feat: tuple support

Author: Frando

README.md

@@ -4,8 +4,6 @@
 
 A error library that supports tracking the call-site location of errors. Also features an anyhow-style `AnyError`.
 
-Usage
-
 ```rust
 use n0_error::{e, add_meta, Error, Result, StackResultExt, StdResultExt};
 
@@ -66,4 +64,20 @@ fn main() -> Result<()> {
     }
     Ok(())
 }
+
+// You can also use the macros with tuple structs or enums.
+// In this case the meta field will be added as the last field.
+
+#[add_meta]
+#[derive(Error)]
+#[display("tuple fail ({_0})")]
+struct TupleStruct(u32);
+
+#[add_meta]
+#[derive(Error)]
+enum TupleEnum {
+    #[display("io failed")]
+    Io(#[error(source, std_err)] std::io::Error),
+}
+
 ```

n0-error-macros/src/lib.rs

@@ -227,9 +227,6 @@ impl<'a> VariantInfo<'a> {
         }
         None
     }
-    fn fields(&self) -> &Vec<FieldInfo<'_>> {
-        &self.fields
-    }
 
     fn field_binding_idents(&self) -> impl Iterator<Item = Ident> + '_ {
         self.fields.iter().map(|f| match f.ident {
@@ -398,7 +395,13 @@ impl<'a> VariantInfo<'a> {
                         .iter()
                         .zip(binds.iter())
                         .map(|(f, b)| match f.ident {
-                            FieldIdent::Named(id) => quote! { #id: #b },
+                            FieldIdent::Named(id) => {
+                                if *id == *b {
+                                    quote! { #id }
+                                } else {
+                                    quote! { #id: #b }
+                                }
+                            }
                             FieldIdent::Unnamed(_) => unreachable!(),
                         });
                     quote! { Self::#v_ident { #( #pairs ),* } }