Flow: `Function` has no callable signature

[Naddiseo]

Function.prototype should be a callable property, currently flow complains that there is no "Callable signature".

The following is valid javascript, thus should not have flow errors:

/* @flow */
const noop = Function.prototype;
noop();

flow try

[ndbroadbent]

I think I may be running into this issue when I use import type to import the type of a Function from another file.

import type {
  actionCreator,
} from 'redux/modules/reducer'

type Props = {
  action: actionCreator,
}

export default class TestComponent extends PureComponent<Props> {
  props: Props

  onClickHandler() {
    this.props.action()
    // ~~~~~~~~~~~~~~~
    //  [flow] call of method `action` (Callable signature not found in prototype)
  }
}

Is this the same issue?

[ndbroadbent]

Oh sorry, I need to use import typeof instead of import type. https://flow.org/en/docs/types/modules/#toc-importing-and-exporting-values

• Use import type for classes.
• Use import typeof for instances of classes and exported values, e.g. numbers, strings, functions.

[duffytilleman]

Another example of something that should work that doesn't:

// This works in JS, but flow rejects
Function('return {}')()

flow try

Use case in MDN docs