[nativeaot] fix typemap logic involving duplicates

This is WIP.

The bug I'm seeing now is `Java.Interop.JavaObject` is in the typemap
in favor of `Java.Lang.Object`.

There was also some missing logic regarding `*Invoker` types and
abstract types.

The new test assertion can verify the entire typemap, so we should
assert a couple types are in there.

Author: jonathanpeppers

src/Microsoft.Android.Sdk.ILLink/TypeMappingStep.cs

@@ -16,7 +16,7 @@ public class TypeMappingStep : BaseStep
 {
 	const string AssemblyName = "Microsoft.Android.Runtime.NativeAOT";
 	const string TypeName = "Microsoft.Android.Runtime.NativeAotTypeManager";
-	readonly IDictionary<string, TypeDefinition> TypeMappings = new Dictionary<string, TypeDefinition> (StringComparer.Ordinal);
+	readonly IDictionary<string, List<TypeDefinition>> TypeMappings = new Dictionary<string, List<TypeDefinition>> (StringComparer.Ordinal);
 	AssemblyDefinition? MicrosoftAndroidRuntimeNativeAot;
 
 	protected override void ProcessAssembly (AssemblyDefinition assembly)
@@ -66,7 +66,7 @@ protected override void EndProcess ()
 		var il = method.Body.GetILProcessor ();
 		var addMethod = module.ImportReference (typeof (IDictionary<string, Type>).GetMethod ("Add"));
 		var getTypeFromHandle = module.ImportReference (typeof (Type).GetMethod ("GetTypeFromHandle"));
-		foreach (var (javaKey, typeDefinition) in TypeMappings) {
+		foreach (var (javaName, list) in TypeMappings) {
 			/*
 			 * IL_0000: ldarg.0
 			 * IL_0001: ldfld class [System.Runtime]System.Collections.Generic.IDictionary`2<string, class [System.Runtime]System.Type> Microsoft.Android.Runtime.NativeAotTypeManager::TypeMappings
@@ -77,22 +77,47 @@ protected override void EndProcess ()
 			 */
 			il.Emit (Mono.Cecil.Cil.OpCodes.Ldarg_0);
 			il.Emit (Mono.Cecil.Cil.OpCodes.Ldfld, field);
-			il.Emit (Mono.Cecil.Cil.OpCodes.Ldstr, javaKey);
-			il.Emit (Mono.Cecil.Cil.OpCodes.Ldtoken, module.ImportReference (typeDefinition));
+			il.Emit (Mono.Cecil.Cil.OpCodes.Ldstr, javaName);
+			il.Emit (Mono.Cecil.Cil.OpCodes.Ldtoken, module.ImportReference (SelectTypeDefinition (javaName, list)));
 			il.Emit (Mono.Cecil.Cil.OpCodes.Call, getTypeFromHandle);
 			il.Emit (Mono.Cecil.Cil.OpCodes.Callvirt, addMethod);
 		}
 
 		il.Emit (Mono.Cecil.Cil.OpCodes.Ret);
 	}
 
+	TypeDefinition SelectTypeDefinition (string javaName, List<TypeDefinition> list)
+	{
+		if (list.Count == 1)
+			return list[0];
+
+		var best = list[0];
+		foreach (var type in list) {
+			if (type == best)
+				continue;
+			if ((type.IsAbstract || type.IsInterface) &&
+					!best.IsAbstract &&
+					!best.IsInterface &&
+					type.IsAssignableFrom (best, Context)) {
+				best = type;
+			}
+		}
+		foreach (var type in list) {
+			if (type == best)
+				continue;
+			Context.LogMessage ($"Duplicate typemap entry for {javaName} => {type.FullName}");
+		}
+		return best;
+	}
+
 	void ProcessType (AssemblyDefinition assembly, TypeDefinition type)
 	{
 		if (type.HasJavaPeer (Context)) {
 			var javaName = JavaNativeTypeManager.ToJniName (type, Context);
-			if (!TypeMappings.TryAdd (javaName, type)) {
-				Context.LogMessage ($"Duplicate typemap entry for {javaName}");
+			if (!TypeMappings.TryGetValue (javaName, out var list)) {
+				TypeMappings.Add (javaName, list = new List<TypeDefinition> ());
 			}
+			list.Add (type);
 		}
 
 		if (!type.HasNestedTypes)

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -135,6 +135,7 @@ public void NativeAOT ()
 			proj.SetProperty ("PublishAot", "true");
 			proj.SetProperty ("PublishAotUsingRuntimePack", "true");
 			proj.SetProperty ("AndroidNdkDirectory", AndroidNdkPath);
+			proj.SetProperty ("_ExtraTrimmerArgs", "--verbose");
 
 			using var b = CreateApkBuilder ();
 			Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
@@ -165,6 +166,31 @@ public void NativeAOT ()
 				Assert.IsNotNull (method, $"{linkedMonoAndroidAssembly} should contain {typeName}.{methodName}");
 			}
 
+			var linkedRuntimeAssembly = Path.Combine (intermediate, "linked", "Microsoft.Android.Runtime.NativeAOT.dll");
+			FileAssert.Exists (linkedRuntimeAssembly);
+			using (var assembly = AssemblyDefinition.ReadAssembly (linkedRuntimeAssembly)) {
+				var type = assembly.MainModule.Types.FirstOrDefault (t => t.Name == "NativeAotTypeManager");
+				Assert.IsNotNull (type, $"{linkedRuntimeAssembly} should contain NativeAotTypeManager");
+				var method = type.Methods.FirstOrDefault (m => m.Name == "InitializeTypeMappings");
+				Assert.IsNotNull (method, "NativeAotTypeManager should contain InitializeTypeMappings");
+
+				var typemap = new Dictionary<string, TypeReference> ();
+				foreach (var i in method.Body.Instructions) {
+					if (i.OpCode != Mono.Cecil.Cil.OpCodes.Ldstr)
+						continue;
+					if (i.Operand is not string javaName)
+						continue;
+					if (i.Next.Operand is not TypeReference t)
+						continue;
+					typemap.Add (javaName, t);
+				}
+				if (typemap.TryGetValue ("java/lang/Object", out var reference)) {
+					Assert.AreEqual ("Java.Lang.Object", $"{reference.Namespace}.{reference.Name}");
+				} else {
+					Assert.Fail ("InitializeTypeMappings should contain Ldstr \"java/lang/Object\"!");
+				}				
+			}
+
 			var dexFile = Path.Combine (intermediate, "android", "bin", "classes.dex");
 			FileAssert.Exists (dexFile);
 			foreach (var className in mono_classes) {