Calling function with bound arguments

[Example](https://flow.org/try/#0PQKgBAAgZgNg9gdzCYAoVAXAngBwKZgBGcArgHYAmYAvGABRkkC2heATgJQ0B8YAbnACWFdAGM4ZAM4YwUOHABcxclVp0AhgrCMW7LtV7ipcGHgB08AOYaOAblRHpRdWyWlKNWfLOFBlOhgAFoKSADRgAMx26IQudHZAA)

```
type bound = (number) => void

const foo:bound = (a: number) => console.log(a);
const bar:bound = foo.bind(this, 3);

bar();

8: bar();
^ undefined (too few arguments, expected default/rest parameters). This type is incompatible with
3: type bound = (number) => void
^ number
```

Is this a bug, or am I doing something wrong? What's the best practice to handle this kind of situation?