[Generator] Refactor TypeManager and add nullability. (#17559)

This has several small changes:

1. Move the maps to the TypeManager which makes more sense.
2. Enable nullability which triggers a number of changes, the biggest
one, in a dict TKey is not nullable (makes perfect sense).

---------

Co-authored-by: GitHub Actions Autoformatter <github-actions-autoformatter@xamarin.com>
Co-authored-by: Alex Soto <alex@alexsoto.me>
Co-authored-by: Rolf Bjarne Kvinge <rolf@xamarin.com>

src/Resources.resx

@@ -143,6 +143,10 @@
 		<value>Frameworks were not loaded for platform {0}.</value>
 	</data>
 
+	<data name="BI0004" xml:space="preserve">
+		<value>Universe was not loaded for platform {0}.</value>
+	</data>
+
 	<data name="BI0026" xml:space="preserve">
 		<value>Could not parse the command line argument '--warnaserror': {0}</value>
 	</data>

src/bgen/BindingTouch.cs

@@ -66,7 +66,8 @@ public class BindingTouch : IDisposable {
 	List<string> references = new List<string> ();
 
 	public MetadataLoadContext? universe;
-	public TypeManager TypeManager = new TypeManager ();
+	public TypeManager? typeManager;
+	public TypeManager TypeManager => typeManager!;
 	public Frameworks? Frameworks;
 	public AttributeManager? AttributeManager;
 	bool disposedValue;
@@ -521,7 +522,7 @@ public class BindingTouch : IDisposable {
 			// Explicitly load our attribute library so that IKVM doesn't try (and fail) to find it.
 			universe.LoadFromAssemblyPath (GetAttributeLibraryPath ());
 
-			TypeManager.Initialize (this, api, universe.CoreAssembly, baselib);
+			typeManager ??= new (this, api, universe.CoreAssembly, baselib);
 
 			foreach (var linkWith in AttributeManager.GetCustomAttributes<LinkWithAttribute> (api)) {
 				if (!linkwith.Contains (linkWith.LibraryName)) {

src/bgen/Generator.cs

@@ -524,72 +524,6 @@ public partial class Generator : IMemberGatherer {
 		return temp;
 	}
 
-	Dictionary<Type, string> nsnumber_return_map;
-	Dictionary<Type, string> NSNumberReturnMap {
-		get {
-			if (nsnumber_return_map == null) {
-				nsnumber_return_map = new Dictionary<Type, string> {
-					{ TypeManager.System_Boolean, ".BoolValue" },
-					{ TypeManager.System_Byte, ".ByteValue" },
-					{ TypeManager.System_Double, ".DoubleValue" },
-					{ TypeManager.System_Float, ".FloatValue" },
-					{ TypeManager.System_Int16, ".Int16Value" },
-					{ TypeManager.System_Int32, ".Int32Value" },
-					{ TypeManager.System_Int64, ".Int64Value" },
-					{ TypeManager.System_SByte, ".SByteValue" },
-					{ TypeManager.System_UInt16, ".UInt16Value" },
-					{ TypeManager.System_UInt32, ".UInt32Value" },
-					{ TypeManager.System_UInt64, ".UInt64Value" },
-				};
-				nsnumber_return_map [TypeManager.System_nfloat] = ".NFloatValue";
-				nsnumber_return_map [TypeManager.System_nint] = ".NIntValue";
-				nsnumber_return_map [TypeManager.System_nuint] = ".NUIntValue";
-			}
-			return nsnumber_return_map;
-		}
-	}
-
-	Dictionary<Type, string> nsvalue_return_map;
-	Dictionary<Type, string> NSValueReturnMap {
-		get {
-			if (nsvalue_return_map == null) {
-				nsvalue_return_map = new Dictionary<Type, string> {
-					{ TypeManager.CGAffineTransform, ".CGAffineTransformValue" },
-					{ TypeManager.NSRange, ".RangeValue" },
-					{ TypeManager.CGVector, ".CGVectorValue" },
-					{ TypeManager.SCNMatrix4, ".SCNMatrix4Value" },
-					{ TypeManager.CLLocationCoordinate2D, ".CoordinateValue" },
-					{ TypeManager.SCNVector3, ".Vector3Value" },
-					{ TypeManager.SCNVector4, ".Vector4Value" }
-				};
-
-				nsvalue_return_map [TypeManager.CoreGraphics_CGPoint] = ".CGPointValue";
-				nsvalue_return_map [TypeManager.CoreGraphics_CGRect] = ".CGRectValue";
-				nsvalue_return_map [TypeManager.CoreGraphics_CGSize] = ".CGSizeValue";
-
-				if (Frameworks.HaveUIKit) {
-					nsvalue_return_map [TypeManager.UIEdgeInsets] = ".UIEdgeInsetsValue";
-					nsvalue_return_map [TypeManager.UIOffset] = ".UIOffsetValue";
-					nsvalue_return_map [TypeManager.NSDirectionalEdgeInsets] = ".DirectionalEdgeInsetsValue";
-				}
-
-				if (TypeManager.MKCoordinateSpan != null)
-					nsvalue_return_map [TypeManager.MKCoordinateSpan] = ".CoordinateSpanValue";
-
-				if (Frameworks.HaveCoreMedia) {
-					nsvalue_return_map [TypeManager.CMTimeRange] = ".CMTimeRangeValue";
-					nsvalue_return_map [TypeManager.CMTime] = ".CMTimeValue";
-					nsvalue_return_map [TypeManager.CMTimeMapping] = ".CMTimeMappingValue";
-					nsvalue_return_map [TypeManager.CMVideoDimensions] = ".CMVideoDimensionsValue";
-				}
-
-				if (Frameworks.HaveCoreAnimation)
-					nsvalue_return_map [TypeManager.CATransform3D] = ".CATransform3DValue";
-			}
-			return nsvalue_return_map;
-		}
-	}
-
 	string GetFromBindAsWrapper (MemberInformation minfo, out string suffix)
 	{
 		var declaringType = minfo.mi.DeclaringType;
@@ -609,10 +543,10 @@ public partial class Generator : IMemberGatherer {
 		var originalReturnType = method?.ReturnType ?? property?.PropertyType;
 
