typeArgument of JsxOpeningLikeElement ignored while checking JsxAttributes

[ajafff]

TypeScript Version: 2.9.0-dev.20180328

Search Terms: jsx generic type arguments

Code

export {};

declare namespace JSX {
    interface Element {
        render(): Element | string | false;
    }
}

function SFC<T>(props: Record<string, T>) {
    return '';
}

/*1*/<SFC<string> prop={1}></SFC>;

Expected behavior:

Error on the prop attribute, because number is not assignable to string.

Actual behavior:

No error. Signature help incorrectly shows function SFC<number>(props: Record<string, number>): string

Playground Link:

Related Issues:

#22873

[weswigham]

Attributes still get typechecked against any unless ElementAttributesProperty is specified with a interface ElementAttributesProperty { props: any; } declaration. (So even though you've said Record<string, string>, we ignore it and check against any because we failed to find the declaration.) We proooooooooooooobably don't need to look up props like this anymore, since we know we can always just use the the first argument of the ctor/function; but for now you can get the error you expect just by adding the required interface ElementAttributesProperty {} declaration into your JSX namespace.

[ajafff]

@weswigham I actually have ElementAttributesProperty declared. I just omitted it for the report:

export {};

declare namespace JSX {
    interface IntrinsicElements {
        [elemName: string]: any;
    }

    interface Element {
        render(): Element | string | false;
    }

    interface ElementAttributesProperty {
        props: any;
    }
}

function SFC<T>(props: Record<string, T>) {
    return '';
}

<SFC<string> prop={1}></SFC>; // still no error

[weswigham]

@ajafff We only look up a global JSX or a JSX under the factory function - your export {} makes it non-global, which means we don't find a JSX namespace at all.

[weswigham]

Update: ElementAttributesProperty is now optional. We'll use the first parameter of the element's constructor/function for the type if it is not present.