Questions
Rust questions
Choose a question page, learn the concept, then test your understanding with a quiz.
Rust Copy vs Clone: What’s the Difference?
Learn the difference between Copy and Clone in Rust, when each is used, and how ownership affects assignment and duplication.
Rust Multiline String Literals: Syntax, Raw Strings, and Line Breaks
Learn Rust multiline string literal syntax, including normal and raw strings, line breaks, escapes, and common mistakes beginners make.
Rust Package with Both a Library and a Binary
Learn how to structure a Rust package with both a reusable library and an executable using Cargo.toml, src/lib.rs, and src/main.rs.
Rust String vs str: Differences, Uses, and When to Choose Each
Learn the difference between Rust `String` and `str`, when to use each, and how owned and borrowed string types work in practice.
Rust `iter()` vs `into_iter()`: Understanding Borrowed and Owned Iteration
Learn the difference between Rust `iter()` and `into_iter()`, including ownership, borrowing, arrays, vectors, and practical examples.
Understanding Cargo Registry Locking in Rust: Why `cargo build` Waits for a File Lock
Learn why Rust Cargo shows "Blocking waiting for file lock on the registry index" on macOS and how to diagnose and fix it safely.
Why Explicit Lifetimes Are Needed in Rust
Learn why Rust needs explicit lifetimes, when inference is enough, and when lifetime annotations are required for safe references.
Why Rust Avoids &String, &Vec, and &Box in Function Arguments
Learn why Rust functions usually take &str, slices, or plain references instead of &String, &Vec, and &Box, with examples and best practices.
Why Rust Cannot Store a Value and a Reference to It in the Same Struct
Learn why self-referential structs fail in Rust, what lifetime errors mean, and practical ways to model owned data safely.
Why Rust Executables Are So Large: Understanding Binary Size in Rust
Learn why Rust binaries can seem large, what gets included in a build, and how debug, release, stripping, and panic settings affect size.
Why Rust May Not Optimize Non-Aliasing Mutable References Yet
Learn why Rust mutable references imply no aliasing, why LLVM may still avoid some optimizations, and how this relates to UB and codegen.
Why `println!` Doesn’t Show in Rust Unit Tests
Learn why `println!` output is hidden in Rust unit tests, how test output capture works, and how to display debug prints when needed.
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