Calling function with bound arguments

[borlaym]

Example

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?

[dperetti]

I would say that foo is not bound yet, while bar is bound with a parameter so its signature is () => void.

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

bar();

[borlaym]

So binding a function changes the signature, and this is normal. Makes sense.

[mroch]

it does seem like the error here should be on the const bar:bound = foo.bind(this, 3) line, not the call of bar().

cc @gabelevi @samwgoldman