IDE0057 incorrectly handles substrings on String itself

[stephentoub]

Version Used:
3.3.0-beta3-19413-06+ac06df1bffb7b7fd0e5bf63cc91921af76b21e03

Steps to Reproduce:
This is a super corner-case only relevant to a few people in the world, so I'll understand if you want to close it. Just opening the issue in case.

The definition of System.String itself uses its own Substring in a few places, e.g.

splitStrings[arrIndex++] = Substring(currIndex, sepList[i] - currIndex);

IDE0057 fires here, and transforms it into:

splitStrings[arrIndex++] = Substring[currIndex..sepList[i]];

which doesn't compile. It should have been transformed instead into:

splitStrings[arrIndex++] = this[currIndex..sepList[i]];

which works fine.

[CyrusNajmabadi]

i definitely did not consider this case :)