Auto merge of #75308 - JohnTitor:rollup-vnnny43, r=JohnTitor

Rollup of 15 pull requests

Successful merges:

 - #74712 (Update E0271 explanation)
 - #74842 (adjust remaining targets)
 - #75151 (Consistent variable name alloc for raw_vec)
 - #75162 (Fix the documentation for move about Fn traits implementations)
 - #75248 (Add `as_mut_ptr` to `NonNull<[T]>`)
 - #75262 (Show multi extension example for Path in doctests)
 - #75266 (Add safety section to `NonNull::as_*` method docs)
 - #75284 (Show relative example for Path ancestors)
 - #75285 (Separate example for Path strip_prefix)
 - #75287 (Show Path extension example change multi extension)
 - #75288 (Use assert! for Path exists example to check bool)
 - #75289 (Remove ambiguity from PathBuf pop example)
 - #75290 (fix `min_const_generics` version)
 - #75291 (Clean up E0750)
 - #75292 (Clean up E0502)

Failed merges:

r? @ghost

library/alloc/src/raw_vec.rs

@@ -203,13 +203,15 @@ impl<T, A: AllocRef> RawVec<T, A> {
     ///
     /// # Safety
     ///
-    /// The `ptr` must be allocated (via the given allocator `a`), and with the given `capacity`.
+    /// The `ptr` must be allocated (via the given allocator `alloc`), and with the given
+    /// `capacity`.
     /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit
     /// systems). ZST vectors may have a capacity up to `usize::MAX`.
-    /// If the `ptr` and `capacity` come from a `RawVec` created via `a`, then this is guaranteed.
+    /// If the `ptr` and `capacity` come from a `RawVec` created via `alloc`, then this is
+    /// guaranteed.
     #[inline]
-    pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, a: A) -> Self {
-        Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc: a }
+    pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self {
+        Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc }
     }
 
     /// Gets a raw pointer to the start of the allocation. Note that this is

library/core/src/ptr/non_null.rs

@@ -117,6 +117,24 @@ impl<T: ?Sized> NonNull<T> {
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
     /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+    ///
+    /// # Safety
+    ///
+    /// When calling this method, you have to ensure that all of the following is true:
+    /// - `self` is properly aligned
+    /// - `self` must point to an initialized instance of T; in particular, the pointer must be
+    ///   "dereferencable" in the sense defined [here].
+    ///
+    /// This applies even if the result of this method is unused!
+    /// (The part about being initialized is not yet fully decided, but until
+    /// it is, the only safe approach is to ensure that they are indeed initialized.)
+    ///
+    /// Additionally, the lifetime of `self` does not necessarily reflect the actual
+    /// lifetime of the data. *You* must enforce Rust's aliasing rules. In particular,
+    /// for the duration of this lifetime, the memory the pointer points to must not
+    /// get mutated (except inside `UnsafeCell`).
+    ///
+    /// [here]: crate::ptr#safety
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
     pub unsafe fn as_ref(&self) -> &T {
@@ -130,6 +148,24 @@ impl<T: ?Sized> NonNull<T> {
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
     /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+    ///
+    /// # Safety
+    ///
+    /// When calling this method, you have to ensure that all of the following is true:
+    /// - `self` is properly aligned
+    /// - `self` must point to an initialized instance of T; in particular, the pointer must be
+    ///   "dereferenceable" in the sense defined [here].
+    ///
+    /// This applies even if the result of this method is unused!
+    /// (The part about being initialized is not yet fully decided, but until
+    /// it is the only safe approach is to ensure that they are indeed initialized.)
+    ///
+    /// Additionally, the lifetime of `self` does not necessarily reflect the actual
+    /// lifetime of the data. *You* must enforce Rust's aliasing rules. In particular,
+    /// for the duration of this lifetime, the memory this pointer points to must not
+    /// get accessed (read or written) through any other pointer.
+    ///
+    /// [here]: crate::ptr#safety
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
     pub unsafe fn as_mut(&mut self) -> &mut T {
@@ -224,6 +260,24 @@ impl<T> NonNull<[T]> {
         unsafe { NonNull::new_unchecked(self.as_ptr().as_mut_ptr()) }
     }
 
+    /// Returns a raw pointer to the slice's buffer.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)]
+    /// use std::ptr::NonNull;
+    ///
+    /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
+    /// assert_eq!(slice.as_mut_ptr(), 1 as *mut i8);
+    /// ```
+    #[inline]
+    #[unstable(feature = "slice_ptr_get", issue = "74265")]
+    #[rustc_const_unstable(feature = "slice_ptr_get", issue = "74265")]
+    pub const fn as_mut_ptr(self) -> *mut T {
+        self.as_non_null_ptr().as_ptr()
+    }
+
     /// Returns a raw pointer to an element or subslice, without doing bounds
     /// checking.
     ///

