E083: A deferred statement can't return, break or continue

defer schedules one statement to run when the function ends, however it ends. That statement runs while the function is already leaving, so it can’t also choose to leave in a different way:

fn main(): int {    defer return 5;          // return from where, exactly?    return 0;}

break and continue have the same problem: they would jump out of the enclosing loop from the middle of the function’s cleanup.

Keep the deferred statement to the cleanup itself – close the file, free the buffer, print the message – and put any decision about leaving in the normal flow of the function:

fn main(): int {    defer cleanup();    return 5;}

If the cleanup itself can fail, handle that failure inside the deferred statement: defer f() recover run { ... };.

Run turf --explain E083 in a terminal to read this again.