Merge pull request #1730 from icsharpcode/async-streams

C# 8.0 Async streams

BuildTools/update-assemblyinfo.ps1

@@ -53,7 +53,7 @@ function gitCommitHash() {
 }
 
 function gitBranch() {
-    if (-not ((Test-Dir ".git") -and (Find-Git))) {
+    if (-not ((Test-Dir ".git" -or Test-File ".git") -and (Find-Git))) {
         return "no-branch";
     }
 

ICSharpCode.Decompiler.Tests/Helpers/RemoveCompilerAttribute.cs

@@ -13,7 +13,7 @@ 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 == "PermissionSet" || type.Identifier == "AssemblyVersion" || type.Identifier == "Debuggable"))
+				(type.Identifier == "CompilationRelaxations" || type.Identifier == "RuntimeCompatibility" || type.Identifier == "SecurityPermission" || type.Identifier == "PermissionSet" || type.Identifier == "AssemblyVersion" || type.Identifier == "Debuggable" || type.Identifier == "TargetFramework"))
 			{
 				attribute.Remove();
 				if (section.Attributes.Count == 0)

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -55,6 +55,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 		UseRoslyn = 0x10,
 		UseMcs = 0x20,
 		ReferenceVisualBasic = 0x40,
+		ReferenceCore = 0x80,
 	}
 
 	[Flags]
@@ -89,12 +90,12 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				outputFile += ".exe";
 				otherOptions += "/exe ";
 			}
-			
-			
+
+
 			if (options.HasFlag(AssemblerOptions.UseDebug)) {
 				otherOptions += "/debug ";
 			}
-			
+
 			ProcessStartInfo info = new ProcessStartInfo(ilasmPath);
 			info.Arguments = $"/nologo {otherOptions}/output=\"{outputFile}\" \"{sourceFileName}\"";
 			info.RedirectStandardError = true;
@@ -115,7 +116,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 
 			return outputFile;
 		}
-		
+
 		public static string Disassemble(string sourceFileName, string outputFile, AssemblerOptions asmOptions)
 		{
 			if (asmOptions.HasFlag(AssemblerOptions.UseOwnDisassembler)) {
@@ -141,7 +142,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			}
 
 			string ildasmPath = SdkUtility.GetSdkPath("ildasm.exe");
-			
+
 			ProcessStartInfo info = new ProcessStartInfo(ildasmPath);
 			info.Arguments = $"/nobar /utf8 /out=\"{outputFile}\" \"{sourceFileName}\"";
 			info.RedirectStandardError = true;
@@ -182,8 +183,10 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			return Regex.Replace(il, @"'<PrivateImplementationDetails>\{[0-9A-F-]+\}'", "'<PrivateImplementationDetails>'");
 		}
 
+		static readonly string coreRefAsmPath = new DotNetCorePathFinder(new Version(3, 0)).GetReferenceAssemblyPath(".NETCoreApp, Version = v3.0");
+		
 		static readonly string refAsmPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86),
-				@"Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2");
+			@"Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2");
 		static readonly string thisAsmPath = Path.GetDirectoryName(typeof(Tester).Assembly.Location);
 
 		static readonly Lazy<IEnumerable<MetadataReference>> defaultReferences = new Lazy<IEnumerable<MetadataReference>>(delegate {
@@ -202,6 +205,21 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			};
 		});
 
+		static readonly Lazy<IEnumerable<MetadataReference>> coreDefaultReferences = new Lazy<IEnumerable<MetadataReference>>(GetDefaultReferences);
+
+		const string targetFrameworkAttributeSnippet = @"
+
+[assembly: System.Runtime.Versioning.TargetFramework("".NETCoreApp, Version = v3.0"", FrameworkDisplayName = """")]
+
+";
+
+		static IEnumerable<MetadataReference> GetDefaultReferences()
+		{
+			foreach (var reference in Directory.EnumerateFiles(coreRefAsmPath, "*.dll")) {
+				yield return MetadataReference.CreateFromFile(reference);
+			}
+		}
+
 		static readonly Lazy<IEnumerable<MetadataReference>> visualBasic = new Lazy<IEnumerable<MetadataReference>>(delegate {
 			return new[] {
 				MetadataReference.CreateFromFile(Path.Combine(refAsmPath, "Microsoft.VisualBasic.dll"))
@@ -217,6 +235,9 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			if (flags.HasFlag(CompilerOptions.Optimize)) {
 				preprocessorSymbols.Add("OPT");
 			}
+			if (flags.HasFlag(CompilerOptions.ReferenceCore)) {
+				preprocessorSymbols.Add("NETCORE");
+			}
 			if (flags.HasFlag(CompilerOptions.UseRoslyn)) {
 				preprocessorSymbols.Add("ROSLYN");
 				preprocessorSymbols.Add("CS60");
@@ -252,7 +273,15 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 					languageVersion: Microsoft.CodeAnalysis.CSharp.LanguageVersion.CSharp8
 				);
 				var syntaxTrees = sourceFileNames.Select(f => SyntaxFactory.ParseSyntaxTree(File.ReadAllText(f), parseOptions, path: f));
-				var references = defaultReferences.Value;
+				if (flags.HasFlag(CompilerOptions.ReferenceCore)) {
+					syntaxTrees = syntaxTrees.Concat(new[] { SyntaxFactory.ParseSyntaxTree(targetFrameworkAttributeSnippet) });
+				}
+				IEnumerable<MetadataReference> references;
+				if (flags.HasFlag(CompilerOptions.ReferenceCore)) {
+					references = coreDefaultReferences.Value;
+				} else {
+					references = defaultReferences.Value;
+				}
 				if (flags.HasFlag(CompilerOptions.ReferenceVisualBasic)) {
 					references = references.Concat(visualBasic.Value);
 				}
@@ -466,16 +495,16 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				return fileName;
 			}
 		}
-		
+
 		public static void RunAndCompareOutput(string testFileName, string outputFile, string decompiledOutputFile, string decompiledCodeFile = null)
 		{
 			string output1, output2, error1, error2;
 			int result1 = Tester.Run(outputFile, out output1, out error1);
 			int result2 = Tester.Run(decompiledOutputFile, out output2, out error2);
-			
+
 			Assert.AreEqual(0, result1, "Exit code != 0; did the test case crash?" + Environment.NewLine + error1);
 			Assert.AreEqual(0, result2, "Exit code != 0; did the decompiled code crash?" + Environment.NewLine + error2);
-			
+
 			if (output1 != output2 || error1 != error2) {
 				StringBuilder b = new StringBuilder();
 				b.AppendLine($"Test {testFileName} failed: output does not match.");

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

@@ -81,6 +81,8 @@
     <Compile Include="DisassemblerPrettyTestRunner.cs" />
     <Compile Include="TestCases\Correctness\StringConcat.cs" />
     <Compile Include="TestCases\ILPretty\ConstantBlobs.cs" />
+    <None Include="TestCases\Pretty\AsyncStreams.cs" />
+    <None Include="TestCases\Pretty\AsyncUsing.cs" />
     <Compile Include="TestCases\Pretty\OutVariables.cs" />
     <Compile Include="TestCases\Pretty\CustomTaskType.cs" />
     <None Include="TestCases\Ugly\NoForEachStatement.Expected.cs" />

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -59,6 +59,12 @@ namespace ICSharpCode.Decompiler.Tests
 			CompilerOptions.Optimize | CompilerOptions.UseRoslyn
 		};
 
+		static readonly CompilerOptions[] dotnetCoreOnlyOptions =
+		{
+			CompilerOptions.UseRoslyn | CompilerOptions.ReferenceCore,
+			CompilerOptions.Optimize | CompilerOptions.UseRoslyn | CompilerOptions.ReferenceCore
+		};
+
 		static readonly CompilerOptions[] defaultOptions =
 		{
 			CompilerOptions.None,
@@ -301,6 +307,18 @@ namespace ICSharpCode.Decompiler.Tests
 			Run(cscOptions: cscOptions);
 		}
 
+		[Test]
+		public void AsyncStreams([ValueSource(nameof(dotnetCoreOnlyOptions))] CompilerOptions cscOptions)
+		{
+			RunForLibrary(cscOptions: cscOptions);
+		}
+
+		[Test]
+		public void AsyncUsing([ValueSource(nameof(dotnetCoreOnlyOptions))] CompilerOptions cscOptions)
+		{
+			RunForLibrary(cscOptions: cscOptions);
+		}
+
 		[Test]
 		public void CustomTaskType([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
 		{
@@ -436,7 +454,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void InterfaceTests([ValueSource(nameof(defaultOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions);
+			RunForLibrary(cscOptions: cscOptions | CompilerOptions.ReferenceCore);
 		}
 
 		[Test]

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

@@ -17,6 +17,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Linq;
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 {
@@ -27,6 +28,8 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			InterestingConstants();
 			TruncatedComp();
 			StringConcat();
+			LinqNullableMin();
+			LinqNullableMin(1, 2, 3);
 		}
 
 		static void Print<T>(T val)
@@ -101,5 +104,11 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			Print(string.Concat(1, 2));
 			Print(string.Concat(1, 2, "str"));
 		}
+
+		static void LinqNullableMin(params int[] arr)
+		{
+			Print(string.Format("LinqNullableMin {0}:", arr.Length));
+			Print(arr.Min(v => (int?)v));
+		}
 	}
 }

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

@@ -14,14 +14,12 @@ using System.Diagnostics;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Runtime.Versioning;
 
 [assembly: FSharpInterfaceDataVersion(2, 0, 0)]
 [assembly: AssemblyTitle("ConsoleApplication1")]
 [assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("ConsoleApplication1")]
 [assembly: AssemblyFileVersion("1.0.0.0")]
-[assembly: TargetFramework(".NETFramework,Version=v4.6.1", FrameworkDisplayName = ".NET Framework 4.6.1")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCopyright("Copyright ©  2017")]

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

@@ -15,14 +15,12 @@ using System.Diagnostics;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Runtime.Versioning;
 
 [assembly: FSharpInterfaceDataVersion(2, 0, 0)]
 [assembly: AssemblyTitle("ConsoleApplication1")]
 [assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("ConsoleApplication1")]
 [assembly: AssemblyFileVersion("1.0.0.0")]
-[assembly: TargetFramework(".NETFramework,Version=v4.6.1", FrameworkDisplayName = ".NET Framework 4.6.1")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCopyright("Copyright ©  2017")]

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue1325.cs

@@ -6,10 +6,8 @@ using System.Diagnostics;
 using System.IO;
 using System.Reflection;
 using System.Runtime.CompilerServices;
-using System.Runtime.Versioning;
 [assembly: Embedded]
 [assembly: AssemblyInformationalVersion("1.0.0")]
-[assembly: TargetFramework(".NETCoreApp,Version=v2.1", FrameworkDisplayName = "")]
 [assembly: AssemblyConfiguration("Debug")]
 [assembly: AssemblyFileVersion("1.0.0.0")]
 

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

@@ -0,0 +1,37 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
+{
+	public class AsyncStreams
+	{
+		public static async IAsyncEnumerable<int> CountTo(int until)
+		{
+			for (int i = 0; i < until; i++) {
+				yield return i;
+				await Task.Delay(10);
+			}
+		}
+
+		public static async IAsyncEnumerable<int> AlwaysThrow()
+		{
+			throw null;
+			yield break;
+		}
+
+		public static async IAsyncEnumerator<int> InfiniteLoop()
+		{
+			while (true) {
+			}
+			yield break;
+		}
+
+		public static async IAsyncEnumerable<int> InfiniteLoopWithAwait()
+		{
+			while (true) {
+				await Task.Delay(10);
+			}
+			yield break;
+		}
+	}
+}

