is duplicated by:

• SR-14150 Bogus Diagnostic When 'await' is Missing in async Closure Parameter

Issue Description:

There appear to have been previous attempts at improving the diagnostic produced when calling async functions without the async keyword. However, this behavior seems to have regressed (or I'm in the wrong context).

This code:

func makeNetworkCall(id: String) async throws -> String {}

runAsyncAndBlock {
    do {
        try makeNetworkCall(id: "1")
    } catch {
        
    }
}

Produces the diagnostic "'async' in a function that does not support concurrency". If I understand correctly it should instead say that the async keyword is required and offer a fixit to add it.