Simplify error messages against intersections of weak types

I spoke a bit with @sandersn about ways we can tackle the type madness issue (#14662). I noted that JSX scenarios are much more broadly applicable right now and are pretty prevalent given the sorts of type arithmetic we see a lot of in the React community. 😃

Problem: JSX optional attributes make errors too hard to read

interface FooProps {
    name: string;
    age: number;
}

class Foo extends React.Component<FooProps> {
    constructor(props: FooProps) {
        super(props)
    }
    render() {
        const {name, age} = this.props;
        return <div>I'm {name} and am {age} years old</div>;
    }
}

// Type '{ blah: number; }' is not assignable to type 'IntrinsicAttributes & IntrinsicClassAttributes<Foo> & Readonly<{ children?: ReactNode; }> & Reado...'.
//   Type '{ blah: number; }' is not assignable to type 'Readonly<FooProps>'.
//     Property 'name' is missing in type '{ blah: number; }'.
<Foo blah={10} />;

Proposal

When doing relation checks against an intersection target, if a check fails, see if relating against the same type with weak types removed would result in the same outcome. If so, use that comparison when elaborating types.

The great part is that this actually solves a broader set of problems than just JSX.

Inizia con la riproduzione JSX nell’issue e segui i controlli delle relazioni tra tipi per una destinazione di intersezione con tipi deboli. Confronta la diagnostica attuale con il confronto proposto che rimuove i tipi deboli; il lavoro è completato quando l’errore JSX viene semplificato senza modificare il risultato della relazione, continuando a coprire i casi interessati più ampi.