Add try_into for usize to isize

releasenotes/notes/fix-gnp-random-directed-41f2a436c49b9064.yaml

@@ -4,4 +4,4 @@ fixes:
     Fixed an issue where the :func:`~rustworkx.generators.directed_gnp_random_graph`
     and the :func:`~rustworkx-core.generators.gnp_random_graph` for directed graphs
     produced a graph where lower node numbers had only a small number of edges
-    compared to what was expected and the output was therefore not random.
+    compared to what was expected.

rustworkx-core/src/generators/random_graph.rs

@@ -114,7 +114,7 @@ where
                 }
             }
         } else {
-            let num_nodes = num_nodes as isize;
+            let num_nodes: isize = num_nodes.try_into().map_err(|_| InvalidInputError).unwrap();
             let lp: f64 = (1.0 - probability).ln();
             let between = Uniform::new(0.0, 1.0);