Add support for 'with' expressions

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

@@ -214,6 +214,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.InitializerTests
 				get;
 				set;
 			}
+
+#if CS90
+			public Fields Value7 {
+				get;
+				set;
+			}
+#endif
 		}
 
 		public class OtherItem
@@ -277,6 +284,18 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.InitializerTests
 				z = _z;
 			}
 		}
+
+#if CS90
+		public record Fields
+		{
+			public int A;
+			public double B = 1.0;
+			public object C;
+			public dynamic D;
+			public string S = "abc";
+			public Item I;
+		}
+#endif
 		#endregion
 
 		#region Field initializer tests
@@ -1547,6 +1566,19 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.InitializerTests
 			return null;
 		}
 
+#if CS90
+		private Fields RecordWithNestedClass(Fields input)
+		{
+			return input with {
+				A = 42,
+				I = new Item {
+					Value7 = input with {
+						A = 43
+					}
+				}
+			}
+		}
+#endif
 		#endregion
 
 		#region Collection initializer

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

@@ -54,6 +54,28 @@
 		}
 	}
 
+	public class WithExpressionTests
+	{
+		public Fields Test(Fields input)
+		{
+			return input with {
+				A = 42,
+				B = 3.141,
+				C = input
+			};
+		}
+		public Fields Test2(Fields input)
+		{
+			return input with {
+				A = 42,
+				B = 3.141,
+				C = input with {
+					A = 43
+				}
+			};
+		}
+	}
+
 	public abstract record WithNestedRecords
 	{
 		public record A : WithNestedRecords

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -790,8 +790,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			{
 				// Reference comparison using Unsafe intrinsics
 				Debug.Assert(!inst.IsLifted);
-				(string methodName, bool negate) = inst.Kind switch
-				{
+				(string methodName, bool negate) = inst.Kind switch {
 					ComparisonKind.Equality => ("AreSame", false),
 					ComparisonKind.Inequality => ("AreSame", true),
 					ComparisonKind.LessThan => ("IsAddressLessThan", false),
@@ -3052,6 +3051,8 @@ namespace ICSharpCode.Decompiler.CSharp
 				case BlockKind.CollectionInitializer:
 				case BlockKind.ObjectInitializer:
 					return TranslateObjectAndCollectionInitializer(block);
+				case BlockKind.WithInitializer:
+					return TranslateWithInitializer(block);
 				case BlockKind.CallInlineAssign:
 					return TranslateSetterCallAssignment(block);
 				case BlockKind.CallWithNamedArgs:
@@ -3112,7 +3113,13 @@ namespace ICSharpCode.Decompiler.CSharp
 				default:
 					throw new ArgumentException("given Block is invalid!");
 			}
-			// Build initializer expression
+			var oce = (ObjectCreateExpression)expr.Expression;
+			oce.Initializer = BuildArrayInitializerExpression(block, initObjRR);
+			return expr.WithILInstruction(block);
+		}
+
+		private ArrayInitializerExpression BuildArrayInitializerExpression(Block block, InitializedObjectResolveResult initObjRR)
+		{
 			var elementsStack = new Stack<List<TranslatedExpression>>();
 			var elements = new List<TranslatedExpression>(block.Instructions.Count);
 			elementsStack.Push(elements);
@@ -3199,9 +3206,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					MakeInitializerAssignment(initObjRR, methodElement, pathElement, values, indexVariables)
 				);
 			}
-			var oce = (ObjectCreateExpression)expr.Expression;
-			oce.Initializer = new ArrayInitializerExpression(elements.SelectArray(e => e.Expression));
-			return expr.WithILInstruction(block);
+			return new ArrayInitializerExpression(elements.SelectArray(e => e.Expression));
 		}
 
 		IEnumerable<ILInstruction> GetIndices(IEnumerable<ILInstruction> indices, Dictionary<ILVariable, ILInstruction> indexVariables)
@@ -3427,6 +3432,21 @@ namespace ICSharpCode.Decompiler.CSharp
 				.WithRR(new ResolveResult(stloc.Variable.Type));
 		}
 
+		TranslatedExpression TranslateWithInitializer(Block block)
+		{
+			var stloc = block.Instructions.FirstOrDefault() as StLoc;
+			var final = block.FinalInstruction as LdLoc;
+			if (stloc == null || final == null || stloc.Variable != final.Variable || stloc.Variable.Kind != VariableKind.InitializerTarget)
+				throw new ArgumentException("given Block is invalid!");
+
+			WithInitializerExpression withInitializerExpression = new WithInitializerExpression();
+			withInitializerExpression.Expression = Translate(stloc.Value, stloc.Variable.Type);
+			withInitializerExpression.Initializer = BuildArrayInitializerExpression(block, new InitializedObjectResolveResult(stloc.Variable.Type));
+
+			return withInitializerExpression.WithILInstruction(block)
+				.WithRR(new ResolveResult(stloc.Variable.Type));
+		}
+
 		/// <summary>
 		/// If expr is a constant integer expression, and its value fits into type,
 		/// convert the expression into the target type.

