bug#61369: Problem with keeping tree-sitter parse tree up-to-date

[Dmitry Gutov]

On 10/02/2023 03:22, Yuan Fu wrote:
> >   I just want to confirm that I can reproduce this, and that if you skip
> >   the trailing newline from the use-statement, I don't get this behavior.
> >   So it seems like the newline is the crucial point, right?
> >
> > Yes, same.
> >
> > Thr trailing newline is necessary.
> >
> > The empty lines at the beginning of the buffer (being copied to) are necessary 
> > to reproduce this as well.
> Hmmm, it might be related to how does tree-sitter does incremental
> parsing? If the newline is necessary, then I guess it’s not because
> Emacs missed characters when reporting edits to tree-sitter.

The newline is somewhat necessary: the scenario doesn't work, for 
example, if the pasted text doesn't include the newline but the buffer 
had an additional (third) one at the top.

But the scenario also doesn't work if some other (any) character is 
removed from the yanked line before pasting: it could be even one after 
the comment instruction (//).

OTOH, if I add an extra char to the yanked line, anywhere, I can skip 
the newline. E.g. I can paste

  use std::path::{self, Path, PathBuf};  // good: std is a crate namee

without a newline and still see the exact same syntax error.

So it looks more like an off-by-one error somewhere. Maybe in our code, 
but maybe in tree-sitter somewhere.