Records: Support new EqualityContract pattern.

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -518,7 +518,7 @@ namespace ICSharpCode.Decompiler.Tests
 		}
 
 		[Test]
-		public async Task Records([ValueSource(nameof(roslynLatestOnlyOptions))] CompilerOptions cscOptions)
+		public async Task Records([ValueSource(nameof(roslyn3OrNewerOptions))] CompilerOptions cscOptions)
 		{
 			await RunForLibrary(cscOptions: cscOptions | CompilerOptions.NullableEnable);
 		}

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

@@ -1,5 +1,7 @@
 using System;
+#if ROSLYN4
 using System.Runtime.InteropServices;
+#endif
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 {
@@ -127,6 +129,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		}
 
 	}
+#if ROSLYN4
 	internal class RecordStructs
 	{
 		public record struct Base(string A);
@@ -227,6 +230,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 		}
 	}
+#endif
 }
 namespace System.Runtime.CompilerServices
 {

ICSharpCode.Decompiler/CSharp/RecordDecompiler.cs

@@ -445,11 +445,23 @@ namespace ICSharpCode.Decompiler.CSharp
 			var getter = property.Getter;
 			if (!(getter != null && !property.CanSet))
 				return false;
-			if (property.GetAttributes().Any())
+			var attrs = property.GetAttributes().ToList();
-				return false;
+			switch (attrs.Count)
+			{
+				case 0:
+					// Roslyn 3.x does not emit a CompilerGeneratedAttribute on the property itself.
+					break;
+				case 1:
+					// Roslyn 4.4 started doing so.
+					if (!attrs[0].AttributeType.IsKnownType(KnownAttribute.CompilerGenerated))
+						return false;
+					break;
+				default:
+					return false;
+			}
 			if (getter.GetReturnTypeAttributes().Any())
 				return false;
-			var attrs = getter.GetAttributes().ToList();
+			attrs = getter.GetAttributes().ToList();
 			if (attrs.Count != 1)
 				return false;
 			if (!attrs[0].AttributeType.IsKnownType(KnownAttribute.CompilerGenerated))