hdl.ir: bring new naming rules to top-level ports

amaranth/hdl/_ir.py

@@ -559,6 +559,7 @@ def _assign_port_names(self):
                     raise TypeError("Signals with private names cannot be used in unnamed top-level ports")
                 name = _add_name(assigned_names, conn.name)
                 assigned_names.add(name)
+            validate_name(name, "Top-level port name")
             new_ports.append((name, conn, dir))
         self.ports = new_ports
 

tests/test_hdl_ir.py

@@ -1054,6 +1054,12 @@ def test_assign_names_to_fragments_duplicate(self):
         self.assertEqual(design.fragments[a1_f].name, ("top", "a"))
         self.assertEqual(design.fragments[a2_f].name, ("top", "a$1"))
 
+    def test_port_wrong_name(self):
+        f = Fragment()
+        with self.assertRaisesRegex(NameError,
+                r"^Top-level port name must be a non-empty string$"):
+            design = Design(f, ports=[("", Signal(), None)], hierarchy=("top",))
+
 
 class ElaboratesTo(Elaboratable):
     def __init__(self, lower):