Auto merge of #79319 - m-ou-se:rollup-d9n5viq, r=m-ou-se

Rollup of 10 pull requests

Successful merges:

 - #76941 (Add f{32,64}::is_subnormal)
 - #77697 (Split each iterator adapter and source into individual modules)
 - #78305 (Stabilize alloc::Layout const functions)
 - #78608 (Stabilize refcell_take)
 - #78793 (Clean up `StructuralEq` docs)
 - #79267 (BTreeMap: address namespace conflicts)
 - #79293 (Add test for eval order for a+=b)
 - #79295 (BTreeMap: fix minor testing mistakes in #78903)
 - #79297 (BTreeMap: swap the names of NodeRef::new and Root::new_leaf)
 - #79299 (Stabilise `then`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

3 files changed, 81 insertions, 3 deletions

diff --git a/src/test/ui/expr/compound-assignment/eval-order.rs b/src/test/ui/expr/compound-assignment/eval-order.rs
new file mode 100644
index 00000000000..658adae193e
--- /dev/null
+++ b/src/test/ui/expr/compound-assignment/eval-order.rs
@@ -0,0 +1,76 @@
+// Test evaluation order of operands of the compound assignment operators
+
+// run-pass
+
+use std::ops::AddAssign;
+
+enum Side {
+    Lhs,
+    Rhs,
+}
+
+// In the following tests, we place our value into a wrapper type so that we
+// can do an element access as the outer place expression. If we just had the
+// block expression, it'd be a value expression and not compile.
+struct Wrapper<T>(T);
+
+// Evaluation order for `a op= b` where typeof(a) and typeof(b) are primitives
+// is first `b` then `a`.
+fn primitive_compound() {
+    let mut side_order = vec![];
+    let mut int = Wrapper(0);
+
+    {
+        side_order.push(Side::Lhs);
+        int
+    }.0 += {
+        side_order.push(Side::Rhs);
+        0
+    };
+
+    assert!(matches!(side_order[..], [Side::Rhs, Side::Lhs]));
+}
+
+// Evaluation order for `a op=b` otherwise is first `a` then `b`.
+fn generic_compound<T: AddAssign<T> + Default>() {
+    let mut side_order = vec![];
+    let mut add_assignable: Wrapper<T> = Wrapper(Default::default());
+
+    {
+        side_order.push(Side::Lhs);
+        add_assignable
+    }.0 += {
+        side_order.push(Side::Rhs);
+        Default::default()
+    };
+
+    assert!(matches!(side_order[..], [Side::Lhs, Side::Rhs]));
+}
+
+fn custom_compound() {
+    struct Custom;
+
+    impl AddAssign<()> for Custom {
+        fn add_assign(&mut self, _: ()) {
+            // this block purposely left blank
+        }
+    }
+
+    let mut side_order = vec![];
+    let mut custom = Wrapper(Custom);
+
+    {
+        side_order.push(Side::Lhs);
+        custom
+    }.0 += {
+        side_order.push(Side::Rhs);
+    };
+
+    assert!(matches!(side_order[..], [Side::Lhs, Side::Rhs]));
+}
+
+fn main() {
+    primitive_compound();
+    generic_compound::<i32>();
+    custom_compound();
+}
diff --git a/src/test/ui/issues/issue-31173.stderr b/src/test/ui/issues/issue-31173.stderr
index 818e004ffc8..d371703e295 100644
--- a/src/test/ui/issues/issue-31173.stderr
+++ b/src/test/ui/issues/issue-31173.stderr
@@ -13,11 +13,13 @@ error[E0599]: no method named `collect` found for struct `Cloned<TakeWhile<&mut
 LL |         .collect();
    |          ^^^^^^^ method not found in `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>`
    | 
-  ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL
+  ::: $SRC_DIR/core/src/iter/adapters/cloned.rs:LL:COL
    |
 LL | pub struct Cloned<I> {
    | -------------------- doesn't satisfy `_: Iterator`
-...
+   | 
+  ::: $SRC_DIR/core/src/iter/adapters/take_while.rs:LL:COL
+   |
 LL | pub struct TakeWhile<I, P> {
    | -------------------------- doesn't satisfy `<_ as Iterator>::Item = &_`
    |
diff --git a/src/test/ui/mismatched_types/issue-36053-2.stderr b/src/test/ui/mismatched_types/issue-36053-2.stderr
index 0b1fcf58e2e..2efd37b4738 100644
--- a/src/test/ui/mismatched_types/issue-36053-2.stderr
+++ b/src/test/ui/mismatched_types/issue-36053-2.stderr
@@ -15,7 +15,7 @@ LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
    |                                       doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool`
    |                                       doesn't satisfy `_: FnMut<(&&str,)>`
    | 
-  ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL
+  ::: $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
    |
 LL | pub struct Filter<I, P> {
    | ----------------------- doesn't satisfy `_: Iterator`