Auto merge of rust-lang#73115 - RalfJung:rollup-jecowhz, r=RalfJung

Rollup of 10 pull requests

Successful merges:

 - rust-lang#72026 (Update annotate-snippets-rs to 0.8.0)
 - rust-lang#72583 (impl AsRef<[T]> for vec::IntoIter<T>)
 - rust-lang#72615 (Fix documentation example for gcov profiling)
 - rust-lang#72761 (Added the documentation for the 'use' keyword)
 - rust-lang#72799 (Add `-Z span-debug` to allow for easier debugging of proc macros)
 - rust-lang#72811 (Liballoc impl)
 - rust-lang#72963 (Cstring `from_raw` and `into_raw` safety precisions)
 - rust-lang#73001 (Free `default()` forwarding to `Default::default()`)
 - rust-lang#73075 (Add comments to `Resolve::get_module`)
 - rust-lang#73092 (Clean up E0646)

Failed merges:

r? @ghost

Cargo.lock

@@ -48,6 +48,12 @@ dependencies = [
  "ansi_term",
 ]
 
+[[package]]
+name = "annotate-snippets"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d78ea013094e5ea606b1c05fe35f1dd7ea1eb1ea259908d040b25bd5ec677ee5"
+
 [[package]]
 name = "ansi_term"
 version = "0.11.0"
@@ -3316,7 +3322,7 @@ version = "659.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c374e89b3c9714869ef86076942155383804ba6778c26be2169d324563c31f9"
 dependencies = [
- "annotate-snippets",
+ "annotate-snippets 0.6.1",
  "atty",
  "log",
  "rustc-ap-rustc_data_structures",
@@ -3810,7 +3816,7 @@ version = "0.0.0"
 name = "rustc_errors"
 version = "0.0.0"
 dependencies = [
- "annotate-snippets",
+ "annotate-snippets 0.8.0",
  "atty",
  "log",
  "rustc_data_structures",
@@ -4477,7 +4483,7 @@ dependencies = [
 name = "rustfmt-nightly"
 version = "1.4.15"
 dependencies = [
- "annotate-snippets",
+ "annotate-snippets 0.6.1",
  "bytecount",
  "cargo_metadata 0.8.0",
  "derive-new",

src/doc/unstable-book/src/compiler-flags/profile.md

@@ -12,10 +12,16 @@ For example:
 ```Bash
 cargo new testgcov --bin
 cd testgcov
-export RUSTFLAGS="-Zprofile"
+export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
+export CARGO_INCREMENTAL=0
 cargo build
 cargo run
 ```
 
 Once you've built and run your program, files with the `gcno` (after build) and `gcda` (after execution) extensions will be created.
 You can parse them with [llvm-cov gcov](https://llvm.org/docs/CommandGuide/llvm-cov.html#llvm-cov-gcov) or [grcov](https://github.com/mozilla/grcov).
+
+Please note that `RUSTFLAGS` by default applies to everything that cargo builds and runs during a build!
+When the `--target` flag is explicitly passed to cargo, the `RUSTFLAGS` no longer apply to build scripts and procedural macros. 
+For more fine-grained control consider passing a `RUSTC_WRAPPER` program to cargo that only adds the profiling flags to 
+rustc for the specific crates you want to profile.

src/doc/unstable-book/src/library-features/default-free-fn.md

@@ -0,0 +1,45 @@
+# `default_free_fn`
+
+The tracking issue for this feature is: [#73014]
+
+[#73014]: https://github.com/rust-lang/rust/issues/73014
+
+------------------------
+
+Adds a free `default()` function to the `std::default` module.  This function
+just forwards to [`Default::default()`], but may remove repetition of the word
+"default" from the call site.
+
+Here is an example:
+
+```rust
+#![feature(default_free_fn)]
+use std::default::default;
+
+#[derive(Default)]
+struct AppConfig {
+    foo: FooConfig,
+    bar: BarConfig,
+}
+
+#[derive(Default)]
+struct FooConfig {
+    foo: i32,
+}
+
+#[derive(Default)]
+struct BarConfig {
+    bar: f32,
+    baz: u8,
+}
+
+fn main() {
+    let options = AppConfig {
+        foo: default(),
+        bar: BarConfig {
+            bar: 10.1,
+            ..default()
+        },
+    };
+}
+```

src/liballoc/raw_vec.rs

@@ -118,6 +118,30 @@ impl<T> RawVec<T, Global> {
             RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len())
         }
     }
+
+    /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`.
+    ///
+    /// Note that this will correctly reconstitute any `cap` changes
+    /// that may have been performed. (See description of type for details.)
+    ///
+    /// # Safety
+    ///
+    /// * `len` must be greater than or equal to the most recently requested capacity, and
+    /// * `len` must be less than or equal to `self.capacity()`.
+    ///
+    /// Note, that the requested capacity and `self.capacity()` could differ, as
+    /// an allocator could overallocate and return a greater memory block than requested.
+    pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>]> {
+        // Sanity-check one half of the safety requirement (we cannot check the other half).
+        debug_assert!(
+            len <= self.capacity(),
+            "`len` must be smaller than or equal to `self.capacity()`"
+        );
+
+        let me = ManuallyDrop::new(self);
+        let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len);
+        Box::from_raw(slice)
+    }
 }
 
 impl<T, A: AllocRef> RawVec<T, A> {
@@ -520,32 +544,6 @@ where
     Ok(memory)
 }
 
