For loop syntax was changed since 0.10.1.

Zig 0.10.1:

    for(items) |value| {}
    for(items) |value, index| {}

Zig 0.11-dev:

    for(items) |value| {}
    for(items, 0..) |value, index| {}
    for(as, bs, cs, ds, 0..) |a, b, c, d, index| {}