[bgen] Fix detecting NSObject types and generating block code with ty…

…pes that aren't NSObjects. (xamarin#21181)

src/bgen/Generator.cs

@@ -167,7 +167,22 @@ public bool IsNSObject (Type type)
 			return false;
 		}
 
-		return type.IsInterface;
+		// If any of the interfaces this type implements is an NSObject,
+		// then this type is also an NSObject
+		var ifaces = type.GetInterfaces ();
+		foreach (var iface in ifaces)
+			if (IsNSObject (iface))
+				return true;
+
+		if (type.IsInterface) {
+			var bta = ReflectionExtensions.GetBaseTypeAttribute (type, this);
+			if (bta?.BaseType is not null)
+				return IsNSObject (bta.BaseType);
+
+			return false;
+		}
+
+		return false;
 	}
 
 	public string PrimitiveType (Type t, bool formatted = false)
@@ -604,8 +619,10 @@ public TrampolineInfo MakeTrampoline (Type t)
 					invoke.AppendFormat (" Runtime.GetINativeObject<{1}> ({0}, false)!", safe_name, pi.ParameterType);
 				} else if (isForced) {
 					invoke.AppendFormat (" Runtime.GetINativeObject<{1}> ({0}, true, {2})!", safe_name, TypeManager.RenderType (pi.ParameterType), isForcedOwns);
-				} else {
+				} else if (IsNSObject (pi.ParameterType)) {
 					invoke.AppendFormat (" Runtime.GetNSObject<{1}> ({0})!", safe_name, TypeManager.RenderType (pi.ParameterType));
+				} else {
+					invoke.AppendFormat (" Runtime.GetINativeObject<{1}> ({0}, false)!", safe_name, TypeManager.RenderType (pi.ParameterType));
 				}
 				continue;
 			}

tests/generator/BGenTests.cs

@@ -404,6 +404,20 @@ public void Bug35176 ()
 			Assert.AreEqual (expectedAttributes, renderedAttributes, "Introduced attributes");
 		}
 
+		[Test]
+		[TestCase (Profile.iOS)]
+		public void INativeObjectsInBlocks (Profile profile)
+		{
+			var bgen = new BGenTool ();
+			bgen.Profile = profile;
+			bgen.Defines = BGenTool.GetDefaultDefines (bgen.Profile);
+			bgen.AddTestApiDefinition ("tests/inativeobjects-in-blocks.cs");
+			bgen.AddExtraSourcesRelativeToGeneratorDirectory ("tests/inativeobjects-in-blocks-sources.cs");
+			bgen.CreateTemporaryBinding ();
+			bgen.AssertExecute ("build");
+			bgen.AssertNoWarnings ();
+		}
+
 		[Test]
 		public void Bug36457 ()
 		{

tests/generator/BGenTool.cs

@@ -26,6 +26,7 @@ class BGenTool : Tool {
 
 		public List<string> ApiDefinitions = new List<string> ();
 		public List<string> Sources = new List<string> ();
+		public List<string> ExtraSources = new List<string> ();
 		public List<string> References = new List<string> ();
 #if NET
 		public List<string>? CompileCommand = null;
@@ -71,6 +72,16 @@ public void AddTestApiDefinition (string filename)
 			ApiDefinitions.Add (Path.Combine (Configuration.SourceRoot, "tests", "generator", filename));
 		}
 
+		public void AddExtraSourcesRelativeToGeneratorDirectory (string pathRelativeToGeneratorDirectory)
+		{
+			ExtraSources.Add (GetFullPathRelativeToGeneratorDirectory (pathRelativeToGeneratorDirectory));
+		}
+
+		public string GetFullPathRelativeToGeneratorDirectory (string pathRelativeToGeneratorDirectory)
+		{
+			return Path.Combine (Configuration.SourceRoot, "tests", "generator", pathRelativeToGeneratorDirectory);
+		}
+
 		public AssemblyDefinition ApiAssembly {
 			get {
 				return LoadAssembly ();
@@ -169,6 +180,9 @@ string [] BuildArgumentArray ()
 			foreach (var s in Sources)
 				sb.Add ($"-s={s}");
 
+			foreach (var x in ExtraSources)
+				sb.Add ($"-x={x}");
+
 			if (ReferenceBclByDefault) {
 				if (tf is null) {
 					// do nothing

tests/generator/tests/inativeobjects-in-blocks-sources.cs

@@ -0,0 +1,9 @@
+using System;
+
+using CoreFoundation;
+using Foundation;
+using ObjCRuntime;
+
+namespace NS {
+	public partial class DispatchData2 : NativeObject { }
+}

tests/generator/tests/inativeobjects-in-blocks.cs

@@ -0,0 +1,21 @@
+using System;
+
+using CoreFoundation;
+using Foundation;
+using ObjCRuntime;
+
+namespace NS {
+
+	[Partial]
+	interface DispatchData2 {
+	}
+
+	delegate void DispatchB (DispatchData2 data);
+	delegate void DispatchA (DispatchData2 data, [BlockCallback] DispatchB dispatch);
+
+	[BaseType (typeof (NSObject))]
+	interface INativeObjectInBlocks {
+		[Export ("someProperty")]
+		DispatchA SomeProperty { get; set; }
+	}
+}