Fix crash when the element instance type was undefined

[RyanCavanaugh]

Fixes issue #3903

[DanielRosenwasser]

Under what situations does getJsxElementInstanceType return undefined?

[RyanCavanaugh]

When type of the specified element has no call or construct signatures

[s-panferov]

@RyanCavanaugh just tried the solution we discussed in #3960 and it fails to:

import * as React from 'react';

class C extends React.Component<any, any> {
    render() {
        return null
    }
}

type ReactCtor<P, S> = new() => React.Component<P, S> & { render(): React.ReactElement<P> };
let C1: ReactCtor<any, any> = C;
let a = <C1 />;

So maybe the error is not because of call or construct signature?

https://github.com/s-panferov/ts-jsx-issue

[s-panferov]

@RyanCavanaugh output from your branch:

➜  ts-jsx-issue git:(master) ✗ ../TypeScript/bin/tsc --target es6 --jsx react issue.tsx
issue.tsx(17,10): error TS2601: The return type of a JSX element constructor must return an object type.

[s-panferov]

@RyanCavanaugh I found a working example

interface JsxClass<P, S> extends React.Component<P, S> {
    render(): React.ReactElement<P>
}

interface ReactCtor<P, S> {
    new(props: P): JsxClass<P, S>;
}

let C1: ReactCtor<any, any> = C;
let a = <C1 />;

[RyanCavanaugh]

Hadn't tested with intersection types before. Updating.

[RyanCavanaugh]

Anyone care to take a look? We should get this in for 1.6

[JsonFreeman]

You can reduce this lambda

[JsonFreeman]

👍