Auto merge of #136185 - matthiaskrgr:rollup-zqzy6wb, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #133151 (Trim extra whitespace in fn ptr suggestion span)
 - #133829 (Implement `AtomicT::update` & `AtomicT::try_update`)
 - #135367 (Enable `unreachable_pub` lint in `alloc`)
 - #135748 (Lower index bounds checking to `PtrMetadata`, this time with the right fake borrow semantics 😸)
 - #135805 (Add missing allocator safety in alloc crate)
 - #135886 (Document purpose of closure in from_fn.rs more clearly)
 - #135961 (Fix 2/4 tests skipped by opt-dist)
 - #136012 (Document powf and powi values that are always 1.0)

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

Author: bors

tests/pass/disjoint-array-accesses.rs

@@ -0,0 +1,35 @@
+// This is a regression test for issue #135671 where a MIR refactor about arrays and their lengths
+// unexpectedly caused borrowck errors for disjoint borrows of array elements, for which we had no
+// tests. This is a collection of a few code samples from that issue.
+
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+
+struct Test {
+    a: i32,
+    b: i32,
+}
+
+fn one() {
+    let inputs: &mut [_] = &mut [Test { a: 0, b: 0 }];
+    let a = &mut inputs[0].a;
+    let b = &mut inputs[0].b;
+
+    *a = 0;
+    *b = 1;
+}
+
+fn two() {
+    let slice = &mut [(0, 0)][..];
+    std::mem::swap(&mut slice[0].0, &mut slice[0].1);
+}
+
+fn three(a: &mut [(i32, i32)], i: usize, j: usize) -> (&mut i32, &mut i32) {
+    (&mut a[i].0, &mut a[j].1)
+}
+
+fn main() {
+    one();
+    two();
+    three(&mut [(1, 2), (3, 4)], 0, 1);
+}