Improve NullPropagation (?.) when fields of value-type are involved.

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

@@ -25,6 +25,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		private class MyClass
 		{
 			public int IntVal;
+			public readonly int ReadonlyIntVal;
+			public MyStruct StructField;
+			public readonly MyStruct ReadonlyStructField;
 			public string Text;
 			public MyClass Field;
 			public MyClass Property {
@@ -45,6 +48,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		private struct MyStruct
 		{
 			public int IntVal;
+			public readonly int ReadonlyIntVal;
 			public MyClass Field;
 			public MyStruct? Property1 => null;
 			public MyStruct Property2 => default(MyStruct);
@@ -178,6 +182,16 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		{
 			Use(GetMyClass()?.Text ?? "Hello");
 		}
+		
+		public void CallOnValueTypeField()
+		{
+			Use(GetMyClass()?.IntVal.ToString());
+			Use(GetMyStruct()?.IntVal.ToString());
+			Use(GetMyClass()?.ReadonlyIntVal.ToString());
+			Use(GetMyStruct()?.ReadonlyIntVal.ToString());
+			GetMyClass()?.StructField.Done();
+			GetMyClass()?.ReadonlyStructField.Done();
+		}
 
 		public void InvokeDelegate(EventHandler eh)
 		{

ICSharpCode.Decompiler/IL/Transforms/NullPropagationTransform.cs

@@ -186,6 +186,12 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					return chainLength >= 1;
 				} else if (inst.MatchLdFld(out var target, out _)) {
 					inst = target;
+				} else if (inst.MatchLdFlda(out target, out var f)) {
+					if (target is AddressOf addressOf && f.DeclaringType.Kind == TypeKind.Struct) {
+						inst = addressOf.Value;
+					} else {
+						inst = target;
+					}
 				} else if (inst is CallInstruction call && call.OpCode != OpCode.NewObj) {
 					if (call.Arguments.Count == 0) {
 						return false;