Rust

Rust’s “Edition Guide” is also the known-incompatibilities surface. Edition boundaries (2015 → 2018 → 2021 → 2024) are explicit breaking-change announcements: the language commits in advance to what will change, and the guide documents the migration.

This is unusually disciplined for an actively-evolving language. Most breakages between editions are mechanical (cargo fix handles them), but the cases that need human judgment are called out specifically in the guide. Worth bookmarking before any cross-edition migration.