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1224,6 +1224,15 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			EndNode(uncheckedExpression);
 		}
 
+		public virtual void VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression)
+		{
+			StartNode(withInitializerExpression);
+			withInitializerExpression.Expression.AcceptVisitor(this);
+			WriteKeyword("with", WithInitializerExpression.WithKeywordRole);
+			withInitializerExpression.Initializer.AcceptVisitor(this);
+			EndNode(withInitializerExpression);
+		}
+
 		#endregion
 
 		#region Query Expressions

ICSharpCode.Decompiler/CSharp/Syntax/DepthFirstAstVisitor.cs

@@ -691,6 +691,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		{
 			VisitChildren(placeholder);
 		}
+
+		public virtual void VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression)
+		{
+			VisitChildren(withInitializerExpression);
+		}
 	}
 
 	/// <summary>
@@ -1359,6 +1364,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		{
 			return VisitChildren(placeholder);
 		}
+
+		public virtual T VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression)
+		{
+			return VisitChildren(withInitializerExpression);
+		}
 	}
 
 	/// <summary>
@@ -2027,5 +2037,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		{
 			return VisitChildren(placeholder, data);
 		}
+
+		public virtual S VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression, T data)
+		{
+			return VisitChildren(withInitializerExpression, data);
+		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/WithInitializerExpression.cs

@@ -0,0 +1,67 @@
+// Copyright (c) 2010-2021 AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using ICSharpCode.Decompiler.CSharp.Syntax.PatternMatching;
+
+namespace ICSharpCode.Decompiler.CSharp.Syntax
+{
+	/// <summary>
+	/// Expression with Initializer
+	/// </summary>
+	public class WithInitializerExpression : Expression
+	{
+		public readonly static TokenRole WithKeywordRole = new TokenRole("with");
+		public readonly static Role<ArrayInitializerExpression> InitializerRole = ArrayCreateExpression.InitializerRole;
+
+		public Expression Expression {
+			get { return GetChildByRole(Roles.Expression); }
+			set { SetChildByRole(Roles.Expression, value); }
+		}
+
+		public CSharpTokenNode WithToken {
+			get { return GetChildByRole(WithKeywordRole); }
+		}
+
+		public ArrayInitializerExpression Initializer {
+			get { return GetChildByRole(InitializerRole); }
+			set { SetChildByRole(InitializerRole, value); }
+		}
+
+		public override void AcceptVisitor(IAstVisitor visitor)
+		{
+			visitor.VisitWithInitializerExpression(this);
+		}
+
+		public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
+		{
+			return visitor.VisitWithInitializerExpression(this);
+		}
+
+		public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
+		{
+			return visitor.VisitWithInitializerExpression(this, data);
+		}
+
+		protected internal override bool DoMatch(AstNode other, Match match)
+		{
+			return other is WithInitializerExpression o
+				&& this.Expression.DoMatch(o.Expression, match)
+				&& this.Initializer.DoMatch(o.Initializer, match);
+		}
+	}
+}

ICSharpCode.Decompiler/CSharp/Syntax/IAstVisitor.cs

@@ -63,6 +63,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		void VisitUnaryOperatorExpression(UnaryOperatorExpression unaryOperatorExpression);
 		void VisitUncheckedExpression(UncheckedExpression uncheckedExpression);
 		void VisitUndocumentedExpression(UndocumentedExpression undocumentedExpression);
+		void VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression);
 
 		void VisitQueryExpression(QueryExpression queryExpression);
 		void VisitQueryContinuationClause(QueryContinuationClause queryContinuationClause);
@@ -209,6 +210,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		S VisitUnaryOperatorExpression(UnaryOperatorExpression unaryOperatorExpression);
 		S VisitUncheckedExpression(UncheckedExpression uncheckedExpression);
 		S VisitUndocumentedExpression(UndocumentedExpression undocumentedExpression);
+		S VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression);
 
 		S VisitQueryExpression(QueryExpression queryExpression);
 		S VisitQueryContinuationClause(QueryContinuationClause queryContinuationClause);
@@ -355,6 +357,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		S VisitUnaryOperatorExpression(UnaryOperatorExpression unaryOperatorExpression, T data);
 		S VisitUncheckedExpression(UncheckedExpression uncheckedExpression, T data);
 		S VisitUndocumentedExpression(UndocumentedExpression undocumentedExpression, T data);
+		S VisitWithInitializerExpression(WithInitializerExpression withInitializerExpression, T data);
 
