Derive parameter type with Roslyn

Question

I have created the following object to walk my constructor:

internal class ConstructorWalker : CSharpSyntaxWalker
{
    private string className = String.Empty;
    private readonly SemanticModel semanticModel;
    private readonly Action<string> callback;

    public ConstructorWalker(Document document, Action<string> callback)
    {
        this.semanticModel = document.GetSemanticModelAsync().Result;
        this.callback = callback;
    }

    public override void VisitConstructorDeclaration(ConstructorDeclarationSyntax node)
    {
        var typeToMatch = typeof(Dictionary<string, Func<GenericMobileRequest, Result<object>, Task>>);
        var parameters = node.ParameterList;

        foreach (var param in parameters.ChildNodes()) {
            //This does not work... .Symbol is null
            var paramType = ((IParameterSymbol)semanticModel.GetSymbolInfo(param).Symbol).Type;
            if(paramType == typeToMatch) {
               //PROFIT!!!
            }
        }

How can I determine the type of the parameter so I can ensure it is of the type I am interested in?

Answer 1

Getting the actual Type of a parameter can't be done so easily with Roslyn. You can get the TypeSyntax and ITypeSymbol as shown below, but unless you use reflection you can't really get a Type object (as far as I know).

string typeToMatchString = "Dictionary<string, Func<Exception, HashSet<object>, Task>>"

foreach (var parameter in node.ParameterList.Parameters)
{
    var typeSyntax = parameter.Type;
    var typeSymbol = semanticModel.GetTypeInfo(typeSyntax).Type;

    // Maybe comparing the name is enough?
    if (typeSymbol.ToDisplayString() == typeToMatchString) 
        //PROFIT???       
}

You might want to check out this related question as well.