Fix #1060: Enter/Exit V2 variation failing to convert to lock()

ICSharpCode.Decompiler.Tests/Helpers/RemoveCompilerAttribute.cs

@@ -10,7 +10,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			var section = (AttributeSection)attribute.Parent;
 			SimpleType type = attribute.Type as SimpleType;
 			if (section.AttributeTarget == "assembly" &&
-				(type.Identifier == "CompilationRelaxations" || type.Identifier == "RuntimeCompatibility" || type.Identifier == "SecurityPermission" || type.Identifier == "AssemblyVersion" || type.Identifier == "Debuggable"))
+				(type.Identifier == "CompilationRelaxations" || type.Identifier == "RuntimeCompatibility" || type.Identifier == "SecurityPermission" || type.Identifier == "PermissionSet" || type.Identifier == "AssemblyVersion" || type.Identifier == "Debuggable"))
 			{
 				attribute.Remove();
 				if (section.Attributes.Count == 0)

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -66,6 +66,16 @@ namespace ICSharpCode.Decompiler.Tests
 			CompilerOptions.Optimize | CompilerOptions.UseRoslyn
 		};
 
+		static readonly CompilerOptions[] defaultOptionsWithMcs =
+		{
+			CompilerOptions.None,
+			CompilerOptions.Optimize,
+			CompilerOptions.UseRoslyn,
+			CompilerOptions.Optimize | CompilerOptions.UseRoslyn,
+			CompilerOptions.UseMcs,
+			CompilerOptions.Optimize | CompilerOptions.UseMcs
+		};
+
 		[Test]
 		public void HelloWorld()
 		{
@@ -124,7 +134,7 @@ namespace ICSharpCode.Decompiler.Tests
 		}
 
 		[Test]
-		public void Lock([ValueSource("defaultOptions")] CompilerOptions cscOptions)
+		public void Lock([ValueSource("defaultOptionsWithMcs")] CompilerOptions cscOptions)
 		{
 			RunForLibrary(cscOptions: cscOptions);
 		}

ICSharpCode.Decompiler/IL/Transforms/LockTransform.cs

@@ -36,7 +36,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			for (int i = block.Instructions.Count - 1; i >= 0; i--) {
 				if (!TransformLockRoslyn(block, i))
 					if (!TransformLockV4(block, i))
-						TransformLockV2(block, i);
+						if (!TransformLockV2(block, i))
+							TransformLockMCS(block, i);
 				// This happens in some cases:
 				// Use correct index after transformation.
 				if (i >= block.Instructions.Count)
@@ -44,6 +45,51 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			}
 		}
 
+		/// <summary>
+		///	stloc lockObj(lockExpression)
+		///	call Enter(ldloc lockObj)
+		///	.try BlockContainer {
+		///		Block lockBlock (incoming: 1) {
+		///			call WriteLine()
+		///			leave lockBlock (nop)
+		///		}
+		///
+		///	} finally BlockContainer {
+		///		Block exitBlock (incoming: 1) {
+		///			call Exit(ldloc lockObj)
+		///			leave exitBlock (nop)
+		///		}
+		///
+		///	}
+		/// =>
+		/// .lock (lockExpression) BlockContainer {
+		/// 	Block lockBlock (incoming: 1) {
+		///			call WriteLine()
+		///			leave lockBlock (nop)
+		///		}
+		/// }
+		/// </summary>
+		bool TransformLockMCS(Block block, int i)
+		{
+			if (i < 2) return false;
+			if (!(block.Instructions[i] is TryFinally body) || !(block.Instructions[i - 2] is StLoc objectStore) ||
+				!MatchCall(block.Instructions[i - 1] as Call, "Enter", objectStore.Variable))
+				return false;
+			if (!objectStore.Variable.IsSingleDefinition)
+				return false;
+			if (!(body.TryBlock is BlockContainer tryContainer) || tryContainer.EntryPoint.Instructions.Count == 0 || tryContainer.EntryPoint.IncomingEdgeCount != 1)
+				return false;
+			if (!(body.FinallyBlock is BlockContainer finallyContainer) || !MatchExitBlock(finallyContainer.EntryPoint, null, objectStore.Variable))
+				return false;
+			if (objectStore.Variable.LoadCount > 2)
+				return false;
+			context.Step("LockTransformMCS", block);
+			block.Instructions.RemoveAt(i - 1);
+			block.Instructions.RemoveAt(i - 2);
+			body.ReplaceWith(new LockInstruction(objectStore.Value, body.TryBlock) { ILRange = objectStore.ILRange });
+			return true;
+		}
+
 		/// <summary>
 		///	stloc lockObj(ldloc tempVar)
 		///	call Enter(ldloc tempVar)