code: public function isUnarySuccessorOperator($index)
      {
          static $allowedPrevToken = [
              ']',
              [T_STRING],
              [T_VARIABLE],
              [CT::T_DYNAMIC_PROP_BRACE_CLOSE],
              [CT::T_DYNAMIC_VAR_BRACE_CLOSE],
          ];
  
          $tokens = $this->tokens;
          $token = $tokens[$index];
  
          if (!$token->isGivenKind([T_INC, T_DEC])) {
              return false;
          }
  
          $prevToken = $tokens[$tokens->getPrevMeaningfulToken($index)];
  
          return $prevToken->equalsAny($allowedPrevToken);
      }
docs: Checks if there is an unary successor operator under given index.
  
  @param int $index
  
  @return bool