Merge pull request #900 from icsharpcode/fsharp_using

Implement F# Using: Fixes #670: [Feature Request] Detect F# using patterns when decompiling to C#

ICSharpCode.Decompiler.Tests/FSharpPatterns/FSharpPatternTests.cs

@@ -1,30 +0,0 @@
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace ICSharpCode.Decompiler.Tests.FSharpPatterns
-{
-	[TestFixture]
-	public class FSharpPatternTests
-	{
-		[Test]
-		public void FSharpUsingDecompilesToCSharpUsing_Debug()
-		{
-			var ilCode = TestHelpers.FuzzyReadResource("FSharpUsing.fs.Debug.il");
-			var csharpCode = TestHelpers.FuzzyReadResource("FSharpUsing.fs.Debug.cs");
-			TestHelpers.RunIL(ilCode, csharpCode);
-		}
-
-		[Test]
-		public void FSharpUsingDecompilesToCSharpUsing_Release()
-		{
-			var ilCode = TestHelpers.FuzzyReadResource("FSharpUsing.fs.Release.il");
-			var csharpCode = TestHelpers.FuzzyReadResource("FSharpUsing.fs.Release.cs");
-			TestHelpers.RunIL(ilCode, csharpCode);
-		}
-	}
-}

ICSharpCode.Decompiler.Tests/FSharpPatterns/FSharpUsing.fs.Debug.cs

@@ -1,64 +0,0 @@
-using System;
-using System.IO;
-
-public static class FSharpUsingPatterns
-{
-	public static void sample1()
-	{
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte((byte)1);
-		}
-	}
-
-	public static void sample2()
-	{
-		Console.WriteLine("some text");
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte((byte)2);
-			Console.WriteLine("some text");
-		}
-	}
-
-	public static void sample3()
-	{
-		Console.WriteLine("some text");
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte((byte)3);
-		}
-		Console.WriteLine("some text");
-	}
-
-	public static void sample4()
-	{
-		Console.WriteLine("some text");
-		int num;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			num = fs.ReadByte();
-		}
-		int firstByte = num;
-		Console.WriteLine("read:" + firstByte.ToString());
-	}
-
-	public static void sample5()
-	{
-		Console.WriteLine("some text");
-		int num;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			num = fs.ReadByte();
-		}
-		int firstByte = num;
-		int num3;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			int num2 = fs.ReadByte();
-			num3 = fs.ReadByte();
-		}
-		int secondByte = num3;
-		Console.WriteLine("read: {0}, {1}", firstByte, secondByte);
-	}
-}

ICSharpCode.Decompiler.Tests/FSharpPatterns/FSharpUsing.fs.Release.cs

@@ -1,64 +0,0 @@
-using System;
-using System.IO;
-
-public static class FSharpUsingPatterns
-{
-	public static void sample1()
-	{
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte(1);
-		}
-	}
-
-	public static void sample2()
-	{
-		Console.WriteLine("some text");
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte(2);
-			Console.WriteLine("some text");
-		}
-	}
-
-	public static void sample3()
-	{
-		Console.WriteLine("some text");
-		using (FileStream fs = File.Create("x.txt"))
-		{
-			fs.WriteByte(3);
-		}
-		Console.WriteLine("some text");
-	}
-
-	public static void sample4()
-	{
-		Console.WriteLine("some text");
-		int num;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			num = fs.ReadByte();
-		}
-		int firstByte = num;
-		Console.WriteLine("read:" + firstByte.ToString());
-	}
-
-	public static void sample5()
-	{
-		Console.WriteLine("some text");
-		int secondByte;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			secondByte = fs.ReadByte();
-		}
-		int firstByte = secondByte;
-		int num2;
-		using (FileStream fs = File.OpenRead("x.txt"))
-		{
-			int num = fs.ReadByte();
-			num2 = fs.ReadByte();
-		}
-		secondByte = num2;
-		Console.WriteLine("read: {0}, {1}", firstByte, secondByte);
-	}
-}

