Add basic unit tests for ref returns, locals and conditional

ICSharpCode.Decompiler.Tests/CorrectnessTestRunner.cs

@@ -190,6 +190,12 @@ namespace ICSharpCode.Decompiler.Tests
 			RunCS(options: options);
 		}
 
+		[Test]
+		public void RefLocalsAndReturns([ValueSource("roslynOnlyOptions")] CSharpCompilerOptions options)
+		{
+			RunCS(options: options);
+		}
+
 		[Test]
 		public void BitNot([Values(false, true)] bool force32Bit)
 		{

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

@@ -63,6 +63,7 @@
 
   <ItemGroup>
     <Compile Include="DataFlowTest.cs" />
+    <Compile Include="TestCases\Correctness\RefLocalsAndReturns.cs" />
     <Compile Include="VBPrettyTestRunner.cs" />
     <Compile Include="TestCases\VBPretty\Async.cs" />
     <Compile Include="UglyTestRunner.cs" />

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

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
+{
+	class RefLocalsAndReturns
+	{
+		static int[] numbers = { 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023 };
+		static string[] strings = { "Hello", "World" };
+		static string NullString = "";
+		static int DefaultInt = 0;
+
+		public delegate ref TReturn RefFunc<T1, TReturn>(T1 param1);
+
+		public static TReturn Invoker<T1, TReturn>(RefFunc<T1, TReturn> action, T1 value)
+		{
+			return action(value);
+		}
+
+		public static ref int FindNumber(int target)
+		{
+			for (int ctr = 0; ctr < numbers.Length; ctr++) {
+				if (numbers[ctr] >= target)
+					return ref numbers[ctr];
+			}
+			return ref numbers[0];
+		}
+
+		public static ref int LastNumber()
+		{
+			return ref numbers[numbers.Length - 1];
+		}
+
+		public static ref int ElementAtOrDefault(int index)
+		{
+			return ref index < 0 || index >= numbers.Length ? ref DefaultInt : ref numbers[index];
+		}
+
+		public static ref int LastOrDefault()
+		{
+			return ref numbers.Length > 0 ? ref numbers[numbers.Length - 1] : ref DefaultInt;
+		}
+
+		public static void DoubleNumber(ref int num)
+		{
+			Console.WriteLine("old: " + num);
+			num *= 2;
+			Console.WriteLine("new: " + num);
+		}
+
+		public static ref string GetOrSetString(int index)
+		{
+			if (index < 0 || index >= strings.Length)
+				return ref NullString;
+			return ref strings[index];
+		}
+
+		public static void Main(string[] args)
+		{
+			DoubleNumber(ref FindNumber(32));
+			Console.WriteLine(string.Join(", ", numbers));
+			DoubleNumber(ref LastNumber());
+			Console.WriteLine(string.Join(", ", numbers));
+			Console.WriteLine(GetOrSetString(0));
+			GetOrSetString(0) = "Goodbye";
+			Console.WriteLine(string.Join(" ", strings));
+			GetOrSetString(5) = "Here I mutated the null value!?";
+			Console.WriteLine(GetOrSetString(-5));
+
+			Console.WriteLine(Invoker(x => ref numbers[x], 0));
+			Console.WriteLine(LastOrDefault());
+			LastOrDefault() = 10000;
+			Console.WriteLine(ElementAtOrDefault(-5));
+		}
+	}
+}

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1359,12 +1359,22 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		protected internal override TranslatedExpression VisitCall(Call inst, TranslationContext context)
 		{
-			return new CallBuilder(this, typeSystem, settings).Build(inst);
+			return WrapInRef(new CallBuilder(this, typeSystem, settings).Build(inst), inst.Method.ReturnType);
 		}
-		
+
 		protected internal override TranslatedExpression VisitCallVirt(CallVirt inst, TranslationContext context)
 		{
-			return new CallBuilder(this, typeSystem, settings).Build(inst);
+			return WrapInRef(new CallBuilder(this, typeSystem, settings).Build(inst), inst.Method.ReturnType);
+		}
+
+		TranslatedExpression WrapInRef(TranslatedExpression expr, IType type)
+		{
+			if (type.Kind == TypeKind.ByReference) {
+				return new DirectionExpression(FieldDirection.Ref, expr.Expression)
+					.WithoutILInstruction()
+					.WithRR(new ByReferenceResolveResult(expr.ResolveResult, isOut: false));
+			}
+			return expr;
 		}
 
 		internal ExpressionWithResolveResult TranslateFunction(IType delegateType, ILFunction function)

ICSharpCode.Decompiler/Semantics/MemberResolveResult.cs

@@ -76,6 +76,8 @@ namespace ICSharpCode.Decompiler.Semantics
 						return new PointerType(member.ReturnType);
 					break;
 			}
+			if (member.ReturnType.Kind == TypeKind.ByReference)
+				return ((ByReferenceType)member.ReturnType).ElementType;
 			return member.ReturnType;
 		}