Function parse_units_with_warnings_from 

pub fn parse_units_with_warnings_from(
    tokens: &[Token],
    source: &str,
    next_id: &mut u32,
) -> Result<(Vec<SourceUnit>, Vec<CompileError>), Vec<CompileError>>

parse_units_with_warnings, continuing ExprId allocation from next_id rather than starting at 0 — see parse_unit_with_warnings_from for why this exists. The one production caller is bynk-emit’s per-file parse loop (phase_parse), which owns one counter across every file in a single project parse so two files whose methods later get merged into one check_record call (a multi-file commons) never collide.