Ensuring Trait Constants Are Validated at Compile Time
By Ugochukwu Chizaram Omumusinachi. Updated Tue Jun 24 2025You've probably written trait constants before, but have you ever needed to validate them? Maybe ensure a string isn't too long, or a number falls within a specific range? Here's the thing, you can actually enforce these constraints at compile time, not runtime.
Let's say you're building a system where different types need to provide error messages, but you want to keep them concise for logging purposes:
Your code won't compile. there's a problem — len()
isn't a const function.

The key is using const functions that can run at compile time. Here's how you fix it: