[Rgen] Add method in the syntaxt factory to cast a bool to a byte.

This is needed because the pinvokes do not use bools but bytes.

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

@@ -6,6 +6,7 @@
 using System.Linq;
 using System.Text;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.DataModel;
@@ -47,6 +48,34 @@ static partial class BindingSyntaxFactory {
 		return castExpression;
 	}
 
+	/// <summary>
+	/// Returns the expression needed to cast a bool to a byte to be used in a native call. 
+	/// </summary>
+	/// <param name="parameter">The parameter to cast.</param>
+	/// <returns>A conditional expression that casts a bool to a byte.</returns>
+	internal static ConditionalExpressionSyntax? CastToByte (in Parameter parameter)
+	{
+		if (parameter.Type.SpecialType != SpecialType.System_Boolean)
+			return null;
+		// (byte) 1
+		var castOne = CastExpression (
+				PredefinedType (Token (SyntaxKind.ByteKeyword)),
+				LiteralExpression (SyntaxKind.NumericLiteralExpression, Literal (1)).WithLeadingTrivia (Space).WithTrailingTrivia (Space)
+				);
+		// (byte) 0
+		var castZero = CastExpression (
+				PredefinedType (Token (SyntaxKind.ByteKeyword)),
+				LiteralExpression (SyntaxKind.NumericLiteralExpression, Literal (0)).WithLeadingTrivia (Space)
+				).WithLeadingTrivia (Space);
+
+		// with this exact space count
+		// foo ? (byte) 1 : (byte) 0
+		return ConditionalExpression (
+			condition: IdentifierName (parameter.Name).WithTrailingTrivia (Space),
+			whenTrue: castOne.WithLeadingTrivia (Space),
+			whenFalse: castZero);
+	}
+
 	static string? GetObjCMessageSendMethodName<T> (ExportData<T> exportData,
 		TypeInfo returnType, ImmutableArray<Parameter> parameters, bool isSuper = false, bool isStret = false) where T : Enum
 	{

tests/rgen/Microsoft.Macios.Generator.Tests/Emitters/BindingSyntaxFactoryObjCRuntimeTests.cs

@@ -13,7 +13,7 @@ namespace Microsoft.Macios.Generator.Tests.Emitters;
 
 public class BindingSyntaxFactoryObjCRuntimeTests {
 
-	class TestDataCodeChangesFromClassDeclaration : IEnumerable<object []> {
+	class TestDataCastToNativeTests : IEnumerable<object []> {
 		public IEnumerator<object []> GetEnumerator ()
 		{
 
@@ -51,7 +51,7 @@ public IEnumerator<object []> GetEnumerator ()
 	}
 
 	[Theory]
-	[ClassData (typeof (TestDataCodeChangesFromClassDeclaration))]
+	[ClassData (typeof (TestDataCastToNativeTests))]
 	void CastToNativeTests (Parameter parameter, string? expectedCast)
 	{
 		var expression = CastToNative (parameter);
@@ -62,4 +62,17 @@ void CastToNativeTests (Parameter parameter, string? expectedCast)
 			Assert.Equal (expectedCast, expression?.ToString ());
 		}
 	}
+
+	[Fact]
+	void CastToByteTests ()
+	{
+		var boolParameter = new Parameter (0, ReturnTypeForBool (), "myParameter");
+		var conditionalExpr = CastToByte (boolParameter);
+		Assert.NotNull (conditionalExpr);
+		Assert.Equal ("myParameter ? (byte) 1 : (byte) 0", conditionalExpr.ToString ());
+
+		var intParameter = new Parameter (1, ReturnTypeForInt (), "myParameter");
+		conditionalExpr = CastToByte (intParameter);
+		Assert.Null (conditionalExpr);
+	}
 }