fixup! Don’t require explicit index for skipped fields

Author: robin-nitrokey

src/lib.rs

@@ -55,6 +55,7 @@ fn serialize_fields(
         .iter()
         .filter(|field| !field.skip_serializing_if.is_always())
         .map(|field| {
+            // index should only be none if the field is always skipped, so this should never panic
             let index = field.index.expect("index must be set for fields that are not skipped") + offset;
             let member = &field.member;
             let serialize_member = match &field.serialize_with {
@@ -223,6 +224,7 @@ fn match_fields(
         .map(|field| {
             let label = field.label.clone();
             let ident = format_ident!("{}", &field.label);
+            // index should only be none if the field is always skipped, so this should never panic
             let index = field.index.expect("index must be set for fields that are not skipped") + offset;
             let span = field.original_span;