SyntaxWalker

foreach (var argument in genericTypeParameters.Arguments)
{
	var typeInfo = semanticModel.GetTypeInfo(argument);
	
	var dir = @"C:\Users\Jeroen\Documents\Visual Studio 2013\Projects\RoslynTester";
	var solution = MSBuildWorkspace.Create().OpenSolutionAsync(dir).Result;
	
	var syntaxRoots =
		from project in solution.Projects
		from document in project.Documents
		select document.GetSyntaxRootAsync().Result;
	
	var diagnostic = Diagnostic.Create(Rule, declaration.GetLocation(), typeInfo.Type.Name, declaration.Variables[0].Identifier);
	foreach (var root in syntaxRoots)
	{
		new FindOverrides(addDiagnostic, diagnostic).Visit(root);
	}
}

public class FindOverrides : CSharpSyntaxWalker
{
	private Action<Diagnostic> _addDiagnostic;
	private Diagnostic _diagnostic;
	
	public FindOverrides(Action<Diagnostic> addDiagnostic, Diagnostic diagnostic)
	{
		_addDiagnostic = addDiagnostic;
		_diagnostic = diagnostic;
	}
	
	public override void VisitMethodDeclaration(MethodDeclarationSyntax node)
	{
		base.VisitMethodDeclaration(node);
		
		if (node.Identifier.Text == "Equals"
		&& node.Modifiers.Any(m => m.Text == "override"))
		{
			_addDiagnostic(_diagnostic);    
		}
	}
}