 		S VisitQueryExpression(QueryExpression queryExpression, T data);
 		S VisitQueryContinuationClause(QueryContinuationClause queryContinuationClause, T data);

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -136,6 +136,7 @@ namespace ICSharpCode.Decompiler
 				functionPointers = false;
 				forEachWithGetEnumeratorExtension = false;
 				recordClasses = false;
+				withExpressions = false;
 			}
 		}
 
@@ -225,6 +226,24 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool withExpressions = true;
+
+		/// <summary>
+		/// Use C# 9 <c>with</c> initializer expressions.
+		/// </summary>
+		[Category("C# 9.0 / VS 2019.8")]
+		[Description("DecompilerSettings.WithExpressions")]
+		public bool WithExpressions {
+			get { return withExpressions; }
+			set {
+				if (withExpressions != value)
+				{
+					withExpressions = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool functionPointers = true;
 
 		/// <summary>

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -73,6 +73,7 @@
     <Compile Include="CSharp\ProjectDecompiler\TargetServices.cs" />
     <Compile Include="CSharp\Syntax\Expressions\DeclarationExpression.cs" />
     <Compile Include="CSharp\Syntax\Expressions\SwitchExpression.cs" />
+    <Compile Include="CSharp\Syntax\Expressions\WithInitializerExpression.cs" />
     <Compile Include="CSharp\Syntax\FunctionPointerAstType.cs" />
     <Compile Include="CSharp\Syntax\VariableDesignation.cs" />
     <Compile Include="Humanizer\Vocabularies.cs" />

ICSharpCode.Decompiler/IL/Instructions/Block.cs

@@ -158,7 +158,10 @@ namespace ICSharpCode.Decompiler.IL
 					IType type2 = null;
 					bool condition = Instructions[0].MatchStLoc(final2.Variable, out var init2);
 					Debug.Assert(condition);
-					Debug.Assert(init2 is NewObj || init2 is DefaultValue || (init2 is Block named && named.Kind == BlockKind.CallWithNamedArgs));
+					Debug.Assert(init2 is NewObj
+						|| init2 is DefaultValue
+						|| (init2 is CallInstruction ci && TransformCollectionAndObjectInitializers.IsRecordCloneMethodCall(ci))
+						|| (init2 is Block named && named.Kind == BlockKind.CallWithNamedArgs));
 					switch (init2)
 					{
 						case NewObj newObj:
@@ -454,5 +457,6 @@ namespace ICSharpCode.Decompiler.IL
 		/// <see cref="DeconstructInstruction"/>
 		/// </summary>
 		DeconstructionAssignments,
+		WithInitializer,
 	}
 }

