ZST behavior

Understanding zero-sized types in Rust

This question tests your knowledge of zero-sized types (ZSTs) in Rust—a foundational concept that affects memory layout, generics, and performance tuning. It's the kind of thing that catches candidates who haven't thought deeply about how Rust's type system handles types with no runtime data.

To reason about struct sizes in Rust, you need to understand which types occupy zero bytes at runtime, how the compiler handles them, and the rules governing struct layout and padding. This is particularly relevant when working with phantom types, marker types, and generic abstractions where you're using the type system for compile-time guarantees rather than runtime storage.

• Zero-sized types and their compile-time vs. runtime implications
• Struct field layout and alignment
• How the Rust compiler optimizes away types that carry no data