Auto merge of #59949 - Centril:rollup-lsiqq1g, r=Centril

Rollup of 16 pull requests

Successful merges:

 - #59675 (Stabilize the `alloc` crate.)
 - #59708 (Mark variables captured by reference as mutable correctly)
 - #59735 (remove lookup_char_pos_adj)
 - #59747 (Copy book.toml unstable book generator)
 - #59796 (Retire `IsNotConst` naming)
 - #59804 (Clean up jobserver integration)
 - #59818 (Eliminate `FnBox` usages from libstd.)
 - #59830 (Fix links on keyword docs.)
 - #59835 (Re-export NonZero signed variant in std)
 - #59852 (std: Add `{read,write}_vectored` for more types)
 - #59855 (Fix attributes position in type declaration)
 - #59858 (Make duplicate matcher bindings a hard error)
 - #59899 (In `-Zprint-type-size` output, sort enum variants by size.)
 - #59912 (MaybeUninit: remove deprecated functions)
 - #59925 (Fix paste error in split_ascii_whitespace docs.)
 - #59930 (Exclude some copies of old book editions from search engines)

Failed merges:

r? @ghost

2 files changed, 3 insertions, 5 deletions

diff --git a/src/libstd/sys_common/at_exit_imp.rs b/src/libstd/sys_common/at_exit_imp.rs
index 1181b861611..cdb72ee872e 100644
--- a/src/libstd/sys_common/at_exit_imp.rs
+++ b/src/libstd/sys_common/at_exit_imp.rs
@@ -2,12 +2,11 @@
 //!
 //! Documentation can be found on the `rt::at_exit` function.
 
-use crate::boxed::FnBox;
 use crate::ptr;
 use crate::mem;
 use crate::sys_common::mutex::Mutex;
 
-type Queue = Vec<Box<dyn FnBox()>>;
+type Queue = Vec<Box<dyn FnOnce()>>;
 
 // NB these are specifically not types from `std::sync` as they currently rely
 // on poisoning and this module needs to operate at a lower level than requiring
@@ -61,7 +60,7 @@ pub fn cleanup() {
     }
 }
 
-pub fn push(f: Box<dyn FnBox()>) -> bool {
+pub fn push(f: Box<dyn FnOnce()>) -> bool {
     unsafe {
         let _guard = LOCK.lock();
         if init() {
diff --git a/src/libstd/sys_common/thread.rs b/src/libstd/sys_common/thread.rs
index b2142e75308..6ab0d5cbe9c 100644
--- a/src/libstd/sys_common/thread.rs
+++ b/src/libstd/sys_common/thread.rs
@@ -1,4 +1,3 @@
-use crate::boxed::FnBox;
 use crate::env;
 use crate::sync::atomic::{self, Ordering};
 use crate::sys::stack_overflow;
@@ -11,7 +10,7 @@ pub unsafe fn start_thread(main: *mut u8) {
     let _handler = stack_overflow::Handler::new();
 
     // Finally, let's run some code.
-    Box::from_raw(main as *mut Box<dyn FnBox()>)()
+    Box::from_raw(main as *mut Box<dyn FnOnce()>)()
 }
 
 pub fn min_stack() -> usize {