Add missing DecompilerSettings for new language features

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -4575,7 +4575,7 @@ namespace ICSharpCode.Decompiler.CSharp
 						}
 						foreach (var subPattern in matchInstruction.SubPatterns)
 						{
-							if (!MatchInstruction.IsPatternMatch(subPattern, out var testedOperand))
+							if (!MatchInstruction.IsPatternMatch(subPattern, out var testedOperand, settings))
 							{
 								Debug.Fail("Invalid sub pattern");
 								continue;

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -130,6 +130,7 @@ namespace ICSharpCode.Decompiler
 				staticLocalFunctions = false;
 				ranges = false;
 				switchExpressions = false;
+				recursivePatternMatching = false;
 			}
 			if (languageVersion < CSharp.LanguageVersion.CSharp9_0)
 			{
@@ -141,6 +142,8 @@ namespace ICSharpCode.Decompiler
 				withExpressions = false;
 				usePrimaryConstructorSyntax = false;
 				covariantReturns = false;
+				relationalPatterns = false;
+				patternCombinators = false;
 			}
 			if (languageVersion < CSharp.LanguageVersion.CSharp10_0)
 			{
@@ -166,10 +169,11 @@ namespace ICSharpCode.Decompiler
 			if (fileScopedNamespaces || recordStructs)
 				return CSharp.LanguageVersion.CSharp10_0;
 			if (nativeIntegers || initAccessors || functionPointers || forEachWithGetEnumeratorExtension
-				|| recordClasses || withExpressions || usePrimaryConstructorSyntax || covariantReturns)
+				|| recordClasses || withExpressions || usePrimaryConstructorSyntax || covariantReturns
+				|| relationalPatterns || patternCombinators)
 				return CSharp.LanguageVersion.CSharp9_0;
 			if (nullableReferenceTypes || readOnlyMethods || asyncEnumerator || asyncUsingAndForEachStatement
-				|| staticLocalFunctions || ranges || switchExpressions)
+				|| staticLocalFunctions || ranges || switchExpressions || recursivePatternMatching)
 				return CSharp.LanguageVersion.CSharp8_0;
 			if (introduceUnmanagedConstraint || tupleComparisons || stackAllocInitializers
 				|| patternBasedFixedStatement)
@@ -1678,6 +1682,60 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool recursivePatternMatching = true;
+
+		/// <summary>
+		/// Gets/Sets whether C# 8.0 recursive patterns should be detected.
+		/// </summary>
+		[Category("C# 8.0 / VS 2019")]
+		[Description("DecompilerSettings.RecursivePatternMatching")]
+		public bool RecursivePatternMatching {
+			get { return recursivePatternMatching; }
+			set {
+				if (recursivePatternMatching != value)
+				{
+					recursivePatternMatching = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
+		bool patternCombinators = true;
+
+		/// <summary>
+		/// Gets/Sets whether C# 9.0 and, or, not patterns should be detected.
+		/// </summary>
+		[Category("C# 9.0 / VS 2019.8")]
+		[Description("DecompilerSettings.PatternCombinators")]
+		public bool PatternCombinators {
+			get { return patternCombinators; }
+			set {
+				if (patternCombinators != value)
+				{
+					patternCombinators = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
+		bool relationalPatterns = true;
+
+		/// <summary>
+		/// Gets/Sets whether C# 9.0 relational patterns should be detected.
+		/// </summary>
+		[Category("C# 9.0 / VS 2019.8")]
+		[Description("DecompilerSettings.RelationalPatterns")]
+		public bool RelationalPatterns {
+			get { return relationalPatterns; }
+			set {
+				if (relationalPatterns != value)
+				{
+					relationalPatterns = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool staticLocalFunctions = true;
 
 		/// <summary>

ICSharpCode.Decompiler/IL/Instructions/MatchInstruction.cs

@@ -119,7 +119,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// (even if the pattern fails to match!).
 		/// The pattern matching instruction evaluates to 1 (as I4) if the pattern matches, or 0 otherwise.
 		/// </summary>
-		public static bool IsPatternMatch(ILInstruction? inst, [NotNullWhen(true)] out ILInstruction? testedOperand)
+		public static bool IsPatternMatch(ILInstruction? inst, [NotNullWhen(true)] out ILInstruction? testedOperand, DecompilerSettings? settings)
 		{
 			switch (inst)
 			{
@@ -127,13 +127,23 @@ namespace ICSharpCode.Decompiler.IL
 					testedOperand = m.testedOperand;
 					return true;
 				case Comp comp:
-					if (comp.MatchLogicNot(out var operand) && IsPatternMatch(operand, out testedOperand))
+					if (comp.MatchLogicNot(out var operand) && IsPatternMatch(operand, out testedOperand, settings))
 					{
-						return true;
+						return settings?.PatternCombinators ?? true;
 					}
 					else
 					{
 						testedOperand = comp.Left;
+						if (!(settings?.RelationalPatterns ?? true))
+						{
+							if (comp.Kind is not (ComparisonKind.Equality or ComparisonKind.Inequality))
+								return false;
+						}
+						if (!(settings?.PatternCombinators ?? true))
+						{
+							if (comp.Kind is ComparisonKind.Inequality)
+								return false;
+						}
 						return IsConstant(comp.Right);
 					}
 				case Call call when IsCallToString_op_Equality(call):
@@ -201,7 +211,7 @@ namespace ICSharpCode.Decompiler.IL
 			Debug.Assert(SubPatterns.Count >= NumPositionalPatterns);
 			foreach (var subPattern in SubPatterns)
 			{
-				if (!IsPatternMatch(subPattern, out ILInstruction? operand))
+				if (!IsPatternMatch(subPattern, out ILInstruction? operand, null))
 					throw new InvalidOperationException("Sub-Pattern must be a valid pattern");
 				// the first child is TestedOperand
 				int subPatternIndex = subPattern.ChildIndex - 1;

