Function phase_parse 

pub fn phase_parse(
    trees: &[(PathBuf, PathBuf)],
    file_lists: &[Vec<PathBuf>],
    overlay: &HashMap<PathBuf, String>,
    errors: &mut ErrorSink,
    snapshots: &mut Vec<(PathBuf, String)>,
) -> Result<(Vec<ParsedFile>, InjectedUnits, BrokenDeclNames), ()>

Phase 2: parse every discovered file into a ParsedFile, recording each file’s source text into snapshots and any parse errors into errors. Then inject the first-party units the project consumes or uses (inject_firstparty). Returns the parsed units, the registry entries injected, and (#1710) each unit’s BrokenDeclNames; signals a pipeline bail via Err(()) when parsing produced errors and yielded no units at all.