Auto merge of #99315 - JohnTitor:rollup-77wzoc1, r=JohnTitor

Rollup of 7 pull requests

Successful merges:

 - #98387 (Add new unstable API `downcast` to `std::io::Error`)
 - #98662 (Add std::fs::write documentation precision)
 - #99253 (Remove FIXME from MIR `always_storage_live_locals`)
 - #99264 (Fix typo in mod.rs)
 - #99270 (Add `#[must_use]` to `Box::from_raw`)
 - #99277 (Stabilize `core::ffi::CStr`, `alloc::ffi::CString`, and friends)
 - #99307 (Add regression test for #64401)

Failed merges:

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

19 files changed, 226 insertions, 39 deletions

diff --git a/compiler/rustc_mir_dataflow/src/storage.rs b/compiler/rustc_mir_dataflow/src/storage.rs
index 566c9d2d505..c909648ea01 100644
--- a/compiler/rustc_mir_dataflow/src/storage.rs
+++ b/compiler/rustc_mir_dataflow/src/storage.rs
@@ -4,9 +4,6 @@ use rustc_middle::mir::{self, Local};
 /// The set of locals in a MIR body that do not have `StorageLive`/`StorageDead` annotations.
 ///
 /// These locals have fixed storage for the duration of the body.
-//
-// FIXME: Currently, we need to traverse the entire MIR to compute this. We should instead store it
-// as a field in the `LocalDecl` for each `Local`.
 pub fn always_storage_live_locals(body: &mir::Body<'_>) -> BitSet<Local> {
     let mut always_live_locals = BitSet::new_filled(body.local_decls.len());
 
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index d83bab7bbbd..c1ceeb0deb8 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -949,6 +949,7 @@ impl<T: ?Sized> Box<T> {
     /// [`Layout`]: crate::Layout
     #[stable(feature = "box_raw", since = "1.4.0")]
     #[inline]
+    #[must_use = "call `drop(from_raw(ptr))` if you intend to drop the `Box`"]
     pub unsafe fn from_raw(raw: *mut T) -> Self {
         unsafe { Self::from_raw_in(raw, Global) }
     }
diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index cde4219be84..ae61b1f1e8e 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -108,7 +108,7 @@ use crate::sync::Arc;
 /// and other memory errors.
 #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "cstring_type")]
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub struct CString {
     // Invariant 1: the slice ends with a zero byte and has a length of at least one.
     // Invariant 2: the slice contains only one zero byte.
@@ -132,7 +132,7 @@ pub struct CString {
 /// let _: NulError = CString::new(b"f\0oo".to_vec()).unwrap_err();
 /// ```
 #[derive(Clone, PartialEq, Eq, Debug)]
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub struct NulError(usize, Vec<u8>);
 
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -157,7 +157,7 @@ enum FromBytesWithNulErrorKind {
 /// let _: FromVecWithNulError = CString::from_vec_with_nul(b"f\0oo".to_vec()).unwrap_err();
 /// ```
 #[derive(Clone, PartialEq, Eq, Debug)]
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub struct FromVecWithNulError {
     error_kind: FromBytesWithNulErrorKind,
     bytes: Vec<u8>,
@@ -223,7 +223,7 @@ impl FromVecWithNulError {
 /// This `struct` is created by [`CString::into_string()`]. See
 /// its documentation for more.
 #[derive(Clone, PartialEq, Eq, Debug)]
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub struct IntoStringError {
     inner: CString,
     error: Utf8Error,
diff --git a/library/alloc/src/ffi/mod.rs b/library/alloc/src/ffi/mod.rs
index fec2bec566a..e8530fbc1f0 100644
--- a/library/alloc/src/ffi/mod.rs
+++ b/library/alloc/src/ffi/mod.rs
@@ -78,11 +78,11 @@
 //! [`String`]: crate::string::String
 //! [`CStr`]: core::ffi::CStr
 
-#![unstable(feature = "alloc_ffi", issue = "94079")]
+#![stable(feature = "alloc_ffi", since = "1.64.0")]
 
