particular_derive improvements

Canleskis · Jun 2, 2023 · f9101a9 · f9101a9
1 parent 055b038
commit f9101a9
Showing 1 changed file with 12 additions and 15 deletions.
diff --git a/particular_derive/src/lib.rs b/particular_derive/src/lib.rs
@@ -1,5 +1,3 @@
-use syn::spanned::Spanned;
-
 /// Derive macro generating an implementation of the trait `Particle`.
 #[proc_macro_derive(Particle)]
 pub fn particle_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
@@ -11,14 +9,14 @@ pub fn particle_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
 fn impl_particle(input: syn::Result<syn::DeriveInput>) -> syn::Result<proc_macro::TokenStream> {
     let input = input?;
 
-    let (pty, sty) = get_field_types(input.data)?;
-
     let name = input.ident;
+    let (pty, sty) = get_field_types(input.data)?;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
 
     Ok(quote::quote! {
         impl #impl_generics Particle for #name #ty_generics #where_clause {
             type Scalar = #sty;
+
             type Vector = #pty;
 
             #[inline]
@@ -36,29 +34,28 @@ fn impl_particle(input: syn::Result<syn::DeriveInput>) -> syn::Result<proc_macro
 }
 
 fn get_field_types(data: syn::Data) -> syn::Result<(syn::Type, syn::Type)> {
-    match data {
-        syn::Data::Struct(struct_data) => get_type_of(&struct_data, "position")
-            .and_then(|pty| get_type_of(&struct_data, "mu").map(|mty| (pty, mty))),
+    match &data {
+        syn::Data::Struct(struct_data) => Ok((
+            get_type_of(struct_data, "position")?,
+            get_type_of(struct_data, "mu")?,
+        )),
         syn::Data::Enum(enum_data) => Err(syn::Error::new_spanned(
             enum_data.enum_token,
-            "an enum cannot represent a Particle",
+            "the `Particle` trait can only be derived for struct types",
         )),
         syn::Data::Union(union_data) => Err(syn::Error::new_spanned(
             union_data.union_token,
-            "a union cannot represent a Particle",
+            "the `Particle` trait can only be derived for struct types",
         )),
     }
 }
 
 fn get_type_of(struct_data: &syn::DataStruct, field_name: &str) -> syn::Result<syn::Type> {
-    let fields_span = struct_data.fields.span();
-
     struct_data
         .fields
         .iter()
-        .find_map(|field| match &field.ident {
-            Some(ident) => (ident == field_name).then_some(field.ty.clone()),
-            None => None,
+        .find_map(|field| (field.ident.as_ref()? == field_name).then(|| field.ty.clone()))
+        .ok_or_else(|| {
+            syn::Error::new_spanned(&struct_data.fields, format!("no {field_name} field"))
         })
-        .ok_or_else(|| syn::Error::new(fields_span, format!("no {field_name} field")))
 }