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

@@ -0,0 +1,60 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
+{
+	internal class AsyncUsing
+	{
+		internal class AsyncDisposableClass : IAsyncDisposable
+		{
+			public ValueTask DisposeAsync()
+			{
+				throw new NotImplementedException();
+			}
+		}
+
+		[StructLayout(LayoutKind.Sequential, Size = 1)]
+		internal struct AsyncDisposableStruct : IAsyncDisposable
+		{
+			public ValueTask DisposeAsync()
+			{
+				throw new NotImplementedException();
+			}
+		}
+
+		public static async void TestAsyncUsing(IAsyncDisposable disposable)
+		{
+			await using (disposable) {
+				Console.WriteLine("Hello");
+			}
+		}
+
+		public static async void TestAsyncUsingClass()
+		{
+			await using (AsyncDisposableClass test = new AsyncDisposableClass()) {
+				Use(test);
+			}
+		}
+
+		public static async void TestAsyncUsingStruct()
+		{
+			await using (AsyncDisposableStruct asyncDisposableStruct = default(AsyncDisposableStruct)) {
+				Use(asyncDisposableStruct);
+			}
+		}
+
+		public static async void TestAsyncUsingNullableStruct()
+		{
+			await using (AsyncDisposableStruct? asyncDisposableStruct = new AsyncDisposableStruct?(default(AsyncDisposableStruct))) {
+				Use(asyncDisposableStruct);
+			}
+		}
+
+		private static void Use(IAsyncDisposable test)
+		{
+			throw new NotImplementedException();
+		}
+
+	}
+}

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

@@ -16,9 +16,6 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-// We can't test this because "error CS8701: Target runtime doesn't support default interface implementation."
-#undef CS80
-
 using System;
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -305,6 +305,8 @@ namespace ICSharpCode.Decompiler.CSharp
 							return true;
 						if (settings.AsyncAwait && AsyncAwaitDecompiler.IsCompilerGeneratedStateMachine(typeHandle, metadata))
 							return true;
+						if (settings.AsyncEnumerator && AsyncAwaitDecompiler.IsCompilerGeneratorAsyncEnumerator(typeHandle, metadata))
+							return true;
 						if (settings.FixedBuffers && name.StartsWith("<", StringComparison.Ordinal) && name.Contains("__FixedBuffer"))
 							return true;
 					} else if (type.IsCompilerGenerated(metadata)) {
@@ -1343,7 +1345,11 @@ namespace ICSharpCode.Decompiler.CSharp
 					if (localSettings.DecompileMemberBodies && !body.Descendants.Any(d => d is YieldReturnStatement || d is YieldBreakStatement)) {
 						body.Add(new YieldBreakStatement());
 					}
-					RemoveAttribute(entityDecl, KnownAttribute.IteratorStateMachine);
+					if (function.IsAsync) {
+						RemoveAttribute(entityDecl, KnownAttribute.AsyncIteratorStateMachine);
+					} else {
+						RemoveAttribute(entityDecl, KnownAttribute.IteratorStateMachine);
+					}
 					if (function.StateMachineCompiledWithMono) {
 						RemoveAttribute(entityDecl, KnownAttribute.DebuggerHidden);
 					}

ICSharpCode.Decompiler/CSharp/CallBuilder.cs

@@ -989,6 +989,10 @@ namespace ICSharpCode.Decompiler.CSharp
 			foundMember = null;
 			bestCandidateIsExpandedForm = false;
 			var lookup = new MemberLookup(resolver.CurrentTypeDefinition, resolver.CurrentTypeDefinition.ParentModule);
+
+			Log.WriteLine("IsUnambiguousCall: Performing overload resolution for " + method);
+			Log.WriteCollection("  Arguments: ", arguments.Select(a => a.ResolveResult));
+
 			var or = new OverloadResolution(resolver.Compilation,
 				firstOptionalArgumentIndex < 0 ? arguments.SelectArray(a => a.ResolveResult) : arguments.Take(firstOptionalArgumentIndex).Select(a => a.ResolveResult).ToArray(),
 				argumentNames: firstOptionalArgumentIndex < 0 || argumentNames == null ? argumentNames : argumentNames.Take(firstOptionalArgumentIndex).ToArray(),
@@ -1043,6 +1047,9 @@ namespace ICSharpCode.Decompiler.CSharp
 		bool IsUnambiguousAccess(ExpectedTargetDetails expectedTargetDetails, ResolveResult target, IMethod method,
 			IList<TranslatedExpression> arguments, string[] argumentNames, out IMember foundMember)
 		{
+			Log.WriteLine("IsUnambiguousAccess: Performing overload resolution for " + method);
+			Log.WriteCollection("  Arguments: ", arguments.Select(a => a.ResolveResult));
+
 			foundMember = null;
 			if (target == null) {
 				var result = resolver.ResolveSimpleName(method.AccessorOwner.Name,
@@ -1404,6 +1411,8 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		bool IsUnambiguousMethodReference(ExpectedTargetDetails expectedTargetDetails, IMethod method, ResolveResult target, IReadOnlyList<IType> typeArguments, out ResolveResult result)
 		{
+			Log.WriteLine("IsUnambiguousMethodReference: Performing overload resolution for " + method);
+
 			var lookup = new MemberLookup(resolver.CurrentTypeDefinition, resolver.CurrentTypeDefinition.ParentModule);
 			var or = new OverloadResolution(resolver.Compilation,
 				arguments: method.Parameters.SelectReadOnlyArray(p => new TypeResolveResult(p.Type)), // there are no arguments, use parameter types

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1112,6 +1112,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			var opSymbol = UnaryOperatorExpression.GetOperatorRole(opType);
 			if (opType == UnaryOperatorType.Await) {
 				WriteKeyword(opSymbol);
+				Space();
 			} else if (!IsPostfixOperator(opType) && opSymbol != null) {
 				WriteToken(opSymbol);
 			}
@@ -1863,6 +1864,9 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 		public virtual void VisitUsingStatement(UsingStatement usingStatement)
 		{
 			StartNode(usingStatement);
+			if (usingStatement.IsAsync) {
+				WriteKeyword(UsingStatement.AwaitRole);
+			}
 			WriteKeyword(UsingStatement.UsingKeywordRole);
 			Space(policy.SpaceBeforeUsingParentheses);
 			LPar();

ICSharpCode.Decompiler/CSharp/Resolver/LambdaResolveResult.cs

@@ -152,7 +152,7 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 				if (this.Parameters.Count != parameterTypes.Length)
 					return Conversion.None;
 				for (int i = 0; i < parameterTypes.Length; ++i) {
-					if (!parameterTypes[i].Equals(this.Parameters[i].Type)) {
+					if (!conversions.IdentityConversion(parameterTypes[i], this.Parameters[i].Type)) {
 						if (IsImplicitlyTyped) {
 							// it's possible that different parameter types also lead to a valid conversion
 							return LambdaConversion.Instance;
@@ -162,7 +162,8 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 					}
 				}
 			}
-			if (returnType.Equals(this.ReturnType)) {
+			if (conversions.IdentityConversion(this.ReturnType, returnType)
+				|| conversions.ImplicitConversion(this.InferredReturnType, returnType).IsValid) {
 				return LambdaConversion.Instance;
 			} else {
 				return Conversion.None;

ICSharpCode.Decompiler/CSharp/Resolver/TypeInference.cs

@@ -393,11 +393,10 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		
 		static IMethod GetDelegateOrExpressionTreeSignature(IType t)
 		{
-			ParameterizedType pt = t as ParameterizedType;
-			if (pt != null && pt.TypeParameterCount == 1 && pt.Name == "Expression"
-			    && pt.Namespace == "System.Linq.Expressions")
+			if (t.TypeParameterCount == 1 && t.Name == "Expression"
+			    && t.Namespace == "System.Linq.Expressions")
 			{
-				t = pt.GetTypeArgument(0);
+				t = t.TypeArguments[0];
 			}
 			return t.GetDelegateInvokeMethod();
 		}
@@ -569,8 +568,9 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		{
 			Log.WriteLine("MakeExactInference from " + U + " to " + V);
 
-			if (V is NullabilityAnnotatedTypeParameter nullableTP) {
-				V = nullableTP.OriginalTypeParameter;
+			if (U.Nullability == V.Nullability) {
+				U = U.WithoutNullability();
+				V = V.WithoutNullability();
 			}
 
 			// If V is one of the unfixed Xi then U is added to the set of bounds for Xi.
@@ -611,8 +611,10 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		
 		TP GetTPForType(IType v)
 		{
-			ITypeParameter p = v as ITypeParameter;
-			if (p != null) {
+			if (v is NullabilityAnnotatedTypeParameter natp) {
+				v = natp.OriginalTypeParameter;
+			}
+			if (v is ITypeParameter p) {
 				int index = p.Index;
 				if (index < typeParameters.Length && typeParameters[index].TypeParameter == p)
 					return typeParameters[index];
@@ -629,7 +631,11 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		void MakeLowerBoundInference(IType U, IType V)
 		{
 			Log.WriteLine(" MakeLowerBoundInference from " + U + " to " + V);
-			
+			if (U.Nullability == V.Nullability) {
+				U = U.WithoutNullability();
+				V = V.WithoutNullability();
+			}
+
 			// If V is one of the unfixed Xi then U is added to the set of bounds for Xi.
 			TP tp = GetTPForType(V);
 			if (tp != null && tp.IsFixed == false) {
@@ -726,7 +732,11 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 		void MakeUpperBoundInference(IType U, IType V)
 		{
 			Log.WriteLine(" MakeUpperBoundInference from " + U + " to " + V);
-			
+			if (U.Nullability == V.Nullability) {
+				U = U.WithoutNullability();
+				V = V.WithoutNullability();
+			}
+
 			// If V is one of the unfixed Xi then U is added to the set of bounds for Xi.
 			TP tp = GetTPForType(V);
 			if (tp != null && tp.IsFixed == false) {

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -412,14 +412,29 @@ namespace ICSharpCode.Decompiler.CSharp
 				return transformed;
 			AstNode usingInit = resource;
 			var var = inst.Variable;
-			if (!inst.ResourceExpression.MatchLdNull() && !NullableType.GetUnderlyingType(var.Type).GetAllBaseTypes().Any(b => b.IsKnownType(KnownTypeCode.IDisposable))) {
+			KnownTypeCode knownTypeCode;
+			IType disposeType;
+			string disposeTypeMethodName;
+			if (inst.IsAsync) {
+				knownTypeCode = KnownTypeCode.IAsyncDisposable;
+				disposeType = exprBuilder.compilation.FindType(KnownTypeCode.IAsyncDisposable);
+				disposeTypeMethodName = "DisposeAsync";
+			} else {
+				knownTypeCode = KnownTypeCode.IDisposable;
+				disposeType = exprBuilder.compilation.FindType(KnownTypeCode.IDisposable);
+				disposeTypeMethodName = "Dispose";
+			}
+			if (!inst.ResourceExpression.MatchLdNull() && !NullableType.GetUnderlyingType(var.Type).GetAllBaseTypes().Any(b => b.IsKnownType(knownTypeCode))) {
 				Debug.Assert(var.Kind == VariableKind.UsingLocal);
 				var.Kind = VariableKind.Local;
-				var disposeType = exprBuilder.compilation.FindType(KnownTypeCode.IDisposable);
 				var disposeVariable = currentFunction.RegisterVariable(
 					VariableKind.Local, disposeType,
 					AssignVariableNames.GenerateVariableName(currentFunction, disposeType)
 				);
+				Expression disposeInvocation = new InvocationExpression(new MemberReferenceExpression(exprBuilder.ConvertVariable(disposeVariable).Expression, disposeTypeMethodName));
+				if (inst.IsAsync) {
+					disposeInvocation = new UnaryOperatorExpression { Expression = disposeInvocation, Operator = UnaryOperatorType.Await };
+				}
 				return new BlockStatement {
 					new ExpressionStatement(new AssignmentExpression(exprBuilder.ConvertVariable(var).Expression, resource.Detach())),
 					new TryCatchStatement {
@@ -428,7 +443,7 @@ namespace ICSharpCode.Decompiler.CSharp
 							new ExpressionStatement(new AssignmentExpression(exprBuilder.ConvertVariable(disposeVariable).Expression, new AsExpression(exprBuilder.ConvertVariable(var).Expression, exprBuilder.ConvertType(disposeType)))),
 							new IfElseStatement {
 								Condition = new BinaryOperatorExpression(exprBuilder.ConvertVariable(disposeVariable), BinaryOperatorType.InEquality, new NullReferenceExpression()),
-								TrueStatement = new ExpressionStatement(new InvocationExpression(new MemberReferenceExpression(exprBuilder.ConvertVariable(disposeVariable).Expression, "Dispose")))
+								TrueStatement = new ExpressionStatement(disposeInvocation)
 							}
 						}
 					},
@@ -442,6 +457,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				}
 				return new UsingStatement {
 					ResourceAcquisition = usingInit,
+					IsAsync = inst.IsAsync,
 					EmbeddedStatement = ConvertAsBlock(inst.Body)
 				};
 			}

