In the react types, the definition of React.Component is React.Component<P = {}, S = {}, SS = never>, meaning that type-wise, props defaults to {}, state defaults to {}, and snapshot defaults to never. Snapshot is used as the return value of the new React getSnapshotBeforeUpdate lifecycle method, whose return type is SS | null.

What that means, however, is that unless the third generic type parameter is overridden, the return value of getSnapshotBeforeUpdate is resolved to never | null, which is resolved to null. This causes an issue where any components that do define getSnapshotBeforeUpdate are unable to be used by something expecting a React.Component, because getSnapshotBeforeUpdate returns something other than null.

This PR changes the default to be SS = any, which allows other libraries to do things like the following:

const func = (comp: React.Component<any>) => {...}

There are many third-party libraries that do something similar, which I believe necessitates this change. Additionally, at the moment it is not possible to even use a component that uses the new lifecycle method as it is not considered to be a valid JSX component type (for the same reason, see #24820).

I have added several test cases to catch actually using components that contain getSnapshotBeforeUpdate, using them with React.createElement, and using the new lifecycle method on PureComponent, which previously did not accept the SS type param.

Fixes #24820. See #24820 for more context. Replaces #24985.

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