[using] Add more test cases.

ICSharpCode.Decompiler.Tests/TestCases/Correctness/Using.cs

@@ -40,9 +40,11 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 		static void Main()
 		{
 			SimpleUsingNullStatement();
-			NoUsing();
+			NoUsingDueToAssignment();
-			NoUsing2();
+			NoUsingDueToAssignment2();
-			ThisIsNotAUsingBlock();
+			NoUsingDueToByRefCall();
+			NoUsingDueToContinuedDisposableUse();
+			ContinuedObjectUse();
 			UsingObject();
 		}
 
@@ -58,7 +60,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			Console.WriteLine("after using");
 		}
 
-		public static void NoUsing()
+		public static void NoUsingDueToAssignment()
 		{
 			PrintOnDispose printOnDispose = new PrintOnDispose("Wrong");
 			try {
@@ -68,7 +70,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			}
 		}
 
-		public static void NoUsing2()
+		public static void NoUsingDueToAssignment2()
 		{
 			PrintOnDispose printOnDispose = new PrintOnDispose("NoUsing(): Wrong");
 			try {
@@ -81,12 +83,31 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			}
 		}
 
-		public static void ThisIsNotAUsingBlock()
+		static void Clear<T>(ref T t)
+		{
+			t = default(T);
+		}
+
+		public static void NoUsingDueToByRefCall()
+		{
+			PrintOnDispose printOnDispose = new PrintOnDispose("NoUsingDueToByRefCall(): Wrong");
+			try {
+				Console.WriteLine("NoUsingDueToByRefCall");
+				Clear(ref printOnDispose);
+			} finally {
+				IDisposable disposable = (object)printOnDispose as IDisposable;
+				if (disposable != null) {
+					disposable.Dispose();
+				}
+			}
+		}
+
+		public static void NoUsingDueToContinuedDisposableUse()
 		{
 			var obj = new System.IO.StringWriter();
 			IDisposable disposable;
 			try {
-				obj.WriteLine("ThisIsNotAUsingBlock");
+				obj.WriteLine("NoUsingDueToContinuedDisposableUse");
 			} finally {
 				disposable = (object)obj as IDisposable;
 				if (disposable != null) {
@@ -96,6 +117,36 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			Console.WriteLine(disposable);
 		}
 
+		public static void ContinuedObjectUse()
+		{
+			var obj = new System.IO.StringWriter();
+			try {
+				obj.WriteLine("ContinuedObjectUse");
+			} finally {
+				IDisposable disposable = (object)obj as IDisposable;
+				if (disposable != null) {
+					disposable.Dispose();
+				}
+			}
+			Console.WriteLine(obj);
+		}
+
+		public static void VariableAlreadyUsedBefore()
+		{
+			System.IO.StringWriter obj = new System.IO.StringWriter();
+			obj.Write("VariableAlreadyUsedBefore - 1");
+			Console.WriteLine(obj);
+			obj = new System.IO.StringWriter();
+			try {
+				obj.WriteLine("VariableAlreadyUsedBefore - 2");
+			} finally {
+				IDisposable disposable = (object)obj as IDisposable;
+				if (disposable != null) {
+					disposable.Dispose();
+				}
+			}
+		}
+
 		public static void UsingObject()
 		{
 			object obj = new object();

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Using.cs

@@ -86,6 +86,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 		}
 
+		private void UsingStatementOnNullableStruct(UsingStruct? us)
+		{
+			using (us) {
+				Console.WriteLine("using-body: " + us);
+			}
+		}
+
 		public void GenericUsing<T>(T t) where T : IDisposable
 		{
 			using (t) {
@@ -106,5 +113,12 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				Console.WriteLine(t);
 			}
 		}
+
+		public void GenericNullableUsing<T>(T? t) where T : struct, IDisposable
+		{
+			using (t) {
+				Console.WriteLine(t);
+			}
+		}
 	}
 }