Curriculum Ownership & borrowing Lifetime intuition exercise 3 · mcq
Lifetime intuition
A function takes a &str and returns a NEW string with extra
characters. The new string is built inside the function. Pick
the return type that lets it escape.
About this theme
Lifetimes are not a separate runtime feature; they describe how long references are valid. This theme avoids advanced annotation syntax at first and focuses on why Rust rejects dangling references. Planned exercises: 1. choose the value that lives long enough. 2. recognise a dangling reference. 3. choose owned return instead of borrowed return. 4. fill a scope change that extends an owner. 5. fill a returned String. 6. write a function that returns one of two borrowed inputs with an explicit lifetime. 7. write code that avoids returning a local reference. 8. translate a TS closure over local data. 9. fix a lifetime error by changing ownership rather than adding random annotations.