Use "record" instead of "class" for C# 9 record class types.

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -18,14 +18,11 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection.Metadata;
-using System.Reflection.Metadata.Ecma335;
 using System.Reflection.PortableExecutable;
-using System.Runtime.InteropServices;
 using System.Threading;
 
 using ICSharpCode.Decompiler.CSharp.OutputVisitor;
@@ -415,6 +412,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			typeSystemAstBuilder.AddResolveResultAnnotations = true;
 			typeSystemAstBuilder.UseNullableSpecifierForValueTypes = settings.LiftNullables;
 			typeSystemAstBuilder.SupportInitAccessors = settings.InitAccessors;
+			typeSystemAstBuilder.SupportRecordClasses = settings.RecordClasses;
 			return typeSystemAstBuilder;
 		}
 

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpAmbience.cs

@@ -80,6 +80,9 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 						case ClassType.Enum:
 							writer.WriteKeyword(Roles.EnumKeyword, "enum");
 							break;
+						case ClassType.RecordClass:
+							writer.WriteKeyword(Roles.RecordKeyword, "record");
+							break;
 						default:
 							throw new Exception("Invalid value for ClassType");
 					}

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1480,6 +1480,10 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 					WriteKeyword(Roles.StructKeyword);
 					braceStyle = policy.StructBraceStyle;
 					break;
+				case ClassType.RecordClass:
+					WriteKeyword(Roles.RecordKeyword);
+					braceStyle = policy.ClassBraceStyle;
+					break;
 				default:
 					WriteKeyword(Roles.ClassKeyword);
 					braceStyle = policy.ClassBraceStyle;

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/TypeDeclaration.cs

@@ -33,7 +33,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		Class,
 		Struct,
 		Interface,
-		Enum
+		Enum,
+		/// <summary>
+		/// C# 9 'record'
+		/// </summary>
+		RecordClass,
 	}
 
 	/// <summary>
@@ -63,6 +67,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 						return GetChildByRole(Roles.InterfaceKeyword);
 					case ClassType.Enum:
 						return GetChildByRole(Roles.EnumKeyword);
+					case ClassType.RecordClass:
+						return GetChildByRole(Roles.RecordKeyword);
 					default:
 						return CSharpTokenNode.Null;
 				}

ICSharpCode.Decompiler/CSharp/Syntax/Roles.cs

@@ -87,7 +87,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole InterfaceKeyword = new TokenRole("interface");
 		public static readonly TokenRole StructKeyword = new TokenRole("struct");
 		public static readonly TokenRole ClassKeyword = new TokenRole("class");
+		public static readonly TokenRole RecordKeyword = new TokenRole("record");
 
 	}
 }
-

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -213,6 +213,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		/// If disabled, emits "set /*init*/;" instead.
 		/// </summary>
 		public bool SupportInitAccessors { get; set; }
+
+		/// <summary>
+		/// Controls whether C# 9 "record" class types are supported.
+		/// </summary>
+		public bool SupportRecordClasses { get; set; }
 		#endregion
 
 		#region Convert Type
@@ -1744,6 +1749,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 					}
 				default:
 					classType = ClassType.Class;
+					if (SupportRecordClasses && typeDefinition.IsRecord)
+					{
+						classType = ClassType.RecordClass;
+					}
 					break;
 			}
 

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -135,12 +135,13 @@ namespace ICSharpCode.Decompiler
 				initAccessors = false;
 				functionPointers = false;
 				forEachWithGetEnumeratorExtension = false;
+				recordClasses = false;
 			}
 		}
 
 		public CSharp.LanguageVersion GetMinimumRequiredVersion()
 		{
-			if (nativeIntegers || initAccessors || functionPointers || forEachWithGetEnumeratorExtension)
+			if (nativeIntegers || initAccessors || functionPointers || forEachWithGetEnumeratorExtension || recordClasses)
 				return CSharp.LanguageVersion.Preview;
 			if (nullableReferenceTypes || readOnlyMethods || asyncEnumerator || asyncUsingAndForEachStatement
 				|| staticLocalFunctions || ranges || switchExpressions)
@@ -206,6 +207,24 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool recordClasses = true;
+
+		/// <summary>
+		/// Use C# 9 <c>init;</c> property accessors.
+		/// </summary>
+		[Category("C# 9.0 (experimental)")]
+		[Description("DecompilerSettings.RecordClasses")]
+		public bool RecordClasses {
+			get { return recordClasses; }
+			set {
+				if (recordClasses != value)
+				{
+					recordClasses = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool functionPointers = true;
 