 		if (originalReturnType == TypeManager.NSNumber) {
-			if (!NSNumberReturnMap.TryGetValue (retType, out append)) {
+			if (!TypeManager.NSNumberReturnMap.TryGetValue (retType, out append)) {
 				if (retType.IsEnum) {
 					var enumType = retType.GetEnumUnderlyingType ();
-					if (!NSNumberReturnMap.TryGetValue (enumType, out append))
+					if (!TypeManager.NSNumberReturnMap.TryGetValue (enumType, out append))
 						throw GetBindAsException ("unbox", retType.Name, originalReturnType.Name, "container", minfo.mi);
 				} else
 					throw GetBindAsException ("unbox", retType.Name, originalReturnType.Name, "container", minfo.mi);
@@ -620,7 +554,7 @@ public partial class Generator : IMemberGatherer {
 			if (isNullable)
 				append = $"?{append}";
 		} else if (originalReturnType == TypeManager.NSValue) {
-			if (!NSValueReturnMap.TryGetValue (retType, out append)) {
+			if (!TypeManager.NSValueReturnMap.TryGetValue (retType, out append)) {
 				// HACK: These are problematic for X.M due to we do not ship System.Drawing for Full profile
 				if (retType.Name == "RectangleF" || retType.Name == "SizeF" || retType.Name == "PointF")
 					append = $".{retType.Name}Value";
@@ -641,7 +575,7 @@ public partial class Generator : IMemberGatherer {
 			if (arrType == TypeManager.NSString && !arrIsNullable)
 				append = $"ptr => {{\n\tusing (var str = Runtime.GetNSObject<NSString> (ptr)!) {{\n\t\treturn {FormatType (arrRetType.DeclaringType, arrRetType)}Extensions.GetValue (str);\n\t}}\n}}";
 			else if (arrType == TypeManager.NSNumber && !arrIsNullable) {
-				if (NSNumberReturnMap.TryGetValue (arrRetType, out valueFetcher) || arrRetType.IsEnum) {
+				if (TypeManager.NSNumberReturnMap.TryGetValue (arrRetType, out valueFetcher) || arrRetType.IsEnum) {
 					var getterStr = string.Format ("{0}{1}", arrIsNullable ? "?" : string.Empty, arrRetType.IsEnum ? ".Int32Value" : valueFetcher);
 					append = string.Format ("ptr => {{\n\tusing (var num = Runtime.GetNSObject<NSNumber> (ptr)!) {{\n\t\treturn ({1}) num{0};\n\t}}\n}}", getterStr, FormatType (arrRetType.DeclaringType, arrRetType));
 				} else
@@ -649,7 +583,7 @@ public partial class Generator : IMemberGatherer {
 			} else if (arrType == TypeManager.NSValue && !arrIsNullable) {
 				if (arrRetType.Name == "RectangleF" || arrRetType.Name == "SizeF" || arrRetType.Name == "PointF")
 					valueFetcher = $"{(arrIsNullable ? "?" : string.Empty)}.{arrRetType.Name}Value";
-				else if (!NSValueReturnMap.TryGetValue (arrRetType, out valueFetcher))
+				else if (!TypeManager.NSValueReturnMap.TryGetValue (arrRetType, out valueFetcher))
 					throw GetBindAsException ("unbox", retType.Name, arrType.Name, "array", minfo.mi);
 
 				append = string.Format ("ptr => {{\n\tusing (var val = Runtime.GetNSObject<NSValue> (ptr)!) {{\n\t\treturn val{0};\n\t}}\n}}", valueFetcher);

src/bgen/MarshalTypeList.cs

@@ -42,15 +42,15 @@ public class MarshalTypeList : List<MarshalType> {
 			Add (typeManager.CVImageBuffer);
 		}
 		if (frameworks.HaveMediaToolbox)
-			Add (new MarshalType (typeManager.MTAudioProcessingTap, create: "MediaToolbox.MTAudioProcessingTap.FromHandle("));
+			Add (new MarshalType (typeManager.MTAudioProcessingTap!, create: "MediaToolbox.MTAudioProcessingTap.FromHandle("));
 		if (frameworks.HaveAddressBook) {
 			Add (typeManager.ABAddressBook);
-			Add (new MarshalType (typeManager.ABPerson, create: "(ABPerson) ABRecord.FromHandle (", closingCreate: ")!"));
+			Add (new MarshalType (typeManager.ABPerson!, create: "(ABPerson) ABRecord.FromHandle (", closingCreate: ")!"));
-			Add (new MarshalType (typeManager.ABRecord, create: "ABRecord.FromHandle (", closingCreate: ")!"));
+			Add (new MarshalType (typeManager.ABRecord!, create: "ABRecord.FromHandle (", closingCreate: ")!"));
 		}
 		if (frameworks.HaveCoreVideo) {
 			// owns `false` like ptr ctor https://github.com/xamarin/xamarin-macios/blob/6f68ab6f79c5f1d96d2cbb1e697330623164e46d/src/CoreVideo/CVBuffer.cs#L74-L90
-			Add (new MarshalType (typeManager.CVPixelBuffer, create: "Runtime.GetINativeObject<CVPixelBuffer> (", closingCreate: ", false)!"));
+			Add (new MarshalType (typeManager.CVPixelBuffer!, create: "Runtime.GetINativeObject<CVPixelBuffer> (", closingCreate: ", false)!"));
 		}
 		Add (typeManager.CGLayer);
 		if (frameworks.HaveCoreMedia)
@@ -63,7 +63,7 @@ public class MarshalTypeList : List<MarshalType> {
 		if (frameworks.HaveAudioUnit)
 			Add (typeManager.AudioComponent);
 		if (frameworks.HaveCoreMedia) {
-			Add (new MarshalType (typeManager.CMFormatDescription, create: "CMFormatDescription.Create (", closingCreate: ")!"));
+			Add (new MarshalType (typeManager.CMFormatDescription!, create: "CMFormatDescription.Create (", closingCreate: ")!"));
 			Add (typeManager.CMAudioFormatDescription);
 			Add (typeManager.CMVideoFormatDescription);
 		}
@@ -82,6 +82,12 @@ public class MarshalTypeList : List<MarshalType> {
 		}
 	}
 
