[Rgen] Add factory method to cast a byte result to a bool.

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

@@ -108,6 +108,20 @@ static partial class BindingSyntaxFactory {
 			whenFalse: castZero);
 	}
 
+	/// <summary>
+	/// Return the expression needed to cast an invocation that returns a byte to a bool.
+	/// </summary>
+	/// <param name="invocation">The byte returning invocation expression.</param>
+	/// <returns>The expression need to cast the invocation to a byte.</returns>
+	internal static BinaryExpressionSyntax ByteToBool (InvocationExpressionSyntax invocation)
+	{
+		// generates: invocation != 0
+		return BinaryExpression (
+			SyntaxKind.NotEqualsExpression,
+			invocation.WithTrailingTrivia (Space),
+			LiteralExpression (SyntaxKind.NumericLiteralExpression, Literal (0)).WithLeadingTrivia (Space));
+	}
+
 	/// <summary>
 	/// Returns the aux nsarray variable for an array object. This method will do the following:
 	/// 1. Check if the object is nullable or not.

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

@@ -4,9 +4,11 @@
 using System.Collections;
 using System.Collections.Generic;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.Macios.Generator.DataModel;
 using Xunit;
+using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 using static Microsoft.Macios.Generator.Emitters.BindingSyntaxFactory;
 using static Microsoft.Macios.Generator.Tests.TestDataFactory;
 using TypeInfo = Microsoft.Macios.Generator.DataModel.TypeInfo;
@@ -112,6 +114,44 @@ void CastToPrimitiveTests (Parameter parameter, string? expectedCast)
 		}
 	}
 
+	class TestDataByteToBoolTests : IEnumerable<object []> {
+		public IEnumerator<object []> GetEnumerator ()
+		{
+			yield return [
+				InvocationExpression (
+					MemberAccessExpression (
+						SyntaxKind.SimpleMemberAccessExpression,
+						IdentifierName ("NSObject"),
+						IdentifierName ("TestFunction").WithTrailingTrivia (Space))),
+				"NSObject.TestFunction () != 0"
+			];
+
+			yield return [
+				InvocationExpression (
+						MemberAccessExpression (
+							SyntaxKind.SimpleMemberAccessExpression,
+							IdentifierName ("NSObject"),
+							IdentifierName ("TestFunction").WithTrailingTrivia (Space)))
+					.WithArgumentList (
+						ArgumentList (
+							SingletonSeparatedList<ArgumentSyntax> (
+								Argument (
+									IdentifierName ("arg1"))))),
+				"NSObject.TestFunction (arg1) != 0"
+			];
+		}
+
+		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();
+	}
+
+	[Theory]
+	[ClassData (typeof (TestDataByteToBoolTests))]
+	void ByteToBoolTests (InvocationExpressionSyntax invocationExpressionSyntax, string expectedDeclaration)
+	{
+		var declaration = ByteToBool (invocationExpressionSyntax);
+		Assert.Equal (expectedDeclaration, declaration.ToString ());
+	}
+
 	[Fact]
 	void CastToByteTests ()
 	{