Auto merge of #37090 - GuillaumeGomez:rollup, r=GuillaumeGomez

Rollup of 9 pull requests

- Successful merges: #36679, #36699, #36997, #37040, #37060, #37065, #37072, #37073, #37081
- Failed merges:

Author: bors

src/doc/book/lifetimes.md

@@ -56,8 +56,12 @@ To fix this, we have to make sure that step four never happens after step
 three. The ownership system in Rust does this through a concept called
 lifetimes, which describe the scope that a reference is valid for.
 
-When we have a function that takes an argument by reference, we can be
-implicit or explicit about the lifetime of the reference:
+**Note** It's important to understand that lifetime annotations are
+_descriptive_, not _prescriptive_. This means that how long a reference is valid
+is determined by the code, not by the annotations. The annotations, however,
+give information about lifetimes to the compiler that uses them to check the
+validity of references. The compiler can do so without annotations in simple
+cases, but needs the programmers support in complex scenarios.
 
 ```rust
 // implicit

src/libcollections/fmt.rs

@@ -327,7 +327,7 @@
 //! format := '{' [ argument ] [ ':' format_spec ] '}'
 //! argument := integer | identifier
 //!
-//! format_spec := [[fill]align][sign]['#'][0][width]['.' precision][type]
+//! format_spec := [[fill]align][sign]['#']['0'][width]['.' precision][type]
 //! fill := character
 //! align := '<' | '^' | '>'
 //! sign := '+' | '-'

src/libcollections/str.rs

@@ -1789,4 +1789,24 @@ impl str {
             String::from_utf8_unchecked(slice.into_vec())
         }
     }
+
+    /// Create a [`String`] by repeating a string `n` times.
+    ///
+    /// [`String`]: string/struct.String.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(repeat_str)]
+    ///
+    /// assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
+    /// ```
+    #[unstable(feature = "repeat_str", issue = "37079")]
+    pub fn repeat(&self, n: usize) -> String {
+        let mut s = String::with_capacity(self.len() * n);
+        s.extend((0..n).map(|_| self));
+        s
+    }
 }

src/libcollections/string.rs

@@ -14,12 +14,11 @@
 //! [`ToString`]s, and several error types that may result from working with
 //! [`String`]s.
 //!
-//! [`String`]: struct.String.html
 //! [`ToString`]: trait.ToString.html
 //!
 //! # Examples
 //!
-//! There are multiple ways to create a new `String` from a string literal:
+//! There are multiple ways to create a new [`String`] from a string literal:
 //!
 //! ```
 //! let s = "Hello".to_string();
@@ -28,9 +27,11 @@
 //! let s: String = "also this".into();
 //! ```
 //!
-//! You can create a new `String` from an existing one by concatenating with
+//! You can create a new [`String`] from an existing one by concatenating with
 //! `+`:
 //!
+//! [`String`]: struct.String.html
+//!
 //! ```
 //! let s = "Hello".to_string();
 //!

src/libcollectionstest/lib.rs

@@ -19,6 +19,7 @@
 #![feature(enumset)]
 #![feature(pattern)]
 #![feature(rand)]
+#![feature(repeat_str)]
 #![feature(step_by)]
 #![feature(str_escape)]
 #![feature(str_replacen)]

src/libcollectionstest/str.rs

@@ -1286,6 +1286,13 @@ fn test_cow_from() {
     }
 }
 
+#[test]
+fn test_repeat() {
+    assert_eq!("".repeat(3), "");
+    assert_eq!("abc".repeat(0), "");
+    assert_eq!("α".repeat(3), "ααα");
+}
+
 mod pattern {
     use std::str::pattern::Pattern;
     use std::str::pattern::{Searcher, ReverseSearcher};

src/librustc_const_eval/check_match.rs

@@ -1238,8 +1238,10 @@ impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> {
         match pat.node {
             PatKind::Binding(.., ref subpat) => {
                 if !self.bindings_allowed {
-                    span_err!(self.cx.tcx.sess, pat.span, E0303,
-                              "pattern bindings are not allowed after an `@`");
+                    struct_span_err!(self.cx.tcx.sess, pat.span, E0303,
+                                     "pattern bindings are not allowed after an `@`")
+                        .span_label(pat.span,  &format!("not allowed after `@`"))
+                        .emit();
                 }
 
                 if subpat.is_some() {