Unable to display suggestions with method overloading and generictypes

[mattiamanzati]

TypeScript Version: 2.0.0
I am trying to implement a React Hyperscript-like helper in order to avoid using JSX and implement dependency injection. I think there is some trouble with the method overloading I have declared below, because vscode is'nt able to provide correct autosuggestion and typings, and sometimes also tsc itself fails to compile. So I think that either tsc is unable to understand what's going on, or there's something wrong with my code.
Thanks for any further help.

Mattia.

Code

import * as React from 'react'

// just some react type alias
export type ComponentClass<P> = React.StatelessComponent<P> | React.ComponentClass<P>
export type ChildComponent = React.ReactChild

// definition of my "hypescript-like" helper
export function h<P>(Component: string, props?: P & React.DOMAttributes, children?: ChildComponent | ChildComponent[])
export function h<P>(component: ComponentClass<P>, props?: P & React.Attributes, children?: ChildComponent | ChildComponent[])
export function h(component, props?, children?){
    const childrens = children ? children : []
    const componentChildrens = Array.isArray(childrens) ? childrens : [childrens]
    const componentProps = props ? props : {}

    return typeof component === 'string' ?
        React.createElement(component, componentProps, childrens) :
        React.createElement(component, componentProps, childrens)
}

// using this for an HTML tag seems to work
const Button = ({label}: {label: string}) => h('input', {type: 'text'})

// when I start typing label, VSCode and typescript should suggest to me "label" and ensure it's a string
// unfortunately, when I start to write it, I see the DOMAttributes instead and no suggestion for "label".
h(Button, {label: 'test'}

// if I user h<IButtonProps>(Button, {... seems to work nicely

Expected behavior:
After typing h(Button, { vscode should be able to suggest me all the available properties such as "label".

Actual behavior:
After typing h(Button, { DOMAttributes completions are shown.

[DanielRosenwasser]

It's not clear to me exactly why, but it looks like type inference and overload resolution are not playing well as you type out the object literal.

[mattiamanzati]

Exactly, however vscode is able to detect when I am using missing properties from IButton. So it's weird because there's checks but no auto completion :/

[mhegazy]

The issue here is we do not do partial overload resolution, so we do not know what the P really is. if we do not have the same number of parameters we expect we do not go through the process of overload resolution and that is what you see in the IDE. this is the same issue as #8005