ICSharpCode.Decompiler.Tests/FSharpPatterns/TestHelpers.cs

@@ -1,87 +0,0 @@
-using ICSharpCode.Decompiler.Ast;
-using ICSharpCode.Decompiler.Tests.Helpers;
-using ICSharpCode.NRefactory.CSharp;
-using Mono.Cecil;
-using NUnit.Framework;
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.IO;
-using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace ICSharpCode.Decompiler.Tests.FSharpPatterns
-{
-	public class TestHelpers
-	{
-		public static string FuzzyReadResource(string resourceName)
-		{
-			var asm = Assembly.GetExecutingAssembly();
-			var allResources = asm.GetManifestResourceNames();
-			var fullResourceName = allResources.Single(r => r.EndsWith(resourceName, StringComparison.OrdinalIgnoreCase));
-			return new StreamReader(asm.GetManifestResourceStream(fullResourceName)).ReadToEnd();
-		}
-
-		static Lazy<string> ilasm = new Lazy<string>(() => ToolLocator.FindTool("ilasm.exe"));
-		static Lazy<string> ildasm = new Lazy<string>(() => ToolLocator.FindTool("ildasm.exe"));
-
-		public static string CompileIL(string source)
-		{
-			if (ilasm.Value == null)
-				Assert.NotNull(ilasm.Value, "Could not find ILASM.exe");
-			var tmp = Path.GetTempFileName();
-			File.Delete(tmp);
-			var sourceFile = Path.ChangeExtension(tmp, ".il");
-			File.WriteAllText(sourceFile, source);
-			var asmFile = Path.ChangeExtension(sourceFile, ".dll");
-
-			var args = string.Format("{0} /dll /debug /output:{1}", sourceFile, asmFile);
-			using (var proc = Process.Start(new ProcessStartInfo(ilasm.Value, args) { UseShellExecute = false,  }))
-			{
-				proc.WaitForExit();
-				Assert.AreEqual(0, proc.ExitCode);
-			}
-
-			File.Delete(sourceFile);
-			Assert.True(File.Exists(asmFile), "Assembly File does not exist");
-			return asmFile;
-		}
-
-		public static void RunIL(string ilCode, string expectedCSharpCode)
-		{
-			var asmFilePath = CompileIL(ilCode);
-			CompareAssemblyAgainstCSharp(expectedCSharpCode, asmFilePath);
-		}
-
-		private static void CompareAssemblyAgainstCSharp(string expectedCSharpCode, string asmFilePath)
-		{
-			var module = ModuleDefinition.ReadModule(asmFilePath);
-			try
-			{
-				try { module.ReadSymbols(); } catch { }
-				AstBuilder decompiler = new AstBuilder(new DecompilerContext(module));
-				decompiler.AddAssembly(module);
-				new Helpers.RemoveCompilerAttribute().Run(decompiler.SyntaxTree);
-				StringWriter output = new StringWriter();
-
-				// the F# assembly contains a namespace `<StartupCode$tmp6D55>` where the part after tmp is randomly generated.
-				// remove this from the ast to simplify the diff
-				var startupCodeNode = decompiler.SyntaxTree.Children.OfType<NamespaceDeclaration>().SingleOrDefault(d => d.Name.StartsWith("<StartupCode$", StringComparison.Ordinal));
-				if (startupCodeNode != null)
-					startupCodeNode.Remove();
-
-				decompiler.GenerateCode(new PlainTextOutput(output));
-				var fullCSharpCode = output.ToString();
-
-				CodeAssert.AreEqual(expectedCSharpCode, output.ToString());
-			}
-			finally
-			{
-				File.Delete(asmFilePath);
-				File.Delete(Path.ChangeExtension(asmFilePath, ".pdb"));
-			}
-		}
-	}
-}

ICSharpCode.Decompiler.Tests/FSharpPatterns/ToolLocator.cs

@@ -1,99 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace ICSharpCode.Decompiler.Tests.FSharpPatterns
-{
-	public class ToolLocator
-	{
-		public static string FindTool(string fileName)
-		{
-			var allPaths = FindPathForDotNetFramework().Concat(FindPathForWindowsSdk());
-			return allPaths.Select(dir => Path.Combine(dir, fileName)).FirstOrDefault(File.Exists);
-		}
-
-		private static IEnumerable<string> FindPathForWindowsSdk()
-		{
-			string[] windowsSdkPaths = new[]
-			{
-				@"Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\",
-				@"Microsoft SDKs\Windows\v8.0A\bin\",
-				@"Microsoft SDKs\Windows\v8.0\bin\NETFX 4.0 Tools\",
-				@"Microsoft SDKs\Windows\v8.0\bin\",
-				@"Microsoft SDKs\Windows\v7.1A\bin\NETFX 4.0 Tools\",
-				@"Microsoft SDKs\Windows\v7.1A\bin\",
-				@"Microsoft SDKs\Windows\v7.0A\bin\NETFX 4.0 Tools\",
-				@"Microsoft SDKs\Windows\v7.0A\bin\",
-				@"Microsoft SDKs\Windows\v6.1A\bin\",
-				@"Microsoft SDKs\Windows\v6.0A\bin\",
-				@"Microsoft SDKs\Windows\v6.0\bin\",
-				@"Microsoft.NET\FrameworkSDK\bin"
-			};
-
-			foreach (var possiblePath in windowsSdkPaths)
-			{
-				string fullPath = string.Empty;
-
-				// Check alternate program file paths as well as 64-bit versions.
-				if (Environment.Is64BitProcess)
-				{
-					fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), possiblePath, "x64");
-					if (Directory.Exists(fullPath))
-					{
-						yield return fullPath;
-					}
-
-					fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), possiblePath, "x64");
-					if (Directory.Exists(fullPath))
-					{
-						yield return fullPath;
-					}
-				}
-
-				fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), possiblePath);
-				if (Directory.Exists(fullPath))
-				{
-					yield return fullPath;
-				}
-
-				fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), possiblePath);
-				if (Directory.Exists(fullPath))
-				{
-					yield return fullPath;
-				}
-			}
-		}
-		
-		private static IEnumerable<string> FindPathForDotNetFramework()
-		{
-			string[] frameworkPaths = new[]
-			{
-				@"Microsoft.NET\Framework\v4.0.30319",
-				@"Microsoft.NET\Framework\v2.0.50727"
-			};
-
-			foreach (var possiblePath in frameworkPaths)
-			{
-				string fullPath = string.Empty;
-
-				if (Environment.Is64BitProcess)
-				{
-					fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Windows), possiblePath.Replace(@"\Framework\", @"\Framework64\"));
-					if (Directory.Exists(fullPath))
-					{
-						yield return fullPath;
-					}
-				}
-
-				fullPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Windows), possiblePath);
-				if (Directory.Exists(fullPath))
-				{
-					yield return fullPath;
-				}
-			}
-		}
-	}
-}

