fix(cargo): Update aster, quasi, and syntex

serde_codegen/src/field.rs

@@ -7,9 +7,9 @@ use attr::{FieldAttrs, FieldAttrsBuilder};
 pub fn struct_field_attrs(
     _cx: &ExtCtxt,
     builder: &aster::AstBuilder,
-    struct_def: &ast::StructDef,
+    fields: &[ast::StructField],
 ) -> Vec<FieldAttrs> {
-    struct_def.fields.iter()
+    fields.iter()
         .map(|field| {
             FieldAttrsBuilder::new(builder).field(field).build()
         })