Bug 21808 - Internal compiler error when using "async delegate" syntax for a generic method argument.
Summary: Internal compiler error when using "async delegate" syntax for a generic meth...
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 3.4.0
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: ---
Assignee: Marek Safar
Depends on:
Reported: 2014-08-05 00:47 UTC by bugzilla
Modified: 2014-08-06 01:56 UTC (History)
1 user (show)

Is this bug a regression?: ---
Last known good build:

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Description bugzilla 2014-08-05 00:47:42 UTC
The can be reproduced on both mono 3.4 and 3.6.  The following program causes the C# compiler to crash:

using System.Threading.Tasks;

class MainClass
	public static void Main(string [] args)
		EnqueueTask(async delegate {
			await Task.Yield();
			return 0;
	static Task<T> EnqueueTask<T>(Func<Task<T>> func)
		return null;

The compiler error is "Error CS0584: Internal compiler error: Object reference not set to an instance of an object"

The same code works fine on Microsoft's compiler. The problem seems to be the usage of "async delegate" syntax.  No error is reported when the "delegate" keyword is changed to the lambda syntax "() =>".  It also seems to be related to the use of generics; no error is reported if type parameter "T" is removed from the EnqueueTask method.
Comment 1 Marek Safar 2014-08-06 01:52:37 UTC

*** This bug has been marked as a duplicate of bug 20849 ***
Comment 2 Marek Safar 2014-08-06 01:56:12 UTC
Already fixed in mono master