Add proposal for async main codegen update #9826
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| + Otherwise, the synthesized entry point waits for the returned task to complete, either passing the task to `System.Runtime.CompilerServices.AsyncHelpers.HandleAsyncEntryPoint` (if it exists) or calling `GetAwaiter().GetResult()` on the task, using either the parameterless instance method or the extension method described by [§C.3](standard-library.md#c3-standard-library-types-not-defined-in-isoiec-23271). If the task fails, the calling method form will throw an exception, and this exception is propagated by the synthesized method. | ||
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| The compiler will look for the following APIs from the core libraries. We do not look at implementations defined outside the core library: |
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How is the determination in the second sentence accomplished?
Also, why add this restriction?
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The determination is done in the same way all core libraries checks are made.
The restriction is there because this is a key runtime scenario. Looking for user-defined handling isn't relevant.
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I'm not able to find an example of the C# specification stating that any of the standard library APIs must not be found in third-party references. Do you know of an example of such an API where the compiler already has that requirement?
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All of the special types, anything coming from runtime async, all of the first-class span feature work, all of string.Concat, anything to do with decimal... anything in this file must come from corelib.
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any of the standard library APIs must not be found in third-party references
Nothing about the specification or this proposal states that other references cannot define methods. It just states that we won't use it.
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The current C# implementation depends on a reference being given from the SDK as a way to provide that API set, and thus it errors if these APIs are not present, right? In what way does this text require that the APIs came from a particular one of the references passed to the compiler from the SDK? If the compiler can "provide" one of these APIs by getting it from an SDK-provided reference, why can't it "provide" one of these APIs by getting it from a third-party-provided reference?
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This text requires that these types come from the BCL. I don't see any other way of reading it.
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I see it saying that the compiler shall provide the APIs in both C.2 and C.3, where only C.2 is related to something called Base Class Library published in ISO/IEC 23271:2012. It seems presented explicitly as happenstance that some of these are in C.2 and some are in C.3, with an explicit reference to this distinction shifting if a potential newer version of ISO/IEC 23271:2012 is produced. I don't see the process defined anywhere for a compiler to consider some references to be BCL references and other references not to be.
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The compiler does not provide any of these APIs. The APIs defined in C.2 must come from the BCL because they are defined in the BCL, as per "For a formal definition of the types and their members identified in (§C.2), refer to ISO/IEC 23271:2012 Common Language Infrastructure (CLI), Partition IV; Base Class Library (BCL), Extended Numerics Library, and Extended Array Library, which are included by reference in this specification."
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I'm seeing a "this is how it already is" but no requirements or instructions for an implementation. I'm not sure how to bring this thread home, so I'll let it go. I don't think this will affect language users, only potentially those who are incorporating the proposals into the standard.
Co-authored-by: Joseph Musser <[email protected]>
| public class AsyncHelpers | ||
| { | ||
| public static void HandleAsyncEntryPoint(System.Threading.Tasks.Task task); | ||
| public static void HandleAsyncEntryPoint(System.Threading.Tasks.Task<int> task); |
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| public static void HandleAsyncEntryPoint(System.Threading.Tasks.Task<int> task); | |
| public static int HandleAsyncEntryPoint(System.Threading.Tasks.Task<int> task); |
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