fix field derive

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+- Fix `derivedFrom` on field
+
 ## [v0.30.0] - 2023-08-16
 
 - Add `aarch64` target for releases, more readme badges

src/generate/register.rs

@@ -554,12 +554,11 @@ pub fn fields(
     let inline = quote! { #[inline(always)] };
     for &f in fields.iter() {
         let mut f = f.clone();
-        let mut fpath = None;
-        let dpath = f.derived_from.take();
-        if let Some(dpath) = dpath {
-            fpath = derive_field(&mut f, &dpath, rpath, index)?;
+        let mut fdpath = None;
+        if let Some(dpath) = f.derived_from.take() {
+            fdpath = derive_field(&mut f, &dpath, rpath, index)?;
         }
-        let fpath = fpath.unwrap_or_else(|| rpath.new_field(&f.name));
+        let fpath = rpath.new_field(&f.name);
         // TODO(AJM) - do we need to do anything with this range type?
         let BitRange { offset, width, .. } = f.bit_range;
 
@@ -601,6 +600,8 @@ pub fn fields(
             let dpath = ev.derived_from.take();
             if let Some(dpath) = dpath {
                 epath = Some(derive_enumerated_values(&mut ev, &dpath, &fpath, index)?);
+            } else if let Some(path) = fdpath.as_ref() {
+                epath = Some(path.new_enum(ev.name.clone().unwrap()));
             }
             // TODO: remove this hack
             if let Some(epath) = epath.as_ref() {