Elevator Pitch

• Encode invariants in Rust types by “parsing” untrusted/weakly-typed values into stronger newtypes, so illegal states become unrepresentable and checks happen once up front.

Key Takeaways

• Prefer strengthening inputs (e.g., NonZeroF32, NonEmptyVec<T>) over weakening outputs (e.g., returning Option) to avoid repeated checks and runtime surprises.
• Parse early: push validation to constructors/conversions so the rest of the code can rely on invariants without re-checking.
• Type-driven design improves robustness and refactor-safety by making invalid states impossible to represent in the first place.

Most Memorable Quotes

• “we should make illegal states unrepresentable”
• “proving invariants should be done as early as possible”
• “I love creating more types. Five million types for everyone please.”