ICSharpCode.Decompiler/IL/Transforms/ExpressionTransforms.cs

@@ -557,7 +557,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					return;
 				}
 			}
-			if (MatchInstruction.IsPatternMatch(inst.Condition, out _)
+			if (MatchInstruction.IsPatternMatch(inst.Condition, out _, context.Settings)
 				&& inst.TrueInst.MatchLdcI4(1) && inst.FalseInst.MatchLdcI4(0))
 			{
 				context.Step("match(x) ? true : false -> match(x)", inst);

ICSharpCode.Decompiler/IL/Transforms/PatternMatchingTransform.cs

@@ -189,6 +189,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		private static ILInstruction DetectPropertySubPatterns(MatchInstruction parentPattern, ILInstruction trueInst,
 			ILInstruction parentFalseInst, BlockContainer container, ILTransformContext context, ref ControlFlowGraph? cfg)
 		{
+			if (!context.Settings.RecursivePatternMatching)
+			{
+				return trueInst;
+			}
 			while (true)
 			{
 				Block? trueBlock = trueInst as Block;
@@ -230,7 +234,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					ExtensionMethods.Swap(ref trueInst, ref falseInst);
 					negate = true;
 				}
-				if (MatchInstruction.IsPatternMatch(condition, out var operand))
+				if (MatchInstruction.IsPatternMatch(condition, out var operand, context.Settings))
 				{
 					if (!PropertyOrFieldAccess(operand, out var target, out _))
 					{
@@ -240,6 +244,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					{
 						return null;
 					}
+					if (negate && !context.Settings.PatternCombinators)
+					{
+						return null;
+					}
 					context.Step("Move property sub pattern", condition);
 					if (negate)
 					{
@@ -253,8 +261,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					{
 						return null;
 					}
-					context.Step("Move property sub pattern", condition);
-					parentPattern.SubPatterns.Add(new Comp(negate ? ComparisonKind.Equality : ComparisonKind.Inequality, Sign.None, condition, new LdcI4(0)));
+					if (!negate && !context.Settings.PatternCombinators)
+					{
+						return null;
+					}
+					context.Step("Sub pattern: implicit != 0", condition);
+					parentPattern.SubPatterns.Add(new Comp(negate ? ComparisonKind.Equality : ComparisonKind.Inequality,
+						Sign.None, condition, new LdcI4(0)));
 				}
 				else
 				{
@@ -376,7 +389,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				}
 				return null;
 			}
-			if (varPattern.Variable.AddressCount == 1)
+			if (varPattern.Variable.AddressCount == 1 && context.Settings.PatternCombinators)
 			{
 				context.Step("Nullable.HasValue check -> not null pattern", block);
 				varPattern.ReplaceWith(new Comp(ComparisonKind.Inequality, ComparisonLiftingKind.CSharp, StackType.O, Sign.None, varPattern.TestedOperand, new LdNull()));
@@ -412,6 +425,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				{
 					return null;
 				}
+				if (!(context.Settings.RelationalPatterns || comp.Kind is ComparisonKind.Equality or ComparisonKind.Inequality))
+				{
+					return null;
+				}
 				bool negated = false;
 				if (!DetectExitPoints.CompatibleExitInstruction(falseInst, parentFalseInst))
 				{
@@ -426,6 +443,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				{
 					return null;
 				}
+				if (negated && !context.Settings.PatternCombinators)
+				{
+					return null;
+				}
 				context.Step("Nullable.HasValue check + Nullable.GetValueOrDefault pattern", block);
 				// varPattern: match (v = testedOperand)
 				// comp: comp.i4(call GetValueOrDefault(ldloca v) != ldc.i4 42)

ILSpy/Properties/Resources.Designer.cs

@@ -1145,6 +1145,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Pattern combinators (and, or, not).
+        /// </summary>
+        public static string DecompilerSettings_PatternCombinators {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.PatternCombinators", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Use pattern matching expressions.
         /// </summary>
@@ -1199,6 +1208,24 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Recursive pattern matching.
+        /// </summary>
+        public static string DecompilerSettings_RecursivePatternMatching {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.RecursivePatternMatching", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to Relational patterns.
+        /// </summary>
+        public static string DecompilerSettings_RelationalPatterns {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.RelationalPatterns", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Remove dead and side effect free code (use with caution!).
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -405,6 +405,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.ParameterNullCheck" xml:space="preserve">
     <value>Use parameter null checking</value>
   </data>
+  <data name="DecompilerSettings.PatternCombinators" xml:space="preserve">
+    <value>Pattern combinators (and, or, not)</value>
+  </data>
   <data name="DecompilerSettings.PatternMatching" xml:space="preserve">
     <value>Use pattern matching expressions</value>
   </data>
@@ -423,6 +426,12 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.RecordStructs" xml:space="preserve">
     <value>Record structs</value>
   </data>
+  <data name="DecompilerSettings.RecursivePatternMatching" xml:space="preserve">
+    <value>Recursive pattern matching</value>
+  </data>
+  <data name="DecompilerSettings.RelationalPatterns" xml:space="preserve">
+    <value>Relational patterns</value>
+  </data>
   <data name="DecompilerSettings.RemoveDeadAndSideEffectFreeCodeUseWithCaution" xml:space="preserve">
     <value>Remove dead and side effect free code (use with caution!)</value>
   </data>