+	void Add (Type? type)
+	{
+		if (type is not null)
+			base.Add (type);
+	}
+
 #if NET
 	public bool TryGetMarshalType (Type t, [NotNullWhen (true)] out MarshalType? res)
 #else

src/bgen/TypeExtensions.cs

@@ -0,0 +1,14 @@
+using System;
+
+#nullable enable
+
+public static class TypeExtensions {
+
+	public static bool IsSubclassOfNotNullable (this Type? type, Type? parent)
+	{
+		if (type is null || parent is null)
+			return false;
+
+		return type.IsSubclassOf (parent);
+	}
+}

src/bgen/TypeManager.cs

@@ -1,140 +1,256 @@
-
 using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 
+#nullable enable
+
 public class TypeManager {
-	BindingTouch BindingTouch;
+	Frameworks Frameworks { get; }
-	Frameworks Frameworks { get { return BindingTouch.Frameworks; } }
 
-	public Type System_Attribute;
+	public Type System_Attribute { get; }
-	public Type System_Boolean;
+	public Type System_Boolean { get; }
-	public Type System_Byte;
+	public Type System_Byte { get; }
-	public Type System_Char;
+	public Type System_Char { get; }
-	public Type System_Delegate;
+	public Type System_Delegate { get; }
-	public Type System_Double;
+	public Type System_Double { get; }
-	public Type System_Float;
+	public Type System_Float { get; }
-	public Type System_Int16;
+	public Type System_Int16 { get; }
-	public Type System_Int32;
+	public Type System_Int32 { get; }
-	public Type System_Int64;
+	public Type System_Int64 { get; }
-	public Type System_IntPtr;
+	public Type System_IntPtr { get; }
-	public Type System_Object;
+	public Type System_Object { get; }
-	public Type System_SByte;
+	public Type System_SByte { get; }
-	public Type System_String;
+	public Type System_String { get; }
-	public Type System_String_Array;
+	public Type System_String_Array { get; }
-	public Type System_UInt16;
+	public Type System_UInt16 { get; }
-	public Type System_UInt32;
+	public Type System_UInt32 { get; }
-	public Type System_UInt64;
+	public Type System_UInt64 { get; }
-	public Type System_UIntPtr;
+	public Type System_UIntPtr { get; }
-	public Type System_Void;
+	public Type System_Void { get; }
 
-	public Type System_nint;
+	public Type System_nint { get; }
-	public Type System_nuint;
+	public Type System_nuint { get; }
-	public Type System_nfloat;
+	public Type System_nfloat { get; }
 
 	/* fundamental */
-	public Type NSObject;
+	public Type NSObject { get; }
-	public Type INativeObject;
+	public Type INativeObject { get; }
 
 	/* objcruntime */
-	public Type BlockLiteral;
+	public Type BlockLiteral { get; }
-	public Type Class;
+	public Type Class { get; }
-	public Type Protocol;
+	public Type Protocol { get; }
-	public Type Selector;
+	public Type Selector { get; }
 
-	public Type Constants;
+	public Type Constants { get; }
 
 	/* Different binding types */
+	public Type DictionaryContainerType { get; }
+	public Type AudioBuffers { get; }
+	public Type AVCaptureWhiteBalanceGains { get; }
+	public Type CFRunLoop { get; }
+	public Type CGAffineTransform { get; }
+	public Type CGColor { get; }
+	public Type CGColorSpace { get; }
+	public Type CGContext { get; }
+	public Type CGPDFDocument { get; }
+	public Type CGPDFPage { get; }
+	public Type CGGradient { get; }
+	public Type CGImage { get; }
+	public Type CGImageSource { get; }
+	public Type CGLayer { get; }
+	public Type CGPath { get; }
+	public Type CGVector { get; }
+	public Type DispatchQueue { get; }
+	public Type DispatchData { get; }
+	public Type NSNumber { get; }
+	public Type NSRange { get; }
+	public Type NSString { get; }
+	public Type NSValue { get; }
+	public Type NSZone { get; }
+	public Type SCNMatrix4 { get; }
+	public Type SCNVector3 { get; }
+	public Type SCNVector4 { get; }
+	public Type SecAccessControl { get; }
+	public Type SecIdentity { get; }
+	public Type SecTrust { get; }
+	public Type SecProtocolMetadata { get; }
+	public Type SecProtocolOptions { get; }
+	public Type SecTrust2 { get; }
+	public Type SecIdentity2 { get; }
+	public Type CoreGraphics_CGPoint { get; }
+	public Type CoreGraphics_CGRect { get; }
+	public Type CoreGraphics_CGSize { get; }
 
-	public Type DictionaryContainerType;
+	// optional if AddressBook present
+	public Type? ABAddressBook { get; }
+	public Type? ABPerson { get; }
+	public Type? ABRecord { get; }
 
-	public Type ABAddressBook;
+	// optional if AudioToolbox present
-	public Type ABPerson;
+	public Type? MusicSequence { get; }
-	public Type ABRecord;
-	public Type AudioBuffers;
-	public Type AudioComponent;
-	public Type AudioUnit;
-	public Type AURenderEventEnumerator;
-	public Type AVCaptureWhiteBalanceGains;
-	public Type CATransform3D;
-	public Type CFRunLoop;
-	public Type CGAffineTransform;
-	public Type CGColor;
-	public Type CGColorSpace;
-	public Type CGContext;
-	public Type CGPDFDocument;
-	public Type CGPDFPage;
-	public Type CGGradient;
-	public Type CGImage;
-	public Type CGImageSource;
-	public Type CGLayer;
-	public Type CGLContext;
-	public Type CGLPixelFormat;
-	public Type CGPath;
-	public Type CGVector;
-	public Type CLLocationCoordinate2D;
-	public Type CMAudioFormatDescription;
-	public Type CMClock;
-	public Type CMFormatDescription;
-	public Type CMSampleBuffer;
-	public Type CMTime;
-	public Type CMTimebase;
-	public Type CMTimeMapping;
-	public Type CMTimeRange;
-	public Type CMVideoFormatDescription;
-	public Type CMVideoDimensions;
-	public Type CVImageBuffer;
-	public Type CVPixelBuffer;
-	public Type CVPixelBufferPool;
-	public Type DispatchQueue;
-	public Type DispatchData;
-	public Type MidiEndpoint;
-	public Type MKCoordinateSpan;
-	public Type MTAudioProcessingTap;
-	public Type MusicSequence;
-	public Type NSNumber;
-	public Type NSRange;
-	public Type NSString;
-	public Type NSValue;
-	public Type NSZone;
-	public Type SCNMatrix4;
-	public Type SCNVector3;
-	public Type SCNVector4;
-	public Type SecAccessControl;
-	public Type SecIdentity;
-	public Type SecTrust;
-	public Type SecProtocolMetadata;
-	public Type SecProtocolOptions;
-	public Type SecTrust2;
-	public Type SecIdentity2;
-	public Type UIEdgeInsets;
-	public Type UIOffset;
-	public Type NSDirectionalEdgeInsets;
 
