refactor: use min_by in decision making helper

src/solver.rs

@@ -263,22 +263,17 @@ where
     I: Iterator<Item = V>,
     F: Fn(&P) -> I,
 {
-    let mut package: Option<(T, _)> = None;
-    let mut min_key = usize::MAX;
-    for (p, term) in potential_packages {
-        let key = list_available_versions(p.borrow())
-            .filter(|v| term.borrow().contains(v.borrow()))
-            .count();
-
-        if key < min_key {
-            min_key = key;
-            package = Some((p, term));
-        }
-    }
-    let (package, term) = package.expect("potential_packages gave us an empty iterator");
-    let ver =
-        list_available_versions(package.borrow()).find(|v| term.borrow().contains(v.borrow()));
-    (package, ver)
+    let count_valid = |(p, range): &(T, U)| {
+        list_available_versions(p.borrow())
+            .filter(|v| range.borrow().contains(v.borrow()))
+            .count()
+    };
+    let (pkg, range) = potential_packages
+        .min_by_key(count_valid)
+        .expect("potential_packages gave us an empty iterator");
+    let version =
+        list_available_versions(pkg.borrow()).find(|v| range.borrow().contains(v.borrow()));
+    (pkg, version)
 }
 
 /// A basic implementation of [DependencyProvider].