You just complete to a parsable structure.

This stuff reminds me of intentional programming (Charles Simonyi). That never really panned out but the premise with intentional programming was that programming is about AST transformations that are correct (sort of like refactoring) but all the way down to the machine code level. You get these increasingly more complex languages that are defined in terms of building blocks that are ASTs.

Refactoring of course is based on the same notion that manipulating code correctly at the AST level is a lot easier than messing around with text files. That came out of the smalltalk world originally which also had very fancy IDEs already in the nineties where everything (including the IDE) was something you could mess with. Refactorings were defined as syntactically correct transformation of one AST into another (rename, extract class, move function to parent class, etc.).

Charles Simony had a solution for what you describe as well. Just serialize stuff to text if somebody wants to "edit" and then parse it back when they are done. What happens to the text in between of course is the programmer's problem.

I assume it uses an error tolerant parser, same as most language servers.

Ex: https://github.com/microsoft/tolerant-php-parser/blob/main/d...