[RGen] Provide code that generates the sync call for an async implementation. (#23275)

Author: mandel-macaque

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

@@ -70,6 +70,11 @@ static partial class BindingSyntaxFactory {
 			foreach (var parameter in delegateType.Delegate.Parameters [..^1]) {
 				noNSErrorArgs.Add (Argument (IdentifierName (GetTaskCallbackParameterName (parameter.Name))));
 			}
+			var resultsArgs = noNSErrorArgs.ToImmutable ();
+			var resultArgsSyntax = resultsArgs.Length == 1
+				? resultsArgs [0]
+				: Argument (New (resultsArgs));
+
 			// update the if to include the result setting, we are doing by hand to fix the indentation to match monos
 			ifErrorNotNull = IfStatement (
 				attributeLists: default,
@@ -87,7 +92,7 @@ static partial class BindingSyntaxFactory {
 					ExpressionStatement (
 						TcsSetResult (
 							tcsVariableName: completionSourceName,
-							arguments: [Argument (New (noNSErrorArgs.ToImmutable ()))]
+							arguments: [resultArgsSyntax]
 						)
 					).WithLeadingTrivia (LineFeed, Tab, Tab)
 					).WithLeadingTrivia (LineFeed, Tab)
@@ -101,11 +106,17 @@ static partial class BindingSyntaxFactory {
 		foreach (var parameter in delegateType.Delegate.Parameters) {
 			arguments.Add (Argument (IdentifierName (GetTaskCallbackParameterName (parameter.Name))));
 		}
+
+		var argList = arguments.ToImmutable ();
 		// return a single expression that sets the result of the tcs
+		var argSyntax = argList.Length == 1
+			? argList [0]
+			: Argument (New (argList));
+
 		return ExpressionStatement (
 			TcsSetResult (
 				tcsVariableName: completionSourceName,
-				arguments: [Argument (New (arguments.ToImmutable ()))]
+				arguments: [argSyntax]
 			)
 		).WithLeadingTrivia (Tab);
 	}
@@ -140,6 +151,28 @@ internal static ExpressionSyntax GetCallbackDeclaration (in TypeInfo delegateTyp
 			.WithBlock (block);
 	}
 
+	/// <summary>
+	/// Generates an invocation expression for the synchronous part of an async method wrapper.
+	/// </summary>
+	/// <param name="method">The method to be called.</param>
+	/// <returns>An invocation expression syntax.</returns>
+	internal static ExpressionSyntax ExecuteSyncCall (in Method method)
+	{
+		// retrieve the last parameter from the method, since that should be the completion handler
+		var completionHandler = GetCallbackDeclaration (method.Parameters [^1].Type);
+		var arguments = ImmutableArray.CreateBuilder<ArgumentSyntax> (method.Parameters.Length);
+		// build the arguments for the method call, those are the same arguments as the method parameters but the last one
+		foreach (var parameter in method.Parameters [..^1]) {
+			arguments.Add (Argument (IdentifierName (parameter.Name)));
+		}
+		// add the completion handler as the last argument
+		arguments.Add (Argument (completionHandler));
+
+		var argumentList = ArgumentList (
+			SeparatedList<ArgumentSyntax> (arguments.ToSyntaxNodeOrTokenArray ()));
+		return InvocationExpression (IdentifierName (method.Name).WithTrailingTrivia (Space)).WithArgumentList (argumentList);
+	}
+
 	/// <summary>
 	/// Generates an invocation expression for sending an Objective-C message.
 	/// </summary>

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

@@ -378,7 +378,7 @@ public void MyMethod (Callback cb) {}
 			yield return [
 				singleArgNoError,
 				@"(_cbvalue) => {
-	_tcs.SetResult (new (_cbvalue));
+	_tcs.SetResult (_cbvalue);
 }",
 			];
 
@@ -402,7 +402,7 @@ public void MyMethod (Callback cb) {}
 	if (_cberror is not null)
 		_tcs.SetException (new global::Foundation.NSErrorException (_cberror));
 	else
-		_tcs.SetResult (new (_cbvalue));
+		_tcs.SetResult (_cbvalue);
 }",
 			];