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.
>
> Labeled narrowing cannot solve this because it does nothing to alleviate 
> the problems with user-defined narrowing.  So if the user narrows the 
> buffer, we cannot do anything to safely widen in the general case, and 
> labeled narrowing cannot help us.

I must be missing something, but I don't understand what you mean.  If a 
user has narrowed a buffer to a certain region A-B, and if we want to 
limit a parser to a certain region C-D, we can do that safely with

(with-narrowing C D :label 'parser-library BODY)

which will work, independently of the A-B narrowing set by the user, and 
will reset the narrowing to A-B upon return.  And functions inside BODY 
will have to use (without-narrowing :label 'parser-library ...) to get 
access to the whole buffer.