No, the default integer is u32. If type inference can't provide a better type, Rust will pick u32. If type inference can pick a better type it will use it. So if you create an unsuffixed int literal and use it for indexing, that literal will be a usize.

Rust will type error if you try to use u32s with an array so it's all good though. Just means that you need to specifically `: usize` things.

If you need an integer type for counting stuff, u32 is fine. If you actually need to talk about memory, use usize. The compiler will force you to do it.