Fix #2115: Re-introduce the evaluation order bug #2050 when a language version <=C# 5 is selected.

ICSharpCode.Decompiler.Tests/CorrectnessTestRunner.cs

@@ -142,7 +142,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NullableTests([ValueSource("defaultOptions")] CompilerOptions options)
 		{
-			RunCS(options: options, forceRoslynRecompile: true);
+			RunCS(options: options);
 		}
 
 		[Test]
@@ -315,7 +315,7 @@ namespace ICSharpCode.Decompiler.Tests
 			RunCS(options: options);
 		}
 
-		void RunCS([CallerMemberName] string testName = null, CompilerOptions options = CompilerOptions.UseDebug, bool forceRoslynRecompile = false)
+		void RunCS([CallerMemberName] string testName = null, CompilerOptions options = CompilerOptions.UseDebug)
 		{
 			string testFileName = testName + ".cs";
 			string testOutputFileName = testName + Tester.GetSuffix(options) + ".exe";
@@ -326,7 +326,7 @@ namespace ICSharpCode.Decompiler.Tests
 				outputFile = Tester.CompileCSharp(Path.Combine(TestCasePath, testFileName), options,
 					outputFileName: Path.Combine(TestCasePath, testOutputFileName));
 				string decompiledCodeFile = Tester.DecompileCSharp(outputFile.PathToAssembly, Tester.GetSettings(options));
-				if (forceRoslynRecompile || options.HasFlag(CompilerOptions.UseMcs))
+				if (options.HasFlag(CompilerOptions.UseMcs))
 				{
 					// For second pass, use roslyn instead of mcs.
 					// mcs has some compiler bugs that cause it to not accept ILSpy-generated code,

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -464,7 +464,13 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			}
 			else
 			{
-				return new DecompilerSettings(CSharp.LanguageVersion.CSharp5);
+				var settings= new DecompilerSettings(CSharp.LanguageVersion.CSharp5);
+				if (cscOptions.HasFlag(CompilerOptions.UseMcs))
+				{
+					// we don't recompile with mcs but with roslyn, so we can use ref locals
+					settings.UseRefLocalsForAccurateOrderOfEvaluation = true;
+				}
+				return settings;
 			}
 		}
 

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -92,6 +92,7 @@ namespace ICSharpCode.Decompiler
 				stringInterpolation = false;
 				dictionaryInitializers = false;
 				extensionMethodsInCollectionInitializers = false;
+				useRefLocalsForAccurateOrderOfEvaluation = false;
 			}
 			if (languageVersion < CSharp.LanguageVersion.CSharp7)
 			{
@@ -153,7 +154,7 @@ namespace ICSharpCode.Decompiler
 				|| discards || localFunctions)
 				return CSharp.LanguageVersion.CSharp7;
 			if (awaitInCatchFinally || useExpressionBodyForCalculatedGetterOnlyProperties || nullPropagation
-				|| stringInterpolation || dictionaryInitializers || extensionMethodsInCollectionInitializers)
+				|| stringInterpolation || dictionaryInitializers || extensionMethodsInCollectionInitializers || useRefLocalsForAccurateOrderOfEvaluation)
 				return CSharp.LanguageVersion.CSharp6;
 			if (asyncAwait)
 				return CSharp.LanguageVersion.CSharp5;
@@ -445,7 +446,7 @@ namespace ICSharpCode.Decompiler
 		/// Decompile C# 6 ?. and ?[] operators.
 		/// </summary>
 		[Category("C# 6.0 / VS 2015")]
-		[Description("DecompilerSettings.DecompileAndOperators")]
+		[Description("DecompilerSettings.NullPropagation")]
 		public bool NullPropagation {
 			get { return nullPropagation; }
 			set {
@@ -819,6 +820,25 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool useRefLocalsForAccurateOrderOfEvaluation = true;
+
+		/// <summary>
+		/// Gets/Sets whether to use C# 6.0 Extension Add methods in collection initializers.
+		/// Only has an effect if ObjectOrCollectionInitializers is enabled.
+		/// </summary>
+		[Category("C# 6.0 / VS 2015")]
+		[Description("DecompilerSettings.UseRefLocalsForAccurateOrderOfEvaluation")]
+		public bool UseRefLocalsForAccurateOrderOfEvaluation {
+			get { return useRefLocalsForAccurateOrderOfEvaluation; }
+			set {
+				if (useRefLocalsForAccurateOrderOfEvaluation != value)
+				{
+					useRefLocalsForAccurateOrderOfEvaluation = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool refExtensionMethods = true;
 
 		/// <summary>

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -33,6 +33,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		Aggressive = 1,
 		IntroduceNamedArguments = 2,
 		FindDeconstruction = 4,
+		AllowChangingOrderOfEvaluationForExceptions = 8,
 	}
 