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub use self::c_str::FromVecWithNulError;
-#[unstable(feature = "alloc_c_string", issue = "94079")]
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub use self::c_str::{CString, IntoStringError, NulError};
 
 mod c_str;
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 541de5c9029..315469387e5 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -86,7 +86,6 @@
 #![allow(explicit_outlives_requirements)]
 //
 // Library features:
-#![cfg_attr(not(no_global_oom_handling), feature(alloc_c_string))]
 #![feature(alloc_layout_extra)]
 #![feature(allocator_api)]
 #![feature(array_chunks)]
@@ -106,7 +105,6 @@
 #![feature(const_maybe_uninit_write)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
 #![feature(const_refs_to_cell)]
-#![feature(core_c_str)]
 #![feature(core_intrinsics)]
 #![feature(const_eval_select)]
 #![feature(const_pin)]
diff --git a/library/alloc/tests/lib.rs b/library/alloc/tests/lib.rs
index bf5d0c941e9..c29e7b9c81e 100644
--- a/library/alloc/tests/lib.rs
+++ b/library/alloc/tests/lib.rs
@@ -11,7 +11,6 @@
 #![feature(const_nonnull_slice_from_raw_parts)]
 #![feature(const_ptr_write)]
 #![feature(const_try)]
-#![feature(core_c_str)]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
 #![feature(exact_size_is_empty)]
diff --git a/library/core/src/ffi/c_str.rs b/library/core/src/ffi/c_str.rs
index 10bf95abd39..ee9baf811e2 100644
--- a/library/core/src/ffi/c_str.rs
+++ b/library/core/src/ffi/c_str.rs
@@ -76,7 +76,7 @@ use crate::str;
 /// [str]: prim@str "str"
 #[derive(Hash)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "CStr")]
-#[unstable(feature = "core_c_str", issue = "94079")]
+#[stable(feature = "core_c_str", since = "1.64.0")]
 #[rustc_has_incoherent_inherent_impls]
 // FIXME:
 // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
@@ -108,7 +108,7 @@ pub struct CStr {
 /// let _: FromBytesWithNulError = CStr::from_bytes_with_nul(b"f\0oo").unwrap_err();
 /// ```
 #[derive(Clone, PartialEq, Eq, Debug)]
-#[unstable(feature = "core_c_str", issue = "94079")]
+#[stable(feature = "core_c_str", since = "1.64.0")]
 pub struct FromBytesWithNulError {
     kind: FromBytesWithNulErrorKind,
 }
diff --git a/library/core/src/ffi/mod.rs b/library/core/src/ffi/mod.rs
index 3b711c6b72d..ec1eaa99f0b 100644
--- a/library/core/src/ffi/mod.rs
+++ b/library/core/src/ffi/mod.rs
@@ -14,7 +14,7 @@ use crate::marker::PhantomData;
 use crate::num::*;
 use crate::ops::{Deref, DerefMut};
 
-#[unstable(feature = "core_c_str", issue = "94079")]
+#[stable(feature = "core_c_str", since = "1.64.0")]
 pub use self::c_str::{CStr, FromBytesUntilNulError, FromBytesWithNulError};
 
