How to import type `uint` from core

Question

I found code with implementation of b-tree in rust:

https://github.com/rust-lang/rust/blob/b6edc59413f79016a1063c2ec6bc05516bc99cb6/src/libcollections/btree/map.rs

where is used uint

pub struct BTreeMap<K, V> {
    root: Node<K, V>,
    length: uint,
    depth: uint,
    b: uint,
}

I wanted to rewrite this implementation, copied this fragment and saw error

error[E0412]: cannot find type `uint` in this scope
 --> src/bin/prepare-btree.rs:9:13
  |
9 |     length: uint,
  |             ^^^^ not found in this scope

I tried to add

use core::prelude::*;

and

use {core::primitive::uint};

but it did not helped.

All "imports" in my file are listed below:

use std::io::{BufRead, BufReader};
use std::fs::File;
use {core::iter::Map};

In original code that I can't find place where uint is imported.

Docs of uint:

https://doc.rust-lang.org/core/primitive.unit.html

Questions:

• how use core::prelude::*; works and why in code from github link uint is available?
• how to fix cannot find type uint in this scope in my code?

Answer 1

This code is very old (2014) before the 1.0 release. uint was a thing back then. The current code is at https://github.com/rust-lang/rust/blob/3b1c8a94a4e8a6ba8bc7b39cc3580db9e5b72295/library/alloc/src/collections/btree/map.rs#L172:

pub struct BTreeMap<
    K,
    V,
    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
> {
    root: Option<Root<K, V>>,
    length: usize,
    /// `ManuallyDrop` to control drop order (needs to be dropped after all the nodes).
    pub(super) alloc: ManuallyDrop<A>,
    // For dropck; the `Box` avoids making the `Unpin` impl more strict than before
    _marker: PhantomData<crate::boxed::Box<(K, V)>>,
}