Add parser unit test for a no-arg call

src/compiler/compiler.rs

@@ -831,6 +831,18 @@ mod test {
 
         assert!(result.is_ok());
 
+        // TODO should no-arg calls be allowed?
+        let circuit = "
+        machine caller (signal n) (signal b: field) {
+            smth <== a() -> final;
+        }
+        ";
+
+        let debug_sym_ref_factory = DebugSymRefFactory::new("", circuit);
+        let result = TLDeclsParser::new().parse(&debug_sym_ref_factory, circuit);
+
+        assert!(result.is_ok());
+
         // Wrong transition operator
         let circuit = "
         machine caller (signal n) (signal b: field) {

src/parser/build.rs

@@ -67,5 +67,8 @@ pub fn build_hyper_transition<F>(
     state: Identifier,
     call: Statement<F, Identifier>,
 ) -> Statement<F, Identifier> {
-    Statement::HyperTransition(dsym, state, Box::new(call))
+    match call {
+        Statement::Call(_, _, _, _) => Statement::HyperTransition(dsym, state, Box::new(call)),
+        _ => unreachable!("Hyper transition must include a call statement"),
+    }
 }