ICSharpCode.Decompiler/CSharp/Syntax/Statements/UsingStatement.cs

@@ -28,57 +28,67 @@
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
 	/// <summary>
-	/// using (ResourceAcquisition) EmbeddedStatement
+	/// [ await ] using (ResourceAcquisition) EmbeddedStatement
 	/// </summary>
 	public class UsingStatement : Statement
 	{
-		public static readonly TokenRole UsingKeywordRole = new TokenRole ("using");
+		public static readonly TokenRole UsingKeywordRole = new TokenRole("using");
+		public static readonly TokenRole AwaitRole = UnaryOperatorExpression.AwaitRole;
 		public static readonly Role<AstNode> ResourceAcquisitionRole = new Role<AstNode>("ResourceAcquisition", AstNode.Null);
-		
+
 		public CSharpTokenNode UsingToken {
-			get { return GetChildByRole (UsingKeywordRole); }
+			get { return GetChildByRole(UsingKeywordRole); }
+		}
+
+		public CSharpTokenNode AwaitToken {
+			get { return GetChildByRole(AwaitRole); }
 		}
-		
+
+		public bool IsAsync {
+			get { return !GetChildByRole(AwaitRole).IsNull; }
+			set { SetChildByRole(AwaitRole, value ? new CSharpTokenNode(TextLocation.Empty, null) : null); }
+		}
+
 		public CSharpTokenNode LParToken {
-			get { return GetChildByRole (Roles.LPar); }
+			get { return GetChildByRole(Roles.LPar); }
 		}
-		
+
 		/// <summary>
 		/// Either a VariableDeclarationStatement, or an Expression.
 		/// </summary>
 		public AstNode ResourceAcquisition {
-			get { return GetChildByRole (ResourceAcquisitionRole); }
-			set { SetChildByRole (ResourceAcquisitionRole, value); }
+			get { return GetChildByRole(ResourceAcquisitionRole); }
+			set { SetChildByRole(ResourceAcquisitionRole, value); }
 		}
-		
+
 		public CSharpTokenNode RParToken {
-			get { return GetChildByRole (Roles.RPar); }
+			get { return GetChildByRole(Roles.RPar); }
 		}
-		
+
 		public Statement EmbeddedStatement {
-			get { return GetChildByRole (Roles.EmbeddedStatement); }
-			set { SetChildByRole (Roles.EmbeddedStatement, value); }
+			get { return GetChildByRole(Roles.EmbeddedStatement); }
+			set { SetChildByRole(Roles.EmbeddedStatement, value); }
 		}
-		
-		public override void AcceptVisitor (IAstVisitor visitor)
+
+		public override void AcceptVisitor(IAstVisitor visitor)
 		{
-			visitor.VisitUsingStatement (this);
+			visitor.VisitUsingStatement(this);
 		}
-			
-		public override T AcceptVisitor<T> (IAstVisitor<T> visitor)
+
+		public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
 		{
-			return visitor.VisitUsingStatement (this);
+			return visitor.VisitUsingStatement(this);
 		}
-		
-		public override S AcceptVisitor<T, S> (IAstVisitor<T, S> visitor, T data)
+
+		public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
 		{
-			return visitor.VisitUsingStatement (this, data);
+			return visitor.VisitUsingStatement(this, data);
 		}
-		
+
 		protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
 		{
 			UsingStatement o = other as UsingStatement;
-			return o != null && this.ResourceAcquisition.DoMatch(o.ResourceAcquisition, match) && this.EmbeddedStatement.DoMatch(o.EmbeddedStatement, match);
+			return o != null && this.IsAsync == o.IsAsync && this.ResourceAcquisition.DoMatch(o.ResourceAcquisition, match) && this.EmbeddedStatement.DoMatch(o.EmbeddedStatement, match);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -487,7 +487,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				return newTargetType.IsKnownType(KnownTypeCode.FormattableString)
 					|| newTargetType.IsKnownType(KnownTypeCode.IFormattable);
 			}
-			return oldTargetType.Equals(newTargetType);
+			return conversions.IdentityConversion(oldTargetType, newTargetType);
 		}
 		
 		TranslatedExpression LdcI4(ICompilation compilation, int val)

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -108,12 +108,14 @@ namespace ICSharpCode.Decompiler
 			if (languageVersion < CSharp.LanguageVersion.CSharp8_0) {
 				nullableReferenceTypes = false;
 				readOnlyMethods = false;
+				asyncUsingAndForEachStatement = false;
+				asyncEnumerator = false;
 			}
 		}
 
 		public CSharp.LanguageVersion GetMinimumRequiredVersion()
 		{
-			if (nullableReferenceTypes || readOnlyMethods)
+			if (nullableReferenceTypes || readOnlyMethods || asyncEnumerator || asyncUsingAndForEachStatement)
 				return CSharp.LanguageVersion.CSharp8_0;
 			if (introduceUnmanagedConstraint || tupleComparisons || stackAllocInitializers)
 				return CSharp.LanguageVersion.CSharp7_3;
@@ -273,6 +275,24 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool asyncEnumerator = true;
+
+		/// <summary>
+		/// Decompile IAsyncEnumerator/IAsyncEnumerable.
+		/// Only has an effect if <see cref="AsyncAwait"/> is enabled.
+		/// </summary>
+		[Category("C# 8.0 / VS 2019")]
+		[Description("DecompilerSettings.AsyncEnumerator")]
+		public bool AsyncEnumerator {
+			get { return asyncEnumerator; }
+			set {
+				if (asyncEnumerator != value) {
+					asyncEnumerator = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool decimalConstants = true;
 
 		/// <summary>
@@ -846,7 +866,7 @@ namespace ICSharpCode.Decompiler
 		bool readOnlyMethods = true;
 
 		[Category("C# 8.0 / VS 2019")]
-		[Description("DecompilerSettings.IsReadOnlyAttributeShouldBeReplacedWithReadonlyInModifiersOnStructsParameters")]
+		[Description("DecompilerSettings.ReadOnlyMethods")]
 		public bool ReadOnlyMethods {
 			get { return readOnlyMethods; }
 			set {
@@ -857,6 +877,20 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool asyncUsingAndForEachStatement = true;
+
+		[Category("C# 8.0 / VS 2019")]
+		[Description("DecompilerSettings.DetectAsyncUsingAndForeachStatements")]
+		public bool AsyncUsingAndForEachStatement {
+			get { return asyncUsingAndForEachStatement; }
+			set {
+				if (asyncUsingAndForEachStatement != value) {
+					asyncUsingAndForEachStatement = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool introduceUnmanagedConstraint = true;
 
 		/// <summary>

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -62,14 +62,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		{
 			Void,
 			Task,
-			TaskOfT
+			TaskOfT,
+			AsyncEnumerator,
+			AsyncEnumerable
 		}
 
 		ILTransformContext context;
 
-		// These fields are set by MatchTaskCreationPattern()
-		IType taskType; // return type of the async method
-		IType underlyingReturnType; // return type of the method (only the "T" for Task{T})
+		// These fields are set by MatchTaskCreationPattern() or MatchEnumeratorCreationNewObj()
+		IType taskType; // return type of the async method; or IAsyncEnumerable{T}/IAsyncEnumerator{T}
+		IType underlyingReturnType; // return type of the method (only the "T" for Task{T}), for async enumerators this is the type being yielded
 		AsyncMethodType methodType;
 		ITypeDefinition stateMachineType;
 		ITypeDefinition builderType;
@@ -78,15 +80,18 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		int initialState;
 		Dictionary<IField, ILVariable> fieldToParameterMap = new Dictionary<IField, ILVariable>();
 		Dictionary<ILVariable, ILVariable> cachedFieldToParameterMap = new Dictionary<ILVariable, ILVariable>();
+		IField disposeModeField; // 'disposeMode' field (IAsyncEnumerable/IAsyncEnumerator only)
 
 		// These fields are set by AnalyzeMoveNext():
 		ILFunction moveNextFunction;
 		ILVariable cachedStateVar; // variable in MoveNext that caches the stateField.
 		TryCatch mainTryCatch;
 		Block setResultAndExitBlock; // block that is jumped to for return statements
+									 // Note: for async enumerators, a jump to setResultAndExitBlock is a 'yield break;'
 		int finalState;       // final state after the setResultAndExitBlock
 		bool finalStateKnown;
 		ILVariable resultVar; // the variable that gets returned by the setResultAndExitBlock
+		Block setResultYieldBlock; // block that is jumped to for 'yield return' statements
 		ILVariable doFinallyBodies;
 
 		// These fields are set by AnalyzeStateMachine():
@@ -110,11 +115,12 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			awaitBlocks.Clear();
 			awaitDebugInfos.Clear();
 			moveNextLeaves.Clear();
-			if (!MatchTaskCreationPattern(function))
+			if (!MatchTaskCreationPattern(function) && !MatchAsyncEnumeratorCreationPattern(function))
 				return;
 			try {
 				AnalyzeMoveNext();
 				ValidateCatchBlock();
+				AnalyzeDisposeAsync();
 			} catch (SymbolicAnalysisFailedException) {
 				return;
 			}
@@ -133,7 +139,11 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			TranslateCachedFieldsToLocals();
 
 			FinalizeInlineMoveNext(function);
-			((BlockContainer)function.Body).ExpectedResultType = underlyingReturnType.GetStackType();
+			if (methodType == AsyncMethodType.AsyncEnumerable || methodType == AsyncMethodType.AsyncEnumerator) {
+				((BlockContainer)function.Body).ExpectedResultType = StackType.Void;
+			} else {
+				((BlockContainer)function.Body).ExpectedResultType = underlyingReturnType.GetStackType();
+			}
 
