/// <summary>
/// Add return default to the end of the method to prevent "not all code paths return a value" error as a result of mutations
/// </summary>
private SyntaxNode AddReturnDefault(SyntaxNode currentNode)
{
// If it's not a method or the method has no body skip the node
if (!(currentNode is MethodDeclarationSyntax methodNode) || methodNode.Body == null)
{
return(currentNode);
}
// If method return type is void skip the node
if (methodNode.ReturnType is PredefinedTypeSyntax predefinedType && predefinedType.Keyword.IsKind(SyntaxKind.VoidKeyword))
{
return(currentNode);
}
TypeSyntax returnType = methodNode.ReturnType;
// the GenericNameSyntax node can be encapsulated by QualifiedNameSyntax nodes
var genericReturn = returnType.DescendantNodesAndSelf().OfType <GenericNameSyntax>().FirstOrDefault();
if (methodNode.Modifiers.Any(x => x.IsKind(SyntaxKind.AsyncKeyword)))
{
if (genericReturn != null)
{
// if the method is async and returns a generic task, make the return default return the underlying type
returnType = genericReturn.TypeArgumentList.Arguments.First();
}
else
{
// if the method is async but returns a non-generic task, don't add the return default
return(currentNode);
}
}
var newBody = methodNode.Body.AddStatements(MutantPlacer.AnnotateHelper(SyntaxFactory.ReturnStatement(SyntaxFactory.DefaultExpression(returnType))));
currentNode = currentNode.ReplaceNode(methodNode.Body, newBody);
return(currentNode);
}