Function warn_unresolved 

fn warn_unresolved(
    caller: &SessionSlot,
    cx: Option<&CallerContext>,
    cwd_raw: Option<&str>,
    error: ScopeError,
) -> ScopeError

The one WARN a failed scope resolution emits, carrying every field that discriminates the failing step. This is the line to reach for when a caller reports it cannot read its reviews.