M04 Zero Cost

Before you slap another trait bound on that generic function, this prompts you to ask whether you actually need the abstraction. It maps common type errors like E0277 and E0308 to design questions: is this really compile time polymorphism, or should it be an enum, or just a concrete type? The quick reference tables are genuinely useful, showing you when static dispatch bloats your binary versus when dynamic dispatch costs you a vtable lookup. The trace up/down sections connect abstraction choices to other skills in the marketplace, which matters when your "simple" generic suddenly needs Send bounds or domain redesign. Honest take: most Rust codebases over-abstract early, and this at least makes you pause first.

Install to Claude Code

npx -y skills add actionbook/rust-skills --skill m04-zero-cost --agent claude-code