Keep all fields on sequential/explicit layout classes if a field was kept (#1330)

Should fix the issue observed in CoreLib where `RawData` class is used with `Unsafe.As` to break type safety and linker stripped its fields because it's not seen as instantiated.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/Mono.Linker.Tests.Cases/Attributes.StructLayout/SequentialClass.cs b/test/Mono.Linker.Tests.Cases/Attributes.StructLayout/SequentialClass.cs
index fd92a3b6b..f0a4c0072 100644
--- a/test/Mono.Linker.Tests.Cases/Attributes.StructLayout/SequentialClass.cs
+++ b/test/Mono.Linker.Tests.Cases/Attributes.StructLayout/SequentialClass.cs
@@ -29,11 +29,25 @@ namespace Mono.Linker.Tests.Cases.Attributes.StructLayout
 		public int never_used;
 	}
 
+	[Kept]
+	[StructLayout (LayoutKind.Sequential)]
+	class UnallocatedButWithSingleFieldUsedSequentialClassData
+	{
+		[Kept]
+		public int never_used;
+
+		[Kept]
+		public int used;
+	}
+
 	public class SequentialClass
 	{
 		[Kept]
 		static UnallocatedSequentialClassData _field;
 
+		[Kept]
+		static UnallocatedButWithSingleFieldUsedSequentialClassData _otherField;
+
 		public static void Main ()
 		{
 			var c = new SequentialClassData ();
@@ -44,6 +58,10 @@ namespace Mono.Linker.Tests.Cases.Attributes.StructLayout
 			_field = null;
 
 			typeof (UnallocatedButReferencedWithReflectionSequentialClassData).ToString ();
+
+			if (string.Empty.Length > 0) {
+				_otherField.used = 123;
+			}
 		}
 	}
 }