message: Fixes Diagnostic.is not testing code correctly
diff: @@ -663,6 +663,7 @@ export namespace Diagnostic {
  && Is.string(candidate.message)
  && (Is.number(candidate.severity) || Is.undefined(candidate.severity))
  && (Is.number(candidate.code) || Is.string(candidate.code) || Is.undefined(candidate.code))
  + && (Is.undefined(candidate.codeDescription) || (Is.string(candidate.codeDescription?.href)))
  && (Is.string(candidate.source) || Is.undefined(candidate.source))
  && (Is.undefined(candidate.relatedInformation) || Is.typedArray<DiagnosticRelatedInformation>(candidate.relatedInformation, DiagnosticRelatedInformation.is));
  }
  