library/std/src/keyword_docs.rs

@@ -943,8 +943,7 @@ mod mod_keyword {}
 /// Capture a [closure]'s environment by value.
 ///
 /// `move` converts any variables captured by reference or mutable reference
-/// to owned by value variables. The three [`Fn` trait]'s mirror the ways to capture
-/// variables, when `move` is used, the closures is represented by the `FnOnce` trait.
+/// to owned by value variables.
 ///
 /// ```rust
 /// let capture = "hello";
@@ -953,6 +952,23 @@ mod mod_keyword {}
 /// };
 /// ```
 ///
+/// Note: `move` closures may still implement [`Fn`] or [`FnMut`], even though
+/// they capture variables by `move`. This is because the traits implemented by
+/// a closure type are determined by *what* the closure does with captured
+/// values, not *how* it captures them:
+///
+/// ```rust
+/// fn create_fn() -> impl Fn() {
+///     let text = "Fn".to_owned();
+///
+///     move || println!("This is a: {}", text)
+/// }
+///
+///     let fn_plain = create_fn();
+///
+///     fn_plain();
+/// ```
+///
 /// `move` is often used when [threads] are involved.
 ///
 /// ```rust

library/std/src/path.rs

@@ -1232,10 +1232,10 @@ impl PathBuf {
     /// ```
     /// use std::path::{Path, PathBuf};
     ///
-    /// let mut p = PathBuf::from("/test/test.rs");
+    /// let mut p = PathBuf::from("/spirited/away.rs");
     ///
     /// p.pop();
-    /// assert_eq!(Path::new("/test"), p);
+    /// assert_eq!(Path::new("/spirited"), p);
     /// p.pop();
     /// assert_eq!(Path::new("/"), p);
     /// ```
@@ -1992,6 +1992,13 @@ impl Path {
     /// assert_eq!(ancestors.next(), Some(Path::new("/foo")));
     /// assert_eq!(ancestors.next(), Some(Path::new("/")));
     /// assert_eq!(ancestors.next(), None);
+    ///
+    /// let mut ancestors = Path::new("../foo/bar").ancestors();
+    /// assert_eq!(ancestors.next(), Some(Path::new("../foo/bar")));
+    /// assert_eq!(ancestors.next(), Some(Path::new("../foo")));
+    /// assert_eq!(ancestors.next(), Some(Path::new("..")));
+    /// assert_eq!(ancestors.next(), Some(Path::new("")));
+    /// assert_eq!(ancestors.next(), None);
     /// ```
     ///
     /// [`None`]: ../../std/option/enum.Option.html#variant.None
@@ -2053,8 +2060,9 @@ impl Path {
     /// assert_eq!(path.strip_prefix("/test/"), Ok(Path::new("haha/foo.txt")));
     /// assert_eq!(path.strip_prefix("/test/haha/foo.txt"), Ok(Path::new("")));
     /// assert_eq!(path.strip_prefix("/test/haha/foo.txt/"), Ok(Path::new("")));
-    /// assert_eq!(path.strip_prefix("test").is_ok(), false);
-    /// assert_eq!(path.strip_prefix("/haha").is_ok(), false);
+    ///
+    /// assert!(path.strip_prefix("test").is_err());
+    /// assert!(path.strip_prefix("/haha").is_err());
     ///
     /// let prefix = PathBuf::from("/test/");
     /// assert_eq!(path.strip_prefix(prefix), Ok(Path::new("haha/foo.txt")));
@@ -2140,9 +2148,8 @@ impl Path {
     /// ```
     /// use std::path::Path;
     ///
-    /// let path = Path::new("foo.rs");
-    ///
-    /// assert_eq!("foo", path.file_stem().unwrap());
+    /// assert_eq!("foo", Path::new("foo.rs").file_stem().unwrap());
+    /// assert_eq!("foo.tar", Path::new("foo.tar.gz").file_stem().unwrap());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn file_stem(&self) -> Option<&OsStr> {
@@ -2166,9 +2173,8 @@ impl Path {
     /// ```
     /// use std::path::Path;
     ///
-    /// let path = Path::new("foo.rs");
-    ///
-    /// assert_eq!("rs", path.extension().unwrap());
+    /// assert_eq!("rs", Path::new("foo.rs").extension().unwrap());
+    /// assert_eq!("gz", Path::new("foo.tar.gz").extension().unwrap());
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn extension(&self) -> Option<&OsStr> {
@@ -2247,6 +2253,8 @@ impl Path {
     ///
     /// let path = Path::new("foo.tar.gz");
     /// assert_eq!(path.with_extension(""), PathBuf::from("foo.tar"));
+    /// assert_eq!(path.with_extension("xz"), PathBuf::from("foo.tar.xz"));
+    /// assert_eq!(path.with_extension("").with_extension("txt"), PathBuf::from("foo.txt"));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn with_extension<S: AsRef<OsStr>>(&self, extension: S) -> PathBuf {
@@ -2473,7 +2481,7 @@ impl Path {
     ///
     /// ```no_run
     /// use std::path::Path;
-    /// assert_eq!(Path::new("does_not_exist.txt").exists(), false);
+    /// assert!(!Path::new("does_not_exist.txt").exists());
     /// ```
     ///
     /// # See Also

