autojanet/skills/understand/languages/rust.md

Rust Language Prompt Snippet

Key Concepts

• Ownership and Borrowing: Each value has one owner; references borrow without taking ownership
• Lifetimes: Annotations ('a) ensuring references remain valid for their required duration
• Traits and Trait Objects: Shared behavior definitions; dyn Trait for dynamic dispatch
• Pattern Matching: Exhaustive match expressions deconstructing enums, structs, and tuples
• Enums with Data: Algebraic data types — each variant can carry different associated data
• Result/Option Error Handling: Result<T, E> for fallible ops; Option<T> for nullable values
• Macros: Declarative (macro_rules!) and procedural (derive, attribute, function-like) code generation
• Async/Await with Tokio: Zero-cost async using Future trait and runtime executors
• Unsafe Blocks: Opt-in blocks for raw pointer dereferencing, FFI, and bypassing borrow checker
• Generics with Trait Bounds: <T: Clone + Send> constraining generic parameters
• Closures and Fn Traits: Fn, FnMut, FnOnce determine how closures capture environment

Import Patterns

• use crate::module::Item — import from current crate
• use std::collections::HashMap — import from standard library
• use super::* — import everything from parent module
• mod module_name — declare a submodule (loads from file)

File Patterns

• mod.rs — module barrel file (older convention) or module_name.rs (2018+ edition)
• lib.rs — library crate root defining the public API
• main.rs — binary crate entry point
• Cargo.toml — project manifest with dependencies and metadata
• build.rs — build script executed before compilation

Common Frameworks

• Actix-web — Actor-based, high-performance web framework
• Axum — Ergonomic web framework built on Tower and Hyper
• Rocket — Type-safe web framework with declarative routing
• Diesel — Safe, composable ORM and query builder
• Tokio — Async runtime providing I/O, timers, and task scheduling

Example Language Notes

Takes &self borrow to read state without transferring ownership; returns Result<T, Error> for explicit error propagation. The ? operator propagates errors up the call stack concisely, replacing verbose match blocks.

The module system maps to the filesystem: mod handlers; loads either handlers.rs or handlers/mod.rs, establishing the module tree at compile time.