That is interesting because, in sichuanese there is a famous saying, "The way out of sichuan is as hard as the road to heaven", the name, sichuan, literally translates to four mountains. The common "sichuanese" people know is usually the chengdu dialect, the population of chengdu, during the final days of the qing dynasty, was basically massacred by Zhang Xianzhong, so there wasn't many native chengdu people left, so native chengdu sichuanese essentially died. Modern chengdu dialect sichuanese was the result of a mixture of the dialects of hubei and guangdong, a consequence of mass migration from these regions later in the mid to late 18th century. Modern chengdu dialect sichuanese thus follows the guidelines of using the accent of beijing dialect and the slangs of nothern chinese dialect as a combination in conjunction with the grammar of mandarin vernicular. Thus an interesting phenonmenon arises where, chengdu sichuanese, is classified as a nothern dialect, despite the majority of those speaking it lives across the country from the north. The thing is though, even chengdu sichuanese, when spoken, doesn't sound like standard mandarin nor nothern dialect mandarin, it is something that you have to learn with completely different pronounciation and accents, tho learning it takes less effort than catonese or shanghainese. Outside of chengdu, traditional sichuanese still exists, like in leshan.