Store parent field type in TemplateInput

1 files changed, 4 insertions, 17 deletions

diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
index 5d16f2c..6c6e1e7 100644
--- a/askama_derive/src/generator.rs
+++ b/askama_derive/src/generator.rs
@@ -61,9 +61,10 @@ impl<'a> Generator<'a> {
             if ctx.extends.is_none() {
                 self.define_trait(ctx);
             } else {
-                let parent_type = get_parent_type(self.input.ast)
-                    .expect("expected field '_parent' in extending template struct");
-                self.deref_to_parent(parent_type);
+                match self.input.parent {
+                    Some(ty) => self.deref_to_parent(ty),
+                    None => panic!("expected field '_parent' in extending template struct"),
+                }
             }
 
             let trait_nodes = if ctx.extends.is_none() {
@@ -930,20 +931,6 @@ where
     }
 }
 
-fn get_parent_type(ast: &syn::DeriveInput) -> Option<&syn::Type> {
-    match ast.data {
-        syn::Data::Struct(syn::DataStruct {
-            fields: syn::Fields::Named(ref fields),
-            ..
-        }) => fields.named.iter().filter_map(|f| {
-            f.ident
-                .as_ref()
-                .and_then(|name| if name == "_parent" { Some(&f.ty) } else { None })
-        }),
-        _ => panic!("derive(Template) only works for struct items"),
-    }.next()
-}
-
 #[derive(Clone, PartialEq)]
 enum AstLevel {
     Top,