Parametricity, or Comptime is Bonkers

The article explores parametricity—a property where a generic function's type signature constrains its possible implementations—using Rust's type system as an example. It contrasts this with Zig's comptime, which allows functions to inspect and branch on type parameters at compile time, breaking parametric guarantees. While comptime is powerful, the author argues that understanding what parametricity provides (modularity, reasoning from signatures alone) enriches the discussion of Zig's design tradeoffs.