[heycam/webidl] Consider adding [LegacyASCIICaseInsentiveEnum] for `element.insertAdjacent*` APIs (#968)

The <code>[<var>element</var>.insertAdjacentElement](https://dom.spec.whatwg.org/#dom-element-insertadjacentelement)</code>, <code>[<var>element</var>.insertAdjacentText](https://dom.spec.whatwg.org/#dom-element-insertadjacenttext)</code> and <code>[<var>element</var>.insertAdjacentHTML](https://w3c.github.io/DOM-Parsing/#dom-element-insertadjacenthtml)</code> APIs take a <var>where</var>/<var>position</var> argument of <code>[DOMString](https://heycam.github.io/webidl/#idl-DOMString)</code> that is [ASCII lowercased](https://infra.spec.whatwg.org/#ascii-lowercase) and treated as if it were converted to the following enum:
```webidl
enum InsertPosition {
 "beforebegin",
 "afterbegin",

 "beforeend",
 "afterend"
};
```

Except that instead of throwing a <code>[TypeError](https://heycam.github.io/webidl/#exceptiondef-typeerror)</code> or a <code>[RangeError](https://heycam.github.io/webidl/#exceptiondef-rangeerror)</code><sup> <https://github.com/heycam/webidl/issues/489></sup>, a "<code>[SyntaxError](https://heycam.github.io/webidl/#syntaxerror)</code>" <code>[DOMException](https://heycam.github.io/webidl/#idl-DOMException)</code> is thrown instead.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/heycam/webidl/issues/968