[std][BTree] Create tests for keys which can be == without being identical

library/alloc/src/collections/btree/map/tests.rs

@@ -11,7 +11,7 @@ use crate::fmt::Debug;
 use crate::rc::Rc;
 use crate::string::{String, ToString};
 use crate::testing::crash_test::{CrashTestDummy, Panic};
-use crate::testing::ord_chaos::{Cyclic3, Governed, Governor};
+use crate::testing::ord_chaos::{Cyclic3, Governed, Governor, IdBased};
 use crate::testing::rng::DeterministicRng;
 
 // Minimum number of elements to insert, to guarantee a tree with 2 levels,
@@ -2587,3 +2587,31 @@ fn cursor_peek_prev_agrees_with_cursor_mut() {
     let prev = cursor.peek_prev();
     assert_matches!(prev, Some((&3, _)));
 }
+
+#[test]
+fn test_id_based_insert() {
+    let mut lhs = BTreeMap::new();
+    let mut rhs = BTreeMap::new();
+
+    lhs.insert(IdBased { id: 0, name: "lhs_k".to_string() }, "lhs_v".to_string());
+    rhs.insert(IdBased { id: 0, name: "rhs_k".to_string() }, "rhs_v".to_string());
+
+    for (k, v) in rhs.into_iter() {
+        lhs.insert(k, v);
+    }
+
+    assert_eq!(lhs.pop_first().unwrap().0.name, "lhs_k".to_string());
+}
+
+#[test]
+fn test_id_based_append() {
+    let mut lhs = BTreeMap::new();
+    let mut rhs = BTreeMap::new();
+
+    lhs.insert(IdBased { id: 0, name: "lhs_k".to_string() }, "lhs_v".to_string());
+    rhs.insert(IdBased { id: 0, name: "rhs_k".to_string() }, "rhs_v".to_string());
+
+    lhs.append(&mut rhs);
+
+    assert_eq!(lhs.pop_first().unwrap().0.name, "lhs_k".to_string());
+}

library/alloctests/testing/ord_chaos.rs

@@ -2,6 +2,8 @@ use std::cell::Cell;
 use std::cmp::Ordering::{self, *};
 use std::ptr;
 
+use crate::string::String;
+
 // Minimal type with an `Ord` implementation violating transitivity.
 #[derive(Debug)]
 pub(crate) enum Cyclic3 {
@@ -79,3 +81,31 @@ impl<T: PartialEq> PartialEq for Governed<'_, T> {
 }
 
 impl<T: Eq> Eq for Governed<'_, T> {}
+
+// Comparison based only on the ID, the name is ignored.
+#[derive(Debug)]
+pub(crate) struct IdBased {
+    pub id: u32,
+    #[allow(dead_code)]
+    pub name: String,
+}
+
+impl PartialEq for IdBased {
+    fn eq(&self, other: &Self) -> bool {
+        self.id == other.id
+    }
+}
+
+impl Eq for IdBased {}
+
+impl PartialOrd for IdBased {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for IdBased {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.id.cmp(&other.id)
+    }
+}