public AliasAndExternAliasDirective(AliasSymbol alias, ExternAliasDirectiveSyntax?externAliasDirective, bool skipInLookup)
 {
     this.Alias = alias;
     this.ExternAliasDirectiveReference = externAliasDirective?.GetReference();
     this.SkipInLookup = skipInLookup;
 }