Scope and Shadowing

Variable bindings have a scope, and are constrained to live in a block. A block is a collection of statements enclosed by braces {}. Also, variable shadowing is allowed.

1. fn main() {
2. // This binding lives in the main function
3. let long_lived_binding = 1;

5. // This is a block, and has a smaller scope than the main function
6. {
7. // This binding only exists in this block
8. let short_lived_binding = 2;

10. println!("inner short: {}", short_lived_binding);

12. // This binding *shadows* the outer one
13. let long_lived_binding = 5_f32;

15. println!("inner long: {}", long_lived_binding);
16. }
17. // End of the block

19. // Error! `short_lived_binding` doesn't exist in this scope
20. println!("outer short: {}", short_lived_binding);
21. // FIXME ^ Comment out this line

23. println!("outer long: {}", long_lived_binding);

25. // This binding also *shadows* the previous binding
26. let long_lived_binding = 'a';

28. println!("outer long: {}", long_lived_binding);
29. }