[RGen] Remove all the Nullable<Accessor> boxing that happens in the generator. (#23430)

Similar to #23428 we remove the
Nullable boxing of the Accessor struct to reduce the references of the
struct from the heap.

---------

Co-authored-by: Copilot <[email protected]>
Co-authored-by: GitHub Actions Autoformatter <[email protected]>

Author: 3 people

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

@@ -35,7 +35,7 @@ public Accessor (AccessorKind accessorKind,
 		SymbolAvailability symbolAvailability,
 		ExportData<ObjCBindings.Property>? exportPropertyData,
 		ImmutableArray<AttributeCodeChange> attributes,
-		ImmutableArray<SyntaxToken> modifiers)
+		ImmutableArray<SyntaxToken> modifiers) : this (StructState.Initialized)
 	{
 		Kind = accessorKind;
 		SymbolAvailability = symbolAvailability;

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

@@ -2,16 +2,30 @@
 // Licensed under the MIT License.
 using System;
 using System.Collections.Immutable;
-using System.Linq;
 using System.Runtime.InteropServices;
-using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.Macios.Generator.Availability;
 
 namespace Microsoft.Macios.Generator.DataModel;
 
 [StructLayout (LayoutKind.Auto)]
 readonly partial struct Accessor : IEquatable<Accessor> {
+
+	/// <summary>
+	/// The initialization state of the struct.
+	/// </summary>
+	StructState State { get; init; } = StructState.Default;
+
+	/// <summary>
+	/// Gets the default, uninitialized instance of <see cref="Accessor"/>.
+	/// </summary>
+	public static Accessor Default { get; } = new (StructState.Default);
+
+	/// <summary>
+	/// Gets a value indicating whether the instance is the default, uninitialized instance.
+	/// </summary>
+	public bool IsNullOrDefault => State == StructState.Default;
+
 	/// <summary>
 	/// The kind of accessor.
 	/// </summary>
@@ -32,9 +46,21 @@ namespace Microsoft.Macios.Generator.DataModel;
 	/// </summary>
 	public ImmutableArray<SyntaxToken> Modifiers { get; }
 
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Accessor"/> struct with a specific state.
+	/// Used to create the default, uninitialized instance.
+	/// </summary>
+	/// <param name="state">The initialization state of the struct.</param>
+	Accessor (StructState state)
+	{
+		State = state;
+	}
+
 	/// <inheritdoc />
 	public bool Equals (Accessor other)
 	{
+		if (State == StructState.Default && other.State == StructState.Default)
+			return true;
 		if (Kind != other.Kind)
 			return false;
 		if (SymbolAvailability != other.SymbolAvailability)

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

@@ -329,13 +329,13 @@ public Property ToStrongDelegate ()
 
 		var getter = GetAccessor (AccessorKind.Getter);
 		Method? getterMethod = null;
-		if (getter is not null)
+		if (!getter.IsNullOrDefault)
 			getterMethod = new Method (
 				type: typeInfo.FullyQualifiedName,
 				name: $"_Get{Name}",
 				returnType: ReturnType,
-				symbolAvailability: getter.Value.SymbolAvailability,
-				exportMethodData: new (getter.Value.GetSelector (this)),
+				symbolAvailability: getter.SymbolAvailability,
+				exportMethodData: new (getter.GetSelector (this)),
 				attributes: [],
 				modifiers: [Token (SyntaxKind.InternalKeyword), Token (SyntaxKind.StaticKeyword)],
 				parameters: [thisParameter]) {
@@ -344,7 +344,7 @@ public Property ToStrongDelegate ()
 
 		var setter = GetAccessor (AccessorKind.Setter);
 		Method? setterMethod = null;
-		if (setter is not null) {
+		if (!setter.IsNullOrDefault) {
 			// we need a second parameter for the setter
 			var valueParameter = new Parameter (1, ReturnType, "value") {
 				BindAs = BindAs // parameter bindas is the same as the property bindas
@@ -353,8 +353,8 @@ public Property ToStrongDelegate ()
 				type: typeInfo.FullyQualifiedName,
 				name: $"_Set{Name}",
 				returnType: TypeInfo.Void,
-				symbolAvailability: setter.Value.SymbolAvailability,
-				exportMethodData: new (setter.Value.GetSelector (this)),
+				symbolAvailability: setter.SymbolAvailability,
+				exportMethodData: new (setter.GetSelector (this)),
 				attributes: [],
 				modifiers: [Token (SyntaxKind.InternalKeyword), Token (SyntaxKind.StaticKeyword)],
 				parameters: [thisParameter, valueParameter]);

