Add support for lock statements within yield return state machines

[ElektroKill]

Link to issue(s) this covers:
N/A

Problem

ILSpy did not properly decompile lock statements in yield return state machines generated by the legacy C# compiler. This was due to a variation in the ILAst pattern. The difference is an extra variable.

Before changes:

public static IEnumerable<int> YieldReturnInLock1(object o)
{
	bool lockTaken = false;
	object obj2 = default(object);
	try
	{
		object obj;
		obj2 = (obj = o);
		Monitor.Enter(obj, ref lockTaken);
		yield return 1;
	}
	finally
	{
		if (lockTaken)
		{
			Monitor.Exit(obj2);
		}
	}
}

After changes:

public static IEnumerable<int> YieldReturnInLock1(object o)
{
	lock (o)
	{
		yield return 1;
	}
}

Solution

• Added support for the ILAst pattern mentioned above
• Enabled the previously disabled test cases for lock statements in yield return state machines.

[siegfriedpammer]

Thank you for your contribution!