gistfile1.cs

var tree = CSharpSyntaxTree.ParseText(@"
class C
{
    void M()
    {
        int variable = 0;
        //Does not bind to a symbol (as there is no class called MissingClass)
        //but it is not a true nameof expression
        MissingClass.nameof(x);
    }
}");


var Mscorlib = PortableExecutableReference.CreateFromAssembly(typeof(object).Assembly);
var compilation = CSharpCompilation.Create("MyCompilation",
    syntaxTrees: new[] { tree }, references: new[] { Mscorlib });
var model = compilation.GetSemanticModel(tree);

var nameofInvocations = tree.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>();
var validNameOfs = nameofInvocations.Where(n => n.Ancestors().OfType<MemberAccessException>().Count() == 0);

foreach (var validNameOfSyntax in validNameOfs)
{
    if (model.GetSymbolInfo(validNameOfSyntax).Symbol == null)
    {
    	//validNameOfSyntax is the nameof operator
        Console.WriteLine("We've found a nameof!");
    }
}