 mod c_str;
diff --git a/library/std/src/ffi/mod.rs b/library/std/src/ffi/mod.rs
index 484f42dafc3..d987bf69b25 100644
--- a/library/std/src/ffi/mod.rs
+++ b/library/std/src/ffi/mod.rs
@@ -146,24 +146,10 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-/// See [alloc::ffi::FromVecWithNulError].
-#[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
-pub type FromVecWithNulError = alloc::ffi::FromVecWithNulError;
-/// See [alloc::ffi::CString].
-#[stable(feature = "rust1", since = "1.0.0")]
-pub type CString = alloc::ffi::CString;
-/// See [alloc::ffi::IntoStringError].
-#[stable(feature = "rust1", since = "1.0.0")]
-pub type IntoStringError = alloc::ffi::IntoStringError;
-/// See [alloc::ffi::NulError].
-#[stable(feature = "rust1", since = "1.0.0")]
-pub type NulError = alloc::ffi::NulError;
-/// See [core::ffi::CStr].
-#[stable(feature = "rust1", since = "1.0.0")]
-pub type CStr = core::ffi::CStr;
-/// See [core::ffi::FromBytesWithNulError].
-#[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-pub type FromBytesWithNulError = core::ffi::FromBytesWithNulError;
+#[stable(feature = "alloc_c_string", since = "1.64.0")]
+pub use alloc::ffi::{CString, FromVecWithNulError, IntoStringError, NulError};
+#[stable(feature = "core_c_str", since = "1.64.0")]
+pub use core::ffi::{CStr, FromBytesWithNulError};
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::os_str::{OsStr, OsString};
diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index f46997b807a..d799776548a 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -295,6 +295,9 @@ pub fn read_to_string<P: AsRef<Path>>(path: P) -> io::Result<String> {
 /// This function will create a file if it does not exist,
 /// and will entirely replace its contents if it does.
 ///
+/// Depending on the platform, this function may fail if the
+/// full directory path does not exist.
+///
 /// This is a convenience function for using [`File::create`] and [`write_all`]
 /// with fewer imports.
 ///
@@ -349,6 +352,9 @@ impl File {
     /// This function will create a file if it does not exist,
     /// and will truncate it if it does.
     ///
+    /// Depending on the platform, this function may fail if the
+    /// full directory path does not exist.
+    ///
     /// See the [`OpenOptions::open`] function for more details.
     ///
     /// # Examples
diff --git a/library/std/src/io/error.rs b/library/std/src/io/error.rs
index 4a50e647c64..ff7fdcae16f 100644
--- a/library/std/src/io/error.rs
+++ b/library/std/src/io/error.rs
@@ -795,6 +795,68 @@ impl Error {
         }
     }
 
+    /// Attempt to downgrade the inner error to `E` if any.
+    ///
+    /// If this [`Error`] was constructed via [`new`] then this function will
+    /// attempt to perform downgrade on it, otherwise it will return [`Err`].
+    ///
+    /// If downgrade succeeds, it will return [`Ok`], otherwise it will also
+    /// return [`Err`].
+    ///
+    /// [`new`]: Error::new
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(io_error_downcast)]
+    ///
+    /// use std::fmt;
+    /// use std::io;
+    /// use std::error::Error;
+    ///
+    /// #[derive(Debug)]
+    /// enum E {
+    ///     Io(io::Error),
+    ///     SomeOtherVariant,
+    /// }
+    ///
+    /// impl fmt::Display for E {
+    ///    // ...
+    /// #    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    /// #        todo!()
+    /// #    }
+    /// }
+    /// impl Error for E {}
+    ///
+    /// impl From<io::Error> for E {
+    ///     fn from(err: io::Error) -> E {
+    ///         err.downcast::<E>()
+    ///             .map(|b| *b)
+    ///             .unwrap_or_else(E::Io)
+    ///     }
+    /// }
+    /// ```
+    #[unstable(feature = "io_error_downcast", issue = "99262")]
+    pub fn downcast<E>(self) -> result::Result<Box<E>, Self>
+    where
+        E: error::Error + Send + Sync + 'static,
+    {
+        match self.repr.into_data() {
+            ErrorData::Custom(b) if b.error.is::<E>() => {
+                let res = (*b).error.downcast::<E>();
+
+                // downcast is a really trivial and is marked as inline, so
+                // it's likely be inlined here.
+                //
+                // And the compiler should be able to eliminate the branch
+                // that produces `Err` here since b.error.is::<E>()
+                // returns true.
+                Ok(res.unwrap())
+            }
+            repr_data => Err(Self { repr: Repr::new(repr_data) }),
+        }
+    }
+
     /// Returns the corresponding [`ErrorKind`] for this error.
     ///
     /// # Examples
diff --git a/library/std/src/io/error/repr_bitpacked.rs b/library/std/src/io/error/repr_bitpacked.rs
index e80068b46ab..292bf4826fd 100644
--- a/library/std/src/io/error/repr_bitpacked.rs
+++ b/library/std/src/io/error/repr_bitpacked.rs
@@ -132,6 +132,15 @@ unsafe impl Send for Repr {}
 unsafe impl Sync for Repr {}
 
