A JavaScript object pattern over an untyped source (the result of an untyped function, a parameter, a property of an untyped object) now checks the source first when V8 can spell it, as the `any` path in TypeScript files does: a null or undefined source throws "Cannot destructure property 'size' of 'lookup(...)' as it is null." instead of "Cannot read properties of null (reading 'size')". When the first element has a default and a static key (`{ size = 0 }`), the source is not checked first and the read throws, as in V8; this also applies to `any` sources in TypeScript files and to nullable union sources.
The TypeError check for a null or undefined source now reads the unit arm the value holds as a dyn null or undefined, instead of converting the whole union to dyn. A union whose data arm has no dyn form, such as a record holding a generator, compiles again instead of failing with SC9001.
In JavaScript files, a destructuring declaration whose source is one object or array type or null/undefined (`text.match(re)`, `items.find(...)`) threw a plain Error when the source was null or undefined. It now throws Node's TypeError with V8's message: "Cannot destructure property 'index' of 'text.match(...)' as it is null." for an object pattern, and "found is not iterable" or "object null is not iterable (cannot read property Symbol(Symbol.iterator))" for an array pattern. An object pattern whose source V8 spells in a form the compiler does not reproduce keeps the runtime fence.
Chris Tate