typescript inconsistent never behavior

failed-narrow.ts

// variable we want to narrow
const { channel } = {} as Record<string,string | undefined>;
// if this simpler definition is used instead, it's all ok
// const channel: undefined | string = 'hi';


// method returning never
const api = {} as { cancel(): never; };

if (!channel) api.cancel();
channel.length; // error... possibly undefined


// function returning never
const cancelType = (() => {}) as () => never;

if (!channel) cancelType();
channel.length; // error... possibly undefined


// implemented function returning never
function cancelReal(): never { while (true) {} }

if (!channel) cancelReal();
channel.length; // this is ok??