The Compiler Is Your Best Friend, Stop Lying to It

4 months ago

The article discusses the importance of not lying to the compiler to avoid runtime errors and improve code safety.
It explains what a compiler is and its typical pipeline: parsing, typechecking, optimization, and code generation.
Different languages have different compiler behaviors: Rust's ahead-of-time compilation, Java's JIT compilation, and TypeScript's transpilation.
Common lies to the compiler include using null, unchecked exceptions, casts, and side-effects, which can lead to runtime errors.
The article suggests stopping these lies by using Option types for null, Result types for exceptions, avoiding casts, and separating pure functions from side-effects.
By being truthful to the compiler, it can help enforce invariants, making illegal states unrepresentable and improving code safety.
Using typed wrappers and union types can help the compiler track more information, making refactoring and understanding code easier.
The article concludes with a real-world example of how lying to the compiler (using null) led to a major outage, and how being truthful could have prevented it.

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