SKILL.md
RTK Rust Design Patterns
Patterns that apply to RTK's filter module architecture. Focused on CLI tool patterns, not web/service patterns.
Pattern 1: Newtype (Type Safety)
Use when: wrapping primitive types to prevent misuse (command names, paths, token counts).
// Without Newtype — easy to mix up
fn track(input_tokens: usize, output_tokens: usize) { ... }
track(output_tokens, input_tokens); // Silent bug!
// With Newtype — compile error on swap
pub struct InputTokens(pub usize);
pub struct OutputTokens(pub usize);
fn track(input: InputTokens, output: OutputTokens) { ... }
track(OutputTokens(100), InputTokens(400)); // Compile error ✅