Emit async-iterators with runtime-async when possible #81314
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| The `GetAsyncEnumerator` method either returns the current instance if it can be reused, | ||
| or creates a new instance of the state machine class. | ||
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| Assuming that the unspeakble state machine class is named `Unspeakable`, `GetAsyncEnumerator` is emitted as: |
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Nit:
| Assuming that the unspeakble state machine class is named `Unspeakable`, `GetAsyncEnumerator` is emitted as: | |
| Assuming that the unspeakable state machine class is named `Unspeakable`, `GetAsyncEnumerator` is emitted as: | |
| ``` #Resolved |
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| #### Lowering of `yield return` | ||
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| `yield return` is disallowed in finally, in try with catch and in catch. |
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Unrelated to this PR, we were going to look at removing some of these restrictions, in particular for yields inside of a try with a catch, right? #Resolved
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Yes, there's a proposal for that, tracked independently: dotnet/csharplang#8414
It's not clear whether this would make it into C# 15 yet
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| ## Open issues | ||
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| Question: AsyncIteratorStateMachineAttribute, or IteratorStateMachineAttribute, or other attribute on kickoff method? |
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Why would this need to differ from what we do today? #Resolved
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I'm not sure yet. We introduced a different attribute for each state machine design so far.
Edit&Continue looks at this attribute and also relies on Symreader which also looks at the attribute. Symreader uses it to find the MoveNext method, but here the naming convention is different (it's "MoveNextAsync").
I didn't investigate the debug symbols or EnC yet. Need to talk to Tomas ;-)
src/Compilers/CSharp/Portable/Lowering/AsyncRewriter/AsyncRewriter.AsyncIteratorRewriter.cs
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333fred
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Done review pass (commit 1). Tests are not looked at yet.
src/Compilers/CSharp/Portable/Lowering/AsyncRewriter/RuntimeAsyncRewriter.cs
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.../Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.MoveNextAsyncRewriter.cs
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.../Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.MoveNextAsyncRewriter.cs
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.../Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.MoveNextAsyncRewriter.cs
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...pilers/CSharp/Portable/Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.cs
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...pilers/CSharp/Portable/Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.cs
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...rs/CSharp/Portable/Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorStateMachine.cs
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src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/SynthesizedStateMachineMethod.cs
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| Async methods that return `IAsyncEnumerable<T>` or `IAsyncEnumerator<T>` are transformed by the compiler into state machines. | ||
| States are created for each `await` and `yield`. | ||
| Runtime-async support was added in .NET 10 as a preview feature and reduces the overhead of async methods by letting the runtime handling `await` suspensions. |
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| Runtime-async support was added in .NET 10 as a preview feature and reduces the overhead of async methods by letting the runtime handling `await` suspensions. | |
| Runtime-async support was added in .NET 10 as a preview feature and reduces the overhead of async methods by letting the runtime handle `await` suspensions. | |
| ``` #Resolved |
333fred
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Mostly LGTM. Just a couple of small comments.
...pilers/CSharp/Portable/Lowering/RuntimeAsyncIteratorRewriter/RuntimeAsyncIteratorRewriter.cs
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Relates to test plan #75960