[beta] backports

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1349,17 +1349,25 @@ fn link_natively(
             continue;
         }
 
-        // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
-        // Fallback from '-static-pie' to '-static' in that case.
+        // Detect '-static-pie' used with an older version of gcc or clang not supporting it,
+        // or with glibc that's missing crt objects, e.g. for arches that don't support it.
+        // Fallback from '-static-pie' to '-static' in either case.
+        let mut static_pie_message = None;
         if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
-            && unknown_arg_regex.is_match(&out)
-            && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
             && cmd.get_args().iter().any(|e| e == "-static-pie")
         {
+            if unknown_arg_regex.is_match(&out)
+                && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
+            {
+                static_pie_message =
+                    Some("Linker does not support -static-pie command line option.");
+            } else if Regex::new(r"cannot (find|open) g?rcrt1\.o:").unwrap().is_match(&out) {
+                static_pie_message = Some("C library is missing static-PIE startup objects.");
+            }
+        }
+        if let Some(message) = static_pie_message {
             info!("linker output: {:?}", out);
-            warn!(
-                "Linker does not support -static-pie command line option. Retrying with -static instead."
-            );
+            warn!("{message} Retrying with -static instead.");
             // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
             let self_contained_crt_objects = self_contained_components.is_crt_objects_enabled();
             let opts = &sess.target;

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -6764,7 +6764,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     tcx,
                     ObligationCause::dummy(),
                     param_env,
-                    ty::TraitRef::new(tcx, trait_def_id, trait_args),
+                    parent_trait_pred.rebind(ty::TraitRef::new(tcx, trait_def_id, trait_args)),
                 );
                 self.predicate_may_hold(&obligation)
             })

library/alloc/src/string.rs

@@ -940,6 +940,10 @@ impl String {
     /// into a `String` with the [`from_raw_parts`] function, allowing
     /// the destructor to perform the cleanup.
     ///
+    /// If `capacity == 0`, then `pointer` may be dangling. Otherwise,
+    /// it will always be valid for reads and writes over `capacity`
+    /// bytes, and point to the start of the string.
+    ///
     /// [`from_raw_parts`]: String::from_raw_parts
     ///
     /// # Examples

library/core/src/convert/mod.rs

@@ -863,6 +863,28 @@ const impl AsMut<str> for str {
     }
 }
 
+#[stable(feature = "never_type", since = "1.100.0")]
+#[expect(
+    clippy::explicit_auto_deref,
+    reason = "https://github.com/rust-lang/rust-clippy/issues/17713"
+)]
+impl<T: ?Sized> AsRef<T> for ! {
+    fn as_ref(&self) -> &T {
+        *self
+    }
+}
+
+#[stable(feature = "never_type", since = "1.100.0")]
+#[expect(
+    clippy::explicit_auto_deref,
+    reason = "https://github.com/rust-lang/rust-clippy/issues/17713"
+)]
+impl<T: ?Sized> AsMut<T> for ! {
+    fn as_mut(&mut self) -> &mut T {
+        *self
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // THE NO-ERROR ERROR TYPE
 ////////////////////////////////////////////////////////////////////////////////

src/ci/github-actions/jobs.yml

@@ -621,10 +621,10 @@ auto:
         --skip tests
         --skip library
         --skip tidyselftest
-        && ./x.py --stage 2 test
-        --host=aarch64-apple-darwin
-        --target=aarch64-apple-darwin
-        src/tools/cargo
+#        && ./x.py --stage 2 test
+#        --host=aarch64-apple-darwin
+#        --target=aarch64-apple-darwin
+#        src/tools/cargo
       RUST_CONFIGURE_ARGS: >-
         --enable-sanitizers
         --enable-profiler
@@ -674,10 +674,10 @@ auto:
         --skip tests
         --skip library
         --skip tidyselftest
-        && ./x.py --stage 2 test
-        --host=aarch64-apple-darwin
-        --target=aarch64-apple-darwin
-        src/tools/cargo
+#        && ./x.py --stage 2 test
+#        --host=aarch64-apple-darwin
+#        --target=aarch64-apple-darwin
+#        src/tools/cargo
       RUST_CONFIGURE_ARGS: >-
         --enable-sanitizers
         --enable-profiler