-	public Type CoreGraphics_CGPoint;
+	// optional if AudioUnit present 
-	public Type CoreGraphics_CGRect;
+	public Type? AudioComponent { get; }
-	public Type CoreGraphics_CGSize;
+	public Type? AudioUnit { get; }
+	public Type? AURenderEventEnumerator { get; }
 
-	Assembly api_assembly;
+	// optional if CoreAnimation present
-	Assembly corlib_assembly;
+	public Type? CATransform3D { get; }
-	Assembly platform_assembly;
 
-	Type Lookup (Assembly assembly, string @namespace, string @typename, bool inexistentOK = false)
+	// optional if OpenGL present
-	{
+	public Type? CGLContext { get; }
-		string fullname;
+	public Type? CGLPixelFormat { get; }
 
-		if (string.IsNullOrEmpty (@namespace)) {
+	// optional if CoreLocation present
-			fullname = @typename;
+	public Type? CLLocationCoordinate2D { get; }
-		} else {
+
-			fullname = @namespace + "." + @typename;
+	// optional if CoreMedia present
+	public Type? CMAudioFormatDescription { get; }
+	public Type? CMClock { get; }
+	public Type? CMFormatDescription { get; }
+	public Type? CMSampleBuffer { get; }
+	public Type? CMTime { get; }
+	public Type? CMTimebase { get; }
+	public Type? CMTimeMapping { get; }
+	public Type? CMTimeRange { get; }
+	public Type? CMVideoFormatDescription { get; }
+	public Type? CMVideoDimensions { get; }
+
+	// optional if CoreVideo present
+	public Type? CVImageBuffer { get; }
+	public Type? CVPixelBuffer { get; }
+	public Type? CVPixelBufferPool { get; }
+
+	// optional if CoreMidi present
+	public Type? MidiEndpoint { get; }
+
+	// optional if MapKit present
+	public Type? MKCoordinateSpan { get; }
+
+	// optional if MediaToolbox is present 
+	public Type? MTAudioProcessingTap { get; }
+
+	// optional if UIKit is present
+	public Type? UIOffset { get; }
+	public Type? UIEdgeInsets { get; }
+	public Type? NSDirectionalEdgeInsets { get; }
+
+	Dictionary<Type, string>? nsnumberReturnMap;
+	public Dictionary<Type, string> NSNumberReturnMap {
+		get {
+			if (nsnumberReturnMap is not null)
+				return nsnumberReturnMap;
+			Tuple<Type?, string> [] typeMap = {
+				new (System_Boolean, ".BoolValue"),
+				new (System_Byte, ".ByteValue"),
+				new (System_Double, ".DoubleValue"),
+				new (System_Float, ".FloatValue"),
+				new (System_Int16, ".Int16Value"),
+				new (System_Int32, ".Int32Value"),
+				new (System_Int64, ".Int64Value"),
+				new (System_SByte, ".SByteValue"),
+				new (System_UInt16, ".UInt16Value"),
+				new (System_UInt32, ".UInt32Value"),
+				new (System_UInt64, ".UInt64Value"),
+				new (System_nfloat, ".NFloatValue"),
+				new (System_nint, ".NIntValue"),
+				new (System_nuint, ".NUIntValue"),
+			};
+			nsnumberReturnMap = new ();
+			foreach (var tuple in typeMap) {
+				if (tuple.Item1 is not null)
+					nsnumberReturnMap [tuple.Item1] = tuple.Item2;
+			}
+			return nsnumberReturnMap;
 		}
-
-		var rv = assembly.GetType (fullname);
-		if (rv == null && !inexistentOK)
-			throw new BindingException (1052, true, fullname, assembly);
-		return rv;
 	}
 
