bug#66732: tree-sitter fontification doesn't update multi-line syntax reliably

[Dmitry Gutov <dmitry@gutov.dev>]

Hi Dominik,

On 24/10/2023 17:22, Dominik Honnef wrote:
> Steps to reproduce:
> 
> 1. Start emacs -q
> 2. Clear the scratch buffer
> 3. Switch to c-ts-mode
> 4. Type the following:
> 
>      /* foo
>      bar
>      baz
>      */
> 
> Notice the following:
> 
> 1. tree-sitter will not parse the buffer contents as a comment until the
> closing comment marker is typed (not an issue per se.)
> 
> 2. When you type the closing comment marker, only that line will be
> fontified.
> 
> 3. Moving to the previous line will refontify the whole comment.
> 
> Similarly, removing the closing comment marker will not instantly
> refontify the buffer, either.
> 
> The expected behavior would be for the whole comment to be refontified
> immediately after typing the closing comment marker.
> 
> Other buffer contents often lead to even worse refontifying, where even
> motion will not fix things.

Can repro.

Only with 'emacs -Q', though (note to others who will try).