tests/ui/derives/imperfect-derive-higher-ranked.rs

@@ -0,0 +1,11 @@
+// regression test for #164376
+
+#[derive(Clone)]
+struct S<'a, T>(&'a T);
+
+fn require<T>() where for<'a> S<'a, T>: Clone {}
+
+fn main() {
+    require::<&'static mut u8>();
+    //~^ ERROR the trait bound `&'static mut u8: Clone` is not satisfied
+}

tests/ui/derives/imperfect-derive-higher-ranked.stderr

@@ -0,0 +1,29 @@
+error[E0277]: the trait bound `&'static mut u8: Clone` is not satisfied
+  --> $DIR/imperfect-derive-higher-ranked.rs:9:15
+   |
+LL |     require::<&'static mut u8>();
+   |               ^^^^^^^^^^^^^^^ the trait `Clone` is not implemented for `&'static mut u8`
+   |
+help: the trait `Clone` is implemented for `u8`
+  --> $SRC_DIR/core/src/clone.rs:LL:COL
+  ::: $SRC_DIR/core/src/clone.rs:LL:COL
+   |
+   = note: in this macro invocation
+note: required for `S<'a, &'static mut u8>` to implement `for<'a> Clone`
+  --> $DIR/imperfect-derive-higher-ranked.rs:4:8
+   |
+LL | #[derive(Clone)]
+   |          ----- in this derive macro expansion
+LL | struct S<'a, T>(&'a T);
+   |        ^     - type parameter would need to implement `for<'a> Clone`
+   = help: consider manually implementing `for<'a> Clone` to avoid undesired bounds caused by "imperfect derives"
+   = note: to learn more, visit <https://github.com/rust-lang/rust/issues/26925>
+note: required by a bound in `require`
+  --> $DIR/imperfect-derive-higher-ranked.rs:6:41
+   |
+LL | fn require<T>() where for<'a> S<'a, T>: Clone {}
+   |                                         ^^^^^ required by this bound in `require`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/impl-trait/generic-with-implicit-hrtb-without-dyn.pre2021.stderr

@@ -1,16 +1,11 @@
-error[E0277]: the trait bound `!: AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not satisfied
+error[E0277]: the trait bound `(): AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not satisfied
   --> $DIR/generic-with-implicit-hrtb-without-dyn.rs:7:13
    |
 LL | fn ice() -> impl AsRef<Fn(&())> {
-   |             ^^^^^^^^^^^^^^^^^^^ the trait `AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not implemented for `!`
+   |             ^^^^^^^^^^^^^^^^^^^ the trait `AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not implemented for `()`
 ...
-LL |     todo!()
-   |     ------- return type was inferred to be `!` here
-   |
-help: `!` can be coerced to any type; consider casting it to a concrete type that implements the trait
-   |
-LL |     todo!() as /* Type */
-   |             +++++++++++++
+LL |     ()
+   |     -- return type was inferred to be `()` here
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/generic-with-implicit-hrtb-without-dyn.rs

@@ -5,10 +5,10 @@
 #![allow(warnings)]
 
 fn ice() -> impl AsRef<Fn(&())> {
-    //[pre2021]~^ ERROR: the trait bound `!: AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not satisfied [E0277]
+    //[pre2021]~^ ERROR: the trait bound `(): AsRef<(dyn for<'a> Fn(&'a ()) + 'static)>` is not satisfied [E0277]
     //[edition2021]~^^ ERROR: expected a type, found a trait [E0782]
     //[edition2021]~| ERROR: expected a type, found a trait [E0782]
-    todo!()
+    ()
 }
 
 fn main() {}