 impl Repr {
+    pub(super) fn new(dat: ErrorData<Box<Custom>>) -> Self {
+        match dat {
+            ErrorData::Os(code) => Self::new_os(code),
+            ErrorData::Simple(kind) => Self::new_simple(kind),
+            ErrorData::SimpleMessage(simple_message) => Self::new_simple_message(simple_message),
+            ErrorData::Custom(b) => Self::new_custom(b),
+        }
+    }
+
     pub(super) fn new_custom(b: Box<Custom>) -> Self {
         let p = Box::into_raw(b).cast::<u8>();
         // Should only be possible if an allocator handed out a pointer with
diff --git a/library/std/src/io/error/repr_unpacked.rs b/library/std/src/io/error/repr_unpacked.rs
index 3729c039c42..d6ad55b99f5 100644
--- a/library/std/src/io/error/repr_unpacked.rs
+++ b/library/std/src/io/error/repr_unpacked.rs
@@ -10,6 +10,10 @@ type Inner = ErrorData<Box<Custom>>;
 pub(super) struct Repr(Inner);
 
 impl Repr {
+    #[inline]
+    pub(super) fn new(dat: ErrorData<Box<Custom>>) -> Self {
+        Self(dat)
+    }
     pub(super) fn new_custom(b: Box<Custom>) -> Self {
         Self(Inner::Custom(b))
     }
diff --git a/library/std/src/io/error/tests.rs b/library/std/src/io/error/tests.rs
index 8d7877bcad3..c897a5e8701 100644
--- a/library/std/src/io/error/tests.rs
+++ b/library/std/src/io/error/tests.rs
@@ -1,4 +1,4 @@
-use super::{const_io_error, Custom, Error, ErrorData, ErrorKind, Repr};
+use super::{const_io_error, Custom, Error, ErrorData, ErrorKind, Repr, SimpleMessage};
 use crate::assert_matches::assert_matches;
 use crate::error;
 use crate::fmt;
@@ -141,3 +141,54 @@ fn test_custom_error_packing() {
         }) if error.downcast_ref::<Bojji>().as_deref() == Some(&Bojji(true)),
     );
 }
+
+#[derive(Debug)]
+struct E;
+
+impl fmt::Display for E {
+    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        Ok(())
+    }
+}
+
+impl error::Error for E {}
+
+#[test]
+fn test_std_io_error_downcast() {
+    // Case 1: custom error, downcast succeeds
+    let io_error = Error::new(ErrorKind::Other, Bojji(true));
+    let e: Box<Bojji> = io_error.downcast().unwrap();
+    assert!(e.0);
+
+    // Case 2: custom error, downcast fails
+    let io_error = Error::new(ErrorKind::Other, Bojji(true));
+    let io_error = io_error.downcast::<E>().unwrap_err();
+
+    //   ensures that the custom error is intact
+    assert_eq!(ErrorKind::Other, io_error.kind());
+    let e: Box<Bojji> = io_error.downcast().unwrap();
+    assert!(e.0);
+
+    // Case 3: os error
+    let errno = 20;
+    let io_error = Error::from_raw_os_error(errno);
+    let io_error = io_error.downcast::<E>().unwrap_err();
+
+    assert_eq!(errno, io_error.raw_os_error().unwrap());
+
+    // Case 4: simple
+    let kind = ErrorKind::OutOfMemory;
+    let io_error: Error = kind.into();
+    let io_error = io_error.downcast::<E>().unwrap_err();
+
+    assert_eq!(kind, io_error.kind());
+
+    // Case 5: simple message
+    const SIMPLE_MESSAGE: SimpleMessage =
+        SimpleMessage { kind: ErrorKind::Other, message: "simple message error test" };
+    let io_error = Error::from_static_message(&SIMPLE_MESSAGE);
+    let io_error = io_error.downcast::<E>().unwrap_err();
+
+    assert_eq!(SIMPLE_MESSAGE.kind, io_error.kind());
+    assert_eq!(SIMPLE_MESSAGE.message, &*format!("{io_error}"));
+}
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 8fbc5e27d02..ab50845e2b2 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -264,7 +264,6 @@