 			// Re-run control flow simplification over the newly constructed set of gotos,
 			// and inlining because TranslateFieldsToLocalAccess() might have opened up new inlining opportunities.
@@ -164,9 +174,14 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				CopyPropagation.Propagate(stloc, context);
 			}
 			new RemoveDeadVariableInit().Run(function, context);
-			// Run inlining, but don't remove dead variables (they might get revived by TranslateFieldsToLocalAccess)
 			foreach (var block in function.Descendants.OfType<Block>()) {
+				// Run inlining, but don't remove dead variables (they might get revived by TranslateFieldsToLocalAccess)
 				ILInlining.InlineAllInBlock(function, block, context);
+				if (IsAsyncEnumerator) {
+					// Remove lone 'ldc.i4', those are sometimes left over after C# compiler
+					// optimizes out stores to the state variable.
+					block.Instructions.RemoveAll(inst => inst.OpCode == OpCode.LdcI4);
+				}
 			}
 			context.StepEndGroup();
 		}
@@ -337,6 +352,160 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		}
 		#endregion
 
+		#region MatchAsyncEnumeratorCreationPattern
+		private bool MatchAsyncEnumeratorCreationPattern(ILFunction function)
+		{
+			if (!context.Settings.AsyncEnumerator)
+				return false;
+			taskType = function.ReturnType;
+			if (taskType.IsKnownType(KnownTypeCode.IAsyncEnumeratorOfT)) {
+				methodType = AsyncMethodType.AsyncEnumerator;
+			} else if (taskType.IsKnownType(KnownTypeCode.IAsyncEnumerableOfT)) {
+				methodType = AsyncMethodType.AsyncEnumerable;
+			} else {
+				return false;
+			}
+			underlyingReturnType = taskType.TypeArguments.Single();
+			if (!(function.Body is BlockContainer blockContainer))
+				return false;
+			if (blockContainer.Blocks.Count != 1)
+				return false;
+			var body = blockContainer.EntryPoint;
+			if (body.Instructions.Count == 1) {
+				// No parameters passed to enumerator (not even 'this'):
+				// ret(newobj(...))
+				if (!body.Instructions[0].MatchReturn(out var newObj))
+					return false;
+				if (MatchEnumeratorCreationNewObj(newObj, context, out initialState, out stateMachineType)) {
+					// HACK: the normal async/await logic expects 'initialState' to be the 'in progress' state
+					initialState = -1;
+					try {
+						AnalyzeEnumeratorCtor(((NewObj)newObj).Method, context, out builderField, out builderType, out stateField);
+					} catch (SymbolicAnalysisFailedException) {
+						return false;
+					}
+					return true;
+				} else {
+					return false;
+				}
+			} else {
+
+				// stloc v(newobj<CountUpSlowly> d__0..ctor(ldc.i4 - 2))
+				// stfld <>4__this(ldloc v, ldloc this)
+				// stfld <>3__otherParam(ldloc v, ldloc otherParam)
+				// leave IL_0000(ldloc v)
+				int pos = 0;
+				if (!body.Instructions[pos].MatchStLoc(out var v, out var newObj))
+					return false;
+				if (!MatchEnumeratorCreationNewObj(newObj, context, out initialState, out stateMachineType))
+					return false;
+				pos++;
+
+				while (MatchStFld(body.Instructions[pos], v, out var field, out var value)) {
+					if (!value.MatchLdLoc(out var p))
+						return false;
+					fieldToParameterMap[field] = p;
+					pos++;
+				}
+				if (!body.Instructions[pos].MatchReturn(out var returnValue))
+					return false;
+				if (!returnValue.MatchLdLoc(v))
+					return false;
+				
+				// HACK: the normal async/await logic expects 'initialState' to be the 'in progress' state
+				initialState = -1;
+				try {
+					AnalyzeEnumeratorCtor(((NewObj)newObj).Method, context, out builderField, out builderType, out stateField);
+					if (methodType == AsyncMethodType.AsyncEnumerable) {
+						ResolveIEnumerableIEnumeratorFieldMapping();
+					}
+				} catch (SymbolicAnalysisFailedException) {
+					return false;
+				}
+				return true;
+			}
+		}
+
+		static bool MatchEnumeratorCreationNewObj(ILInstruction inst, ILTransformContext context,
+			out int initialState, out ITypeDefinition stateMachineType)
+		{
+			initialState = default;
+			stateMachineType = default;
+			// newobj(CurrentType/...::.ctor, ldc.i4(-2))
+			if (!(inst is NewObj newObj))
+				return false;
+			if (newObj.Arguments.Count != 1)
+				return false;
+			if (!newObj.Arguments[0].MatchLdcI4(out initialState))
+				return false;
+			stateMachineType = newObj.Method.DeclaringTypeDefinition;
+			if (stateMachineType == null)
+				return false;
+			if (stateMachineType.DeclaringTypeDefinition != context.Function.Method.DeclaringTypeDefinition)
+				return false;
+			return IsCompilerGeneratorAsyncEnumerator(
+				(TypeDefinitionHandle)stateMachineType.MetadataToken,
+				context.TypeSystem.MainModule.metadata);
+		}
+
+		public static bool IsCompilerGeneratorAsyncEnumerator(TypeDefinitionHandle type, MetadataReader metadata)
+		{
+			TypeDefinition td;
+			if (type.IsNil || !type.IsCompilerGeneratedOrIsInCompilerGeneratedClass(metadata) || (td = metadata.GetTypeDefinition(type)).GetDeclaringType().IsNil)
+				return false;
+			foreach (var i in td.GetInterfaceImplementations()) {
+				var tr = metadata.GetInterfaceImplementation(i).Interface.GetFullTypeName(metadata);
+				if (!tr.IsNested && tr.TopLevelTypeName.Namespace == "System.Collections.Generic" && tr.TopLevelTypeName.Name == "IAsyncEnumerator" && tr.TopLevelTypeName.TypeParameterCount == 1)
+					return true;
+			}
+			return false;
+		}
+
+		static void AnalyzeEnumeratorCtor(IMethod ctor, ILTransformContext context, out IField builderField, out ITypeDefinition builderType, out IField stateField)
+		{
+			builderField = null;
+			stateField = null;
+
+			var ctorHandle = (MethodDefinitionHandle)ctor.MetadataToken;
+			Block body = YieldReturnDecompiler.SingleBlock(YieldReturnDecompiler.CreateILAst(ctorHandle, context).Body);
+			if (body == null)
+				throw new SymbolicAnalysisFailedException("Missing enumeratorCtor.Body");
+			// Block IL_0000 (incoming: 1) {
+			//   call Object..ctor(ldloc this)
+			// 	 stfld <>1__state(ldloc this, ldloc <>1__state)
+			// 	 stfld <>t__builder(ldloc this, call Create())
+			// 	 leave IL_0000 (nop)
+			// }
+			foreach (var inst in body.Instructions) {
+				if (inst.MatchStFld(out var target, out var field, out var value)
+				&& target.MatchLdThis()
+				&& value.MatchLdLoc(out var arg)
+				&& arg.Kind == VariableKind.Parameter && arg.Index == 0) {
+					stateField = (IField)field.MemberDefinition;
+				}
+				if (inst.MatchStFld(out target, out field, out value)
+					&& target.MatchLdThis()
+					&& value is Call call && call.Method.Name == "Create") {
+					builderField = (IField)field.MemberDefinition;
+				}
+			}
+			if (stateField == null || builderField == null)
+				throw new SymbolicAnalysisFailedException();
+
+			builderType = builderField.Type.GetDefinition();
+			if (builderType == null)
+				throw new SymbolicAnalysisFailedException();
+		}
+
+		private void ResolveIEnumerableIEnumeratorFieldMapping()
+		{
+			var getAsyncEnumerator = stateMachineType.Methods.FirstOrDefault(m => m.Name.EndsWith(".GetAsyncEnumerator", StringComparison.Ordinal));
+			if (getAsyncEnumerator == null)
+				throw new SymbolicAnalysisFailedException();
+			YieldReturnDecompiler.ResolveIEnumerableIEnumeratorFieldMapping((MethodDefinitionHandle)getAsyncEnumerator.MetadataToken, context, fieldToParameterMap);
+		}
+		#endregion
+
 		#region AnalyzeMoveNext
 		/// <summary>
 		/// First peek into MoveNext(); analyzes everything outside the big try-catch.
@@ -353,8 +522,6 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			moveNextFunction = YieldReturnDecompiler.CreateILAst(moveNextMethod, context);
 			if (!(moveNextFunction.Body is BlockContainer blockContainer))
 				throw new SymbolicAnalysisFailedException();
-			if (blockContainer.Blocks.Count != 2 && blockContainer.Blocks.Count != 1)
-				throw new SymbolicAnalysisFailedException();
 			if (blockContainer.EntryPoint.IncomingEdgeCount != 1)
 				throw new SymbolicAnalysisFailedException();
 			cachedStateVar = null;
@@ -385,12 +552,51 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			if (((BlockContainer)mainTryCatch.TryBlock).EntryPoint.Instructions[0] is StLoc initDoFinallyBodies
 				&& initDoFinallyBodies.Variable.Kind == VariableKind.Local
 				&& initDoFinallyBodies.Variable.Type.IsKnownType(KnownTypeCode.Boolean)
-				&& initDoFinallyBodies.Value.MatchLdcI4(1))
-			{
+				&& initDoFinallyBodies.Value.MatchLdcI4(1)) {
 				doFinallyBodies = initDoFinallyBodies.Variable;
 			}
 
-			setResultAndExitBlock = blockContainer.Blocks.ElementAtOrDefault(1);
+			Debug.Assert(blockContainer.Blocks[0] == blockContainer.EntryPoint); // already checked this block
+			pos = 1;
+			if (MatchYieldBlock(blockContainer, pos)) {
+				setResultYieldBlock = blockContainer.Blocks[pos];
+				pos++;
+			} else {
+				setResultYieldBlock = null;
+			}
+
+			setResultAndExitBlock = blockContainer.Blocks.ElementAtOrDefault(pos);
+			CheckSetResultAndExitBlock(blockContainer);
+
+			if (pos + 1 < blockContainer.Blocks.Count)
+				throw new SymbolicAnalysisFailedException("too many blocks");
+		}
+
+		private bool IsAsyncEnumerator => methodType == AsyncMethodType.AsyncEnumerable || methodType == AsyncMethodType.AsyncEnumerator;
+
+		bool MatchYieldBlock(BlockContainer blockContainer, int pos)
+		{
+			if (!IsAsyncEnumerator)
+				return false;
+			var block = blockContainer.Blocks.ElementAtOrDefault(pos);
+			if (block == null)
+				return false;
+			// call SetResult(ldflda <>v__promiseOfValueOrEnd(ldloc this), ldc.i4 1)
+			// leave IL_0000(nop)
+			if (block.Instructions.Count != 2)
+				return false;
+			if (!MatchCall(block.Instructions[0], "SetResult", out var args))
+				return false;
+			if (args.Count != 2)
+				return false;
+			if (!IsBuilderOrPromiseFieldOnThis(args[0]))
+				return false;
+			if (!args[1].MatchLdcI4(1))
+				return false;
+			return block.Instructions[1].MatchLeave(blockContainer);
+		}
+		void CheckSetResultAndExitBlock(BlockContainer blockContainer)
+		{
 			if (setResultAndExitBlock == null) {
 				// This block can be absent if the function never exits normally,
 				// but always throws an exception/loops infinitely.
@@ -408,17 +614,29 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			finalStateKnown = true;
 			if (!MatchCall(setResultAndExitBlock.Instructions[1], "SetResult", out var args))
 				throw new SymbolicAnalysisFailedException();
-			if (!IsBuilderFieldOnThis(args[0]))
+			if (!IsBuilderOrPromiseFieldOnThis(args[0]))
 				throw new SymbolicAnalysisFailedException();
-			if (methodType == AsyncMethodType.TaskOfT) {
-				if (args.Count != 2)
-					throw new SymbolicAnalysisFailedException();
-				if (!args[1].MatchLdLoc(out resultVar))
-					throw new SymbolicAnalysisFailedException();
-			} else {
-				resultVar = null;
-				if (args.Count != 1)
-					throw new SymbolicAnalysisFailedException();
+			switch (methodType) {
+				case AsyncMethodType.TaskOfT:
+					if (args.Count != 2)
+						throw new SymbolicAnalysisFailedException();
+					if (!args[1].MatchLdLoc(out resultVar))
+						throw new SymbolicAnalysisFailedException();
+					break;
+				case AsyncMethodType.Task:
+				case AsyncMethodType.Void:
+					resultVar = null;
+					if (args.Count != 1)
+						throw new SymbolicAnalysisFailedException();
+					break;
+				case AsyncMethodType.AsyncEnumerable:
+				case AsyncMethodType.AsyncEnumerator:
+					resultVar = null;
+					if (args.Count != 2)
+						throw new SymbolicAnalysisFailedException();
+					if (!args[1].MatchLdcI4(0))
+						throw new SymbolicAnalysisFailedException();
+					break;
 			}
 			if (!setResultAndExitBlock.Instructions[2].MatchLeave(blockContainer))
 				throw new SymbolicAnalysisFailedException();
@@ -442,8 +660,10 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			if (!handler.Filter.MatchLdcI4(1))
 				throw new SymbolicAnalysisFailedException();
 			var catchBlock = YieldReturnDecompiler.SingleBlock(handler.Body);
+			if (catchBlock == null)
+				throw new SymbolicAnalysisFailedException();
 			catchHandlerOffset = catchBlock.StartILOffset;
-			if (catchBlock?.Instructions.Count != 4)
+			if (catchBlock.Instructions.Count != 4)
 				throw new SymbolicAnalysisFailedException();
 			// stloc exception(ldloc E_143)
 			if (!(catchBlock.Instructions[0] is StLoc stloc))
@@ -465,7 +685,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				throw new SymbolicAnalysisFailedException();
 			if (args.Count != 2)
 				throw new SymbolicAnalysisFailedException();
-			if (!IsBuilderFieldOnThis(args[0]))
+			if (!IsBuilderOrPromiseFieldOnThis(args[0]))
 				throw new SymbolicAnalysisFailedException();
 			if (!args[1].MatchLdLoc(stloc.Variable))
 				throw new SymbolicAnalysisFailedException();
@@ -490,19 +710,55 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			return target.MatchLdThis() && field.MemberDefinition == builderField;
 		}
 
