Function types are typed as any

[mattcompiles]

Description

Function types (e.g. event handlers) are typed as any. I'm not convinced react-polymorphic-box is at fault here but thought I'd raise it to discuss. In my example typescript seems to infer the correct type for the event handler (pictured below), however when implementing the handler it is not typed.

Reproduction

import React from 'react';
import { Box } from 'react-polymorphic-box'; 

const Test = () => (
  <Box
    as="li"
    onMouseDown={(event) => {
      // event is implicitly typed as any
    }}
  />
);

Expected behaviour

The event handler should be typed as expected.

Actual behaviour

Event handlers seem to be typed as any.

Environment

System:

• OS: macOS Mojave 10.14.6
• CPU: (8) x64 Intel(R) Core(TM) i7-8559U CPU @ 2.70GHz
• Memory: 42.69 MB / 16.00 GB
• Shell: 5.3 - /bin/zsh

Binaries:

• Node: 12.18.2
• Yarn: 1.22.4
• npm: 6.14.5

Browsers:

• Chrome: 84.0.4147.89
• Firefox: 78.0.1
• Safari: 12.1.2

npmPackages:

• react-polymorphic-box: ^2.0.4 => 2.0.4
• typescript: 3.9.6

[kripod]

Thank you for submitting this issue! As far as I know, this might be fixed on the language level by a forthcoming release of TypeScript. Please follow microsoft/TypeScript#31023 for more information!

[mattcompiles]

Cheers bud, you're all over it. 👍

[corbanbrook]

This is what i did to get event handlers to type correctly.

playground link