bug#62333: 30.0.50; Issue with tree-sitter syntax tree during certain changes

[Gregory Heytings]

> > > > Again, I'm talking about using a parser library.  We may need to 
> > > > introduce a way of limiting the parser to a certain range of buffer 
> > > > text positions, independently of narrowing.
> > >
> > > Except it's already limited by narrowing.
> >
> > Which is a fragile, semi-broken means, as we all know.
>
> What is a broken mess, is user-level narrowing. And how the downstream 
> code can never guess the purpose the narrowing was applied for.

Note that this is what labeled narrowings attempts to solve.  It's perhaps 
not the best way to deal with code that has existed for a long time 
(because such code is not prepared to handle that kind of narrowing 
gracefully), but I don't see why it couldn't be used in new code/modes 
such as tree-sitter ones.  It is independent of user-level narrowing, and 
downstream code can act differently depending on the reason for which the 
narrowing was applied.