-impl<T> RawVec<T, Global> {
-    /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`.
-    ///
-    /// Note that this will correctly reconstitute any `cap` changes
-    /// that may have been performed. (See description of type for details.)
-    ///
-    /// # Safety
-    ///
-    /// * `len` must be greater than or equal to the most recently requested capacity, and
-    /// * `len` must be less than or equal to `self.capacity()`.
-    ///
-    /// Note, that the requested capacity and `self.capacity()` could differ, as
-    /// an allocator could overallocate and return a greater memory block than requested.
-    pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>]> {
-        // Sanity-check one half of the safety requirement (we cannot check the other half).
-        debug_assert!(
-            len <= self.capacity(),
-            "`len` must be smaller than or equal to `self.capacity()`"
-        );
-
-        let me = ManuallyDrop::new(self);
-        let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len);
-        Box::from_raw(slice)
-    }
-}
-
 unsafe impl<#[may_dangle] T, A: AllocRef> Drop for RawVec<T, A> {
     /// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
     fn drop(&mut self) {

src/liballoc/vec.rs

@@ -1905,6 +1905,22 @@ unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
 // Common trait implementations for Vec
 ////////////////////////////////////////////////////////////////////////////////
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> ops::Deref for Vec<T> {
+    type Target = [T];
+
+    fn deref(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.as_ptr(), self.len) }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> ops::DerefMut for Vec<T> {
+    fn deref_mut(&mut self) -> &mut [T] {
+        unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) }
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone> Clone for Vec<T> {
     #[cfg(not(test))]
@@ -1960,22 +1976,6 @@ impl<T, I: SliceIndex<[T]>> IndexMut<I> for Vec<T> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> ops::Deref for Vec<T> {
-    type Target = [T];
-
-    fn deref(&self) -> &[T] {
-        unsafe { slice::from_raw_parts(self.as_ptr(), self.len) }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> ops::DerefMut for Vec<T> {
-    fn deref_mut(&mut self) -> &mut [T] {
-        unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) }
-    }
-}
-
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
@@ -2628,6 +2628,13 @@ impl<T> IntoIter<T> {
     }
 }
 
+#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
+impl<T> AsRef<[T]> for IntoIter<T> {
+    fn as_ref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: Send> Send for IntoIter<T> {}
 #[stable(feature = "rust1", since = "1.0.0")]

src/libcore/default.rs

@@ -115,6 +115,50 @@ pub trait Default: Sized {
     fn default() -> Self;
 }
 
+/// Return the default value of a type according to the `Default` trait.
+///
+/// The type to return is inferred from context; this is equivalent to
+/// `Default::default()` but shorter to type.
+///
+/// For example:
+/// ```
+/// #![feature(default_free_fn)]
+///
+/// use std::default::default;
+///
+/// #[derive(Default)]
+/// struct AppConfig {
+///     foo: FooConfig,
+///     bar: BarConfig,
+/// }
+///
+/// #[derive(Default)]
+/// struct FooConfig {
+///     foo: i32,
+/// }
+///
+/// #[derive(Default)]
+/// struct BarConfig {
+///     bar: f32,
+///     baz: u8,
+/// }
+///
+/// fn main() {
+///     let options = AppConfig {
+///         foo: default(),
+///         bar: BarConfig {
+///             bar: 10.1,
+///             ..default()
+///         },
+///     };
+/// }
+/// ```
+#[unstable(feature = "default_free_fn", issue = "73014")]
+#[inline]
+pub fn default<T: Default>() -> T {
+    Default::default()
+}
+
 /// Derive macro generating an impl of the trait `Default`.
 #[rustc_builtin_macro]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]

src/librustc_error_codes/error_codes/E0646.md

@@ -1,4 +1,5 @@
 It is not possible to define `main` with a where clause.
+
 Erroneous code example:
 
 ```compile_fail,E0646

src/librustc_errors/Cargo.toml

@@ -17,7 +17,7 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 unicode-width = "0.1.4"
 atty = "0.2"
 termcolor = "1.0"
-annotate-snippets = "0.6.1"
+annotate-snippets = "0.8.0"
 termize = "0.1.1"
 
 [target.'cfg(windows)'.dependencies]