Isn't this problem inherent in the Soundscript type system, rather than a problem of the DOM? For example: class Node { ... } class FancyNode extends Node { .

Isn't this problem inherent in the Soundscript type system, rather than a problem of the DOM? For example: class Node { ... } class FancyNode extends Node { ... } function createNode() : Node => new FancyNode(); function doStuff(Node n) { ... } doStuff(createNode()); // Static error - developer scratches his head - how do I fix this doStuff(<FancyNode>createNode()); // There I fixed it. But at what cost to productivity. Or perhaps (Not sure how Any<T> works - just guessing): function doStuff2(Any<Node> n) { ... } // Developer - hey what's this Any<T> thing? More head scratching. Is the extra complexity worth it, what benefits does it bring, and what are the productivity costs? Will soundness actually help runtime performance (Not proven). Will it make security harder? i.e. performance optimisations that rely on the sound type system mean that type spoofing can lead to vulnerabilities. I keep on rambling - sorry - I find this stuff fascinating. Fun job you've got ;)