[Tests] Fix cecil tests. (#12853)

-  Added the marshaling attr and a test to ensure it is ok.
- Fix the cecil MarshalAs test to not skip over types when checking.
    This revealed multiple tests failures that needed fixing.

fixes: https://github.com/xamarin/maccore/issues/2519

Co-authored-by: Rolf Bjarne Kvinge <rolf@xamarin.com>

src/CoreFoundation/CFString.cs

@@ -219,6 +219,7 @@ namespace CoreFoundation {
 		}
 
 		[DllImport (Constants.CoreFoundationLibrary, CharSet=CharSet.Unicode)]
+		[return: MarshalAs (UnmanagedType.U2)]
 		extern static char CFStringGetCharacterAtIndex (IntPtr handle, nint p);
 		
 		public char this [nint p] {

src/Foundation/NSObject2.cs

@@ -255,7 +255,7 @@ namespace Foundation {
 		extern static void RegisterToggleRef (NSObject obj, IntPtr handle, bool isCustomType);
 
 		[DllImport ("__Internal")]
-		static extern void xamarin_release_managed_ref (IntPtr handle, bool user_type);
+		static extern void xamarin_release_managed_ref (IntPtr handle, [MarshalAs (UnmanagedType.I1)] bool user_type);
 
 #if NET
 		static void RegisterToggleRefMonoVM (NSObject obj, IntPtr handle, bool isCustomType)
@@ -338,6 +338,7 @@ namespace Foundation {
 		}
 
 		[DllImport ("__Internal")]
+		[return: MarshalAs (UnmanagedType.I1)]
 		static extern bool xamarin_set_gchandle_with_flags_safe (IntPtr handle, IntPtr gchandle, XamarinGCHandleFlags flags);
 
 		void CreateManagedRef (bool retain)

src/GLKit/Defs.cs

@@ -147,6 +147,7 @@ namespace GLKit {
 	public struct GLKVertexAttributeParameters {
 		public uint Type;
 		public uint Size;
+		[MarshalAs (UnmanagedType.I1)]
 		public bool Normalized;
 
 #if !COREBUILD

src/GameController/GCExtendedGamepadSnapshot.cs

@@ -154,6 +154,7 @@ namespace GameController {
 		[SupportedOSPlatform ("tvos12.2")]
 		[SupportedOSPlatform ("macos10.14.4")]
 #endif
+		[MarshalAs (UnmanagedType.I1)]
 		public bool SupportsClickableThumbsticks;
 
 #if !NET
@@ -163,6 +164,7 @@ namespace GameController {
 		[SupportedOSPlatform ("tvos12.2")]
 		[SupportedOSPlatform ("macos10.14.4")]
 #endif
+		[MarshalAs (UnmanagedType.I1)]
 		bool LeftThumbstickButton;
 		
 #if !NET
@@ -172,6 +174,7 @@ namespace GameController {
 		[SupportedOSPlatform ("tvos12.2")]
 		[SupportedOSPlatform ("macos10.14.4")]
 #endif
+		[MarshalAs (UnmanagedType.I1)]
 		bool RightThumbstickButton;
 
 		[DllImport (Constants.GameControllerLibrary)]

src/HealthKit/HKAppleWalkingSteadiness.cs

@@ -19,6 +19,7 @@ namespace HealthKit {
 	{
 
 		[DllImport (Constants.HealthKitLibrary)]
+		[return: MarshalAs (UnmanagedType.I1)]
 		static extern bool HKAppleWalkingSteadinessClassificationForQuantity (HKQuantityRef value, out nint classificationOut, out NSErrorRef errorOut);
 
 		public static bool TryGetClassification (HKQuantity value, out HKAppleWalkingSteadinessClassification? classification, out NSError? error)

tests/cecil-tests/MarshalAsTest.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 
 using NUnit.Framework;
 
@@ -26,6 +27,7 @@ namespace Cecil.Tests {
 			var checkedTypes = new List<TypeReference> ();
 			foreach (var m in Helper.FilterMethods (assembly!, (m) => m.HasPInvokeInfo)) {
 				failures = null;
+				checkedTypes.Clear ();
 				if (!CheckMarshalAs (checkedTypes, m, ref failures)) {
 					failedMethods.Add ($"Found {failures!.Count} issues with {m.FullName}:\n\t{string.Join ("\n\t", failures)}");
 				}
@@ -86,6 +88,9 @@ namespace Cecil.Tests {
 			if (type.IsEnum)
 				return true;
 
+			if ((type.Attributes & TypeAttributes.ExplicitLayout) == TypeAttributes.ExplicitLayout)
+				return true;
+
 			foreach (var field in type.Fields) {
 				if (field.IsStatic)
 					continue;
@@ -100,7 +105,7 @@ namespace Cecil.Tests {
 
 		static string GetTypeName (TypeReference type)
 		{
-			return type.Name.ToLower ();
+			return type.Resolve ().FullName;
 		}
 
 		static bool IsDelegate (TypeReference tr)

tests/monotouch-test/CoreFoundation/StringTest.cs

@@ -31,5 +31,16 @@ namespace MonoTouchFixtures.CoreFoundation {
 		{
 			Assert.Throws<ArgumentNullException> (delegate { new CFString (null); }, "null");
 		}
+
+		[Test]
+		public void Index ()
+		{
+			var str = "Ab🤔日ㅁ名";
+			using var nativeStr = new CFString (str);
+			var array = str.ToCharArray ();
+			for (int i = 0; i < array.Length; i++) {
+				Assert.AreEqual (str[i], nativeStr[i], $"{str[i]} != {nativeStr[i]}");
+			}
+		}
 	}
 }