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

@@ -104,14 +104,14 @@ public ImmutableArray<SyntaxToken> Modifiers {
 
 	public Parameter ValueParameter { get; private init; }
 
-	public Accessor? GetAccessor (AccessorKind accessorKind)
+	public Accessor GetAccessor (AccessorKind accessorKind)
 	{
 		// careful, do not use FirstOrDefault from LINQ because we are using structs!
 		foreach (var accessor in Accessors) {
 			if (accessor.Kind == accessorKind)
 				return accessor;
 		}
-		return null;
+		return Accessor.Default;
 	}
 
 	bool CoreEquals (Property other)

src/rgen/Microsoft.Macios.Generator/Emitters/BindingSyntaxFactory.Property.cs

@@ -26,8 +26,8 @@ internal static (string? Getter, string? Setter) GetObjCMessageSendMethods (in P
 			// export attribute attached
 			var getter = property.GetAccessor (AccessorKind.Getter);
 			string? getterMsgSend = null;
-			if (getter is not null) {
-				var getterExportData = getter.Value.ExportPropertyData ?? property.ExportPropertyData;
+			if (!getter.IsNullOrDefault) {
+				var getterExportData = getter.ExportPropertyData ?? property.ExportPropertyData;
 				if (getterExportData is not null) {
 					getterMsgSend = GetObjCMessageSendMethodName (getterExportData.Value, property.BindAs?.Type ?? property.ReturnType, [],
 						isSuper, isStret);
@@ -36,13 +36,13 @@ internal static (string? Getter, string? Setter) GetObjCMessageSendMethods (in P
 
 			var setter = property.GetAccessor (AccessorKind.Setter);
 			string? setterMsgSend = null;
-			if (setter is not null) {
+			if (!setter.IsNullOrDefault) {
 				// the setter also depends on if we have a bindas attribute or not. If present, the parameter of the
 				// setter will be that indicated by the bind as attribute
 				var valueParameter = property.BindAs is null
 					? property.ValueParameter
 					: new Parameter (0, property.BindAs.Value.Type, "value");
-				var setterExportData = setter.Value.ExportPropertyData ?? property.ExportPropertyData;
+				var setterExportData = setter.ExportPropertyData ?? property.ExportPropertyData;
 				if (setterExportData is not null) {
 					setterMsgSend = GetObjCMessageSendMethodName (setterExportData.Value, TypeInfo.Void,
 						[valueParameter], isSuper, isStret);
@@ -128,13 +128,13 @@ internal static PropertyInvocations GetInvocations (in Property property)
 		// retrieve the objc_msgSend methods
 		var (getter, setter) = GetObjCMessageSendMethods (property, isStret: property.ReturnType.NeedsStret);
 		var (superGetter, superSetter) = GetObjCMessageSendMethods (property, isSuper: true, isStret: property.ReturnType.NeedsStret);
-		var getterSelector = property.GetAccessor (AccessorKind.Getter)?.GetSelector (property);
+		var getterSelector = property.GetAccessor (AccessorKind.Getter).GetSelector (property);
 		var getterInvocations = GetGetterInvocations (property, getterSelector, getter, superGetter);
 
 		(ArgumentConversions Argument, ExpressionSyntax Send, ExpressionSyntax SendSuper)? setterInvocations = null;
 		var setterAccessor = property.GetAccessor (AccessorKind.Setter);
-		if (setterAccessor is not null) {
-			var setterSelector = setterAccessor.Value.GetSelector (property);
+		if (!setterAccessor.IsNullOrDefault) {
+			var setterSelector = setterAccessor.GetSelector (property);
 			setterInvocations = GetSetterInvocations (property, setterSelector, setter, superSetter);
 		}
 

src/rgen/Microsoft.Macios.Generator/Emitters/ClassEmitter.cs

@@ -152,7 +152,7 @@ void EmitProperties (in BindingContext context, TabbedWriter<StringWriter> class
 
 			// we expect to always at least have a getter
 			var getter = property.GetAccessor (AccessorKind.Getter);
-			if (getter is null)
+			if (getter.IsNullOrDefault)
 				continue;
 
 			// add backing variable for the property if it is needed
@@ -168,7 +168,7 @@ void EmitProperties (in BindingContext context, TabbedWriter<StringWriter> class
 
 			using (var propertyBlock = classBlock.CreateBlock (property.ToDeclaration ().ToString (), block: true)) {
 				// be very verbose with the availability, makes the life easier to the dotnet analyzer
-				propertyBlock.AppendMemberAvailability (getter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (getter.SymbolAvailability);
 				// if we deal with a delegate, include the attr:
 				// [return: DelegateProxy (typeof ({staticBridge}))]
 				if (property.ReturnType.IsDelegate)
@@ -202,12 +202,12 @@ void EmitProperties (in BindingContext context, TabbedWriter<StringWriter> class
 				}
 
 				var setter = property.GetAccessor (AccessorKind.Setter);
-				if (setter is null || invocations.Setter is null)
+				if (setter.IsNullOrDefault || invocations.Setter is null)
 					// we are done with the current property
 					continue;
 
