syn: add FieldKind type to data mod

Author: dr-orlovsky

syn/src/data.rs

@@ -48,8 +48,22 @@ pub enum Fields {
     Unnamed(Items<Field>),
 }
 
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
+pub enum FieldKind {
+    Named,
+    Unnamed,
+}
+
 impl Fields {
     pub fn is_unit(&self) -> bool { matches!(self, Fields::Unit) }
+
+    pub fn kind(&self) -> FieldKind {
+        match self {
+            Fields::Unit => FieldKind::Unnamed,
+            Fields::Named(_) => FieldKind::Named,
+            Fields::Unnamed(_) => FieldKind::Unnamed,
+        }
+    }
 }
 
 pub trait Element: Sized {

syn/src/lib.rs

@@ -51,8 +51,8 @@ mod data;
 pub use attr::{Attr, ExtractAttr, ParametrizedAttr, SingularAttr};
 pub use cls::{LiteralClass, TypeClass, ValueClass};
 pub use data::{
-    DataInner, DataType, DeriveInner, Element, Field, Fields, Items, NamedField, Scope, Variant,
-    Vis,
+    DataInner, DataType, DeriveInner, Element, Field, FieldKind, Fields, Items, NamedField, Scope,
+    Variant, Vis,
 };
 pub use error::Error;
 pub use parsers::{MetaArg, MetaArgList, MetaArgNameValue};