-	public Type GetUnderlyingNullableType (Type type)
+	Dictionary<Type, string>? nsvalueReturnMap;
+	public Dictionary<Type, string> NSValueReturnMap {
+		get {
+			if (nsvalueReturnMap is not null)
+				return nsvalueReturnMap;
+			Tuple<Type?, string> [] general = {
+				new (CGAffineTransform, ".CGAffineTransformValue" ),
+				new (NSRange, ".RangeValue" ),
+				new (CGVector, ".CGVectorValue" ),
+				new (SCNMatrix4, ".SCNMatrix4Value" ),
+				new (CLLocationCoordinate2D, ".CoordinateValue" ),
+				new (SCNVector3, ".Vector3Value" ),
+				new (SCNVector4, ".Vector4Value" ),
+				new (CoreGraphics_CGPoint, ".CGPointValue"),
+				new (CoreGraphics_CGRect, ".CGRectValue"),
+				new (CoreGraphics_CGSize, ".CGSizeValue"),
+				new (MKCoordinateSpan, ".CoordinateSpanValue"),
+			};
+
+			Tuple<Type?, string> [] uiKitMap = Array.Empty<Tuple<Type?, string>> ();
+			if (Frameworks.HaveUIKit)
+				uiKitMap = new Tuple<Type?, string> [] {
+					new (UIEdgeInsets, ".UIEdgeInsetsValue"),
+					new (UIOffset, ".UIOffsetValue"),
+					new (NSDirectionalEdgeInsets, ".DirectionalEdgeInsetsValue"),
+				};
+
+			Tuple<Type?, string> [] coreMedia = Array.Empty<Tuple<Type?, string>> ();
+			if (Frameworks.HaveCoreMedia)
+				coreMedia = new Tuple<Type?, string> [] {
+					new (CMTimeRange, ".CMTimeRangeValue"),
+					new (CMTime, ".CMTimeValue"),
+					new (CMTimeMapping, ".CMTimeMappingValue"),
+					new (CMVideoDimensions, ".CMVideoDimensionsValue"),
+				};
+
+			Tuple<Type?, string> [] animation = Array.Empty<Tuple<Type?, string>> ();
+			if (Frameworks.HaveCoreAnimation)
+				animation = new Tuple<Type?, string> [] {
+					new (CATransform3D, ".CATransform3DValue"),
+				};
+
+			nsvalueReturnMap = new ();
+			foreach (var typeMap in new [] { general, uiKitMap, coreMedia, animation }) {
+				foreach (var tuple in typeMap) {
+					if (tuple.Item1 is not null)
+						nsvalueReturnMap [tuple.Item1] = tuple.Item2;
+				}
+			}
+			return nsvalueReturnMap;
+		}
+	}
+
+#if NET
+	static bool TryGetType (Assembly assembly, string @namespace, string typename, out string fullname, [NotNullWhen (true)] out Type? type)
+#else
+	static bool TryGetType (Assembly assembly, string @namespace, string typename, out string fullname, out Type? type)
+#endif
+	{
+		if (string.IsNullOrEmpty (@namespace)) {
+			fullname = typename;
+		} else {
+			fullname = @namespace + "." + typename;
+		}
+
+		type = assembly.GetType (fullname);
+		return type is not null;
+	}
+
+	static Type Lookup (Assembly assembly, string @namespace, string typename)
+	{
+		if (!TryGetType (assembly, @namespace, typename, out var fullname, out var rv))
+			throw new BindingException (1052, true, fullname, assembly);
+		return rv!;
+	}
+
+	static Type? ConditionalLookup (Assembly assembly, string @namespace, string typename, bool inexistentOk = false)
+	{
+		if (!TryGetType (assembly, @namespace, typename, out var fullname, out var rv) && !inexistentOk)
+			throw new BindingException (1052, true, fullname, assembly);
+		return rv; // maybe null
+	}
+
+	public Type? GetUnderlyingNullableType (Type type)
 	{
 		if (!type.IsConstructedGenericType)
 			return null;
@@ -152,149 +268,149 @@ public class TypeManager {
 		return type.GenericTypeArguments [0];
 	}
 
-	public void Initialize (BindingTouch binding_touch, Assembly api, Assembly corlib, Assembly platform)
+	public TypeManager (BindingTouch bindingTouch, Assembly apiAssembly, Assembly corlibAssembly, Assembly platformAssembly)
 	{
-		BindingTouch = binding_touch;
+		if (bindingTouch.Frameworks is null)
+			throw ErrorHelper.CreateError (3, bindingTouch.CurrentPlatform);
+		if (bindingTouch.universe is null)
+			throw ErrorHelper.CreateError (4, bindingTouch.CurrentPlatform);
 
-		api_assembly = api;
+		Frameworks = bindingTouch.Frameworks;
-		corlib_assembly = corlib;
-		platform_assembly = platform;
 
 		/* corlib */
-		System_Attribute = Lookup (corlib_assembly, "System", "Attribute");
+		System_Attribute = Lookup (corlibAssembly, "System", "Attribute");
-		System_Boolean = Lookup (corlib_assembly, "System", "Boolean");
+		System_Boolean = Lookup (corlibAssembly, "System", "Boolean");
-		System_Byte = Lookup (corlib_assembly, "System", "Byte");
+		System_Byte = Lookup (corlibAssembly, "System", "Byte");
-		System_Char = Lookup (corlib_assembly, "System", "Char");
+		System_Char = Lookup (corlibAssembly, "System", "Char");
-		System_Delegate = Lookup (corlib_assembly, "System", "Delegate");
+		System_Delegate = Lookup (corlibAssembly, "System", "Delegate");
-		System_Double = Lookup (corlib_assembly, "System", "Double");
+		System_Double = Lookup (corlibAssembly, "System", "Double");
-		System_Float = Lookup (corlib_assembly, "System", "Single");
+		System_Float = Lookup (corlibAssembly, "System", "Single");
-		System_Int16 = Lookup (corlib_assembly, "System", "Int16");
+		System_Int16 = Lookup (corlibAssembly, "System", "Int16");
-		System_Int32 = Lookup (corlib_assembly, "System", "Int32");
+		System_Int32 = Lookup (corlibAssembly, "System", "Int32");
-		System_Int64 = Lookup (corlib_assembly, "System", "Int64");
+		System_Int64 = Lookup (corlibAssembly, "System", "Int64");
-		System_IntPtr = Lookup (corlib_assembly, "System", "IntPtr");
+		System_IntPtr = Lookup (corlibAssembly, "System", "IntPtr");
-		System_Object = Lookup (corlib_assembly, "System", "Object");
+		System_Object = Lookup (corlibAssembly, "System", "Object");
-		System_SByte = Lookup (corlib_assembly, "System", "SByte");
+		System_SByte = Lookup (corlibAssembly, "System", "SByte");
-		System_String = Lookup (corlib_assembly, "System", "String");
+		System_String = Lookup (corlibAssembly, "System", "String");
-		System_String_Array = Lookup (corlib_assembly, "System", "String").MakeArrayType ();
+		System_String_Array = Lookup (corlibAssembly, "System", "String").MakeArrayType ();
-		System_UInt16 = Lookup (corlib_assembly, "System", "UInt16");
+		System_UInt16 = Lookup (corlibAssembly, "System", "UInt16");
-		System_UInt32 = Lookup (corlib_assembly, "System", "UInt32");
+		System_UInt32 = Lookup (corlibAssembly, "System", "UInt32");
-		System_UInt64 = Lookup (corlib_assembly, "System", "UInt64");
+		System_UInt64 = Lookup (corlibAssembly, "System", "UInt64");
-		System_UIntPtr = Lookup (corlib_assembly, "System", "UIntPtr");
+		System_UIntPtr = Lookup (corlibAssembly, "System", "UIntPtr");
-		System_Void = Lookup (corlib_assembly, "System", "Void");
+		System_Void = Lookup (corlibAssembly, "System", "Void");
 
