In order to insert XML doc comment exterior trivia (e.g. /// or '''), we grab the caret position prior to the new line being inserted into the editor and then perform a bit of analysis afterward using that position. However, if there's a selection in the editor and the caret is at the end of that selection, the position will be in an unexpected place in the syntax tree, causing that bit of analysis to fail. So, in this case (and all cases), we use the start of the selection as the position to perform analysis on since that position will be consistent after the new line is inserted.