private function fixFunction(Tokens $tokens, $startFunctionIndex)
    {
        $endFunctionIndex = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_PARENTHESIS_BRACE, $startFunctionIndex);

        $isMultiline = false;

        $firstWhitespaceIndex = $this->findWhitespaceIndexAfterParenthesis($tokens, $startFunctionIndex, $endFunctionIndex);
        $lastWhitespaceIndex = $this->findWhitespaceIndexAfterParenthesis($tokens, $endFunctionIndex, $startFunctionIndex);

        foreach ([$firstWhitespaceIndex, $lastWhitespaceIndex] as $index) {
            if (null === $index || !Preg::match('/\R/', $tokens[$index]->getContent())) {
                continue;
            }

            if ('ensure_single_line' !== $this->configuration['on_multiline']) {
                $isMultiline = true;

                continue;
            }

            $newLinesRemoved = $this->ensureSingleLine($tokens, $index);
            if (!$newLinesRemoved) {
                $isMultiline = true;
            }
        }

        for ($index = $endFunctionIndex - 1; $index > $startFunctionIndex; --$index) {
            $token = $tokens[$index];

            if ($token->equals(')')) {
                $index = $tokens->findBlockStart(Tokens::BLOCK_TYPE_PARENTHESIS_BRACE, $index);

                continue;
            }

            if ($token->isGivenKind(CT::T_ARRAY_SQUARE_BRACE_CLOSE)) {
                $index = $tokens->findBlockStart(Tokens::BLOCK_TYPE_ARRAY_SQUARE_BRACE, $index);

                continue;
            }

            if ($token->equals('}')) {
                $index = $tokens->findBlockStart(Tokens::BLOCK_TYPE_CURLY_BRACE, $index);

                continue;
            }

            if ($token->equals(',')) {
                $this->fixSpace2($tokens, $index);
                if (!$isMultiline && $this->isNewline($tokens[$index + 1])) {
                    $isMultiline = true;

                    break;
                }
            }
        }

        return $isMultiline;
    }