public async Task Test_ExternAlias()
        {
            await VerifyDiagnosticAndFixAsync(@"// x[||]
extern alias x;

class C
{
}
", @"// x

extern alias x;

class C
{
}
", options : Options.AddAllowedCompilerDiagnosticIds(new[] { "CS0430", "CS8020" }));
        }