 		/// <summary>

ICSharpCode.Decompiler/TypeSystem/ITypeDefinition.cs

@@ -73,5 +73,10 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// This serves as default nullability for members of the type that do not have a [Nullable] attribute.
 		/// </summary>
 		Nullability NullableContext { get; }
+
+		/// <summary>
+		/// Gets whether the type has the necessary members to be considered a C# 9 record type.
+		/// </summary>
+		bool IsRecord { get; }
 	}
 }

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeDefinition.cs

@@ -24,11 +24,8 @@ using System.Reflection;
 using System.Reflection.Metadata;
 using System.Reflection.Metadata.Ecma335;
 using System.Runtime.InteropServices;
-using System.Text;
-using System.Threading;
 
 using ICSharpCode.Decompiler.Metadata;
-using ICSharpCode.Decompiler.Semantics;
 using ICSharpCode.Decompiler.Util;
 
 namespace ICSharpCode.Decompiler.TypeSystem.Implementation
@@ -738,5 +735,38 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 			return false;
 		}
 		#endregion
+
+		#region IsRecord
+		byte isRecord = ThreeState.Unknown;
+
+		public bool IsRecord {
+			get {
+				if (isRecord == ThreeState.Unknown)
+				{
+					isRecord = ThreeState.From(ComputeIsRecord());
+				}
+				return isRecord == ThreeState.True;
+			}
+		}
+
+		private bool ComputeIsRecord()
+		{
+			if (Kind != TypeKind.Class)
+				return false;
+			var metadata = module.metadata;
+			var typeDef = metadata.GetTypeDefinition(handle);
+			bool opEquality = false;
+			bool opInequality = false;
+			bool clone = false;
+			foreach (var methodHandle in typeDef.GetMethods())
+			{
+				var method = metadata.GetMethodDefinition(methodHandle);
+				opEquality |= metadata.StringComparer.Equals(method.Name, "op_Equality");
+				opInequality |= metadata.StringComparer.Equals(method.Name, "op_Inequality");
+				clone |= metadata.StringComparer.Equals(method.Name, "<Clone>$");
+			}
+			return opEquality & opInequality & clone;
+		}
+		#endregion
 	}
 }

ICSharpCode.Decompiler/TypeSystem/Implementation/MinimalCorlib.cs

@@ -302,6 +302,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				return EmptyList<IProperty>.Instance;
 			}
 
+			bool ITypeDefinition.IsRecord => false;
+
 			ITypeDefinition IType.GetDefinition() => this;
 			TypeParameterSubstitution IType.GetSubstitution() => TypeParameterSubstitution.Identity;
 

ILSpy/Languages/CSharpHighlightingTokenWriter.cs

@@ -16,7 +16,6 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -228,6 +227,7 @@ namespace ICSharpCode.ILSpy
 				case "class":
 				case "interface":
 				case "delegate":
+				case "record":
 					color = referenceTypeKeywordsColor;
 					break;
 				case "select":

ILSpy/Properties/Resources.Designer.cs

@@ -1064,6 +1064,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Records.
+        /// </summary>
+        public static string DecompilerSettings_RecordClasses {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.RecordClasses", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Remove dead and side effect free code (use with caution!).
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -384,6 +384,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.ReadOnlyMethods" xml:space="preserve">
     <value>Read-only methods</value>
   </data>
+  <data name="DecompilerSettings.RecordClasses" xml:space="preserve">
+    <value>Records</value>
+  </data>
   <data name="DecompilerSettings.RemoveDeadAndSideEffectFreeCodeUseWithCaution" xml:space="preserve">
     <value>Remove dead and side effect free code (use with caution!)</value>
   </data>