Fix bugs in async/await decompiler.

ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs

@@ -849,7 +849,7 @@ namespace ICSharpCode.Decompiler.Ast
 					args[args.Count - 1].AddAnnotation(new ParameterDeclarationAnnotation(byteCode));
 					return args[args.Count - 1];
 				case ILCode.Await:
-					return new UnaryOperatorExpression(UnaryOperatorType.Await, arg1);
+					return new UnaryOperatorExpression(UnaryOperatorType.Await, UnpackDirectionExpression(arg1));
 				case ILCode.NullableOf:
 				case ILCode.ValueOf: 
 					return arg1;
@@ -975,10 +975,7 @@ namespace ICSharpCode.Decompiler.Ast
 				
 				// Unpack any DirectionExpression that is used as target for the call
 				// (calling methods on value types implicitly passes the first argument by reference)
-				if (target is DirectionExpression) {
-					target = ((DirectionExpression)target).Expression;
-					target.Remove(); // detach from DirectionExpression
-				}
+				target = UnpackDirectionExpression(target);
 				
 				if (cecilMethodDef != null) {
 					// convert null.ToLower() to ((string)null).ToLower()
@@ -1078,6 +1075,15 @@ namespace ICSharpCode.Decompiler.Ast
 			return target.Invoke(cecilMethod.Name, ConvertTypeArguments(cecilMethod), methodArgs).WithAnnotation(cecilMethod);
 		}
 		
+		static Expression UnpackDirectionExpression(Expression target)
+		{
+			if (target is DirectionExpression) {
+				return ((DirectionExpression)target).Expression.Detach();
+			} else {
+				return target;
+			}
+		}
+		
 		static void AdjustArgumentsForMethodCall(MethodReference cecilMethod, List<Expression> methodArgs)
 		{
 			// Convert 'ref' into 'out' where necessary

ICSharpCode.Decompiler/ILAst/AsyncDecompiler.cs

@@ -475,7 +475,8 @@ namespace ICSharpCode.Decompiler.ILAst
 			newBody.RemoveAt(newBody.Count - 1); // remove AwaitUnsafeOnCompleted call
 			if (callAwaitUnsafeOnCompleted == null || callAwaitUnsafeOnCompleted.Code != ILCode.Call)
 				throw new SymbolicAnalysisFailedException();
-			if (((MethodReference)callAwaitUnsafeOnCompleted.Operand).Name != "AwaitUnsafeOnCompleted")
+			string methodName = ((MethodReference)callAwaitUnsafeOnCompleted.Operand).Name;
+			if (methodName != "AwaitUnsafeOnCompleted" && methodName != "AwaitOnCompleted")
 				throw new SymbolicAnalysisFailedException();
 			if (callAwaitUnsafeOnCompleted.Arguments.Count != 3)
 				throw new SymbolicAnalysisFailedException();

ICSharpCode.Decompiler/ILAst/ILInlining.cs

@@ -334,6 +334,7 @@ namespace ICSharpCode.Decompiler.ILAst
 					case ILCode.Stfld:
 					case ILCode.Ldfld:
 					case ILCode.Ldflda:
+					case ILCode.Await:
 						return true;
 				}
 			}

ICSharpCode.Decompiler/Tests/Async.cs

@@ -20,6 +20,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
 
 public class Async
@@ -36,6 +37,16 @@ public class Async
 		Console.WriteLine("No Await");
 	}
 	
+	public async void AwaitYield()
+	{
+		await Task.Yield();
+	}
+	
+	public async void AwaitDefaultYieldAwaitable()
+	{
+		await default(YieldAwaitable);
+	}
+	
 	public async Task SimpleVoidTaskMethod()
 	{
 		Console.WriteLine("Before");