 #![feature(atomic_mut_ptr)]
 #![feature(char_error_internals)]
 #![feature(char_internals)]
-#![feature(core_c_str)]
 #![feature(core_intrinsics)]
 #![feature(cstr_from_bytes_until_nul)]
 #![feature(cstr_internals)]
@@ -297,8 +296,6 @@
 //
 // Library features (alloc):
 #![feature(alloc_layout_extra)]
-#![feature(alloc_c_string)]
-#![feature(alloc_ffi)]
 #![feature(allocator_api)]
 #![feature(get_mut_unchecked)]
 #![feature(map_try_insert)]
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index c70ac8c9806..d28c7b58b20 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -1114,7 +1114,7 @@ impl Thread {
     // Used only internally to construct a thread object without spawning
     // Panics if the name contains nuls.
     pub(crate) fn new(name: Option<CString>) -> Thread {
-        // We have to use `unsafe` here to constuct the `Parker` in-place,
+        // We have to use `unsafe` here to construct the `Parker` in-place,
         // which is required for the UNIX implementation.
         //
         // SAFETY: We pin the Arc immediately after creation, so its address never
diff --git a/src/test/ui/codegen/issue-64401.rs b/src/test/ui/codegen/issue-64401.rs
new file mode 100644
index 00000000000..53f85c63b53
--- /dev/null
+++ b/src/test/ui/codegen/issue-64401.rs
@@ -0,0 +1,51 @@
+// build-pass
+// The ICE didn't happen with `cargo check` but `cargo build`.
+
+use std::marker::PhantomData;
+
+trait Owned<'a> {
+    type Reader;
+}
+
+impl<'a> Owned<'a> for () {
+    type Reader = ();
+}
+
+trait Handler {
+    fn handle(&self);
+}
+
+struct CtxHandlerWithoutState<M, F> {
+    message_type: PhantomData<M>,
+    _function: F,
+}
+
+impl<M, F> CtxHandlerWithoutState<M, F> {
+    pub fn new(_function: F) -> Self {
+        Self {
+            message_type: PhantomData,
+            _function,
+        }
+    }
+}
+
+impl<'a, M, F> Handler for CtxHandlerWithoutState<M, F>
+where
+    F: Fn(<M as Owned<'a>>::Reader),
+    M: Owned<'a>,
+{
+    fn handle(&self) {}
+}
+
+fn e_to_i<M: for<'a> Owned<'a>>(_: <M as Owned<'_>>::Reader) {}
+
+fn send_external_to_internal<M>()
+where
+    M: for<'a> Owned<'a>,
+{
+    let _: Box<dyn Handler> = Box::new(CtxHandlerWithoutState::<M, _>::new(e_to_i::<M>));
+}
+
+fn main() {
+    send_external_to_internal::<()>()
+}
diff --git a/src/test/ui/lint/unused/must-use-box-from-raw.rs b/src/test/ui/lint/unused/must-use-box-from-raw.rs
new file mode 100644
index 00000000000..9ea7726894c
--- /dev/null
+++ b/src/test/ui/lint/unused/must-use-box-from-raw.rs
@@ -0,0 +1,11 @@
+// #99269
+
+// check-pass
+
+#![warn(unused_must_use)]
+
+unsafe fn free<T>(ptr: *mut T) {
+    Box::from_raw(ptr); //~ WARNING unused return value
+}
+
+fn main() {}
diff --git a/src/test/ui/lint/unused/must-use-box-from-raw.stderr b/src/test/ui/lint/unused/must-use-box-from-raw.stderr
new file mode 100644
index 00000000000..7769f09aa52
--- /dev/null
+++ b/src/test/ui/lint/unused/must-use-box-from-raw.stderr
@@ -0,0 +1,15 @@
+warning: unused return value of `Box::<T>::from_raw` that must be used
+  --> $DIR/must-use-box-from-raw.rs:8:5
+   |
+LL |     Box::from_raw(ptr);
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/must-use-box-from-raw.rs:5:9
+   |
+LL | #![warn(unused_must_use)]
+   |         ^^^^^^^^^^^^^^^
+   = note: call `drop(from_raw(ptr))` if you intend to drop the `Box`
+
+warning: 1 warning emitted
+