Error recovery/resilience

Currently, all of the parse functions return Result<ast, ParseError>. This means that if the file has a syntax error, we get the error and nothing else. However, there are some use cases in which having access to parts which did parse successfully would be beneficial:

• Language servers usually want to keep functioning when the file is temporarily broken during editing.
• Linters might want to skip over broken parts and continue reporting lints, or maybe up to the syntax error.

On the other hand, interpreters usually don't have too much use for this AFAIK.

lalrpop seems to have some support for error recovery: https://lalrpop.github.io/lalrpop/tutorial/008_error_recovery.html
Alex Kladov has written about error recovery, most recently here: https://matklad.github.io/2023/05/21/resilient-ll-parsing-tutorial.html

Is RustPython/Parser interested in error recovery or is it out of scope?

Start by reading the parser's parse functions and how they currently return Result<ast, ParseError>. Review the linked LALRPOP and resilient-LL parsing material to compare recovery approaches. Done means the project has an agreed decision on whether error recovery is in scope and, if so, a concrete design for preserving successfully parsed parts.