fix: fail to generate help for recursive custom types

Initial minimal failing example

cmd/crates/soroban-test/tests/fixtures/test-wasms/custom_type/src/lib.rs

@@ -45,6 +45,12 @@ pub enum ComplexEnum {
     Void,
 }
 
+#[contracttype]
+pub enum RecursiveEnum {
+    Vec(Vec<RecursiveEnum>),
+    Void,
+}
+
 #[contracterror]
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
 #[repr(u32)]
@@ -103,6 +109,10 @@ impl Contract {
         complex
     }
 
+    pub fn recursive_enum(_env: Env, recursive: RecursiveEnum) -> RecursiveEnum {
+        recursive
+    }
+
     pub fn addresse(_env: Env, addresse: Address) -> Address {
         addresse
     }

cmd/crates/soroban-test/tests/it/help.rs

@@ -51,6 +51,13 @@ async fn complex_enum_help() {
     assert!(output.contains(r#""Void"'"#));
 }
 
+#[tokio::test]
+async fn recursive_enum_help() {
+    let output = invoke_custom("recursive_enum", "--help").await.unwrap();
+    assert!(output.contains(r#"--complex"#,));
+    assert!(output.contains(r#""Void"'"#));
+}
+
 #[tokio::test]
 async fn multi_arg_failure() {
     assert!(matches!(