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Next (unreleased) · docs c218d875 · core f63c1e69 · built 2026-10-26 22:39 UTC

List<T> iteration

Limitation​

List<T> now implements Iterable<T> for every T. Each for loop receives its own copied cursor, so nested loops over the same list are independent:

fun main() {
    var l: List<i64> := List::new();
    l.push(1);
    for (v in l) { assert(v == 1); }
}

The list's existing eager methods continue to use self.as_slice() because they do not need iterator state.

Impact​

Visible to Metel programmers: lists can now be used directly in for loops. .as_slice() remains available when an immutable array view is specifically required.

Affects​

Resolution​

Implemented for #871. The private cursor is part of the copied list value; the backing array remains the shared list storage.