Added another case in the switch block to handle the object returned by Mono which differs from the object returned by CoreCLR

src/libraries/System.Private.CoreLib/src/System/Reflection/NullabilityInfoContext.cs

@@ -657,6 +657,11 @@ public bool ParseNullableState(int index, ref NullabilityState state)
                         when index < args.Count && args[index].Value is byte elementB:
                         state = TranslateByte(elementB);
                         return true;
+#if MONO
+                    case byte[] ba when index < ba.Length:
+                        state = TranslateByte(ba[index]);
+                        return true;
+#endif
                     default:
                         return false;
                 }

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/NullabilityInfoContextTests.cs

@@ -50,6 +50,57 @@ public void FieldTest(string fieldName, NullabilityState readState, NullabilityS
             Assert.Null(nullability.ElementType);
         }
 
+        public class FI_FieldArray
+        {
+            public int[] intArray;
+            public object?[] objectArray;
+            public string?[] stringArray;
+        }
+
+        public class FI_GenericClassField<T>
+        {
+            public object?[] objectArray;
+            public T? genparamField;
+            public T?[] gparrayField;
+        }
+
+        public static IEnumerable<object[]> FieldArrayTestData()
+        {
+            yield return new object[] { "objectArray", NullabilityState.NotNull, NullabilityState.NotNull, typeof(object[]) };
+            yield return new object[] { "stringArray", NullabilityState.NotNull, NullabilityState.NotNull, typeof(string[]) };
+        }
+
+        [Theory]
+        [MemberData(nameof(FieldArrayTestData))]
+        public void FieldArrayTest(string fieldName, NullabilityState readState, NullabilityState writeState, Type type)
+        {
+            FieldInfo field = typeof(FI_FieldArray).GetField(fieldName, flags);
+            NullabilityInfo nullability = nullabilityContext.Create(field);
+            Assert.Equal(readState, nullability.ReadState);
+            Assert.Equal(writeState, nullability.WriteState);
+            Assert.Equal(type, nullability.Type);
+            Assert.Empty(nullability.GenericTypeArguments);
+        }
+
+        public static IEnumerable<object[]> GenericArrayFieldTypeTestData()
+        {
+            yield return new object[] { "objectArray", NullabilityState.NotNull, NullabilityState.NotNull, typeof(object[]) };
+            yield return new object[] { "genparamField", NullabilityState.NotNull, NullabilityState.NotNull, typeof(int) };
+            yield return new object[] { "gparrayField", NullabilityState.NotNull, NullabilityState.NotNull, typeof(int[]) };
+        }
+
+        [Theory]
+        [MemberData(nameof(GenericArrayFieldTypeTestData))]
+        public void GenericArrayFieldTypeTest(string fieldName, NullabilityState readState, NullabilityState writeState, Type type)
+        {
+            FieldInfo field = typeof(FI_GenericClassField<int>).GetField(fieldName, flags)!;
+            NullabilityInfo nullability = nullabilityContext.Create(field);
+            Assert.Equal(readState, nullability.ReadState);
+            Assert.Equal(writeState, nullability.WriteState);
+            Assert.Equal(type, nullability.Type);
+            Assert.Empty(nullability.GenericTypeArguments);
+        }
+
         public static IEnumerable<object[]> EventTestData()
         {
             yield return new object[] { "EventNullable", NullabilityState.Nullable, NullabilityState.Nullable, typeof(EventHandler) };