Clean up owned values

Owned values clean up when their scope exits, including through return, break, continue, and error propagation. A move transfers this responsibility. Borrowing lends access while leaving cleanup with the owner.

Use drop(value) to release an owner early:

def main() -> Result[(), AllocError | IoError]:
    mut numbers = [1, 2, 3]?
    drop(numbers)
    numbers = [4]?
    print(numbers)?
    Ok(())

[4]

The old contents are released and the consumed binding is unavailable until reinitialized. Borrow checking prevents dropping an owner while a reference still needs it. A borrow ending at its last use does not destroy the owner.

Dropping a string does not invalidate other strings sharing its immutable storage. Fatal runtime traps terminate without running scope cleanup.