Day 13/90: Traits and default implementations

90 Day Rust Challenge: Zero to Production

Today I wanted traits and default implementations to feel like a real engineering decision, not a syntax demo. The useful shift was using traits and default implementations to express shared behavior without making the type story fuzzy.

The checks that mattered were behavior shared through traits, type constraints that explain intent, and generic helpers that stay readable at the call site.

The failure mode I was actively trying to avoid was adding generic or trait machinery before the shared behavior is clear. I wanted traits and default implementations to feel like something I could explain at a whiteboard or in a code review, not just something I recognized from docs.

That is the bar I want from this track: code that stays readable when requirements move, not just code that compiles today.