bug#75164: treesit-font-lock-fontify-region is easy to lost color on parse error. suggest to remain fontify on parse error.

[Yuan Fu]

> On Dec 29, 2024, at 4:28 PM, Charalampos Mitrodimas <charmitro@posteo.net> 
> wrote:
> 
> Hi,
> 
> Eval Exec <execvy@gmail.com> writes:
> 
>> Hello.
>> When I enable rust-ts-mode on a rust file, I found treesitter is easy
>> to make emacs buffer to lost color.
>> For example, on the following rust code:
>> ```rust
>> 
>> struct Dog {
>>    name: String,
>>    age: u8,
>> }
>> 
>> 
>> struct ManyStruct {
>>    a: u8,
>> }
>> 
>> fn many_code(){
>>    fn fib(n: u32) -> u32 {
>>        if n == 0 {
>>            return 0;
>>        }
>>        if n == 1 {
>>            return 1;
>>        }
>>        fib(n - 1) + fib(n - 2)
>>    }
>> }
>> 
>> fn main() {
>>    // change below `//` to `/` to see the difference
>>    // {
>> }
>> ```
>> 
>> the rust code is right, and the emacs buffer color is right on every
>> struct/functions.
>> But, if I change `// {` to `/ {`, then the rust code is wrong, this
>> buffer will lost all colors.
> 
> Thanks for reporting this.
> 
> I attempted to reproduce this, using your example, when I change `// {`
> to `/{` only "main" from `fn main()` loses color. The rest of the syntax
> highlighting remains intact in my setup.

It’s indeed strange to see the whole buffer lost fontification. I don’t see it 
either.

Yuan