library/std/src/sys/hermit/mod.rs

@@ -106,7 +106,7 @@ pub unsafe extern "C" fn runtime_entry(
     argv: *const *const c_char,
     env: *const *const c_char,
 ) -> ! {
-    use crate::sys::hermit::fast_thread_local::run_dtors;
+    use crate::sys::hermit::thread_local_dtor::run_dtors;
     extern "C" {
         fn main(argc: isize, argv: *const *const c_char) -> i32;
     }

library/std/src/sys/hermit/thread.rs

@@ -4,7 +4,7 @@ use crate::ffi::CStr;
 use crate::io;
 use crate::mem;
 use crate::sys::hermit::abi;
-use crate::sys::hermit::fast_thread_local::run_dtors;
+use crate::sys::hermit::thread_local_dtor::run_dtors;
 use crate::time::Duration;
 
 pub type Tid = abi::Tid;

src/librustc_error_codes/error_codes/E0271.md

@@ -5,25 +5,6 @@ Erroneous code example:
 ```compile_fail,E0271
 trait Trait { type AssociatedType; }
 
-fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
-    println!("in foo");
-}
-
-impl Trait for i8 { type AssociatedType = &'static str; }
-
-foo(3_i8);
-```
-
-This is because of a type mismatch between the associated type of some
-trait (e.g., `T::Bar`, where `T` implements `trait Quux { type Bar; }`)
-and another type `U` that is required to be equal to `T::Bar`, but is not.
-Examples follow.
-
-Here is that same example again, with some explanatory comments:
-
-```compile_fail,E0271
-trait Trait { type AssociatedType; }
-
 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
 //                    ~~~~~~~~ ~~~~~~~~~~~~~~~~~~
 //                        |            |
@@ -56,11 +37,9 @@ foo(3_i8);
 // therefore the type-checker complains with this error code.
 ```
 
-To avoid those issues, you have to make the types match correctly.
-So we can fix the previous examples like this:
-
+The issue can be resolved by changing the associated type:
+1) in the `foo` implementation:
 ```
-// Basic Example:
 trait Trait { type AssociatedType; }
 
 fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
@@ -70,13 +49,17 @@ fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
 impl Trait for i8 { type AssociatedType = &'static str; }
 
 foo(3_i8);
-
-// For-Loop Example:
-let vs = vec![1, 2, 3, 4];
-for v in &vs {
-    match v {
-        &1 => {}
-        _ => {}
-    }
-}
+```
+
+2) in the `Trait` implementation for `i8`:
+```
+trait Trait { type AssociatedType; }
+
+fn foo<T>(t: T) where T: Trait<AssociatedType = u32> {
+    println!("in foo");
+}
+
+impl Trait for i8 { type AssociatedType = u32; }
+
+foo(3_i8);
 ```

src/librustc_error_codes/error_codes/E0502.md

@@ -5,7 +5,7 @@ Erroneous code example:
 ```compile_fail,E0502
 fn bar(x: &mut i32) {}
 fn foo(a: &mut i32) {
-    let ref y = a; // a is borrowed as immutable.
+    let y = &a; // a is borrowed as immutable.
     bar(a); // error: cannot borrow `*a` as mutable because `a` is also borrowed
             //        as immutable
     println!("{}", y);
@@ -19,7 +19,7 @@ variable before trying to access it mutably:
 fn bar(x: &mut i32) {}
 fn foo(a: &mut i32) {
     bar(a);
-    let ref y = a; // ok!
+    let y = &a; // ok!
     println!("{}", y);
 }
 ```

src/librustc_error_codes/error_codes/E0750.md

@@ -1,4 +1,18 @@
-Negative impls cannot be default impls. A default impl supplies
-default values for the items within to be used by other impls, whereas
-a negative impl declares that there are no other impls. These don't
-make sense to combine.
+A negative impl was made default impl.
+
+Erroneous code example:
+
+```compile_fail,E0750
+# #![feature(negative_impls)]
+# #![feature(specialization)]
+trait MyTrait {
+    type Foo;
+}
+
+default impl !MyTrait for u32 {} // error!
+# fn main() {}
+```
+
+Negative impls cannot be default impls. A default impl supplies default values
+for the items within to be used by other impls, whereas a negative impl declares
+that there are no other impls. Combining it does not make sense.

src/librustc_feature/active.rs

@@ -580,7 +580,7 @@ declare_features! (
     (active, const_fn_transmute, "1.46.0", Some(53605), None),
 
     /// The smallest useful subset of `const_generics`.
-    (active, min_const_generics, "1.46.0", Some(74878), None),
+    (active, min_const_generics, "1.47.0", Some(74878), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates

src/tools/tidy/src/error_codes_check.rs

@@ -16,8 +16,7 @@ const EXEMPTED_FROM_TEST: &[&str] = &[
 ];
 
 // Some error codes don't have any tests apparently...
-const IGNORE_EXPLANATION_CHECK: &[&str] =
-    &["E0570", "E0601", "E0602", "E0639", "E0729", "E0749", "E0750"];
+const IGNORE_EXPLANATION_CHECK: &[&str] = &["E0570", "E0601", "E0602", "E0639", "E0729", "E0749"];
 
 fn check_error_code_explanation(
     f: &str,