+		bool IsBuilderOrPromiseFieldOnThis(ILInstruction inst)
+		{
+			if (methodType == AsyncMethodType.AsyncEnumerable || methodType == AsyncMethodType.AsyncEnumerator) {
+				return true; // TODO: check against uses of promise fields in other methods?
+			} else {
+				return IsBuilderFieldOnThis(inst);
+			}
+		}
+
 		bool MatchStateAssignment(ILInstruction inst, out int newState)
 		{
 			// stfld(StateMachine::<>1__state, ldloc(this), ldc.i4(stateId))
 			if (inst.MatchStFld(out var target, out var field, out var value)
-				&& target.MatchLdThis()
+				&& StackSlotValue(target).MatchLdThis()
 				&& field.MemberDefinition == stateField
-				&& value.MatchLdcI4(out newState))
+				&& StackSlotValue(value).MatchLdcI4(out newState))
 			{
 				return true;
 			}
 			newState = 0;
 			return false;
 		}
+
+		/// <summary>
+		/// Analyse the DisposeAsync() method in order to find the disposeModeField.
+		/// </summary>
+		private void AnalyzeDisposeAsync()
+		{
+			disposeModeField = null;
+			if (!IsAsyncEnumerator) {
+				return;
+			}
+			var disposeAsync = stateMachineType.Methods.FirstOrDefault(m => m.Name.EndsWith(".DisposeAsync", StringComparison.Ordinal));
+			if (disposeAsync == null)
+				throw new SymbolicAnalysisFailedException("Could not find DisposeAsync()");
+			var disposeAsyncHandle = (MethodDefinitionHandle)disposeAsync.MetadataToken;
+			var function = YieldReturnDecompiler.CreateILAst(disposeAsyncHandle, context);
+			foreach (var store in function.Descendants) {
+				if (!store.MatchStFld(out var target, out var field, out var value))
+					continue;
+				if (!target.MatchLdThis())
+					continue;
+				if (!value.MatchLdcI4(1))
+					throw new SymbolicAnalysisFailedException();
+				if (disposeModeField != null)
+					throw new SymbolicAnalysisFailedException("Multiple stores to disposeMode in DisposeAsync()");
+				disposeModeField = (IField)field.MemberDefinition;
+			}
+		}
 		#endregion
 
 		#region InlineBodyOfMoveNext
@@ -513,6 +769,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			function.AsyncReturnType = underlyingReturnType;
 			function.MoveNextMethod = moveNextFunction.Method;
 			function.CodeSize = moveNextFunction.CodeSize;
+			function.IsIterator = IsAsyncEnumerator;
 			moveNextFunction.Variables.Clear();
 			moveNextFunction.ReleaseRef();
 			foreach (var branch in function.Descendants.OfType<Branch>()) {
@@ -520,6 +777,10 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					branch.ReplaceWith(new Leave((BlockContainer)function.Body, resultVar == null ? null : new LdLoc(resultVar)).WithILRange(branch));
 				}
 			}
+			if (setResultYieldBlock != null) {
+				// We still might have branches to this block; and we can't quite yet get rid of it.
+				((BlockContainer)function.Body).Blocks.Add(setResultYieldBlock);
+			}
 			foreach (var leave in function.Descendants.OfType<Leave>()) {
 				if (leave.TargetContainer == moveNextFunction.Body) {
 					leave.TargetContainer = (BlockContainer)function.Body;
@@ -563,7 +824,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		/// </summary>
 		void AnalyzeStateMachine(ILFunction function)
 		{
-			context.Step("AnalyzeStateMachine()", function);
+			context.StepStartGroup("AnalyzeStateMachine()", function);
 			smallestAwaiterVarIndex = int.MaxValue;
 			foreach (var container in function.Descendants.OfType<BlockContainer>()) {
 				// Use a separate state range analysis per container.
@@ -577,6 +838,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					context.CancellationToken.ThrowIfCancellationRequested();
 					if (block.Instructions.Last() is Leave leave && moveNextLeaves.Contains(leave)) {
 						// This is likely an 'await' block
+						context.Step($"AnalyzeAwaitBlock({block.StartILOffset:x4})", block);
 						if (AnalyzeAwaitBlock(block, out var awaiterVar, out var awaiterField, out int state, out int yieldOffset)) {
 							block.Instructions.Add(new Await(new LdLoca(awaiterVar)));
 							Block targetBlock = stateToBlockMap.GetOrDefault(state);
@@ -591,7 +853,25 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 								smallestAwaiterVarIndex = awaiterVar.Index.Value;
 							}
 						}
+					} else if (block.Instructions.Last().MatchBranch(setResultYieldBlock)) {
+						// This is a 'yield return' in an async enumerator.
+						context.Step($"AnalyzeYieldReturn({block.StartILOffset:x4})", block);
+						if (AnalyzeYieldReturn(block, out var yieldValue, out int state)) {
+							block.Instructions.Add(new YieldReturn(yieldValue));
+							Block targetBlock = stateToBlockMap.GetOrDefault(state);
+							if (targetBlock != null) {
+								block.Instructions.Add(new Branch(targetBlock));
+							} else {
+								block.Instructions.Add(new InvalidBranch("Could not find block for state " + state));
+							}
+						} else {
+							block.Instructions.Add(new InvalidBranch("Could not detect 'yield return'"));
+						}
 					}
+					TransformYieldBreak(block);
+				}
+				foreach (var block in container.Blocks) {
+					SimplifyIfDisposeMode(block);
 				}
 				// Skip the state dispatcher and directly jump to the initial state
 				var entryPoint = stateToBlockMap.GetOrDefault(initialState);
@@ -604,6 +884,89 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				}
 				container.SortBlocks(deleteUnreachableBlocks: true);
 			}
+			context.StepEndGroup();
+		}
+
+		private bool TransformYieldBreak(Block block)
+		{
+			// stfld disposeMode(ldloc this, ldc.i4 1)
+			// br nextBlock
+			if (block.Instructions.Count < 2)
+				return false;
+			if (!(block.Instructions.Last() is Branch branch))
+				return false;
+			if (!block.Instructions[block.Instructions.Count - 2].MatchStFld(out var target, out var field, out var value))
+				return false;
+			if (!target.MatchLdThis())
+				return false;
+			if (field.MemberDefinition != disposeModeField)
+				return false;
+			if (!value.MatchLdcI4(1))
+				return false;
+
+			// Detected a 'yield break;'
+			context.Step($"TransformYieldBreak({block.StartILOffset:x4})", block);
+			var breakTarget = FindYieldBreakTarget(branch.TargetBlock);
+			if (breakTarget is Block targetBlock) {
+				branch.TargetBlock = targetBlock;
+			} else {
+				Debug.Assert(breakTarget is BlockContainer);
+				branch.ReplaceWith(new Leave((BlockContainer)breakTarget).WithILRange(branch));
+			}
+			return true;
+		}
+
+		ILInstruction FindYieldBreakTarget(Block block)
+		{
+			// We'll follow the branch and evaluate the following instructions
+			// under the assumption that disposeModeField==1, which lets us follow a series of jumps
+			// to determine the final target.
+			var visited = new HashSet<Block>();
+			var evalContext = new SymbolicEvaluationContext(disposeModeField);
+			while (true) {
+				for (int i = 0; i < block.Instructions.Count; i++) {
+					ILInstruction inst = block.Instructions[i];
+					while (inst.MatchIfInstruction(out var condition, out var trueInst, out var falseInst)) {
+						var condVal = evalContext.Eval(condition).AsBool();
+						if (condVal.Type == SymbolicValueType.IntegerConstant) {
+							inst = condVal.Constant != 0 ? trueInst : falseInst;
+						} else if (condVal.Type == SymbolicValueType.StateInSet) {
+							inst = condVal.ValueSet.Contains(1) ? trueInst : falseInst;
+						} else {
+							return block;
+						}
+					}
+					if (inst.MatchBranch(out var targetBlock)) {
+						if (visited.Add(block)) {
+							block = targetBlock;
+							break; // continue with next block
+						} else {
+							return block; // infinite loop detected
+						}
+					} else if (inst is Leave leave && leave.Value.OpCode == OpCode.Nop) {
+						return leave.TargetContainer;
+					} else if (inst.OpCode == OpCode.Nop) {
+						continue; // continue with next instruction in this block
+					} else {
+						return block;
+					}
+				}
+			}
+		}
+
+		private bool SimplifyIfDisposeMode(Block block)
+		{
+			// if (logic.not(ldfld disposeMode(ldloc this))) br falseInst
+			// br trueInst
+			if (!block.MatchIfAtEndOfBlock(out var condition, out _, out var falseInst))
+				return false;
+			if (!condition.MatchLdFld(out var target, out var field))
+				return false;
+			if (!(target.MatchLdThis() && field.MemberDefinition == disposeModeField))
+				return false;
+			block.Instructions[block.Instructions.Count - 2] = falseInst;
+			block.Instructions.RemoveAt(block.Instructions.Count - 1);
+			return true;
 		}
 
