HIDE: Hierarchical Isolation via Documentation and Evidence for Rustc Bugs

Tianrong Zhang, Yakun Zhang, Dan Hao

Rustc bugs can prevent valid programs from compiling or cause incorrect compilation results, making the identification of responsible source files essential for repair. Using large language models (LLMs) for rustc bug isolation raises three challenges. First, distributed compiler functionality requires understanding both what individual files do and how they work together. Second, a large source file search space makes exhaustive analysis of all files costly. Third, including documentation and source code for many candidate files in LLM prompts leads to context overload, which can reduce bug isolation accuracy. We propose HIDE, a hierarchical LLM-based approach that combines compiler documentation with bug evidence to rank suspicious rustc source files. Given a rustc revision and a bug context, HIDE consists of two stages that generate compiler documentation and narrow the search space. To understand distributed compiler functionality, the Layered Documentation Aggregation stage summarizes what individual files do and how files with similar functions work together. To reduce the large source file search space, the Hierarchical Bug Isolation stage uses hierarchical candidate…