Fx.Annotate may panic with a constructor that returns a non-nil error

[sywhang]

Given the following annotation:

fx.Provide(fx.Annotate(func() (*bytes.Buffer, error) {
    buf := make([]byte, 1)
    return bytes.NewBuffer(buf), errors.New("some error")
}, fx.ResultTags(`name:"buf"`)))

The reflection done to make a new return type will panic with the following error:

panic: reflect.MakeFunc: value of type errors.errorString is not assignable to type error [recovered]
	panic: reflect.MakeFunc: value of type errors.errorString is not assignable to type error