Ref unwrapping causes generic type inference to fail

[stefnotch]

Version

3.0.0-rc.7

Reproduction link

https://codesandbox.io/s/stupefied-beaver-500yq?file=/src/test.ts:0-404

Steps to reproduce

Write the following, reasonably minimal code.

import { reactive, ComputedRef } from "vue";

interface Foo {
  position: number;
}

interface Bar {
  position: number;
  callback: (data: any) => void;
}

function createStuff(name: string, position: ComputedRef<number>) {
  const a: Foo = reactive({
    position: position,
  });

  const b: Bar = reactive({
    position: position, // Issue happens here
    callback: (v) => {},
  });
}

What is expected?

That the types are inferred correctly.

What is actually happening?

In the Bar case, Typescript complains about Type 'ComputedRef<number>' is not assignable to type 'number'. In the Foo case, everything works as expected.

---

This might as well be a bug with Typescript, but considering that it affects Vue's reactive API due to the automatic ref unwrapping, I thought I'd open it here first.

[pikax]

Not sure if this is a bug, the cause seems to be typescript cannot infer v type correctly, which can be fixed by:

  const b: Bar = reactive({
    position: position,
    callback: (v:any) => {}
  });

We can add an overload to provide a better error message, this is the error with the overload:

That error comes because of the noImplicitAny flag on compilerOptions, if you set it to false you won't get the error.