 #if NET
-		System_nint = Lookup (corlib_assembly, "System", "IntPtr");
+		System_nint = Lookup (corlibAssembly, "System", "IntPtr");
-		System_nuint = Lookup (corlib_assembly, "System", "UIntPtr");
+		System_nuint = Lookup (corlibAssembly, "System", "UIntPtr");
-		var interop_assembly = binding_touch.universe.LoadFromAssemblyName ("System.Runtime.InteropServices");
+		var interopAssembly = bindingTouch.universe.LoadFromAssemblyName ("System.Runtime.InteropServices");
-		System_nfloat = Lookup (interop_assembly, "System.Runtime.InteropServices", "NFloat");
+		System_nfloat = Lookup (interopAssembly, "System.Runtime.InteropServices", "NFloat");
 #else
-		System_nint = Lookup (platform_assembly, "System", "nint");
+		System_nint = Lookup (platformAssembly, "System", "nint");
-		System_nuint = Lookup (platform_assembly, "System", "nuint");
+		System_nuint = Lookup (platformAssembly, "System", "nuint");
-		System_nfloat = Lookup (platform_assembly, "System", "nfloat");
+		System_nfloat = Lookup (platformAssembly, "System", "nfloat");
 #endif
 
 		/* fundamental */
-		NSObject = Lookup (platform_assembly, "Foundation", "NSObject");
+		NSObject = Lookup (platformAssembly, "Foundation", "NSObject");
-		INativeObject = Lookup (platform_assembly, "ObjCRuntime", "INativeObject");
+		INativeObject = Lookup (platformAssembly, "ObjCRuntime", "INativeObject");
 
 		/* objcruntime */
-		BlockLiteral = Lookup (platform_assembly, "ObjCRuntime", "BlockLiteral");
+		BlockLiteral = Lookup (platformAssembly, "ObjCRuntime", "BlockLiteral");
-		Class = Lookup (platform_assembly, "ObjCRuntime", "Class");
+		Class = Lookup (platformAssembly, "ObjCRuntime", "Class");
-		Protocol = Lookup (platform_assembly, "ObjCRuntime", "Protocol");
+		Protocol = Lookup (platformAssembly, "ObjCRuntime", "Protocol");
-		Selector = Lookup (platform_assembly, "ObjCRuntime", "Selector");
+		Selector = Lookup (platformAssembly, "ObjCRuntime", "Selector");
 
-		Constants = Lookup (platform_assembly, "ObjCRuntime", "Constants");
+		Constants = Lookup (platformAssembly, "ObjCRuntime", "Constants");
 
