There are *so many* ways that reading a text file can fail.
Maybe it doesn't exist, it's a broken symlink, it's actually a directory, it's not the encoding you expected, or perhaps you just don't have the correct permissions.
Reporting good errors is surprisingly labour intensive.
In LSP, a position is represented as a line number and a column offset (in Unicode code units):
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#position
This is pretty elegant. You'll get the correct line regardless of encoding bugs, and the editor already knows the line number so it's cheap to compute.
@RenewedRebecca That's correct, but I was thinking that offering threading to a user might make them more tolerant of a slow interpreter.
For example, if I have an AST walker but provide Clojure semantics, users can hopefully get a big speedup by using all the cores in their application.