Allow yield inside of try / catch and catch

[jaredpar]

This proposal expands the use of yield to

• try portion of a try / catch block
• catch portion of a try / catch block with some restrictions around finally

[timcassell]

Regarding yield-inside-catch-with-nested-finally, could that be resolved by generating 2 separate code paths, one for MoveNext and another for Dispose?

[jaredpar]

Regarding yield-inside-catch-with-nested-finally, could that be resolved by generating 2 separate code paths, one for MoveNext and another for Dispose?

I think the big problem is agreeing on what behavior yield should have when it's encountered in the Dispose path? Is it ignored? Do we throw an exception? etc ... My suspicion is that there won't be broad agreement on what is to be done there.

Basically I think the problem is more along agreeing what behavior is correct vs. implementing that behavior. Can add this to open issues though in case there is broad agreement on what the best behavior is.

[jcouv]

I didn't follow this. Async iterators are more like async state machines than iterator state machines.
Instead of generating a MoveNext and a Dispose method with similar structure, we use a single method (MoveNext) for both normal and disposal execution. A flag indicates if we're in disposal and we use it to skip over non-disposal code as appropriate.
So we shouldn't need to generate catch methods.

Here are some notes on disposal in async iterators. Happy to discuss offline.

[jaredpar]

Hmm. Maybe i was looking at the wrong code gen here. Will take a look at this.