[Concurrency] Asynchronous functions

[Lantua]

@Douglas_Gregor

[We are] Banning overloading of async and synchronous methods that otherwise have the same signature (but see the below about overload resolution).

[...]

We are not inclined to eliminate the overload-resolution rule that prefers async in asynchronous contexts and synchronous functions in synchronous contexts.

Just a quick question (without giving my opinion since the reasoning isn't available yet). What kind of scenario could invoke the second rule? Since it's no longer possible to have overload differing only by async-ness as per the first rule.