refactor: bump to syn 2.0 (#663)

Author: molpopgen

Cargo.lock

@@ -12,6 +12,6 @@ homepage = "https://github.com/tskit-dev/tskit-rust"
 proc-macro = true
 
 [dependencies]
-syn = { version = "1.0", features = ["derive"] }
+syn = { version = "2.0", features = ["derive"] }
 quote = "1.0"
 proc-macro-error2 = "2.0"

tskit-derive/Cargo.toml

@@ -55,7 +55,7 @@ fn impl_metadata_roundtrip_macro(ast: &syn::DeriveInput) -> Result<TokenStream,
     let attrs = &ast.attrs;
 
     for attr in attrs.iter() {
-        if attr.path.is_ident("serializer") {
+        if attr.path().is_ident("serializer") {
             let lit: syn::LitStr = attr.parse_args().unwrap();
             let serializer = lit.value();
 
@@ -67,7 +67,7 @@ fn impl_metadata_roundtrip_macro(ast: &syn::DeriveInput) -> Result<TokenStream,
                 proc_macro_error2::abort!(serializer, "is not a supported protocol.");
             }
         } else {
-            proc_macro_error2::abort!(attr.path, "is not a supported attribute.");
+            proc_macro_error2::abort!(attr.path(), "is not a supported attribute.");
         }
     }