What type annotations are required for Petgraph's all_simple_paths() function?

Question

I'm trying to use Petgraph's all_simple_paths(), but I'm not sure what type annotations are required, the the docs don't give an example. It returns a impl Iterator<Item = TargetColl> where TargetColl: FromIterator<G::NodeId>, but I don't know what sort of annotation I should make for that.

for path in algo::all_simple_paths(&graph, x, y, 0, None) {}

error[E0282]: type annotations needed
   --> lib.rs:10:29
   |
10 | for path in algo::all_simple_paths(&graph, x, y, 0, None) {}
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the element type for this iterator is not specified

Answer 1

It should be enough to use

for path in algo::all_simple_paths::<Vec<_>, _>(&graph, x, y, 0, None) {}

Here's a working example:

use petgraph::{algo, prelude::*};

fn main() {
    let mut graph = DiGraph::<&str, i32>::new();

    let a = graph.add_node("a");
    let b = graph.add_node("b");
    let c = graph.add_node("c");
    let d = graph.add_node("d");

    graph.extend_with_edges(&[
        (a, b, 1),
        (b, c, 1),
        (c, d, 1),
        (a, b, 1),
        (b, d, 1),
    ]);

    let ways = algo::all_simple_paths::<Vec<_>, _>(&graph, a, d, 0, None)
        .collect::<Vec<_>>();

    assert_eq!(4, ways.len());
}