 		bool AnalyzeAwaitBlock(Block block, out ILVariable awaiter, out IField awaiterField, out int state, out int yieldOffset)
@@ -705,6 +1068,50 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			}
 			return inst;
 		}
+
+		private bool AnalyzeYieldReturn(Block block, out ILInstruction yieldValue, out int newState)
+		{
+			yieldValue = default;
+			newState = default;
+			Debug.Assert(block.Instructions.Last().MatchBranch(setResultYieldBlock));
+			// stfld current(ldloc this, ldstr "yieldValue")
+			// stloc S_45(ldloc this)
+			// stloc S_46(ldc.i4 -5)
+			// stloc V_0(ldloc S_46)
+			// stfld stateField(ldloc S_45, ldloc S_46)
+			// br setResultYieldBlock
+
+			int pos = block.Instructions.Count - 2;
+			// Immediately before the 'yield return', there should be a state assignment:
+			if (pos < 0 || !MatchStateAssignment(block.Instructions[pos], out newState))
+				return false;
+			pos--;
+
+			if (pos >= 0 && block.Instructions[pos].MatchStLoc(cachedStateVar, out var cachedStateNewValue)) {
+				if (StackSlotValue(cachedStateNewValue).MatchLdcI4(newState)) {
+					pos--; // OK, ignore V_0 store
+				} else {
+					return false;
+				}
+			}
+
+			while (pos >= 0 && block.Instructions[pos] is StLoc stloc) {
+				if (stloc.Variable.Kind != VariableKind.StackSlot)
+					return false;
+				if (!SemanticHelper.IsPure(stloc.Value.Flags))
+					return false;
+				pos--;
+			}
+
+			if (pos < 0 || !block.Instructions[pos].MatchStFld(out var target, out var field, out yieldValue))
+				return false;
+			if (!StackSlotValue(target).MatchLdThis())
+				return false;
+			// TODO: check that we are accessing the current field (compare with get_Current)
+
+			block.Instructions.RemoveRange(pos, block.Instructions.Count - pos);
+			return true;
+		}
 		#endregion
 
 		#region DetectAwaitPattern
@@ -761,7 +1168,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			// continue matching call get_IsCompleted(ldloca awaiterVar)
 			if (!MatchCall(condition, "get_IsCompleted", out var isCompletedArgs) || isCompletedArgs.Count != 1)
 				return;
-			if (!isCompletedArgs[0].MatchLdLocRef(awaiterVar))
+			if (!UnwrapConvUnknown(isCompletedArgs[0]).MatchLdLocRef(awaiterVar))
 				return;
 			// Check awaitBlock and resumeBlock:
 			if (!awaitBlocks.TryGetValue(awaitBlock, out var awaitBlockData))
@@ -779,14 +1186,14 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				return;
 			if (!MatchCall(getResultCall, "GetResult", out var getResultArgs) || getResultArgs.Count != 1)
 				return;
-			if (!getResultArgs[0].MatchLdLocRef(awaiterVar))
+			if (!UnwrapConvUnknown(getResultArgs[0]).MatchLdLocRef(awaiterVar))
 				return;
 			// All checks successful, let's transform.
 			context.Step("Transform await pattern", block);
 			block.Instructions.RemoveAt(block.Instructions.Count - 3); // remove getAwaiter call
 			block.Instructions.RemoveAt(block.Instructions.Count - 2); // remove if (isCompleted)
 			((Branch)block.Instructions.Last()).TargetBlock = completedBlock; // instead, directly jump to completed block
-			Await awaitInst = new Await(getAwaiterCall.Arguments.Single());
+			Await awaitInst = new Await(UnwrapConvUnknown(getAwaiterCall.Arguments.Single()));
 			awaitInst.GetResultMethod = getResultCall.Method;
 			awaitInst.GetAwaiterMethod = getAwaiterCall.Method;
 			getResultCall.ReplaceWith(awaitInst);
@@ -798,7 +1205,15 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				}
 			}
 		}
-		
+
+		static ILInstruction UnwrapConvUnknown(ILInstruction inst)
+		{
+			if (inst is Conv conv && conv.TargetType == PrimitiveType.Unknown) {
+				return conv.Argument;
+			}
+			return inst;
+		}
+
 		bool CheckAwaitBlock(Block block, out Block resumeBlock, out IField stackField)
 		{
 			// awaitBlock:

ICSharpCode.Decompiler/IL/ControlFlow/AwaitInCatchTransform.cs

@@ -197,6 +197,8 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 	{
 		public static void Run(ILFunction function, ILTransformContext context)
 		{
+			if (!context.Settings.AwaitInCatchFinally)
+				return;
 			HashSet<BlockContainer> changedContainers = new HashSet<BlockContainer>();
 
 			// analyze all try-catch statements in the function

ICSharpCode.Decompiler/IL/ControlFlow/ControlFlowSimplification.cs

@@ -46,7 +46,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				context.CancellationToken.ThrowIfCancellationRequested();
 
 				RemoveNopInstructions(block);
-				RemoveDeadStackStores(block, aggressive: context.Settings.RemoveDeadStores);
+				RemoveDeadStackStores(block, context);
 
 				InlineVariableInReturnBlock(block, context);
 				// 1st pass SimplifySwitchInstruction before SimplifyBranchChains()
@@ -70,13 +70,15 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			block.Instructions.RemoveAll(inst => inst.OpCode == OpCode.Nop);
 		}
 
-		private void RemoveDeadStackStores(Block block, bool aggressive)
+		private static void RemoveDeadStackStores(Block block, ILTransformContext context)
 		{
+			bool aggressive = context.Settings.RemoveDeadStores;
 			// Previously copy propagation did this;
 			// ideally the ILReader would already do this,
 			// for now do this here (even though it's not control-flow related).
 			for (int i = block.Instructions.Count - 1; i >= 0; i--) {
 				if (block.Instructions[i] is StLoc stloc && stloc.Variable.IsSingleDefinition && stloc.Variable.LoadCount == 0 && stloc.Variable.Kind == VariableKind.StackSlot) {
+					context.Step($"Remove dead stack store {stloc.Variable.Name}", stloc);
 					if (aggressive ? SemanticHelper.IsPure(stloc.Value.Flags) : IsSimple(stloc.Value)) {
 						Debug.Assert(SemanticHelper.IsPure(stloc.Value.Flags));
 						block.Instructions.RemoveAt(i++);

ICSharpCode.Decompiler/IL/ControlFlow/YieldReturnDecompiler.cs

@@ -305,6 +305,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		/// </summary>
 		bool MatchEnumeratorCreationNewObj(ILInstruction inst)
 		{
+			return MatchEnumeratorCreationNewObj(inst, metadata, currentType,
+				out enumeratorCtor, out enumeratorType);
+		}
+
+		internal static bool MatchEnumeratorCreationNewObj(ILInstruction inst, 
+			MetadataReader metadata, TypeDefinitionHandle currentType,
+			out MethodDefinitionHandle enumeratorCtor, out TypeDefinitionHandle enumeratorType)
+		{
+			enumeratorCtor = default;
+			enumeratorType = default;
 			// newobj(CurrentType/...::.ctor, ldc.i4(-2))
 			if (!(inst is NewObj newObj))
 				return false;
@@ -443,6 +453,12 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			MethodDefinitionHandle getEnumeratorMethod = metadata.GetTypeDefinition(enumeratorType).GetMethods().FirstOrDefault(
 				m => metadata.GetString(metadata.GetMethodDefinition(m).Name).StartsWith("System.Collections.Generic.IEnumerable", StringComparison.Ordinal)
 				&& metadata.GetString(metadata.GetMethodDefinition(m).Name).EndsWith(".GetEnumerator", StringComparison.Ordinal));
+			ResolveIEnumerableIEnumeratorFieldMapping(getEnumeratorMethod, context, fieldToParameterMap);
+		}
+
+		internal static void ResolveIEnumerableIEnumeratorFieldMapping(MethodDefinitionHandle getEnumeratorMethod, ILTransformContext context,
+			Dictionary<IField, ILVariable> fieldToParameterMap)
+		{
 			if (getEnumeratorMethod.IsNil)
 				return; // no mappings (maybe it's just an IEnumerator implementation?)
 			var function = CreateILAst(getEnumeratorMethod, context);

ICSharpCode.Decompiler/IL/Instructions/Block.cs

@@ -311,6 +311,27 @@ namespace ICSharpCode.Decompiler.IL
 				return false;
 			return this.FinalInstruction.MatchLdLoc(tmp);
 		}
+
+		public bool MatchIfAtEndOfBlock(out ILInstruction condition, out ILInstruction trueInst, out ILInstruction falseInst)
+		{
+			condition = null;
+			trueInst = null;
+			falseInst = null;
+			if (Instructions.Count < 2)
+				return false;
+			if (Instructions[Instructions.Count - 2].MatchIfInstruction(out condition, out trueInst)) {
+				// Swap trueInst<>falseInst for every logic.not in the condition.
+				falseInst = Instructions.Last();
+				while (condition.MatchLogicNot(out var arg)) {
+					condition = arg;
+					ILInstruction tmp = trueInst;
+					trueInst = falseInst;
+					falseInst = tmp;
+				}
+				return true;
+			}
+			return false;
+		}
 	}
 	
 	public enum BlockKind

ICSharpCode.Decompiler/IL/Instructions/UsingInstruction.cs

@@ -36,10 +36,16 @@ namespace ICSharpCode.Decompiler.IL
 	/// </remarks>
 	partial class UsingInstruction
 	{
+		public bool IsAsync { get; set; }
+
 		public override void WriteTo(ITextOutput output, ILAstWritingOptions options)
 		{
 			WriteILRange(output, options);
-			output.Write("using (");
+			output.Write("using");
+			if (IsAsync) {
+				output.Write(".async");
+			}
+			output.Write(" (");
 			Variable.WriteTo(output);
 			output.Write(" = ");
 			ResourceExpression.WriteTo(output, options);

ICSharpCode.Decompiler/IL/Transforms/UsingTransform.cs

@@ -34,7 +34,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (!context.Settings.UsingStatement) return;
 			this.context = context;
 			for (int i = block.Instructions.Count - 1; i >= 0; i--) {
-				if (!TransformUsing(block, i) && !TransformUsingVB(block, i))
+				if (!TransformUsing(block, i) && !TransformUsingVB(block, i) && !TransformAsyncUsing(block, i))
 					continue;
 				// This happens in some cases:
 				// Use correct index after transformation.
@@ -167,7 +167,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			return true;
 		}
 
-		bool MatchDisposeBlock(BlockContainer container, ILVariable objVar, bool usingNull)
+		bool MatchDisposeBlock(BlockContainer container, ILVariable objVar, bool usingNull, in string disposeMethodFullName = "System.IDisposable.Dispose", KnownTypeCode disposeTypeCode = KnownTypeCode.IDisposable)
 		{
 			var entryPoint = container.EntryPoint;
 			if (entryPoint.Instructions.Count < 2 || entryPoint.Instructions.Count > 3 || entryPoint.IncomingEdgeCount != 1)
@@ -180,17 +180,17 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (castIndex > -1) {
 				if (!entryPoint.Instructions[castIndex].MatchStLoc(out var tempVar, out var isinst))
 					return false;
-				if (!isinst.MatchIsInst(out var load, out var disposableType) || !load.MatchLdLoc(objVar) || !disposableType.IsKnownType(KnownTypeCode.IDisposable))
+				if (!isinst.MatchIsInst(out var load, out var disposableType) || !load.MatchLdLoc(objVar) || !disposableType.IsKnownType(disposeTypeCode))
 					return false;
 				if (!tempVar.IsSingleDefinition)
 					return false;
 				isReference = true;
-				if (!MatchDisposeCheck(tempVar, checkInst, isReference, usingNull, out int numObjVarLoadsInCheck))
+				if (!MatchDisposeCheck(tempVar, checkInst, isReference, usingNull, out int numObjVarLoadsInCheck, disposeMethodFullName, disposeTypeCode))
 					return false;
 				if (tempVar.LoadCount != numObjVarLoadsInCheck)
 					return false;
 			} else {
-				if (!MatchDisposeCheck(objVar, checkInst, isReference, usingNull, out _))
+				if (!MatchDisposeCheck(objVar, checkInst, isReference, usingNull, out _, disposeMethodFullName, disposeTypeCode))
 					return false;
 			}
 			if (!entryPoint.Instructions[leaveIndex].MatchLeave(container, out var returnValue) || !returnValue.MatchNop())
@@ -198,9 +198,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			return true;
 		}
 
