Add comments for fields order

Author: buyaa-n

src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/SymbolType.cs

@@ -19,9 +19,12 @@ internal enum TypeKind
     internal sealed partial class SymbolType : TypeInfo
     {
         #region Data Members
+        #region Fields need to be kept in order
+        // For Mono runtime its important to keep this declaration order in sync with MonoReflectionSymbolType struct in object-internals.h
         internal Type _baseType = null!;
         internal TypeKind _typeKind;
         internal int _rank;        // count of dimension
+        #endregion
         // If LowerBound and UpperBound is equal, that means one element.
         // If UpperBound is less than LowerBound, then the size is not specified.
         internal int[] _iaLowerBound;

src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.cs

@@ -13,8 +13,11 @@ namespace System.Reflection.Emit
      */
     internal sealed partial class TypeBuilderInstantiation : TypeInfo
     {
+        #region Fields need to be kept in order
+        // For Mono runtime its important to keep this declaration order in sync with MonoReflectionGenericClass struct in object-internals.h
         private Type _genericType;
         private Type[] _typeArguments;
+        #endregion
         private string? _strFullQualName;
         internal Hashtable _hashtable;
 

src/libraries/System.Reflection.Emit/tests/MethodBuilder/MethodBuilderGetILGenerator.cs

@@ -121,7 +121,8 @@ public void LoadArrayTypeInILGeneratedMethod()
             Assert.Equal("TestType[]", createdMethod.Invoke(null, null));
         }
 
-        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotMonoRuntime))]
+        [Fact]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/82257", TestRuntimes.Mono)]
         public void LoadByRefTypeInILGeneratedMethod()
         {
             TypeBuilder type = Helpers.DynamicType(TypeAttributes.Public);

src/mono/System.Private.CoreLib/src/System/Reflection/Emit/SymbolType.Mono.cs

@@ -37,7 +37,7 @@ namespace System.Reflection.Emit
     [StructLayout(LayoutKind.Sequential)]
     internal partial class SymbolType
     {
-        // _baseType, _typeKind and _rank fields defined in shared SymbolType should kept in sync with MonoReflectionSymbolType in object-internals.h
+        // Sequence of _baseType, _typeKind and _rank fields should kept in sync with MonoReflectionSymbolType in object-internals.h
 
         internal override Type InternalResolve()
         {

src/mono/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.Mono.cs

@@ -42,7 +42,7 @@ namespace System.Reflection.Emit
     [StructLayout(LayoutKind.Sequential)]
     internal partial class TypeBuilderInstantiation
     {
-        // _genericType and _typeArguments fields defined in shared TypeBuilderInstantiation should kept in sync with MonoReflectionGenericClass in object-internals.h
+        //  Sequence of _genericType and _typeArguments fields should kept in sync with MonoReflectionGenericClass in object-internals.h
 
         [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2055:UnrecognizedReflectionPattern",
             Justification = "Reflection.Emit is not subject to trimming")]