 	/// <summary>
@@ -73,6 +74,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				if (IsInConstructorInitializer(function, inst))
 					options |= InliningOptions.Aggressive;
 			}
+			if (!context.Settings.UseRefLocalsForAccurateOrderOfEvaluation)
+			{
+				options |= InliningOptions.AllowChangingOrderOfEvaluationForExceptions;
+			}
 			return options;
 		}
 
@@ -666,10 +671,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			{
 				// Match found, we can inline
 				if (expr.SlotInfo == StObj.TargetSlot && !((StObj)expr.Parent).CanInlineIntoTargetSlot(expressionBeingMoved))
+				{
+					if ((options & InliningOptions.AllowChangingOrderOfEvaluationForExceptions) != 0)
+					{
+						// Intentionally change code semantics so that we can avoid a ref local
+						if (expressionBeingMoved is LdFlda ldflda)
+							ldflda.DelayExceptions = true;
+						else if (expressionBeingMoved is LdElema ldelema)
+							ldelema.DelayExceptions = true;
+					}
+					else
 					{
 						// special case: the StObj.TargetSlot does not accept some kinds of expressions
 						return FindResult.Stop;
 					}
+				}
 				return FindResult.Found(expr);
 			}
 			else if (expr is Block block)

ILSpy/Properties/Resources.Designer.cs

@@ -711,15 +711,6 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
-        /// <summary>
-        ///   Looks up a localized string similar to Decompile ?. and ?[] operators.
-        /// </summary>
-        public static string DecompilerSettings_DecompileAndOperators {
-            get {
-                return ResourceManager.GetString("DecompilerSettings.DecompileAndOperators", resourceCulture);
-            }
-        }
-        
         /// <summary>
         ///   Looks up a localized string similar to Decompile anonymous methods/lambdas.
         /// </summary>
@@ -1010,6 +1001,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Decompile ?. and ?[] operators.
+        /// </summary>
+        public static string DecompilerSettings_NullPropagation {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.NullPropagation", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Object/collection initializer expressions.
         /// </summary>
@@ -1217,6 +1217,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Use ref locals to accurately represent order of evaluation.
+        /// </summary>
+        public static string DecompilerSettings_UseRefLocalsForAccurateOrderOfEvaluation {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.UseRefLocalsForAccurateOrderOfEvaluation", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Use new SDK style format for generated project files (*.csproj).
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -267,9 +267,6 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.AsyncEnumerator" xml:space="preserve">
     <value>Decompile async IAsyncEnumerator methods</value>
   </data>
-  <data name="DecompilerSettings.DecompileAndOperators" xml:space="preserve">
-    <value>Decompile ?. and ?[] operators</value>
-  </data>
   <data name="DecompilerSettings.DecompileAnonymousMethodsLambdas" xml:space="preserve">
     <value>Decompile anonymous methods/lambdas</value>
   </data>
@@ -363,6 +360,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.NativeIntegers" xml:space="preserve">
     <value>Use nint/nuint types</value>
   </data>
+  <data name="DecompilerSettings.NullPropagation" xml:space="preserve">
+    <value>Decompile ?. and ?[] operators</value>
+  </data>
   <data name="DecompilerSettings.NullableReferenceTypes" xml:space="preserve">
     <value>Nullable reference types</value>
   </data>
@@ -435,6 +435,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.UsePatternBasedFixedStatement" xml:space="preserve">
     <value>Use pattern-based fixed statement</value>
   </data>
+  <data name="DecompilerSettings.UseRefLocalsForAccurateOrderOfEvaluation" xml:space="preserve">
+    <value>Use ref locals to accurately represent order of evaluation</value>
+  </data>
   <data name="DecompilerSettings.UseSdkStyleProjectFormat" xml:space="preserve">
     <value>Use new SDK style format for generated project files (*.csproj)</value>
   </data>

ILSpy/Properties/Resources.zh-Hans.resx

@@ -258,9 +258,6 @@
   <data name="DecompilerSettings.AsyncEnumerator" xml:space="preserve">
     <value>反编译异步 IAsyncEnumerator 方法</value>
   </data>
-  <data name="DecompilerSettings.DecompileAndOperators" xml:space="preserve">
-    <value>反编译 ?. 和  ?[] 运算符</value>
-  </data>
   <data name="DecompilerSettings.DecompileAnonymousMethodsLambdas" xml:space="preserve">
     <value>反编译匿名方法或 lambda</value>
   </data>
@@ -348,6 +345,9 @@
   <data name="DecompilerSettings.NativeIntegers" xml:space="preserve">
     <value>使用 nint/nuint 类型</value>
   </data>
+  <data name="DecompilerSettings.NullPropagation" xml:space="preserve">
+    <value>反编译 ?. 和  ?[] 运算符</value>
+  </data>
   <data name="DecompilerSettings.NullableReferenceTypes" xml:space="preserve">
     <value>可空引用类型</value>
   </data>