 		/* Different binding types */
 
-		DictionaryContainerType = Lookup (platform_assembly, "Foundation", "DictionaryContainer");
+		DictionaryContainerType = Lookup (platformAssembly, "Foundation", "DictionaryContainer");
-
-		if (Frameworks.HaveAddressBook) {
-			ABAddressBook = Lookup (platform_assembly, "AddressBook", "ABAddressBook");
-			ABPerson = Lookup (platform_assembly, "AddressBook", "ABPerson");
-			ABRecord = Lookup (platform_assembly, "AddressBook", "ABRecord");
-		}
 		// misplaced API, it's really in CoreAudio (now available everywhere)
-		AudioBuffers = Lookup (platform_assembly, "AudioToolbox", "AudioBuffers");
+		AudioBuffers = Lookup (platformAssembly, "AudioToolbox", "AudioBuffers");
+		AVCaptureWhiteBalanceGains = Lookup (platformAssembly, "AVFoundation", "AVCaptureWhiteBalanceGains");
+		CFRunLoop = Lookup (platformAssembly, "CoreFoundation", "CFRunLoop");
+		CGAffineTransform = Lookup (platformAssembly, "CoreGraphics", "CGAffineTransform");
+		CGColor = Lookup (platformAssembly, "CoreGraphics", "CGColor");
+		CGColorSpace = Lookup (platformAssembly, "CoreGraphics", "CGColorSpace");
+		CGContext = Lookup (platformAssembly, "CoreGraphics", "CGContext");
+		CGPDFDocument = Lookup (platformAssembly, "CoreGraphics", "CGPDFDocument");
+		CGPDFPage = Lookup (platformAssembly, "CoreGraphics", "CGPDFPage");
+		CGGradient = Lookup (platformAssembly, "CoreGraphics", "CGGradient");
+		CGImage = Lookup (platformAssembly, "CoreGraphics", "CGImage");
+		CGImageSource = Lookup (platformAssembly, "ImageIO", "CGImageSource");
+		CGLayer = Lookup (platformAssembly, "CoreGraphics", "CGLayer");
+		CGPath = Lookup (platformAssembly, "CoreGraphics", "CGPath");
+		CGVector = Lookup (platformAssembly, "CoreGraphics", "CGVector");
+		DispatchQueue = Lookup (platformAssembly, "CoreFoundation", "DispatchQueue");
+		DispatchData = Lookup (platformAssembly, "CoreFoundation", "DispatchData");
+		NSNumber = Lookup (bindingTouch.BindThirdPartyLibrary ? platformAssembly : apiAssembly, "Foundation", "NSNumber");
+		NSRange = Lookup (platformAssembly, "Foundation", "NSRange");
+		NSString = Lookup (platformAssembly, "Foundation", "NSString");
+		NSValue = Lookup (bindingTouch.BindThirdPartyLibrary ? platformAssembly : apiAssembly, "Foundation", "NSValue");
+		NSZone = Lookup (platformAssembly, "Foundation", "NSZone");
+		SCNVector3 = Lookup (platformAssembly, "SceneKit", "SCNVector3");
+		SCNVector4 = Lookup (platformAssembly, "SceneKit", "SCNVector4");
+		SCNMatrix4 = Lookup (platformAssembly, "SceneKit", "SCNMatrix4");
+		SecAccessControl = Lookup (platformAssembly, "Security", "SecAccessControl");
+		SecIdentity = Lookup (platformAssembly, "Security", "SecIdentity");
+		SecTrust = Lookup (platformAssembly, "Security", "SecTrust");
+		SecProtocolOptions = Lookup (platformAssembly, "Security", "SecProtocolOptions");
+		SecProtocolMetadata = Lookup (platformAssembly, "Security", "SecProtocolMetadata");
+		SecTrust2 = Lookup (platformAssembly, "Security", "SecTrust2");
+		SecIdentity2 = Lookup (platformAssembly, "Security", "SecIdentity2");
+		CoreGraphics_CGRect = Lookup (platformAssembly, "CoreGraphics", "CGRect");
+		CoreGraphics_CGPoint = Lookup (platformAssembly, "CoreGraphics", "CGPoint");
+		CoreGraphics_CGSize = Lookup (platformAssembly, "CoreGraphics", "CGSize");
+
+		// optional types per framework
+		if (Frameworks.HaveAddressBook) {
+			ABAddressBook = ConditionalLookup (platformAssembly, "AddressBook", "ABAddressBook");
+			ABPerson = ConditionalLookup (platformAssembly, "AddressBook", "ABPerson");
+			ABRecord = ConditionalLookup (platformAssembly, "AddressBook", "ABRecord");
+		}
 		if (Frameworks.HaveAudioToolbox) {
-			MusicSequence = Lookup (platform_assembly, "AudioToolbox", "MusicSequence", true /* may not be found */);
+			MusicSequence = ConditionalLookup (platformAssembly, "AudioToolbox", "MusicSequence", true /* may not be found */);
 		}
 		if (Frameworks.HaveAudioUnit) {
-			AudioComponent = Lookup (platform_assembly, "AudioUnit", "AudioComponent");
+			AudioComponent = ConditionalLookup (platformAssembly, "AudioUnit", "AudioComponent");
-			AudioUnit = Lookup (platform_assembly, "AudioUnit", "AudioUnit");
+			AudioUnit = ConditionalLookup (platformAssembly, "AudioUnit", "AudioUnit");
-			AURenderEventEnumerator = Lookup (platform_assembly, "AudioUnit", "AURenderEventEnumerator");
+			AURenderEventEnumerator = ConditionalLookup (platformAssembly, "AudioUnit", "AURenderEventEnumerator");
 		}
-		AVCaptureWhiteBalanceGains = Lookup (platform_assembly, "AVFoundation", "AVCaptureWhiteBalanceGains");
 		if (Frameworks.HaveCoreAnimation)
-			CATransform3D = Lookup (platform_assembly, "CoreAnimation", "CATransform3D");
+			CATransform3D = ConditionalLookup (platformAssembly, "CoreAnimation", "CATransform3D");
-
-		CFRunLoop = Lookup (platform_assembly, "CoreFoundation", "CFRunLoop");
-		CGAffineTransform = Lookup (platform_assembly, "CoreGraphics", "CGAffineTransform");
-		CGColor = Lookup (platform_assembly, "CoreGraphics", "CGColor");
-		CGColorSpace = Lookup (platform_assembly, "CoreGraphics", "CGColorSpace");
-		CGContext = Lookup (platform_assembly, "CoreGraphics", "CGContext");
-		CGPDFDocument = Lookup (platform_assembly, "CoreGraphics", "CGPDFDocument");
-		CGPDFPage = Lookup (platform_assembly, "CoreGraphics", "CGPDFPage");
-		CGGradient = Lookup (platform_assembly, "CoreGraphics", "CGGradient");
-		CGImage = Lookup (platform_assembly, "CoreGraphics", "CGImage");
-		CGImageSource = Lookup (platform_assembly, "ImageIO", "CGImageSource");
-		CGLayer = Lookup (platform_assembly, "CoreGraphics", "CGLayer");
 		if (Frameworks.HaveOpenGL) {
-			CGLContext = Lookup (platform_assembly, "OpenGL", "CGLContext");
+			CGLContext = ConditionalLookup (platformAssembly, "OpenGL", "CGLContext");
-			CGLPixelFormat = Lookup (platform_assembly, "OpenGL", "CGLPixelFormat");
+			CGLPixelFormat = ConditionalLookup (platformAssembly, "OpenGL", "CGLPixelFormat");
