Defer

defer runs a block of code when the current scope exits, whether normally or via early return.

Syntax

defer {
    // cleanup code
}

Use Cases

Resource cleanup:

craft process_file(path: str) -> void {
    make f = fs.open_file(path, "r");
    defer { fs.close(f); }
    make content = fs.read_all(f);
    print(content);
    send;
}

Unlock mutex (when sync primitives exist):

defer { mutex.unlock(); }
// ... critical section ...

Temporary state:

defer { restore_state(); }
set_temp_state();
// ... use temp state ...

Execution Order

Multiple defer blocks in the same scope run in reverse order (last deferred runs first):

defer { print("first"); }
defer { print("second"); }
// When scope exits: "second" then "first"