Add ILInlining.IsUsedAsThisPointerInCall().

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

@@ -45,6 +45,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			NoUsingDueToByRefCall();
 			NoUsingDueToContinuedDisposableUse();
 			ContinuedObjectUse();
+			VariableAlreadyUsedBefore();
 			UsingObject();
 		}
 

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

@@ -94,9 +94,17 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 		
 		static void Box()
 		{
+			Console.WriteLine("Box");
 			object o = new MutValueType { val = 300 };
 			((MutValueType)o).Increment();
 			((MutValueType)o).Increment();
+			MutValueType unboxed1 = (MutValueType)o;
+			unboxed1.Increment();
+			unboxed1.Increment();
+			((MutValueType)o).Increment();
+			MutValueType unboxed2 = (MutValueType)o;
+			unboxed2.val = 100;
+			((MutValueType)o).Dispose();
 		}
 
 		MutValueType instanceField;
@@ -111,11 +119,22 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 		}
 
 		static void Using()
+		{
+			Using1();
+			Using2();
+			Using3();
+		}
+
+		static void Using1()
 		{
 			Console.WriteLine("Using:");
 			using (var x = new MutValueType()) {
 				x.Increment();
 			}
+		}
+
+		static void Using2()
+		{
 			Console.WriteLine("Not using:");
 			var y = new MutValueType();
 			try {
@@ -124,6 +143,10 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 				MutValueType x = y;
 				x.Dispose();
 			}
+		}
+
+		static void Using3()
+		{
 			Console.WriteLine("Using with variable declared outside:");
 			MutValueType z;
 			using (z = new MutValueType()) {

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -164,7 +164,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			ILInstruction loadInst;
 			if (FindLoadInNext(next, v, inlinedExpression, out loadInst) == true) {
 				if (loadInst.OpCode == OpCode.LdLoca) {
-					if (!IsGeneratedValueTypeTemporary(next, loadInst.Parent, loadInst.ChildIndex, v, inlinedExpression))
+					if (!IsGeneratedValueTypeTemporary(next, (LdLoca)loadInst, v, inlinedExpression))
 						return false;
 				} else {
 					Debug.Assert(loadInst.OpCode == OpCode.LdLoc);
@@ -192,31 +192,34 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		/// Is this a temporary variable generated by the C# compiler for instance method calls on value type values
 		/// </summary>
 		/// <param name="next">The next top-level expression</param>
-		/// <param name="parent">The direct parent of the load within 'next'</param>
-		/// <param name="pos">Index of the load within 'parent'</param>
+		/// <param name="loadInst">The load instruction (a descendant within 'next')</param>
 		/// <param name="v">The variable being inlined.</param>
-		static bool IsGeneratedValueTypeTemporary(ILInstruction next, ILInstruction parent, int pos, ILVariable v, ILInstruction inlinedExpression)
+		static bool IsGeneratedValueTypeTemporary(ILInstruction next, LdLoca loadInst, ILVariable v, ILInstruction inlinedExpression)
 		{
-			if (pos == 0 && v.Type != null && v.Type.IsReferenceType == false) {
-				// Inlining a value type variable is allowed only if the resulting code will maintain the semantics
-				// that the method is operating on a copy.
-				// Thus, we have to disallow inlining of other locals, fields, array elements, dereferenced pointers
-				if (IsLValue(inlinedExpression)) {
-					return false;
-				}
+			Debug.Assert(loadInst.Variable == v);
+			// Inlining a value type variable is allowed only if the resulting code will maintain the semantics
+			// that the method is operating on a copy.
+			// Thus, we have to ensure we're operating on an r-value.
+			// Additionally, we cannot inline in cases where the C# compiler prohibits the direct use
+			// of the rvalue (e.g. M(ref (MyStruct)obj); is invalid).
+			return IsUsedAsThisPointerInCall(loadInst) && !IsLValue(inlinedExpression);
+		}
 
-				// inline the compiler-generated variable that are used when accessing a member on a value type:
-				switch (parent.OpCode) {
-					case OpCode.Call:
-						return !((Call)parent).Method.IsStatic;
-					case OpCode.CallVirt:
-						return !((CallVirt)parent).Method.IsStatic;
-					case OpCode.LdFlda:
-					case OpCode.Await:
-						return true;
-				}
+		internal static bool IsUsedAsThisPointerInCall(LdLoca ldloca)
+		{
+			if (ldloca.ChildIndex != 0)
+				return false;
+			if (ldloca.Variable.Type.IsReferenceType != false)
+				return false;
+			switch (ldloca.Parent.OpCode) {
+				case OpCode.Call:
+				case OpCode.CallVirt:
+					return !((CallInstruction)ldloca.Parent).Method.IsStatic;
+				case OpCode.Await:
+					return true;
+				default:
+					return false;
 			}
-			return false;
 		}
 		
 		/// <summary>

ICSharpCode.Decompiler/TypeSystem/NullableType.cs

@@ -50,7 +50,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			if (type == null)
 				throw new ArgumentNullException("type");
 			ParameterizedType pt = type as ParameterizedType;
-			if (pt != null && pt.TypeParameterCount == 1 && pt.FullName == "System.Nullable")
+			if (pt != null && pt.TypeParameterCount == 1 && pt.GetDefinition().KnownTypeCode == KnownTypeCode.NullableOfT)
 				return pt.GetTypeArgument(0);
 			else
 				return type;