Parse, don't Validate and Type-Driven Design in Rust — ramblings of @harudagondi
Hacker News
February 21, 2026
AI-Generated Deep Dive Summary
In the world of Rust programming, leveraging type systems to handle errors and enforce invariants at compile time can lead to more robust and reliable code. The article explores the concept of "Parse, don't Validate," which advocates for encoding business logic and constraints directly into data types rather than relying on runtime validation functions. This approach shifts error handling from potentially dangerous runtime panics or silent failures to safer compile-time guarantees.
The author illustrates this with examples like division functions, where dividing by zero can lead to panics in Rust or unexpected behavior in floating-point operations. Traditional solutions involve adding asserts or using `Option`/`Result` types to handle such cases at runtime. However, the article suggests a more proactive approach: defining custom types that enforce constraints at the type level. For instance, a `NonZeroF32` type ensures its value can never be zero by encapsulating it with private constructors and helper functions.
By encapsulating invariants within data structures through newtypes or enums, developers can create clearer contracts between APIs. This not only reduces runtime errors but also improves code readability and maintainability. For example, a `NonZeroF32` type makes it explicit that zero is an invalid state, encouraging safer usage
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Originally published on Hacker News on 2/21/2026