 				propertyBlock.WriteLine (); // add space between getter and setter since we have the attrs
-				propertyBlock.AppendMemberAvailability (setter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (setter.SymbolAvailability);
 				// if we deal with a delegate, include the attr:
 				// [param: BlockProxy (typeof ({nativeInvoker}))]
 				if (property.ReturnType.IsDelegate)

src/rgen/Microsoft.Macios.Generator/Emitters/ClassEmitterExtensions.cs

@@ -51,17 +51,17 @@ public static void EmitSelectorFields (this IClassEmitter self, in BindingContex
 				// ignore fields
 				continue;
 			var getter = property.GetAccessor (AccessorKind.Getter);
-			if (getter is not null) {
-				var selector = getter.Value.GetSelector (property)!;
+			if (!getter.IsNullOrDefault) {
+				var selector = getter.GetSelector (property)!;
 				var selectorName = selector.GetSelectorFieldName ();
 				if (bindingContext.SelectorNames.TryAdd (selector, selectorName)) {
 					EmitField (selector, selectorName);
 				}
 			}
 
 			var setter = property.GetAccessor (AccessorKind.Setter);
-			if (setter is not null) {
-				var selector = setter.Value.GetSelector (property)!;
+			if (!setter.IsNullOrDefault) {
+				var selector = setter.GetSelector (property)!;
 				var selectorName = selector.GetSelectorFieldName ();
 				if (bindingContext.SelectorNames.TryAdd (selector, selectorName)) {
 					EmitField (selector, selectorName);
@@ -265,7 +265,7 @@ public static void EmitFields (this IClassEmitter self, string className, in Imm
 			classBlock.WriteLine ();
 			// a field should always have a getter, if it does not, we do not generate the property
 			var getter = property.GetAccessor (AccessorKind.Getter);
-			if (getter is null)
+			if (getter.IsNullOrDefault)
 				continue;
 
 			// provide a backing variable for the property if and only if we are dealing with a reference type
@@ -289,7 +289,7 @@ public static void EmitFields (this IClassEmitter self, string className, in Imm
 				var backingField = property.BackingField;
 
 				// be very verbose with the availability, makes the life easier to the dotnet analyzer
-				propertyBlock.AppendMemberAvailability (getter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (getter.SymbolAvailability);
 				using (var getterBlock = propertyBlock.CreateBlock ("get", block: true)) {
 					// fields with a reference type have a backing fields, while value types do not
 					if (property.IsReferenceType) {
@@ -305,12 +305,12 @@ public static void EmitFields (this IClassEmitter self, string className, in Imm
 				}
 
 				var setter = property.GetAccessor (AccessorKind.Setter);
-				if (setter is null)
+				if (setter.IsNullOrDefault)
 					// we are done with the current property
 					continue;
 
 				propertyBlock.WriteLine (); // add space between getter and setter since we have the attrs
-				propertyBlock.AppendMemberAvailability (setter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (setter.SymbolAvailability);
 				using (var setterBlock = propertyBlock.CreateBlock ("set", block: true)) {
 					if (property.IsReferenceType) {
 						// set the backing field

src/rgen/Microsoft.Macios.Generator/Emitters/StrongDictionaryEmitter.cs

@@ -44,26 +44,26 @@ void EmitProperties (in BindingContext context, TabbedWriter<StringWriter> class
 		foreach (var property in context.Changes.StrongDictionaryProperties.OrderBy (p => p.Name)) {
 			// make sure that the user did not forget to add the getter
 			var getter = property.GetAccessor (AccessorKind.Getter);
-			if (getter is null)
+			if (getter.IsNullOrDefault)
 				continue;
 
 			classBlock.WriteLine ();
 			classBlock.AppendMemberAvailability (property.SymbolAvailability);
 			var (getCall, setCall) = GetStrongDictionaryInvocations (property);
 			using (var propertyBlock = classBlock.CreateBlock (property.ToDeclaration ().ToString (), block: true)) {
 
-				propertyBlock.AppendMemberAvailability (getter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (getter.SymbolAvailability);
 				using (var getterBlock = propertyBlock.CreateBlock ("get", block: true)) {
 					getterBlock.WriteLine ($"return {ExpressionStatement (getCall)}");
 				}
 
 				var setter = property.GetAccessor (AccessorKind.Setter);
-				if (setter is null)
+				if (setter.IsNullOrDefault)
 					// we are done with the current property
 					continue;
 
 				propertyBlock.WriteLine (); // add space between getter and setter since we have the attrs
-				propertyBlock.AppendMemberAvailability (setter.Value.SymbolAvailability);
+				propertyBlock.AppendMemberAvailability (setter.SymbolAvailability);
 				using (var setterBlock = propertyBlock.CreateBlock ("set", block: true)) {
 					setterBlock.WriteLine ($"{ExpressionStatement (setCall)}");
 				}