.

Author: joshlf

zerocopy-derive/src/lib.rs

@@ -12,7 +12,7 @@
 // our MSRV.
 #![allow(unknown_lints)]
 #![deny(renamed_and_removed_lints)]
-#![deny(clippy::all, clippy::missing_safety_doc)]
+#![deny(clippy::all, clippy::missing_safety_doc, clippy::undocumented_unsafe_blocks)]
 #![deny(
     rustdoc::bare_urls,
     rustdoc::broken_intra_doc_links,

zerocopy-derive/src/repr.rs

@@ -73,9 +73,7 @@ impl<R: KindRepr> Config<R> {
         }
 
         let initial_sp = metas[0].span();
-        let err_span = metas.iter().skip(1).fold(Some(initial_sp), |sp_option, meta| {
-            sp_option.and_then(|sp| sp.join(meta.span()))
-        });
+        let err_span = metas.iter().skip(1).try_fold(initial_sp, |sp, meta| sp.join(meta.span()));
 
         if self.allowed_combinations.contains(&reprs.as_slice()) {
             Ok(reprs)