Function parse_sources 

pub fn parse_sources(
    root: &Path,
    prefix: &Path,
    path: &Path,
    source: String,
    next_expr_id: &mut u32,
    next_file_id: &mut u32,
) -> Result<(Vec<ParsedFile>, Vec<CompileError>), Vec<CompileError>>

Parse already-read source text into a ParsedFile. The read happens at the call site (v0.24): the pipeline owns the text for snapshots and per-file error attribution, and the overlay supplies unsaved buffers. Slice 0: prefix is this tree’s project-root-relative include prefix (src, tests, …), empty for a single-root project. It builds each file’s identity_path; source_path stays relative to root (the tree), which is what unit validation reads. See ParsedFile.