private static PsiClass resolveQualifier(@NotNull PsiMethodCallExpression expr) {
    PsiExpression qualifier = ExpressionUtils.getEffectiveQualifier(expr.getMethodExpression());
    if (qualifier == null) return null;
    PsiType psiType = null;
    CommonDataflow.DataflowResult result = CommonDataflow.getDataflowResult(qualifier);
    if (result != null) {
      psiType = TypeConstraint.fromDfType(result.getDfTypeNoAssertions(qualifier)).getPsiType(qualifier.getProject());
    }
    if (psiType == null) {
      psiType = qualifier.getType();
    }
    return PsiUtil.resolveClassInClassTypeOnly(psiType);
  }
private static PsiClass resolveQualifier(@NotNull PsiMethodCallExpression expr)