Rust Interview Questions 2026

Rust interviews test ownership and borrowing deeply. Interviewers expect you to reason about memory safety without a GC and explain the borrow checker's decisions.

Ownership and Move Semantics

Every value in Rust has a single owner. When the owner goes out of scope, the value is dropped (destructor runs, memory freed). Assignment moves ownership by default for non-Copy types. After a move, the original binding is invalid.

Copy types (integers, booleans, references) are copied rather than moved. Clone is explicit deep copy. Know which standard types implement Copy (primitives, tuples of Copy types, fixed-size arrays of Copy types) vs those that require Clone (String, Vec).

Borrowing and References

References (&T) borrow without taking ownership. Borrow rules: you can have either one mutable reference OR any number of immutable references at a time, but not both simultaneously. This rule is enforced at compile time.

The borrow checker prevents use-after-free, double-free, and data races at compile time. When you fight the borrow checker, often the design needs adjustment. Common fixes: restructure to reduce borrow scope, use indices instead of references into collections, use Rc<RefCell<T>> for shared mutability when needed.

Traits

Traits define shared behavior, similar to interfaces but more powerful. Key traits: Display and Debug for formatting, Iterator for sequences, From/Into for conversions, Clone/Copy for copying.

Trait objects (dyn Trait) enable dynamic dispatch. impl Trait in function signatures enables static dispatch with type inference. Know when each is appropriate: dyn Trait for heterogeneous collections, impl Trait for single concrete types.

Error Handling with Result

Rust uses Result<T, E> for recoverable errors and panic! for unrecoverable ones. The ? operator propagates errors with early return. Custom error types typically implement std::error::Error.

The thiserror crate simplifies custom error types; anyhow simplifies error propagation in applications where you do not need to match on error types. Know when to use each.

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