Resolve issue of qjit(static_argnums=...) fails when the marked static argument has a default value

frontend/catalyst/jit.py

@@ -642,7 +642,8 @@ def capture(self, args, **kwargs):
             PyTreeDef: PyTree metadata of the function output
             Tuple[Any]: the dynamic argument signature
         """
-        verify_static_argnums(args, self.compile_options.static_argnums)
+
+        verify_static_argnums(args, self.original_function, self.compile_options.static_argnums)
         static_argnums = self.compile_options.static_argnums
         abstracted_axes = self.compile_options.abstracted_axes
 

frontend/catalyst/tracing/type_signatures.py

@@ -104,21 +104,27 @@ def verify_static_argnums_type(static_argnums):
     return None
 
 
-def verify_static_argnums(args, static_argnums):
+def verify_static_argnums(args, fn, static_argnums):
     """Verify that static_argnums have correct type and range.
 
     Args:
         args (Iterable): arguments to a compiled function
+        fn (Callable): the quantum or classical function in question
         static_argnums (Iterable[int]): indices to verify
 
     Returns:
         None
     """
     verify_static_argnums_type(static_argnums)
 
+    # use inspect to get parameters defined in the function declaration
+    sig_args = inspect.signature(fn).parameters
+
+    # `static_argnums` should be compared to the maximum args that can be passed to a function
+    arg_limit = max(len(args), len(sig_args))
     for argnum in static_argnums:
-        if argnum < 0 or argnum >= len(args):
-            msg = f"argnum {argnum} is beyond the valid range of [0, {len(args)})."
+        if argnum < 0 or argnum >= arg_limit:
+            msg = f"argnum {argnum} is beyond the valid range of [0, {arg_limit})."
             raise CompileError(msg)
     return None
 

frontend/test/pytest/test_static_arguments.py

@@ -123,6 +123,19 @@ def f(x: MyClass, y: int, z: MyClass):
         assert f(MyClass(5), 2, MyClass(5)) == 12
         assert function == f.compiled_function
 
+    def test_default_static_arguments(self):
+        """Test QJIT with static arguments that have a default value."""
+
+        @qjit(static_argnums=[1])
+        def f(y, x=9):
+            if x < 10:
+                return x + y
+            return 42000
+
+        assert f(20) == 29
+        assert f(20, 3) == 23
+        assert f(20, 300000) == 42000
+
     def test_mutable_static_arguments(self):
         """Test QJIT with mutable static arguments."""