Motivation

Today, the actor isolation diagnostics are pretty confusing, especially if they come from a custom executor, which does not have as much information as the concurrency runtime about what isolation was expected. The concurrency runtime function could also accept more parameters to allow the compiler to feed through information from the type checker, such as why the expected isolation is what it is (e.g. it could have been inferred). The runtime diagnostic also does not offer any sort of solution, despite several workarounds existing.

Proposed solution

The runtime diagnostic should always state what the expected isolation was, it should give a reason for the expected isolation, and it should offer actionable guidance on how to resolve the issue.

Alternatives considered

No response

Additional information

No response