rust 1.77 Debugging a hashMap with string results in an error

[zxhd863943427]

Hello guys! Thank you for making this excellent tool! I'm learning rust and it has been a great help to me. It runs well most of the time, except for some parts involving hashMap.

Here is a minimally reproducible example:

use std::collections::HashMap;

pub struct UndirectedGraph {
    adjacency_table: HashMap<String, Vec<(String, i32)>>,
}
impl UndirectedGraph {
    fn new() -> UndirectedGraph {
        UndirectedGraph {
            adjacency_table: HashMap::new(),
        }
    }
    
}

#[cfg(test)]
mod test_undirected_graph {

    use super::UndirectedGraph;
    #[test]
    fn test_add_edge() {
        let mut graph = UndirectedGraph::new();

    }
}

It will trigger the following error:

error[E0433]: failed to resolve: use of undeclared crate or module `alloc`
 --> /tmp/1713242065484738109.rs:1:47
  |
1 | type T<'a> = ((&'a u8, usize, usize, ), (&'a (alloc::string::String, i32), usize, usize, ));
  |                                               ^^^^^ use of undeclared crate or module `alloc`
  |
  = help: add `extern crate alloc` to use the `alloc` crate
help: consider importing this module
  |
1 + use std::string;
  |
help: if you import `string`, refer to it directly
  |
1 - type T<'a> = ((&'a u8, usize, usize, ), (&'a (alloc::string::String, i32), usize, usize, ));
1 + type T<'a> = ((&'a u8, usize, usize, ), (&'a (string::String, i32), usize, usize, ));
  |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0433`.
test test_undirected_graph::test_add_edge ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.23s

Is there anything I can do to help fix this? Thanks again!

[billy1624]

Hey @zxhd863943427, thanks for the report! I'm investigating it :)

[billy1624]

Hey @zxhd863943427, please check #41

[billy1624]

Released 1.77.1 to fix it.

[zxhd863943427]

I apologize for not checking this discussion in the past two weeks. It's hard to imagine there would be a response so quickly. Thank you for your outstanding work!

The original minimal reproducible example has been fixed, but a new issue has emerged in the complete code. Here is a more comprehensive minimal reproducible code snippet.

use std::collections::{HashMap};
use std::fmt;
pub struct UndirectedGraph {
    adjacency_table: HashMap<String, Vec<(String, i32)>>,
}
impl  UndirectedGraph {
    fn new() -> UndirectedGraph {
        UndirectedGraph {
            adjacency_table: HashMap::new(),
        }
    }
    fn adjacency_table_mutable(&mut self) -> &mut HashMap<String, Vec<(String, i32)>> {
        &mut self.adjacency_table
    }
    fn add_edge(&mut self, edge: (&str, &str, i32)) {
        //TODO
        let table = self.adjacency_table_mutable();
        match  table.get_mut(edge.0) {
            None=>{
                table.insert(edge.0.to_string(), vec![(edge.1.to_string(),edge.2)]);
            }
            Some(values)=>{
                values.push((edge.1.to_string(),edge.2));
            }
        };
        match  table.get_mut(edge.1) {
            None=>{
                table.insert(edge.1.to_string(), vec![(edge.0.to_string(),edge.2)]);
            }
            Some(values)=>{
                values.push((edge.0.to_string(),edge.2));
            }
        }
    }
}
#[cfg(test)]
mod test_undirected_graph {
    use super::UndirectedGraph;
    #[test]
    fn test_add_edge() {
        let mut graph = UndirectedGraph::new();
        graph.add_edge(("a", "b", 5));
        graph.add_edge(("b", "c", 10));
        graph.add_edge(("c", "a", 7));

    }
}

The full code can be found at: https://github.com/LearningOS/rust-rustlings-2024-spring-zxhd863943427/blob/main/exercises/algorithm/algorithm10.rs

Thank you once again for your outstanding work!

[tyt2y3]

Thank you. We will add this to our test suite, I assume this is MIT licensed. Actually, the exercises are all interesting, may be we should add all of them. Where can I find the description of the exercises?

[zxhd863943427]

It comes from the supplementary exercises of a course,It is a modification based on rust-lang/rustlings, and it is, of course, under the MIT license : https://github.com/LearningOS/rustlings-100exercises-template