Upgrade to unity 4.2.1 causing boo compiler error

Questions & Answers
1

I upgraded from unity 4.2.0 to 4.2.1. The project compiled under unity 4.2.0 without issue and now it fails to compile in 4.2.1 with the following error:
Internal compiler error. See the console log for more information. output was:BCE0011: An error occurred during the execution of the step ‘Boo.Lang.Compiler.Steps.EmitAssembly’: ‘type is not TypeBuilder but System.MonoType
Parameter name: type’.
The console doesn’t appear to really contain any additional useful information. Though if that would help someone in diagnosing it I could add.

The project is a hybrid JavaScript/C# project (not my decision it is how the project was when I inherited it) with various links back and forth between the two languages. I believe the project was started in JavaScript and then later because of them wanting to expand NGUI they started mixing in some C# in a kind of hodge podge sort of way.

This error was apparently happening with Unity 4 when you had empty Javascript files. We do not have any of those (and the project compiles just fine under Unity 4.2.0), I have gone through and double checked to make sure each JS file has the #pragma strict at the top and at least a variable or function declaration.

As well before this compile error started showing up I got some errors that seemed to be about the use of blocks without an if or while before them (basically we had an if statement where we commented out the actual conditional part but had left in the braces that were wrapping the code that the if formerly controlled). To resolve that I simply commented out the braces as well as the if statement itself and those went away. Not sure if that is related but I thought I would add it as well, this struck me as odd.

Any assistance that can be provided would be most valuable as we would like to take advantage of some of the fixes in Unity 4.2.1 for this project.

2

So after a lot of looking through things it turns out that this error is caused by the line:
yield null;
In C# this is the easiest way to do a wait for one frame, and in versions of unity prior to 4.2.1 it appears as even though it is technically incorrect it wouldn’t cause a problem. As of unity 4.2.1 and 4.2.2 however something changed with the compiler and this now causes the above error.
The solution to this issue was pretty simple just take all instance of:
yield null;
and convert them to the correct
yield;
and the project now compiles properly and appears to function the same as before.