Our style guide says "almost never auto," but most people auto everything. They can make the linter replace auto with the actual type if it's really that big a deal. Explicit type wouldn't have avoided this bug.
Arguably an explicit type would have made the bug a little bit more obvious. You basically expect, by default, this kind of string manipulation functions to return a std::string. Obviously in this specific case you can return a view, and that makes it more performant; but it's kind of unexpected and using auto leaves the surprise a bit more hidden.
But sure, you can still make the error with expiclit types.
But sure, you can still make the error with expiclit types.