A 30K-line PR for type resolution sounds scary but this is exactly what pre-1.0 means. Rust went through multiple rounds of similar foundational rework before stabilization, remember the old sigil-based pointer syntax. Getting the type system formalized before committing to backwards compat is worth temporary churn. The real test is whether this new design makes future type system changes smaller and more incremental rather than requiring another 30K-line rewrite.