Add test for IIFE (#3349)

## **Description**

Author: kugesan1105

jac/jaclang/compiler/passes/main/tests/fixtures/checker_iife_expression.jac

@@ -0,0 +1,8 @@
+with entry {
+    # Test: IIFE returning a function
+    let adder = (def make_adder(x: int) {
+        return lambda y: int: x + y;
+    })(10);
+
+    print("Test - IIFE returning function, adder(5):", adder(5));
+}

jac/jaclang/compiler/passes/main/tests/test_checker_pass.py

@@ -412,6 +412,13 @@ def test_cyclic_symbol(self) -> None:
         TypeCheckPass(ir_in=mod, prog=program)
         self.assertEqual(len(program.errors_had), 0)
 
+    def test_get_type_of_iife_expression(self) -> None:
+        path = self.fixture_abs_path("checker_iife_expression.jac")
+        program = JacProgram()
+        mod = program.compile(path)
+        TypeCheckPass(ir_in=mod, prog=program)
+        self.assertEqual(len(program.errors_had), 0)
+
     def test_param_arg_match(self) -> None:
         program = JacProgram()
         path = self.fixture_abs_path("checker_generics.jac")