Pattern switch in async method causes compiler crash

[gafter]

The following code (thanks to @TyOverby) causes a compiler assertion

// csc /t:library /optimize+ repro.cs
using System;
 
public class Foo {}
 
public class C {
    public async void M() {
        switch (new object())
        {
            case Foo _:
            default:
                throw new InvalidOperationException();
        }
    }
}

The lowering temp produced by pattern-matching is not classified as long-lived, and probably should be.