 		}
-		CGPath = Lookup (platform_assembly, "CoreGraphics", "CGPath");
-		CGVector = Lookup (platform_assembly, "CoreGraphics", "CGVector");
 		if (Frameworks.HaveCoreLocation)
-			CLLocationCoordinate2D = Lookup (platform_assembly, "CoreLocation", "CLLocationCoordinate2D");
+			CLLocationCoordinate2D = ConditionalLookup (platformAssembly, "CoreLocation", "CLLocationCoordinate2D");
 		if (Frameworks.HaveCoreMedia) {
-			CMAudioFormatDescription = Lookup (platform_assembly, "CoreMedia", "CMAudioFormatDescription");
+			CMAudioFormatDescription = ConditionalLookup (platformAssembly, "CoreMedia", "CMAudioFormatDescription");
-			CMClock = Lookup (platform_assembly, "CoreMedia", "CMClock");
+			CMClock = ConditionalLookup (platformAssembly, "CoreMedia", "CMClock");
-			CMFormatDescription = Lookup (platform_assembly, "CoreMedia", "CMFormatDescription");
+			CMFormatDescription = ConditionalLookup (platformAssembly, "CoreMedia", "CMFormatDescription");
-			CMSampleBuffer = Lookup (platform_assembly, "CoreMedia", "CMSampleBuffer");
+			CMSampleBuffer = ConditionalLookup (platformAssembly, "CoreMedia", "CMSampleBuffer");
-			CMTime = Lookup (platform_assembly, "CoreMedia", "CMTime");
+			CMTime = ConditionalLookup (platformAssembly, "CoreMedia", "CMTime");
-			CMTimebase = Lookup (platform_assembly, "CoreMedia", "CMTimebase");
+			CMTimebase = ConditionalLookup (platformAssembly, "CoreMedia", "CMTimebase");
-			CMTimeMapping = Lookup (platform_assembly, "CoreMedia", "CMTimeMapping");
+			CMTimeMapping = ConditionalLookup (platformAssembly, "CoreMedia", "CMTimeMapping");
-			CMTimeRange = Lookup (platform_assembly, "CoreMedia", "CMTimeRange");
+			CMTimeRange = ConditionalLookup (platformAssembly, "CoreMedia", "CMTimeRange");
-			CMVideoFormatDescription = Lookup (platform_assembly, "CoreMedia", "CMVideoFormatDescription");
+			CMVideoFormatDescription = ConditionalLookup (platformAssembly, "CoreMedia", "CMVideoFormatDescription");
-			CMVideoDimensions = Lookup (platform_assembly, "CoreMedia", "CMVideoDimensions");
+			CMVideoDimensions = ConditionalLookup (platformAssembly, "CoreMedia", "CMVideoDimensions");
 		}
 		if (Frameworks.HaveCoreVideo) {
-			CVImageBuffer = Lookup (platform_assembly, "CoreVideo", "CVImageBuffer");
+			CVImageBuffer = ConditionalLookup (platformAssembly, "CoreVideo", "CVImageBuffer");
-			CVPixelBuffer = Lookup (platform_assembly, "CoreVideo", "CVPixelBuffer");
+			CVPixelBuffer = ConditionalLookup (platformAssembly, "CoreVideo", "CVPixelBuffer");
-			CVPixelBufferPool = Lookup (platform_assembly, "CoreVideo", "CVPixelBufferPool");
+			CVPixelBufferPool = ConditionalLookup (platformAssembly, "CoreVideo", "CVPixelBufferPool");
 		}
-		DispatchQueue = Lookup (platform_assembly, "CoreFoundation", "DispatchQueue");
-		DispatchData = Lookup (platform_assembly, "CoreFoundation", "DispatchData");
 		if (Frameworks.HaveCoreMidi)
-			MidiEndpoint = Lookup (platform_assembly, "CoreMidi", "MidiEndpoint");
+			MidiEndpoint = ConditionalLookup (platformAssembly, "CoreMidi", "MidiEndpoint");
 		if (Frameworks.HaveMapKit)
-			MKCoordinateSpan = Lookup (platform_assembly, "MapKit", "MKCoordinateSpan", true /* isn't in XM/Classic */);
+			MKCoordinateSpan = ConditionalLookup (platformAssembly, "MapKit", "MKCoordinateSpan", true /* isn't in XM/Classic */);
 		if (Frameworks.HaveMediaToolbox)
-			MTAudioProcessingTap = Lookup (platform_assembly, "MediaToolbox", "MTAudioProcessingTap");
+			MTAudioProcessingTap = ConditionalLookup (platformAssembly, "MediaToolbox", "MTAudioProcessingTap");
-		NSNumber = Lookup (binding_touch.BindThirdPartyLibrary ? platform_assembly : api_assembly, "Foundation", "NSNumber");
-		NSRange = Lookup (platform_assembly, "Foundation", "NSRange");
-		NSString = Lookup (platform_assembly, "Foundation", "NSString");
-		NSValue = Lookup (binding_touch.BindThirdPartyLibrary ? platform_assembly : api_assembly, "Foundation", "NSValue");
-		NSZone = Lookup (platform_assembly, "Foundation", "NSZone");
-		SCNVector3 = Lookup (platform_assembly, "SceneKit", "SCNVector3");
-		SCNVector4 = Lookup (platform_assembly, "SceneKit", "SCNVector4");
-		SCNMatrix4 = Lookup (platform_assembly, "SceneKit", "SCNMatrix4");
-		SecAccessControl = Lookup (platform_assembly, "Security", "SecAccessControl");
-		SecIdentity = Lookup (platform_assembly, "Security", "SecIdentity");
-		SecTrust = Lookup (platform_assembly, "Security", "SecTrust");
-		SecProtocolOptions = Lookup (platform_assembly, "Security", "SecProtocolOptions");
-		SecProtocolMetadata = Lookup (platform_assembly, "Security", "SecProtocolMetadata");
-		SecTrust2 = Lookup (platform_assembly, "Security", "SecTrust2");
-		SecIdentity2 = Lookup (platform_assembly, "Security", "SecIdentity2");
 		if (Frameworks.HaveUIKit) {
-			UIOffset = Lookup (platform_assembly, "UIKit", "UIOffset");
+			UIOffset = ConditionalLookup (platformAssembly, "UIKit", "UIOffset");
-			UIEdgeInsets = Lookup (platform_assembly, "UIKit", "UIEdgeInsets");
+			UIEdgeInsets = ConditionalLookup (platformAssembly, "UIKit", "UIEdgeInsets");
-			NSDirectionalEdgeInsets = Lookup (platform_assembly, "UIKit", "NSDirectionalEdgeInsets");
+			NSDirectionalEdgeInsets = ConditionalLookup (platformAssembly, "UIKit", "NSDirectionalEdgeInsets");
 		}
-
-		CoreGraphics_CGRect = Lookup (platform_assembly, "CoreGraphics", "CGRect");
-		CoreGraphics_CGPoint = Lookup (platform_assembly, "CoreGraphics", "CGPoint");
-		CoreGraphics_CGSize = Lookup (platform_assembly, "CoreGraphics", "CGSize");
 	}
 }

src/generator.csproj

@@ -123,6 +123,7 @@
     <Compile Include="..\src\bgen\StringExtensions.cs" />
     <Compile Include="..\src\bgen\ThreadCheck.cs" />
     <Compile Include="..\src\bgen\TrampolineInfo.cs" />
+    <Compile Include="..\src\bgen\TypeExtensions.cs" />
     <Compile Include="..\src\bgen\TypeManager.cs" />
     <Compile Include="..\src\bgen\WrapPropMemberInformation.cs" />
     <Compile Include="..\tools\common\ApplePlatform.cs" />