-		bool MatchDisposeCheck(ILVariable objVar, ILInstruction checkInst, bool isReference, bool usingNull, out int numObjVarLoadsInCheck)
+		bool MatchDisposeCheck(ILVariable objVar, ILInstruction checkInst, bool isReference, bool usingNull, out int numObjVarLoadsInCheck, in string disposeMethodFullName, KnownTypeCode disposeTypeCode)
 		{
 			numObjVarLoadsInCheck = 2;
+			ILInstruction disposeInvocation;
 			CallVirt callVirt;
 			if (objVar.Type.IsKnownType(KnownTypeCode.NullableOfT)) {
 				if (checkInst.MatchIfInstruction(out var condition, out var disposeInst)) {
@@ -208,22 +209,27 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						return false;
 					if (!(disposeInst is Block disposeBlock) || disposeBlock.Instructions.Count != 1)
 						return false;
-					callVirt = disposeBlock.Instructions[0] as CallVirt;
+					disposeInvocation = disposeBlock.Instructions[0];
 				} else if (checkInst.MatchNullableRewrap(out disposeInst)) {
-					callVirt = disposeInst as CallVirt;
+					disposeInvocation = disposeInst;
 				} else {
 					return false;
 				}
+				if (disposeTypeCode == KnownTypeCode.IAsyncDisposable) {
+					if (!UnwrapAwait(ref disposeInvocation))
+						return false;
+				}
+				callVirt = disposeInvocation as CallVirt;
 				if (callVirt == null)
 					return false;
-				if (callVirt.Method.FullName != "System.IDisposable.Dispose")
+				if (callVirt.Method.FullName != disposeMethodFullName)
 					return false;
 				if (callVirt.Method.Parameters.Count > 0)
 					return false;
 				if (callVirt.Arguments.Count != 1)
 					return false;
 				var firstArg = callVirt.Arguments.FirstOrDefault();
-				if (!(firstArg.MatchUnboxAny(out var innerArg1, out var unboxType) && unboxType.IsKnownType(KnownTypeCode.IDisposable))) {
+				if (!(firstArg.MatchUnboxAny(out var innerArg1, out var unboxType) && unboxType.IsKnownType(disposeTypeCode))) {
 					if (!firstArg.MatchAddressOf(out var innerArg2, out _))
 						return false;
 					return NullableLiftingTransform.MatchGetValueOrDefault(innerArg2, objVar)
@@ -255,7 +261,12 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						return false;
 					if (!(disposeInst is Block disposeBlock) || disposeBlock.Instructions.Count != 1)
 						return false;
-					if (!(disposeBlock.Instructions[0] is CallVirt cv))
+					disposeInvocation = disposeBlock.Instructions[0];
+					if (disposeTypeCode == KnownTypeCode.IAsyncDisposable) {
+						if (!UnwrapAwait(ref disposeInvocation))
+							return false;
+					}
+					if (!(disposeInvocation is CallVirt cv))
 						return false;
 					target = cv.Arguments.FirstOrDefault();
 					if (target == null)
@@ -264,6 +275,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						target = newTarget;
 					callVirt = cv;
 				} else {
+					if (disposeTypeCode == KnownTypeCode.IAsyncDisposable) {
+						if (!UnwrapAwait(ref checkInst))
+							return false;
+					}
 					if (!(checkInst is CallVirt cv))
 						return false;
 					target = cv.Arguments.FirstOrDefault();
@@ -275,7 +290,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					}
 					callVirt = cv;
 				}
-				if (callVirt.Method.FullName != "System.IDisposable.Dispose")
+				if (callVirt.Method.FullName != disposeMethodFullName)
 					return false;
 				if (callVirt.Method.Parameters.Count > 0)
 					return false;
@@ -286,8 +301,74 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					|| (usingNull && callVirt.Arguments[0].MatchLdNull())
 					|| (isReference && checkInst is NullableRewrap
 						&& target.MatchIsInst(out var arg, out var type2)
-						&& arg.MatchLdLoc(objVar) && type2.IsKnownType(KnownTypeCode.IDisposable));
+						&& arg.MatchLdLoc(objVar) && type2.IsKnownType(disposeTypeCode));
 			}
 		}
+
+		/// <summary>
+		/// stloc test(resourceExpression)
+		/// .try BlockContainer {
+		/// 	Block IL_002b (incoming: 1) {
+		/// 		call Use(ldloc test)
+		/// 		leave IL_002b (nop)
+		/// 	}
+		/// 
+		/// } finally BlockContainer {
+		/// 	Block IL_0045 (incoming: 1) {
+		/// 		if (comp.o(ldloc test == ldnull)) leave IL_0045 (nop)
+		/// 		br IL_00ae
+		/// 	}
+		/// 
+		/// 	Block IL_00ae (incoming: 1) {
+		/// 		await(addressof System.Threading.Tasks.ValueTask(callvirt DisposeAsync(ldloc test)))
+		/// 		leave IL_0045 (nop)
+		/// 	}
+		/// 
+		/// }
+		/// </summary>
+		private bool TransformAsyncUsing(Block block, int i)
+		{
+			if (i < 1 || !context.Settings.AsyncUsingAndForEachStatement) return false;
+			if (!(block.Instructions[i] is TryFinally tryFinally) || !(block.Instructions[i - 1] is StLoc storeInst))
+				return false;
+			if (!CheckAsyncResourceType(storeInst.Variable.Type))
+				return false;
+			if (storeInst.Variable.Kind != VariableKind.Local)
+				return false;
+			if (storeInst.Variable.LoadInstructions.Any(ld => !ld.IsDescendantOf(tryFinally)))
+				return false;
+			if (storeInst.Variable.AddressInstructions.Any(la => !la.IsDescendantOf(tryFinally) || (la.IsDescendantOf(tryFinally.TryBlock) && !ILInlining.IsUsedAsThisPointerInCall(la))))
+				return false;
+			if (storeInst.Variable.StoreInstructions.Count > 1)
+				return false;
+			if (!(tryFinally.FinallyBlock is BlockContainer container) || !MatchDisposeBlock(container, storeInst.Variable, usingNull: false, "System.IAsyncDisposable.DisposeAsync", KnownTypeCode.IAsyncDisposable))
+				return false;
+			context.Step("AsyncUsingTransform", tryFinally);
+			storeInst.Variable.Kind = VariableKind.UsingLocal;
+			block.Instructions.RemoveAt(i);
+			block.Instructions[i - 1] = new UsingInstruction(storeInst.Variable, storeInst.Value, tryFinally.TryBlock) { IsAsync = true }
+				.WithILRange(storeInst);
+			return true;
+		}
+
+		bool CheckAsyncResourceType(IType type)
+		{
+			if (NullableType.GetUnderlyingType(type).GetAllBaseTypes().Any(b => b.IsKnownType(KnownTypeCode.IAsyncDisposable)))
+				return true;
+			return false;
+		}
+
+		bool UnwrapAwait(ref ILInstruction awaitInstruction)
+		{
+			if (awaitInstruction == null)
+				return false;
+			if (!awaitInstruction.MatchAwait(out var arg))
+				return false;
+			if (!arg.MatchAddressOf(out awaitInstruction, out var type))
+				return false;
+			if (!type.IsKnownType(KnownTypeCode.ValueTask))
+				return false;
+			return true;
+		}
 	}
 }

ICSharpCode.Decompiler/Metadata/DotNetCorePathFinder.cs

@@ -62,15 +62,18 @@ namespace ICSharpCode.Decompiler.Metadata
 
 		readonly Dictionary<string, DotNetCorePackageInfo> packages;
 		ISet<string> packageBasePaths = new HashSet<string>(StringComparer.Ordinal);
-		readonly string assemblyName;
-		readonly string basePath;
 		readonly Version version;
 		readonly string dotnetBasePath = FindDotNetExeDirectory();
 
+		public DotNetCorePathFinder(Version version)
+		{
+			this.version = version;
+		}
+
 		public DotNetCorePathFinder(string parentAssemblyFileName, string targetFrameworkId, Version version, ReferenceLoadInfo loadInfo = null)
 		{
-			this.assemblyName = Path.GetFileNameWithoutExtension(parentAssemblyFileName);
-			this.basePath = Path.GetDirectoryName(parentAssemblyFileName);
+			string assemblyName = Path.GetFileNameWithoutExtension(parentAssemblyFileName);
+			string basePath = Path.GetDirectoryName(parentAssemblyFileName);
 			this.version = version;
 
 			var depsJsonFileName = Path.Combine(basePath, $"{assemblyName}.deps.json");
@@ -106,6 +109,25 @@ namespace ICSharpCode.Decompiler.Metadata
 			return FallbackToDotNetSharedDirectory(name, version);
 		}
 
+		internal string GetReferenceAssemblyPath(string targetFramework)
+		{
+			var (tfi, version) = UniversalAssemblyResolver.ParseTargetFramework(targetFramework);
+			string identifier, identifierExt;
+			switch (tfi) {
+				case TargetFrameworkIdentifier.NETCoreApp:
+					identifier = "Microsoft.NETCore.App";
+					identifierExt = "netcoreapp" + version.Major + "." + version.Minor;
+					break;
+				case TargetFrameworkIdentifier.NETStandard:
+					identifier = "NETStandard.Library";
+					identifierExt = "netstandard" + version.Major + "." + version.Minor;
+					break;
+				default:
+					throw new NotSupportedException();
+			}
+			return Path.Combine(dotnetBasePath, "packs", identifier + ".Ref", version.ToString(), "ref", identifierExt);
+		}
+
 		static IEnumerable<DotNetCorePackageInfo> LoadPackageInfos(string depsJsonFileName, string targetFramework)
 		{
 			var dependencies = JsonReader.Parse(File.ReadAllText(depsJsonFileName));

ICSharpCode.Decompiler/Metadata/UniversalAssemblyResolver.cs

@@ -26,6 +26,21 @@ using System.Text;
 
 namespace ICSharpCode.Decompiler.Metadata
 {
+	enum TargetFrameworkIdentifier
+	{
+		NETFramework,
+		NETCoreApp,
+		NETStandard,
+		Silverlight
+	}
+
+	enum DecompilerRuntime
+	{
+		NETFramework,
+		NETCoreApp,
+		Mono
+	}
+
 	// This is inspired by Mono.Cecil's BaseAssemblyResolver/DefaultAssemblyResolver.
 	public class UniversalAssemblyResolver : IAssemblyResolver
 	{
@@ -67,21 +82,6 @@ namespace ICSharpCode.Decompiler.Metadata
 			return directories.ToArray();
 		}
 
-		enum TargetFrameworkIdentifier
-		{
-			NETFramework,
-			NETCoreApp,
-			NETStandard,
-			Silverlight
-		}
-
-		enum DecompilerRuntime
-		{
-			NETFramework,
-			NETCoreApp,
-			Mono
-		}
-
 		string targetFramework;
 		TargetFrameworkIdentifier targetFrameworkIdentifier;
 		Version targetFrameworkVersion;
@@ -101,7 +101,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			AddSearchDirectory(baseDirectory);
 		}
 
