fix #560: properly recognize `lock` pattern of C# 2, and add `lock (this)` pattern

ICSharpCode.Decompiler/Ast/Transforms/PatternStatementTransform.cs

@@ -617,6 +617,7 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 		
 		static readonly AstNode lockTryCatchPattern = new TryCatchStatement {
 			TryBlock = new BlockStatement {
+				new OptionalNode(new VariableDeclarationStatement()).ToStatement(),
 				new TypePattern(typeof(System.Threading.Monitor)).ToType().Invoke(
 					"Enter", new AnyNode("enter"),
 					new DirectionExpression {
@@ -629,21 +630,57 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				new IfElseStatement {
 					Condition = new Backreference("flag"),
 					TrueStatement = new BlockStatement {
-						new TypePattern(typeof(System.Threading.Monitor)).ToType().Invoke("Exit", new NamedNode("exit", new IdentifierExpression(Pattern.AnyString)))
+						new TypePattern(typeof(System.Threading.Monitor)).ToType().Invoke("Exit", new AnyNode("exit"))
 					}
 				}
 			}};
+
+		static readonly AstNode oldMonitorCallPattern = new ExpressionStatement(
+			new TypePattern(typeof(System.Threading.Monitor)).ToType().Invoke("Enter", new AnyNode("enter"))
+		);
+
+		static readonly AstNode oldLockTryCatchPattern = new TryCatchStatement
+		{
+			TryBlock = new BlockStatement {
+				new Repeat(new AnyNode()).ToStatement()
+			},
+			FinallyBlock = new BlockStatement {
+				new TypePattern(typeof(System.Threading.Monitor)).ToType().Invoke("Exit", new AnyNode("exit"))
+			}
+		};
+
+		bool AnalyzeLockV2(ExpressionStatement node, out Expression enter, out Expression exit)
+		{
+			enter = null;
+			exit = null;
+			Match m1 = oldMonitorCallPattern.Match(node);
+			if (!m1.Success) return false;
+			Match m2 = oldLockTryCatchPattern.Match(node.NextSibling);
+			if (!m2.Success) return false;
+			enter = m1.Get<Expression>("enter").Single();
+			exit = m2.Get<Expression>("exit").Single();
+			return true;
+		}
+
+		bool AnalyzeLockV4(ExpressionStatement node, out Expression enter, out Expression exit)
+		{
+			enter = null;
+			exit = null;
+			Match m1 = lockFlagInitPattern.Match(node);
+			if (!m1.Success) return false;
+			Match m2 = lockTryCatchPattern.Match(node.NextSibling);
+			if (!m2.Success) return false;
+			enter = m2.Get<Expression>("enter").Single();
+			exit = m2.Get<Expression>("exit").Single();
+			return m1.Get<IdentifierExpression>("variable").Single().Identifier == m2.Get<IdentifierExpression>("flag").Single().Identifier;
+		}
 		
 		public LockStatement TransformLock(ExpressionStatement node)
 		{
-			Match m1 = lockFlagInitPattern.Match(node);
-			if (!m1.Success) return null;
-			AstNode tryCatch = node.NextSibling;
-			Match m2 = lockTryCatchPattern.Match(tryCatch);
-			if (!m2.Success) return null;
-			if (m1.Get<IdentifierExpression>("variable").Single().Identifier == m2.Get<IdentifierExpression>("flag").Single().Identifier) {
-				Expression enter = m2.Get<Expression>("enter").Single();
-				IdentifierExpression exit = m2.Get<IdentifierExpression>("exit").Single();
+			Expression enter, exit;
+			bool isV2 = AnalyzeLockV2(node, out enter, out exit);
+			if (isV2 || AnalyzeLockV4(node, out enter, out exit)) {
+				AstNode tryCatch = node.NextSibling;
 				if (!exit.IsMatch(enter)) {
 					// If exit and enter are not the same, then enter must be "exit = ..."
 					AssignmentExpression assign = enter as AssignmentExpression;
@@ -659,7 +696,8 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				LockStatement l = new LockStatement();
 				l.Expression = enter.Detach();
 				l.EmbeddedStatement = ((TryCatchStatement)tryCatch).TryBlock.Detach();
-				((BlockStatement)l.EmbeddedStatement).Statements.First().Remove(); // Remove 'Enter()' call
+				if (!isV2) // Remove 'Enter()' call
+					((BlockStatement)l.EmbeddedStatement).Statements.First().Remove(); 
 				tryCatch.ReplaceWith(l);
 				node.Remove(); // remove flag variable
 				return l;