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

@@ -45,6 +45,9 @@
 
   <ItemGroup>
     <None Include="TestCases\Correctness\Jmp.il" />
+    <None Include="TestCases\ILPretty\FSharpUsing.fs" />
+    <None Include="TestCases\ILPretty\FSharpUsing_Debug.il" />
+    <None Include="TestCases\ILPretty\FSharpUsing_Release.il" />
     <None Include="TestCases\Correctness\BitNot.il" />
     <None Include="TestCases\Correctness\Readme.txt" />
   </ItemGroup>
@@ -53,6 +56,8 @@
     <Compile Include="DataFlowTest.cs" />
     <Compile Include="TestCases\Correctness\LINQRaytracer.cs" />
     <Compile Include="TestCases\Pretty\DelegateConstruction.cs" />
+    <None Include="TestCases\ILPretty\FSharpUsing_Debug.cs" />
+    <None Include="TestCases\ILPretty\FSharpUsing_Release.cs" />
     <Compile Include="Helpers\CodeAssert.cs" />
     <Compile Include="Helpers\SdkUtility.cs" />
     <Compile Include="Helpers\RemoveCompilerAttribute.cs" />

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -42,6 +42,18 @@ namespace ICSharpCode.Decompiler.Tests
 			Run();
 		}
 		
+		[Test]
+		public void FSharpUsing_Debug()
+		{
+			Run();
+		}
+
+		[Test]
+		public void FSharpUsing_Release()
+		{
+			Run();
+		}
+
 		void Run([CallerMemberName] string testName = null)
 		{
 			var ilFile = Path.Combine(TestCasePath, testName + ".il");

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/FSharpUsing_Debug.cs

@@ -0,0 +1,58 @@
+using System;
+using System.IO;
+
+public static class FSharpUsingPatterns
+{
+	public static void sample1()
+	{
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte((byte)1);
+		}
+	}
+
+	public static void sample2()
+	{
+		Console.WriteLine("some text");
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte((byte)2);
+			Console.WriteLine("some text");
+		}
+	}
+
+	public static void sample3()
+	{
+		Console.WriteLine("some text");
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte((byte)3);
+		}
+		Console.WriteLine("some text");
+	}
+
+	public static void sample4()
+	{
+		Console.WriteLine("some text");
+		int num = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			num = fileStream.ReadByte();
+		}
+		int num2 = num;
+		Console.WriteLine("read:" + num2.ToString());
+	}
+
+	public static void sample5()
+	{
+		Console.WriteLine("some text");
+		int num = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			num = fileStream.ReadByte();
+		}
+		int num2 = num;
+		int num3 = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			fileStream.ReadByte();
+			num3 = fileStream.ReadByte();
+		}
+		int num4 = num3;
+		Console.WriteLine("read: {0}, {1}", num2, num4);
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/FSharpUsing_Release.cs

