Rollup merge of #91746 - ssomers:btree_tests, r=Mark-Simulacrum

Btree: assert more API compatibility

Introducing a member such as `BTreeSet::min()` would silently break compatibility if no code calls the existing `BTreeSet::min(set)`. `BTreeSet` is the only btree class silently bringing in stable members, apart from many occurrences of `#[derive(Debug)]` on iterators.

r? `@Mark-Simulacrum`

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

@@ -1556,7 +1556,7 @@ fn test_clone_from() {
 }
 
 #[allow(dead_code)]
-fn test_variance() {
+fn assert_covariance() {
     fn map_key<'new>(v: BTreeMap<&'static str, ()>) -> BTreeMap<&'new str, ()> {
         v
     }
@@ -1615,7 +1615,7 @@ fn values_val<'a, 'new>(v: Values<'a, (), &'static str>) -> Values<'a, (), &'new
 }
 
 #[allow(dead_code)]
-fn test_sync() {
+fn assert_sync() {
     fn map<T: Sync>(v: &BTreeMap<T, T>) -> impl Sync + '_ {
         v
     }
@@ -1684,7 +1684,7 @@ fn vacant_entry<T: Sync + Ord + Default>(v: &mut BTreeMap<T, T>) -> impl Sync +
 }
 
 #[allow(dead_code)]
-fn test_send() {
+fn assert_send() {
     fn map<T: Send>(v: BTreeMap<T, T>) -> impl Send {
         v
     }

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

@@ -3,6 +3,7 @@
 use super::*;
 use crate::vec::Vec;
 use std::cmp::Ordering;
+use std::hash::{Hash, Hasher};
 use std::iter::FromIterator;
 use std::panic::{catch_unwind, AssertUnwindSafe};
 
@@ -513,7 +514,7 @@ fn cmp(&self, other: &Self) -> Ordering {
 }
 
 #[allow(dead_code)]
-fn test_variance() {
+fn assert_covariance() {
     fn set<'new>(v: BTreeSet<&'static str>) -> BTreeSet<&'new str> {
         v
     }
@@ -530,7 +531,7 @@ fn range<'a, 'new>(v: Range<'a, &'static str>) -> Range<'a, &'new str> {
 }
 
 #[allow(dead_code)]
-fn test_sync() {
+fn assert_sync() {
     fn set<T: Sync>(v: &BTreeSet<T>) -> impl Sync + '_ {
         v
     }
@@ -569,7 +570,7 @@ fn union<T: Sync + Ord>(v: &BTreeSet<T>) -> impl Sync + '_ {
 }
 
 #[allow(dead_code)]
-fn test_send() {
+fn assert_send() {
     fn set<T: Send>(v: BTreeSet<T>) -> impl Send {
         v
     }
@@ -607,6 +608,37 @@ fn union<T: Send + Sync + Ord>(v: &BTreeSet<T>) -> impl Send + '_ {
     }
 }
 
+#[allow(dead_code)]
+// Check that the member-like functions conditionally provided by #[derive()]
+// are not overriden by genuine member functions with a different signature.
+fn assert_derives() {
+    fn hash<T: Hash, H: Hasher>(v: BTreeSet<T>, state: &mut H) {
+        v.hash(state);
+        // Tested much more thoroughly outside the crate in btree_set_hash.rs
+    }
+    fn eq<T: PartialEq>(v: BTreeSet<T>) {
+        let _ = v.eq(&v);
+    }
+    fn ne<T: PartialEq>(v: BTreeSet<T>) {
+        let _ = v.ne(&v);
+    }
+    fn cmp<T: Ord>(v: BTreeSet<T>) {
+        let _ = v.cmp(&v);
+    }
+    fn min<T: Ord>(v: BTreeSet<T>, w: BTreeSet<T>) {
+        let _ = v.min(w);
+    }
+    fn max<T: Ord>(v: BTreeSet<T>, w: BTreeSet<T>) {
+        let _ = v.max(w);
+    }
+    fn clamp<T: Ord>(v: BTreeSet<T>, w: BTreeSet<T>, x: BTreeSet<T>) {
+        let _ = v.clamp(w, x);
+    }
+    fn partial_cmp<T: PartialOrd>(v: &BTreeSet<T>) {
+        let _ = v.partial_cmp(&v);
+    }
+}
+
 #[test]
 fn test_ord_absence() {
     fn set<K>(mut set: BTreeSet<K>) {