Auto merge of #68803 - Dylan-DPC:rollup-b4x6ghj, r=Dylan-DPC

Rollup of 8 pull requests

Successful merges:

 - #68678 (Install robots.txt into rust-docs tarballs)
 - #68711 (Added upper bound of what vecs and boxes can allocate)
 - #68744 (Do not ICE in `type-alias-impl-trait` with save-analysis)
 - #68777 (Clean up E0263 explanation)
 - #68787 (Optimize core::ptr::align_offset (part 1))
 - #68797 (Fix links to types instead of modules)
 - #68798 (Test that `#[track_caller]` as `fn()` respects RT / CTFE equivalence)
 - #68800 (Stabilize `core::iter::once_with()`)

Failed merges:

r? @ghost

Author: bors

src/bootstrap/dist.rs

@@ -105,6 +105,7 @@ impl Step for Docs {
         t!(fs::create_dir_all(&dst));
         let src = builder.doc_out(host);
         builder.cp_r(&src, &dst);
+        builder.install(&builder.src.join("src/doc/robots.txt"), &dst, 0o644);
 
         let mut cmd = rust_installer(builder);
         cmd.arg("generate")

src/doc/robots.txt

@@ -1,4 +1,3 @@
-# NB: This file is not automatically deployed. After changes, it needs to be uploaded manually to doc.rust-lang.org
 User-agent: *
 Disallow: /0.3/
 Disallow: /0.4/

src/liballoc/boxed.rs

@@ -2,7 +2,8 @@
 //!
 //! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
 //! heap allocation in Rust. Boxes provide ownership for this allocation, and
-//! drop their contents when they go out of scope.
+//! drop their contents when they go out of scope. Boxes also ensure that they
+//! never allocate more than `isize::MAX` bytes.
 //!
 //! # Examples
 //!

src/liballoc/vec.rs

@@ -4,6 +4,8 @@
 //! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and
 //! `O(1)` pop (from the end).
 //!
+//! Vectors ensure they never allocate more than `isize::MAX` bytes.
+//!
 //! # Examples
 //!
 //! You can explicitly create a [`Vec<T>`] with [`new`]:

src/libcore/iter/mod.rs

@@ -327,7 +327,7 @@ pub use self::sources::{empty, Empty};
 pub use self::sources::{from_fn, FromFn};
 #[stable(feature = "iter_once", since = "1.2.0")]
 pub use self::sources::{once, Once};
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub use self::sources::{once_with, OnceWith};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::sources::{repeat, Repeat};

src/libcore/iter/sources.rs

@@ -399,12 +399,12 @@ pub fn once<T>(value: T) -> Once<T> {
 ///
 /// [`once_with`]: fn.once_with.html
 #[derive(Copy, Clone, Debug)]
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub struct OnceWith<F> {
     gen: Option<F>,
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
     type Item = A;
 
@@ -420,24 +420,24 @@ impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> DoubleEndedIterator for OnceWith<F> {
     fn next_back(&mut self) -> Option<A> {
         self.next()
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> ExactSizeIterator for OnceWith<F> {
     fn len(&self) -> usize {
         self.gen.iter().len()
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> FusedIterator for OnceWith<F> {}
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 
 /// Creates an iterator that lazily generates a value exactly once by invoking
@@ -458,8 +458,6 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// Basic usage:
 ///
 /// ```
-/// #![feature(iter_once_with)]
-///
 /// use std::iter;
 ///
 /// // one is the loneliest number
@@ -476,8 +474,6 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// `.foorc`:
 ///
 /// ```no_run
-/// #![feature(iter_once_with)]
-///
 /// use std::iter;
 /// use std::fs;
 /// use std::path::PathBuf;
@@ -500,7 +496,7 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// }
 /// ```
 #[inline]
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
     OnceWith { gen: Some(gen) }
 }

src/libcore/lib.rs

@@ -87,7 +87,6 @@
 #![feature(intrinsics)]
 #![feature(try_find)]
 #![feature(is_sorted)]
-#![feature(iter_once_with)]
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]
 #![feature(never_type)]

