Cannot build project with vue-cli-service due to bad types

[cerinoligutom]

Describe the bug
Project fails to build with this error:

To Reproduce

1. Create a new Vue project bootstrapped with vue cli
2. Install @vue/apollo-composable and dependencies
3. Use useMutation
4. Build project

Expected behavior
Should not fail the build. Types must be fixed.

Versions
vue: 2.6.11
vue-apollo: 4.0.0-alpha.8
apollo-client: 2.6.10

Additional context
Maybe PR #962 can fix this?

[bbugh]

Hi, yes, #962 will fix this as well.

[cerinoligutom]

@bbugh Apollo Client 3 just got released, I guess he's waiting for this?