This was a few years ago. The chaos was partly because of a lack of ownership: one team owned inputs, the other owned outputs, and there wasn't a clear spec. The whole pipeline was pretty experimental and people made up new semantics as needed, and were happy to change failing tests (or just added untested codepaths behind boolean flags in existing functions). Compile-time type checking would've enforced a greater degree of rigor about modeling what was happening and made clear all the ways existing code could be affected.