@@ -0,0 +1,58 @@
+using System;
+using System.IO;
+
+public static class FSharpUsingPatterns
+{
+	public static void sample1()
+	{
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte(1);
+		}
+	}
+
+	public static void sample2()
+	{
+		Console.WriteLine("some text");
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte(2);
+			Console.WriteLine("some text");
+		}
+	}
+
+	public static void sample3()
+	{
+		Console.WriteLine("some text");
+		using (FileStream fileStream = File.Create("x.txt")) {
+			fileStream.WriteByte(3);
+		}
+		Console.WriteLine("some text");
+	}
+
+	public static void sample4()
+	{
+		Console.WriteLine("some text");
+		int num = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			num = fileStream.ReadByte();
+		}
+		int num2 = num;
+		Console.WriteLine("read:" + num2.ToString());
+	}
+
+	public static void sample5()
+	{
+		Console.WriteLine("some text");
+		int num = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			num = fileStream.ReadByte();
+		}
+		int num2 = num;
+		int num3 = default(int);
+		using (FileStream fileStream = File.OpenRead("x.txt")) {
+			fileStream.ReadByte();
+			num3 = fileStream.ReadByte();
+		}
+		num = num3;
+		Console.WriteLine("read: {0}, {1}", num2, num);
+	}
+}

ICSharpCode.Decompiler/IL/ControlFlow/ConditionDetection.cs

@@ -172,10 +172,19 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				if (DetectExitPoints.CompatibleExitInstruction(trueExitInst, falseExitInst)) {
 					// if (...) { ...; goto exitPoint; } goto nextBlock; nextBlock: ...; goto exitPoint;
 					// -> if (...) { ... } else { ... } goto exitPoint;
-					context.Step("Inline block as else-branch", ifInst);
+					
-					targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
+					// the else block is not empty or nop-only:
-					targetBlock.Remove();
+					if (targetBlock.Children.Any(inst => !(inst is Nop) && inst != falseExitInst)) {
-					ifInst.FalseInst = targetBlock;
+						context.Step("Inline block as else-branch", ifInst);
+						targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
+						targetBlock.Remove();
+						ifInst.FalseInst = targetBlock;
+					} else {
+						// the else block is empty or nop-only and can be safely removed:
+						context.Step("Remove empty else-branch", ifInst);
+						targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
+						targetBlock.Remove();
+					}
 					exitInst = block.Instructions[block.Instructions.Count - 1] = falseExitInst;
 					Block trueBlock = ifInst.TrueInst as Block;
 					if (trueBlock != null) {

ICSharpCode.Decompiler/IL/Transforms/CopyPropagation.cs

@@ -49,7 +49,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				if (block.Instructions[i].MatchStLoc(out v, out copiedExpr)) {
 					if (v.IsSingleDefinition && v.LoadCount == 0 && v.Kind == VariableKind.StackSlot) {
 						// dead store to stack
-						if (copiedExpr.Flags == InstructionFlags.None) {
+						if (SemanticHelper.IsPure(copiedExpr.Flags)) {
 							// no-op -> delete
 							context.Step("remove dead store to stack: no-op -> delete", block.Instructions[i]);
 							block.Instructions.RemoveAt(i--);

ICSharpCode.Decompiler/IL/Transforms/RemoveDeadVariableInit.cs

@@ -16,6 +16,8 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+using System.Collections.Generic;
+using System.Linq;
 using ICSharpCode.Decompiler.FlowAnalysis;
 
 namespace ICSharpCode.Decompiler.IL.Transforms
@@ -37,13 +39,27 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					v.HasInitialValue = false;
 				}
 			}
-			if (function.IsIterator || function.IsAsync) {
+			// Remove dead stores to variables that are never read from.
-				// In yield return + async, the C# compiler tends to store null/default(T) to variables
+			// If the stored value has some side-effect, the value is unwrapped.
-				// when the variable goes out of scope. Remove such useless stores.
+			// This is necessary to remove useless stores generated by some compilers, e.g., the F# compiler.
-				foreach (var v in function.Variables) {
+			// In yield return + async, the C# compiler tends to store null/default(T) to variables
-					if (v.Kind == VariableKind.Local && v.StoreCount == 1 && v.LoadCount == 0 && v.AddressCount == 0) {
+			// when the variable goes out of scope.
-						if (v.StoreInstructions[0] is StLoc stloc && (stloc.Value.MatchLdNull() || stloc.Value is DefaultValue) && stloc.Parent is Block block) {
+			var variableQueue = new Queue<ILVariable>(function.Variables);
+			while (variableQueue.Count > 0) {
+				var v = variableQueue.Dequeue();
+				if (v.Kind != VariableKind.Local && v.Kind != VariableKind.StackSlot)
+					continue;
+				if (v.LoadCount != 0 || v.AddressCount != 0)
+					continue;
+				foreach (var stloc in v.StoreInstructions.OfType<StLoc>().ToArray()) {
+					if (stloc.Parent is Block block) {
+						if (SemanticHelper.IsPure(stloc.Value.Flags)) {
 							block.Instructions.Remove(stloc);
+						} else {
+							stloc.ReplaceWith(stloc.Value);
+						}
+						if (stloc.Value is LdLoc ldloc) {
+							variableQueue.Enqueue(ldloc.Variable);
 						}
 					}
 				}