Make tests/clipping/canvas-rounded-corners.sky actually run.

sky/engine/bindings/scripts/dart_interface.py

Index: sky/engine/bindings/scripts/dart_interface.py
diff --git a/sky/engine/bindings/scripts/dart_interface.py b/sky/engine/bindings/scripts/dart_interface.py
index 0b21bf4613641d95ee9f6c701245c664b986204f..0b0223fa7167097ecc76d4ef6461c4a3fc5289aa 100644
--- a/sky/engine/bindings/scripts/dart_interface.py
+++ b/sky/engine/bindings/scripts/dart_interface.py
@@ -169,6 +169,9 @@ def interface_context(interface):
             # For overloaded methods, only generate one accessor
             ('overload_index' not in method or method['overload_index'] == 1))
 
+    for method in methods:
+        assert 'overloads' not in method, 'Dart does not support overloads, %s in %s' % (method['name'], interface.name)
+
     generate_method_native_entries(interface, methods, 'Method')
 
     context.update({