src/third_party/web_platform_tests/WebIDL/valid/idl/constructor.widl

// Extracted from http://dev.w3.org/2006/webapi/WebIDL/ on 2011-05-06
[Constructor,
 Constructor(float radius)]
interface Circle {
  attribute float r;
  attribute float cx;
  attribute float cy;
  readonly attribute float circumference;
};