Added error back for derive attribute using the wrong delimiters

someguynamedjosh · Jul 16, 2023 · e49c85a · e49c85a
1 parent cecf2d7
commit e49c85a
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/ouroboros_macro/src/parse.rs b/ouroboros_macro/src/parse.rs
@@ -1,6 +1,6 @@
 use proc_macro2::{Delimiter, Span, TokenTree};
 use quote::format_ident;
-use syn::{spanned::Spanned, Attribute, Error, Fields, GenericParam, ItemStruct, Meta};
+use syn::{spanned::Spanned, Attribute, Error, Fields, GenericParam, ItemStruct, Meta, MacroDelimiter};
 
 use crate::{
     covariance_detection::type_is_covariant_over_this_lifetime,
@@ -116,11 +116,14 @@ fn parse_derive_token(token: &TokenTree) -> Result<Option<Derive>, Error> {
 
 fn parse_derive_attribute(attr: &Attribute) -> Result<Vec<Derive>, Error> {
     let body = match &attr.meta {
-        Meta::List(ml) => &ml.tokens,
+        Meta::List(ml) => ml,
         _ => unreachable!(),
     };
+    if !matches!(body.delimiter, MacroDelimiter::Paren(_)){
+        return Err(Error::new(attr.span(), format!("malformed derive input, derive attributes are of the form `#[derive({})]`",body.tokens.to_string())));
+    }
     let mut derives = Vec::new();
-    for token in body.clone().into_iter() {
+    for token in body.tokens.clone().into_iter() {
         if let Some(derive) = parse_derive_token(&token)? {
             derives.push(derive);
         }