ICSharpCode.Decompiler/IL/Transforms/TransformCollectionAndObjectInitializers.cs

@@ -54,13 +54,18 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		{
 			ILInstruction inst = body.Instructions[pos];
 			// Match stloc(v, newobj)
-			if (inst.MatchStLoc(out var v, out var initInst) && (v.Kind == VariableKind.Local || v.Kind == VariableKind.StackSlot))
-			{
+			if (!inst.MatchStLoc(out var v, out var initInst) || v.Kind != VariableKind.Local && v.Kind != VariableKind.StackSlot)
+				return false;
 			IType instType;
+			var blockKind = BlockKind.CollectionInitializer;
+			var insertionPos = initInst.ChildIndex;
+			var siblings = initInst.Parent.Children;
 			switch (initInst)
 			{
 				case NewObj newObjInst:
-						if (newObjInst.ILStackWasEmpty && v.Kind == VariableKind.Local && !context.Function.Method.IsConstructor && !context.Function.Method.IsCompilerGeneratedOrIsInCompilerGeneratedClass())
+					if (newObjInst.ILStackWasEmpty && v.Kind == VariableKind.Local
+						&& !context.Function.Method.IsConstructor
+						&& !context.Function.Method.IsCompilerGeneratedOrIsInCompilerGeneratedClass())
 					{
 						// on statement level (no other expressions on IL stack),
 						// prefer to keep local variables (but not stack slots),
@@ -70,9 +75,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					}
 					// Do not try to transform delegate construction.
 					// DelegateConstruction transform cannot deal with this.
-						if (DelegateConstruction.MatchDelegateConstruction(newObjInst, out _, out _, out _) || TransformDisplayClassUsage.IsPotentialClosure(context, newObjInst))
+					if (DelegateConstruction.MatchDelegateConstruction(newObjInst, out _, out _, out _)
+						|| TransformDisplayClassUsage.IsPotentialClosure(context, newObjInst))
 						return false;
-						// Cannot build a collection/object initializer attached to an AnonymousTypeCreateExpression:s 
+					// Cannot build a collection/object initializer attached to an AnonymousTypeCreateExpression
 					// anon = new { A = 5 } { 3,4,5 } is invalid syntax.
 					if (newObjInst.Method.DeclaringType.ContainsAnonymousType())
 						return false;
@@ -83,17 +89,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					{
 						// on statement level (no other expressions on IL stack),
 						// prefer to keep local variables (but not stack slots),
-							// unless we are in a constructor (where inlining object initializers might be critical
-							// for the base ctor call)
+						// unless we are in a constructor (where inlining object initializers might be 
+						// critical for the base ctor call)
 						return false;
 					}
 					instType = defaultVal.Type;
 					break;
+				case CallInstruction ci when context.Settings.WithExpressions && IsRecordCloneMethodCall(ci):
+					instType = ci.Method.DeclaringType;
+					blockKind = BlockKind.WithInitializer;
+					initInst = ci.Arguments.Single();
+					break;
 				default:
 					return false;
 			}
 			int initializerItemsCount = 0;
-				var blockKind = BlockKind.CollectionInitializer;
 			possibleIndexVariables = new Dictionary<ILVariable, (int Index, ILInstruction Value)>();
 			currentPath = new List<AccessPathElement>();
 			isCollection = false;
@@ -127,9 +137,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			context.Step("CollectionOrObjectInitializer", inst);
 			// Create a new block and final slot (initializer target variable)
 			var initializerBlock = new Block(blockKind);
-				ILVariable finalSlot = context.Function.RegisterVariable(VariableKind.InitializerTarget, v.Type);
+			ILVariable finalSlot = context.Function.RegisterVariable(VariableKind.InitializerTarget, instType);
 			initializerBlock.FinalInstruction = new LdLoc(finalSlot);
-				initializerBlock.Instructions.Add(new StLoc(finalSlot, initInst.Clone()));
+			initializerBlock.Instructions.Add(new StLoc(finalSlot, initInst));
 			// Move all instructions to the initializer block.
 			for (int i = 1; i <= initializerItemsCount; i++)
 			{
@@ -158,10 +168,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						break;
 				}
 			}
-				initInst.ReplaceWith(initializerBlock);
 			body.Instructions.RemoveRange(pos + 1, initializerItemsCount);
+			siblings[insertionPos] = initializerBlock;
 			ILInlining.InlineIfPossible(body, pos, context);
+			return true;
 		}
+
+		internal static bool IsRecordCloneMethodCall(CallInstruction ci)
+		{
+			if (ci.Method.DeclaringTypeDefinition?.IsRecord != true)
+				return false;
+			if (ci.Method.Name != "<Clone>$")
+				return false;
+			if (ci.Arguments.Count != 1)
+				return false;
+
 			return true;
 		}
 
@@ -234,6 +255,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						return false;
 					if (values.Count != 1 || !IsValidObjectInitializerTarget(currentPath))
 						return false;
+					if (blockKind != BlockKind.ObjectInitializer && blockKind != BlockKind.WithInitializer)
 						blockKind = BlockKind.ObjectInitializer;
 					return true;
 				default:

ILSpy/Languages/CSharpHighlightingTokenWriter.cs

@@ -171,6 +171,10 @@ namespace ICSharpCode.ILSpy
 				case "stackalloc":
 					color = typeKeywordsColor;
 					break;
+				case "with":
+					if (role == WithInitializerExpression.WithKeywordRole)
+						color = typeKeywordsColor;
+					break;
 				case "try":
 				case "throw":
 				case "catch":

ILSpy/Properties/Resources.Designer.cs

@@ -1334,6 +1334,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to &apos;with&apos; initializer expressions.
+        /// </summary>
+        public static string DecompilerSettings_WithExpressions {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.WithExpressions", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to The settings selected below are applied to the decompiler output in combination with the selection in the language drop-down. Selecting a lower language version in the drop-down will deactivate all selected options of the higher versions. Note that some settings implicitly depend on each other, e.g.: LINQ expressions cannot be introduced without first transforming static calls to extension method calls..
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -474,6 +474,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.VBSpecificOptions" xml:space="preserve">
     <value>VB-specific options</value>
   </data>
+  <data name="DecompilerSettings.WithExpressions" xml:space="preserve">
+    <value>'with' initializer expressions</value>
+  </data>
   <data name="DecompilerSettingsPanelLongText" xml:space="preserve">
     <value>The settings selected below are applied to the decompiler output in combination with the selection in the language drop-down. Selecting a lower language version in the drop-down will deactivate all selected options of the higher versions. Note that some settings implicitly depend on each other, e.g.: LINQ expressions cannot be introduced without first transforming static calls to extension method calls.</value>
   </data>