[Rgen] Add more information about the type in the TypeInfo struct.

src/rgen/Microsoft.Macios.Generator/AttributesNames.cs

@@ -22,6 +22,7 @@ static class AttributesNames {
 	public const string SupportedOSPlatformAttribute = "System.Runtime.Versioning.SupportedOSPlatformAttribute";
 	public const string UnsupportedOSPlatformAttribute = "System.Runtime.Versioning.UnsupportedOSPlatformAttribute";
 	public const string ObsoletedOSPlatformAttribute = "System.Runtime.Versioning.ObsoletedOSPlatformAttribute";
+	public const string NativeEnumAttribute = "ObjCRuntime.NativeAttribute";
 
 	public static readonly string [] BindingTypes = [
 		BindingAttribute,

src/rgen/Microsoft.Macios.Generator/DataModel/TypeInfo.cs

@@ -71,6 +71,23 @@ namespace Microsoft.Macios.Generator.DataModel;
 	/// </summary>
 	public bool IsVoid => SpecialType == SpecialType.System_Void;
 
+	/// <summary>
+	/// True if the type is for an interface.
+	/// </summary>
+	public bool IsInterface { get; init; }
+
+	/// <summary>
+	/// True if the type represents an integer that was built using one of the keywords, like byte, int, nint etc.
+	///
+	/// This can be used to decide if we should use the name of the metadata name to cast the value.
+	/// </summary>
+	public bool IsNativeIntegerType { get; init; }
+
+	/// <summary>
+	/// True if an enumerator was marked with the NativeAttribute.
+	/// </summary>
+	public bool IsNativeEnum { get; init; }
+
 	readonly bool isNSObject = false;
 
 	public bool IsNSObject {
@@ -131,6 +148,9 @@ symbol is IArrayTypeSymbol arrayTypeSymbol
 		IsSmartEnum = symbol.IsSmartEnum ();
 		IsArray = symbol is IArrayTypeSymbol;
 		IsReferenceType = symbol.IsReferenceType;
+		IsInterface = symbol.TypeKind == TypeKind.Interface;
+		IsNativeIntegerType = symbol.IsNativeIntegerType;
+		IsNativeEnum = symbol.HasAttribute (AttributesNames.NativeEnumAttribute);
 
 		// data that we can get from the symbol without being INamedType
 		symbol.GetInheritance (
@@ -182,6 +202,12 @@ public bool Equals (TypeInfo other)
 			return false;
 		if (EnumUnderlyingType != other.EnumUnderlyingType)
 			return false;
+		if (IsInterface != other.IsInterface)
+			return false;
+		if (IsNativeIntegerType != other.IsNativeIntegerType)
+			return false;
+		if (IsNativeEnum != other.IsNativeEnum)
+			return false;
 
 		// compare base classes and interfaces, order does not matter at all
 		var listComparer = new CollectionComparer<string> ();
@@ -230,6 +256,9 @@ public override string ToString ()
 		sb.Append ($"IsVoid : {IsVoid}, ");
 		sb.Append ($"IsNSObject : {IsNSObject}, ");
 		sb.Append ($"IsNativeObject: {IsINativeObject}, ");
+		sb.Append ($"IsInterface: {IsInterface}, ");
+		sb.Append ($"IsNativeIntegerType: {IsNativeIntegerType}, ");
+		sb.Append ($"IsNativeEnum: {IsNativeEnum}, ");
 		sb.Append ($"EnumUnderlyingType: '{EnumUnderlyingType?.ToString () ?? "null"}', ");
 		sb.Append ("Parents: [");
 		sb.AppendJoin (", ", parents);

tests/rgen/Microsoft.Macios.Generator.Tests/DataModel/TypeInfoTests.cs

@@ -322,6 +322,67 @@ public class MyClass {
 					parameters: []
 				)
 			];
+
+			const string interfaceMethod = @"
+using System;
+using System.Collections.Generic;
+
+namespace NS {
+	public interface IInterface {}
+
+	public class MyClass {
+		public IInterface MyMethod () {}
+	}
+}
+";
+			yield return [
+				interfaceMethod,
+				new Method (
+					type: "NS.MyClass",
+					name: "MyMethod",
+					returnType: ReturnTypeForInterface ("NS.IInterface"),
+					symbolAvailability: new (),
+					exportMethodData: new (),
+					attributes: [],
+					modifiers: [
+						SyntaxFactory.Token (SyntaxKind.PublicKeyword),
+					],
+					parameters: []
+				)
+			];
+
+			const string nativeEnumMethod = @"
+using System;
+using ObjCRuntime;
+using System.Collections.Generic;
+
+namespace NS {
+	[Native]
+	public enum MyEnum : int {
+		One,
+		Two
+	}
+
+	public class MyClass {
+		public MyEnum MyMethod () {}
+	}
+}
+";
+			yield return [
+				nativeEnumMethod,
+				new Method (
+					type: "NS.MyClass",
+					name: "MyMethod",
+					returnType: ReturnTypeForEnum ("NS.MyEnum", isNativeEnum: true),
+					symbolAvailability: new (),
+					exportMethodData: new (),
+					attributes: [],
+					modifiers: [
+						SyntaxFactory.Token (SyntaxKind.PublicKeyword),
+					],
+					parameters: []
+				)
+			];
 		}
 
 		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();

tests/rgen/Microsoft.Macios.Generator.Tests/TestDataFactory.cs

@@ -125,6 +125,7 @@ public static TypeInfo ReturnTypeForIntPtr (bool isNullable = false)
 					"System.Runtime.Serialization.ISerializable"
 				],
 			MetadataName = "IntPtr",
+			IsNativeIntegerType = !isNullable,
 		};
 
 	public static TypeInfo ReturnTypeForBool ()
@@ -158,14 +159,23 @@ public static TypeInfo ReturnTypeForClass (string className)
 			Parents = ["object"]
 		};
 
+	public static TypeInfo ReturnTypeForInterface (string interfaceName)
+		=> new (
+			name: interfaceName,
+			isReferenceType: true
+		) {
+			Parents = [],
+			IsInterface = true,
+		};
+
 	public static TypeInfo ReturnTypeForStruct (string structName)
 		=> new (
 			name: structName
 		) {
 			Parents = ["System.ValueType", "object"]
 		};
 
-	public static TypeInfo ReturnTypeForEnum (string enumName, bool isSmartEnum = false)
+	public static TypeInfo ReturnTypeForEnum (string enumName, bool isSmartEnum = false, bool isNativeEnum = false)
 		=> new (
 			name: enumName,
 			isBlittable: true,
@@ -182,6 +192,7 @@ public static TypeInfo ReturnTypeForEnum (string enumName, bool isSmartEnum = fa
 				"System.IFormattable",
 				"System.ISpanFormattable"
 			],
+			IsNativeEnum = isNativeEnum,
 			EnumUnderlyingType = SpecialType.System_Int32,
 		};