ICSharpCode.Decompiler/Tests/DecompilerTestBase.cs

@@ -44,10 +44,10 @@ namespace ICSharpCode.Decompiler.Tests
 			return CodeSampleFileParser.ConcatLines(lines.Where(l => !CodeSampleFileParser.IsCommentOrBlank(l)));
 		}
 
-		protected static void AssertRoundtripCode(string fileName, bool optimize = false, bool useDebug = false)
+		protected static void AssertRoundtripCode(string fileName, bool optimize = false, bool useDebug = false, int compilerVersion = 4)
 		{
 			var code = RemoveIgnorableLines(File.ReadLines(fileName));
-			AssemblyDefinition assembly = CompileLegacy(code, optimize, useDebug);
+			AssemblyDefinition assembly = CompileLegacy(code, optimize, useDebug, compilerVersion);
 
 			AstBuilder decompiler = new AstBuilder(new DecompilerContext(assembly.MainModule));
 			decompiler.AddAssembly(assembly);
@@ -58,12 +58,13 @@ namespace ICSharpCode.Decompiler.Tests
 			CodeAssert.AreEqual(code, output.ToString());
 		}
 
-		protected static AssemblyDefinition CompileLegacy(string code, bool optimize, bool useDebug)
+		protected static AssemblyDefinition CompileLegacy(string code, bool optimize, bool useDebug, int compilerVersion)
 		{
-			CSharpCodeProvider provider = new CSharpCodeProvider(new Dictionary<string, string> { { "CompilerVersion", "v4.0" } });
+			CSharpCodeProvider provider = new CSharpCodeProvider(new Dictionary<string, string> { { "CompilerVersion", "v" + new Version(compilerVersion, 0) } });
 			CompilerParameters options = new CompilerParameters();
 			options.CompilerOptions = "/unsafe /o" + (optimize ? "+" : "-") + (useDebug ? " /debug" : "");
-			options.ReferencedAssemblies.Add("System.Core.dll");
+			if (compilerVersion >= 4)
+				options.ReferencedAssemblies.Add("System.Core.dll");
 			CompilerResults results = provider.CompileAssemblyFromSource(options, code);
 			try
 			{

ICSharpCode.Decompiler/Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -75,6 +75,7 @@
     <Compile Include="CustomShortCircuitOperators.cs" />
     <Compile Include="Helpers\CodeAssert.cs" />
     <Compile Include="IncrementDecrement.cs" />
+    <Compile Include="Lock.cs" />
     <Compile Include="PInvoke.cs" />
     <Compile Include="QueryExpressions.cs" />
     <Compile Include="Switch.cs" />

ICSharpCode.Decompiler/Tests/Lock.cs

@@ -0,0 +1,38 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+
+public class Lock
+{
+	public void LockThis()
+	{
+		lock (this)
+		{
+			Console.WriteLine();
+		}
+	}
+
+	public void LockOnType()
+	{
+		lock (typeof(Lock))
+		{
+			Console.WriteLine();
+		}
+	}
+}

ICSharpCode.Decompiler/Tests/TestRunner.cs

@@ -114,6 +114,13 @@ namespace ICSharpCode.Decompiler.Tests
 			TestFile(@"..\..\Tests\LiftedOperators.cs");
 		}
 		
+		[Test]
+		public void Lock()
+		{
+			//TestFile(@"..\..\Tests\Lock.cs", compilerVersion: 2);
+			TestFile(@"..\..\Tests\Lock.cs", compilerVersion: 4);
+		}
+		
 		[Test]
 		public void Loops()
 		{
@@ -180,12 +187,12 @@ namespace ICSharpCode.Decompiler.Tests
 			TestFile(@"..\..\Tests\TypeAnalysisTests.cs");
 		}
 		
-		static void TestFile(string fileName, bool useDebug = false)
+		static void TestFile(string fileName, bool useDebug = false, int compilerVersion = 4)
 		{
-			AssertRoundtripCode(fileName, optimize: false, useDebug: useDebug);
-			AssertRoundtripCode(fileName, optimize: true, useDebug: useDebug);
-			AssertRoundtripCode(fileName, optimize: false, useDebug: useDebug);
-			AssertRoundtripCode(fileName, optimize: true, useDebug: useDebug);
+			AssertRoundtripCode(fileName, optimize: false, useDebug: useDebug, compilerVersion: compilerVersion);
+			AssertRoundtripCode(fileName, optimize: true, useDebug: useDebug, compilerVersion: compilerVersion);
+			AssertRoundtripCode(fileName, optimize: false, useDebug: useDebug, compilerVersion: compilerVersion);
+			AssertRoundtripCode(fileName, optimize: true, useDebug: useDebug, compilerVersion: compilerVersion);
 		}
 	}
 }