Missing error on cyclical computed properties

[Rich-Harris]

It used to be impossible to create computed properties with cyclical dependencies:

<script>
  export default {
    computed: {
      a: ({ b }) => b + 1,
      b: ({ a }) => a + 1
    }
  };
</script>

For some reason (presumably v2 changes) that doesn't fail any more. The same goes for computed properties that depend on themselves.

[Rich-Harris]

Detection is working correctly in Svelte 3