SVG 1.1 defined some interfaces which were a lot like mixins, with wording like this:

Interface SVGTests defines an interface which applies to all elements which have attributes ‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’.

or:

Interface SVGTransformable contains properties and methods that apply to all elements which have attribute ‘transform’.

However, these predated Web IDL mixins, and some of them were implemented in a way which exposed the interface object for them.

A number of interfaces like this are in BCD/MDN:

• https://developer.mozilla.org/en-US/docs/Web/API/SVGAnimatedPoints
• https://developer.mozilla.org/en-US/docs/Web/API/SVGExternalResourcesRequired
• https://developer.mozilla.org/en-US/docs/Web/API/SVGFilterPrimitiveStandardAttributes
• https://developer.mozilla.org/en-US/docs/Web/API/SVGStylable
• https://developer.mozilla.org/en-US/docs/Web/API/SVGTests
• https://developer.mozilla.org/en-US/docs/Web/API/SVGTransformable
• https://developer.mozilla.org/en-US/docs/Web/API/SVGURIReference

This list might not be complete.

We should probably delete all of these pages and their BCD entries, but in the process we should also make sure that the members are instead of the other correct interfaces.

Note that https://developer.mozilla.org/en-US/docs/Web/API/SVGUnitTypes is not to be removed, because https://svgwg.org/svg2-draft/types.html#InterfaceSVGUnitTypes defines it as a plain interface, because there are constants on it that are accessed through the interface object.