Merge from rustc

3 files changed, 50 insertions, 10 deletions

diff --git a/library/alloc/src/fmt.rs b/library/alloc/src/fmt.rs
index 4b9b90fc1f1..571fcd177aa 100644
--- a/library/alloc/src/fmt.rs
+++ b/library/alloc/src/fmt.rs
@@ -581,7 +581,7 @@ pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::Error;
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-pub use core::fmt::FormatterFn;
+pub use core::fmt::{from_fn, FromFn};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{write, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 124230812df..e628be1546f 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -2643,14 +2643,54 @@ impl ToString for i8 {
     }
 }
 
-#[doc(hidden)]
+// Generic/generated code can sometimes have multiple, nested references
+// for strings, including `&&&str`s that would never be written
+// by hand. This macro generates twelve layers of nested `&`-impl
+// for primitive strings.
 #[cfg(not(no_global_oom_handling))]
-#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
-impl ToString for str {
-    #[inline]
-    fn to_string(&self) -> String {
-        String::from(self)
-    }
+macro_rules! to_string_str_wrap_in_ref {
+    {x $($x:ident)*} => {
+        &to_string_str_wrap_in_ref! { $($x)* }
+    };
+    {} => { str };
+}
+#[cfg(not(no_global_oom_handling))]
+macro_rules! to_string_expr_wrap_in_deref {
+    {$self:expr ; x $($x:ident)*} => {
+        *(to_string_expr_wrap_in_deref! { $self ; $($x)* })
+    };
+    {$self:expr ;} => { $self };
+}
+#[cfg(not(no_global_oom_handling))]
+macro_rules! to_string_str {
+    {$($($x:ident)*),+} => {
+        $(
+            #[doc(hidden)]
+            #[stable(feature = "str_to_string_specialization", since = "1.9.0")]
+            impl ToString for to_string_str_wrap_in_ref!($($x)*) {
+                #[inline]
+                fn to_string(&self) -> String {
+                    String::from(to_string_expr_wrap_in_deref!(self ; $($x)*))
+                }
+            }
+        )+
+    };
+}
+
+#[cfg(not(no_global_oom_handling))]
+to_string_str! {
+    x x x x x x x x x x x x,
+    x x x x x x x x x x x,
+    x x x x x x x x x x,
+    x x x x x x x x x,
+    x x x x x x x x,
+    x x x x x x x,
+    x x x x x x,
+    x x x x x,
+    x x x x,
+    x x x,
+    x x,
+    x,
 }
 
 #[doc(hidden)]
diff --git a/library/alloc/tests/task.rs b/library/alloc/tests/task.rs
index 034039a1eae..390dec14484 100644
--- a/library/alloc/tests/task.rs
+++ b/library/alloc/tests/task.rs
@@ -4,7 +4,7 @@ use alloc::task::{LocalWake, Wake};
 use core::task::{LocalWaker, Waker};
 
 #[test]
-#[cfg_attr(miri, should_panic)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it fails
+#[cfg_attr(miri, ignore)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it can fail
 fn test_waker_will_wake_clone() {
     struct NoopWaker;
 
@@ -20,7 +20,7 @@ fn test_waker_will_wake_clone() {
 }
 
 #[test]
-#[cfg_attr(miri, should_panic)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it fails
+#[cfg_attr(miri, ignore)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it can fail
 fn test_local_waker_will_wake_clone() {
     struct NoopWaker;