ff_derive 0.14: update addchain, num-bigint, syn

ff_derive/Cargo.toml

@@ -22,13 +22,13 @@ bits = []
 proc-macro = true
 
 [dependencies]
-addchain = "0.2"
-num-bigint = "0.3"
+addchain = "0.3"
+num-bigint = "0.4"
 num-traits = "0.2"
 num-integer = "0.1"
 proc-macro2 = "1"
 quote = "1"
-syn = { version = "1", features = ["full"] }
+syn = { version = "2", features = ["full"] }
 
 [badges]
 maintenance = { status = "passively-maintained" }

ff_derive/src/lib.rs

@@ -302,21 +302,14 @@ fn validate_struct(ast: &syn::DeriveInput, limbs: usize) -> Option<proc_macro2::
 /// Fetch an attribute string from the derived struct.
 fn fetch_attr(name: &str, attrs: &[syn::Attribute]) -> Option<String> {
     for attr in attrs {
-        if let Ok(meta) = attr.parse_meta() {
-            match meta {
-                syn::Meta::NameValue(nv) => {
-                    if nv.path.get_ident().map(|i| i.to_string()) == Some(name.to_string()) {
-                        match nv.lit {
-                            syn::Lit::Str(ref s) => return Some(s.value()),
-                            _ => {
-                                panic!("attribute {} should be a string", name);
-                            }
-                        }
+        if let syn::Meta::NameValue(nv) = &attr.meta {
+            if nv.path.get_ident().map(|i| i.to_string()) == Some(name.to_string()) {
+                if let syn::Expr::Lit(expr_lit) = &nv.value {
+                    if let syn::Lit::Str(ref s) = expr_lit.lit {
+                        return Some(s.value());
                     }
                 }
-                _ => {
-                    panic!("attribute {} should be a string", name);
-                }
+                panic!("attribute {} should be a string", name);
             }
         }
     }