fix semicolon in rust binding

rust/candid/src/bindings/rust.rs

@@ -134,12 +134,20 @@ fn pp_defs<'a>(env: &'a TypeEnv, def_list: &'a [&'a str], recs: &'a RecPoints) -
         let ty = env.find_type(id).unwrap();
         let name = ident(id).append(" ");
         match ty {
-            Type::Record(fs) => str(derive)
-                .append(RcDoc::line())
-                .append("struct ")
-                .append(name)
-                .append(pp_record_fields(fs, recs))
-                .append(RcDoc::hardline()),
+            Type::Record(fs) => {
+                let separator = if is_tuple(fs) {
+                    RcDoc::text(";")
+                } else {
+                    RcDoc::nil()
+                };
+                str(derive)
+                    .append(RcDoc::line())
+                    .append("struct ")
+                    .append(name)
+                    .append(pp_record_fields(fs, recs))
+                    .append(separator)
+                    .append(RcDoc::hardline())
+            }
             Type::Variant(fs) => str(derive)
                 .append(RcDoc::line())
                 .append("enum ")

rust/candid/tests/assets/ok/example.rs

@@ -45,7 +45,7 @@ struct h_ret0 { _42_: h_ret0_42, id: candid::Nat }
 
 type f = candid::Func;
 #[derive(CandidType, Deserialize)]
-struct b (candid::Int,candid::Nat,)
+struct b (candid::Int,candid::Nat,);
 
 #[derive(CandidType, Deserialize)]
 enum a { a, b(b) }

rust/candid/tests/assets/ok/fieldnat.rs

@@ -13,7 +13,7 @@ struct baz_arg0 { _2_: candid::Int, #[serde(rename="2")] _50_: candid::Nat }
 struct baz_ret0 {}
 
 #[derive(CandidType, Deserialize)]
-struct tuple (String,String,)
+struct tuple (String,String,);
 
 #[derive(CandidType, Deserialize)]
 struct non_tuple { _1_: String, _2_: String }