src/libcore/ptr/mod.rs

@@ -1081,9 +1081,8 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
                 // uses e.g., subtraction `mod n`. It is entirely fine to do them `mod
                 // usize::max_value()` instead, because we take the result `mod n` at the end
                 // anyway.
-                inverse = inverse.wrapping_mul(2usize.wrapping_sub(x.wrapping_mul(inverse)))
-                    & (going_mod - 1);
-                if going_mod > m {
+                inverse = inverse.wrapping_mul(2usize.wrapping_sub(x.wrapping_mul(inverse)));
+                if going_mod >= m {
                     return inverse & (m - 1);
                 }
                 going_mod = going_mod.wrapping_mul(going_mod);
@@ -1115,26 +1114,33 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
     let gcdpow = intrinsics::cttz_nonzero(stride).min(intrinsics::cttz_nonzero(a));
     let gcd = 1usize << gcdpow;
 
-    if p as usize & (gcd - 1) == 0 {
+    if p as usize & (gcd.wrapping_sub(1)) == 0 {
         // This branch solves for the following linear congruence equation:
         //
-        // $$ p + so ≡ 0 mod a $$
+        // ` p + so = 0 mod a `
         //
-        // $p$ here is the pointer value, $s$ – stride of `T`, $o$ offset in `T`s, and $a$ – the
+        // `p` here is the pointer value, `s` - stride of `T`, `o` offset in `T`s, and `a` - the
         // requested alignment.
         //
-        // g = gcd(a, s)
-        // o = (a - (p mod a))/g * ((s/g)⁻¹ mod a)
+        // With `g = gcd(a, s)`, and the above asserting that `p` is also divisible by `g`, we can
+        // denote `a' = a/g`, `s' = s/g`, `p' = p/g`, then this becomes equivalent to:
         //
-        // The first term is “the relative alignment of p to a”, the second term is “how does
-        // incrementing p by s bytes change the relative alignment of p”. Division by `g` is
-        // necessary to make this equation well formed if $a$ and $s$ are not co-prime.
+        // ` p' + s'o = 0 mod a' `
+        // ` o = (a' - (p' mod a')) * (s'^-1 mod a') `
         //
-        // Furthermore, the result produced by this solution is not “minimal”, so it is necessary
-        // to take the result $o mod lcm(s, a)$. We can replace $lcm(s, a)$ with just a $a / g$.
-        let j = a.wrapping_sub(pmoda) >> gcdpow;
-        let k = smoda >> gcdpow;
-        return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow);
+        // The first term is "the relative alignment of `p` to `a`" (divided by the `g`), the second
+        // term is "how does incrementing `p` by `s` bytes change the relative alignment of `p`" (again
+        // divided by `g`).
+        // Division by `g` is necessary to make the inverse well formed if `a` and `s` are not
+        // co-prime.
+        //
+        // Furthermore, the result produced by this solution is not "minimal", so it is necessary
+        // to take the result `o mod lcm(s, a)`. We can replace `lcm(s, a)` with just a `a'`.
+        let a2 = a >> gcdpow;
+        let a2minus1 = a2.wrapping_sub(1);
+        let s2 = smoda >> gcdpow;
+        let minusp2 = a2.wrapping_sub(pmoda >> gcdpow);
+        return (minusp2.wrapping_mul(mod_inv(s2, a2))) & a2minus1;
     }
 
     // Cannot be aligned at all.

src/libcore/tests/lib.rs

@@ -13,7 +13,6 @@
 #![feature(hashmap_internals)]
 #![feature(try_find)]
 #![feature(is_sorted)]
-#![feature(iter_once_with)]
 #![feature(pattern)]
 #![feature(range_is_empty)]
 #![feature(raw)]

src/librustc_error_codes/error_codes/E0263.md

@@ -1,7 +1,16 @@
-A lifetime name cannot be declared more than once in the same scope. For
-example:
+A lifetime was declared more than once in the same scope.
+
+Erroneous code example:
 
 ```compile_fail,E0263
-// error, lifetime name `'a` declared twice in the same scope
-fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
+fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str, z: &'a str) { // error!
+}
+```
+
+Two lifetimes cannot have the same name. To fix this example, change
+the second `'a` lifetime into something else (`'c` for example):
+
+```
+fn foo<'a, 'b, 'c>(x: &'a str, y: &'b str, z: &'c str) { // ok!
+}
 ```