-		(TargetFrameworkIdentifier, Version) ParseTargetFramework(string targetFramework)
+		internal static (TargetFrameworkIdentifier, Version) ParseTargetFramework(string targetFramework)
 		{
 			string[] tokens = targetFramework.Split(',');
 			TargetFrameworkIdentifier identifier;
@@ -131,7 +131,7 @@ namespace ICSharpCode.Decompiler.Metadata
 
 				switch (pair[0].Trim().ToUpperInvariant()) {
 					case "VERSION":
-						var versionString = pair[1].TrimStart('v');
+						var versionString = pair[1].TrimStart('v', ' ', '\t');
 						if (identifier == TargetFrameworkIdentifier.NETCoreApp ||
 							identifier == TargetFrameworkIdentifier.NETStandard)
 						{

ICSharpCode.Decompiler/TypeSystem/Implementation/AbstractTypeParameter.cs

@@ -370,7 +370,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		
 		public override string ToString()
 		{
-			return this.ReflectionName + " (owner=" + owner + ")";
+			return this.ReflectionName;
 		}
 	}
 }

ICSharpCode.Decompiler/TypeSystem/Implementation/KnownAttributes.cs

@@ -64,6 +64,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		IteratorStateMachine,
 		AsyncStateMachine,
 		AsyncMethodBuilder,
+		AsyncIteratorStateMachine,
 
 		// Field attributes:
 		FieldOffset,
@@ -131,6 +132,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			new TopLevelTypeName("System.Runtime.CompilerServices", nameof(IteratorStateMachineAttribute)),
 			new TopLevelTypeName("System.Runtime.CompilerServices", nameof(AsyncStateMachineAttribute)),
 			new TopLevelTypeName("System.Runtime.CompilerServices", "AsyncMethodBuilderAttribute"),
+			new TopLevelTypeName("System.Runtime.CompilerServices", "AsyncIteratorStateMachineAttribute"),
 			// Field attributes:
 			new TopLevelTypeName("System.Runtime.InteropServices", nameof(FieldOffsetAttribute)),
 			new TopLevelTypeName("System", nameof(NonSerializedAttribute)),

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeParameter.cs

@@ -230,7 +230,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 
 		public override string ToString()
 		{
-			return $"{MetadataTokens.GetToken(handle):X8} Index={Index} Owner={Owner}";
+			return $"{MetadataTokens.GetToken(handle):X8} {ReflectionName}";
 		}
 	}
 }

ICSharpCode.Decompiler/TypeSystem/Implementation/NullabilityAnnotatedType.cs

@@ -14,7 +14,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		internal NullabilityAnnotatedType(IType type, Nullability nullability)
 			: base(type)
 		{
-			Debug.Assert(nullability != type.Nullability);
+			Debug.Assert(type.Nullability == Nullability.Oblivious);
+			Debug.Assert(nullability != Nullability.Oblivious);
 			// Due to IType -> concrete type casts all over the type system, we can insert
 			// the NullabilityAnnotatedType wrapper only in some limited places.
 			Debug.Assert(type is ITypeDefinition

ICSharpCode.Decompiler/TypeSystem/KnownTypeReference.cs

@@ -115,10 +115,16 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		Task,
 		/// <summary><c>System.Threading.Tasks.Task{T}</c></summary>
 		TaskOfT,
+		/// <summary><c>System.Threading.Tasks.ValueTask</c></summary>
+		ValueTask,
+		/// <summary><c>System.Threading.Tasks.ValueTask{T}</c></summary>
+		ValueTaskOfT,
 		/// <summary><c>System.Nullable{T}</c></summary>
 		NullableOfT,
 		/// <summary><c>System.IDisposable</c></summary>
 		IDisposable,
+		/// <summary><c>System.IAsyncDisposable</c></summary>
+		IAsyncDisposable,
 		/// <summary><c>System.Runtime.CompilerServices.INotifyCompletion</c></summary>
 		INotifyCompletion,
 		/// <summary><c>System.Runtime.CompilerServices.ICriticalNotifyCompletion</c></summary>
@@ -137,15 +143,19 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		MemoryOfT,
 		/// <summary><c>System.Runtime.CompilerServices.Unsafe</c></summary>
 		Unsafe,
+		/// <summary><c>System.Collections.Generic.IAsyncEnumerable{T}</c></summary>
+		IAsyncEnumerableOfT,
+		/// <summary><c>System.Collections.Generic.IAsyncEnumerator{T}</c></summary>
+		IAsyncEnumeratorOfT,
 	}
-	
+
 	/// <summary>
 	/// Contains well-known type references.
 	/// </summary>
 	[Serializable]
 	public sealed class KnownTypeReference : ITypeReference
 	{
-		internal const int KnownTypeCodeCount = (int)KnownTypeCode.Unsafe + 1;
+		internal const int KnownTypeCodeCount = (int)KnownTypeCode.IAsyncEnumeratorOfT + 1;
 
 		static readonly KnownTypeReference[] knownTypeReferences = new KnownTypeReference[KnownTypeCodeCount] {
 			null, // None
@@ -189,10 +199,13 @@ namespace ICSharpCode.Decompiler.TypeSystem
 
 			new KnownTypeReference(KnownTypeCode.IReadOnlyCollectionOfT, TypeKind.Interface, "System.Collections.Generic", "IReadOnlyCollection", 1),
 			new KnownTypeReference(KnownTypeCode.IReadOnlyListOfT, TypeKind.Interface, "System.Collections.Generic", "IReadOnlyList", 1),
-			new KnownTypeReference(KnownTypeCode.Task,        TypeKind.Class, "System.Threading.Tasks", "Task"),
-			new KnownTypeReference(KnownTypeCode.TaskOfT,     TypeKind.Class, "System.Threading.Tasks", "Task", 1, baseType: KnownTypeCode.Task),
+			new KnownTypeReference(KnownTypeCode.Task,         TypeKind.Class, "System.Threading.Tasks", "Task"),
+			new KnownTypeReference(KnownTypeCode.TaskOfT,      TypeKind.Class, "System.Threading.Tasks", "Task", 1, baseType: KnownTypeCode.Task),
+			new KnownTypeReference(KnownTypeCode.ValueTask,    TypeKind.Struct, "System.Threading.Tasks", "ValueTask"),
+			new KnownTypeReference(KnownTypeCode.ValueTaskOfT, TypeKind.Struct, "System.Threading.Tasks", "ValueTask", 1),
 			new KnownTypeReference(KnownTypeCode.NullableOfT, TypeKind.Struct, "System", "Nullable", 1),
 			new KnownTypeReference(KnownTypeCode.IDisposable, TypeKind.Interface, "System", "IDisposable"),
+			new KnownTypeReference(KnownTypeCode.IAsyncDisposable, TypeKind.Interface, "System", "IAsyncDisposable"),
 			new KnownTypeReference(KnownTypeCode.INotifyCompletion, TypeKind.Interface, "System.Runtime.CompilerServices", "INotifyCompletion"),
 			new KnownTypeReference(KnownTypeCode.ICriticalNotifyCompletion, TypeKind.Interface, "System.Runtime.CompilerServices", "ICriticalNotifyCompletion"),
 
@@ -203,6 +216,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			new KnownTypeReference(KnownTypeCode.ReadOnlySpanOfT, TypeKind.Struct, "System", "ReadOnlySpan", 1),
 			new KnownTypeReference(KnownTypeCode.MemoryOfT, TypeKind.Struct, "System", "Memory", 1),
 			new KnownTypeReference(KnownTypeCode.Unsafe, TypeKind.Class, "System.Runtime.CompilerServices", "Unsafe", 0),
+			new KnownTypeReference(KnownTypeCode.IAsyncEnumerableOfT, TypeKind.Interface, "System.Collections.Generic", "IAsyncEnumerable", 1),
+			new KnownTypeReference(KnownTypeCode.IAsyncEnumeratorOfT, TypeKind.Interface, "System.Collections.Generic", "IAsyncEnumerator", 1),
 		};
 		
 		/// <summary>

ICSharpCode.Decompiler/TypeSystem/TupleType.cs

@@ -373,7 +373,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 	{
 		public static IType TupleUnderlyingTypeOrSelf(this IType type)
 		{
-			return (type as TupleType)?.UnderlyingType ?? type;
+			var t = (type as TupleType)?.UnderlyingType ?? type;
+			return t.WithoutNullability();
 		}
 	}
 }

ICSharpCode.Decompiler/TypeSystem/TypeParameterSubstitution.cs

@@ -18,6 +18,7 @@
 
 using System.Collections.Generic;
 using System.Text;
+using ICSharpCode.Decompiler.TypeSystem.Implementation;
 
 namespace ICSharpCode.Decompiler.TypeSystem
 {
@@ -186,7 +187,21 @@ namespace ICSharpCode.Decompiler.TypeSystem
 				return base.VisitTypeParameter(type);
 			}
 		}
-		
+
+		public override IType VisitNullabilityAnnotatedType(NullabilityAnnotatedType type)
+		{
+			if (type is NullabilityAnnotatedTypeParameter tp) {
+				if (tp.Nullability == Nullability.Nullable) {
+					return VisitTypeParameter(tp).ChangeNullability(Nullability.Nullable);
+				} else {
+					// T! substituted with T=oblivious string should result in oblivious string
+					return VisitTypeParameter(tp);
+				}
+			} else {
+				return base.VisitNullabilityAnnotatedType(type);
+			}
+		}
+
 		public override string ToString()
 		{
 			StringBuilder b = new StringBuilder();

ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs

@@ -535,5 +535,10 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			return KnownAttributes.IsKnownAttributeType(type);
 		}
+
+		public static IType WithoutNullability(this IType type)
+		{
+			return type.ChangeNullability(Nullability.Oblivious);
+		}
 	}
 }

ILSpy/Properties/Resources.Designer.cs

@@ -556,6 +556,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Decompile async IAsyncEnumerator methods.
+        /// </summary>
+        public static string DecompilerSettings_AsyncEnumerator {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.AsyncEnumerator", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Decompile ?. and ?[] operators.
         /// </summary>
@@ -664,6 +673,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Detect awaited using and foreach statements.
+        /// </summary>
+        public static string DecompilerSettings_DetectAsyncUsingAndForeachStatements {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.DetectAsyncUsingAndForeachStatements", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Detect foreach statements.
         /// </summary>
@@ -810,6 +828,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Read-only methods.
+        /// </summary>
+        public static string DecompilerSettings_ReadOnlyMethods {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.ReadOnlyMethods", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Remove dead and side effect free code (use with caution!).
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -447,9 +447,6 @@
   <data name="Version" xml:space="preserve">
     <value>Version</value>
   </data>
-  <data name="Culture" xml:space="preserve">
-    <value>Culture</value>
-  </data>
   <data name="PublicToken" xml:space="preserve">
     <value>Public Key Token</value>
   </data>
@@ -769,4 +766,13 @@ Are you sure you want to continue?</value>
   <data name="DecompileToNewPanel" xml:space="preserve">
     <value>Decompile to new tab</value>
   </data>
+  <data name="DecompilerSettings.AsyncEnumerator" xml:space="preserve">
+    <value>Decompile async IAsyncEnumerator methods</value>
+  </data>
+  <data name="DecompilerSettings.ReadOnlyMethods" xml:space="preserve">
+    <value>Read-only methods</value>
+  </data>
+  <data name="DecompilerSettings.DetectAsyncUsingAndForeachStatements" xml:space="preserve">
+    <value>Detect awaited using and foreach statements</value>
+  </data>
 </root>