Auto merge of #42522 - frewsxcv:rollup, r=frewsxcv

Rollup of 5 pull requests

- Successful merges: #42470, #42490, #42497, #42510, #42512
- Failed merges:

Author: bors

src/Cargo.lock

@@ -262,7 +262,7 @@ pub trait Iterator {
     /// Creates an iterator starting at the same point, but stepping by
     /// the given amount at each iteration.
     ///
-    /// Note that it will always return the first element of the range,
+    /// Note that it will always return the first element of the iterator,
     /// regardless of the step given.
     ///
     /// # Panics

src/libcore/iter/iterator.rs

@@ -309,8 +309,8 @@ use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT};
 
 const A: AtomicUsize = ATOMIC_USIZE_INIT;
 static B: &'static AtomicUsize = &A;
-// error: cannot borrow a constant which contains interior mutability, create a
-//        static instead
+// error: cannot borrow a constant which may contain interior mutability,
+//        create a static instead
 ```
 
 A `const` represents a constant value that should never change. If one takes
@@ -338,8 +338,8 @@ use std::cell::Cell;
 
 const A: Cell<usize> = Cell::new(1);
 const B: &'static Cell<usize> = &A;
-// error: cannot borrow a constant which contains interior mutability, create
-//        a static instead
+// error: cannot borrow a constant which may contain interior mutability,
+//        create a static instead
 
 // or:
 struct C { a: Cell<usize> }

src/librustc_mir/diagnostics.rs

@@ -663,7 +663,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                         self.add(Qualif::NOT_CONST);
                         if self.mode != Mode::Fn {
                             span_err!(self.tcx.sess, self.span, E0492,
-                                      "cannot borrow a constant which contains \
+                                      "cannot borrow a constant which may contain \
                                        interior mutability, create a static instead");
                         }
                     }

src/librustc_mir/transform/qualify_consts.rs

@@ -285,10 +285,7 @@ impl<'a> base::Resolver for Resolver<'a> {
                      -> Result<Option<Rc<SyntaxExtension>>, Determinacy> {
         let def = match invoc.kind {
             InvocationKind::Attr { attr: None, .. } => return Ok(None),
-            _ => match self.resolve_invoc_to_def(invoc, scope, force) {
-                Ok(def) => def,
-                Err(determinacy) => return Err(determinacy),
-            },
+            _ => self.resolve_invoc_to_def(invoc, scope, force)?,
         };
 
         self.macro_defs.insert(invoc.expansion_data.mark, def.def_id());

src/librustc_resolve/macros.rs

@@ -288,6 +288,26 @@ impl CString {
     /// Failure to call [`from_raw`] will lead to a memory leak.
     ///
     /// [`from_raw`]: #method.from_raw
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::CString;
+    ///
+    /// let c_string = CString::new("foo").unwrap();
+    ///
+    /// let ptr = c_string.into_raw();
+    ///
+    /// unsafe {
+    ///     assert_eq!(b'f', *ptr as u8);
+    ///     assert_eq!(b'o', *ptr.offset(1) as u8);
+    ///     assert_eq!(b'o', *ptr.offset(2) as u8);
+    ///     assert_eq!(b'\0', *ptr.offset(3) as u8);
+    ///
+    ///     // retake pointer to free memory
+    ///     let _ = CString::from_raw(ptr);
+    /// }
+    /// ```
     #[stable(feature = "cstr_memory", since = "1.4.0")]
     pub fn into_raw(self) -> *mut c_char {
         Box::into_raw(self.into_inner()) as *mut c_char
@@ -311,6 +331,16 @@ impl CString {
     ///
     /// The returned buffer does **not** contain the trailing nul separator and
     /// it is guaranteed to not have any interior nul bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::CString;
+    ///
+    /// let c_string = CString::new("foo").unwrap();
+    /// let bytes = c_string.into_bytes();
+    /// assert_eq!(bytes, vec![b'f', b'o', b'o']);
+    /// ```
     #[stable(feature = "cstring_into", since = "1.7.0")]
     pub fn into_bytes(self) -> Vec<u8> {
         let mut vec = self.into_inner().into_vec();
@@ -323,6 +353,16 @@ impl CString {
     /// includes the trailing nul byte.
     ///
     /// [`into_bytes`]: #method.into_bytes
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::CString;
+    ///
+    /// let c_string = CString::new("foo").unwrap();
+    /// let bytes = c_string.into_bytes_with_nul();
+    /// assert_eq!(bytes, vec![b'f', b'o', b'o', b'\0']);
+    /// ```
     #[stable(feature = "cstring_into", since = "1.7.0")]
     pub fn into_bytes_with_nul(self) -> Vec<u8> {
         self.into_inner().into_vec()
@@ -332,6 +372,16 @@ impl CString {
     ///
     /// The returned slice does **not** contain the trailing nul separator and
     /// it is guaranteed to not have any interior nul bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::CString;
+    ///
+    /// let c_string = CString::new("foo").unwrap();
+    /// let bytes = c_string.as_bytes();
+    /// assert_eq!(bytes, &[b'f', b'o', b'o']);
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn as_bytes(&self) -> &[u8] {
         &self.inner[..self.inner.len() - 1]
@@ -341,6 +391,16 @@ impl CString {
     /// includes the trailing nul byte.
     ///
     /// [`as_bytes`]: #method.as_bytes
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::ffi::CString;
+    ///
+    /// let c_string = CString::new("foo").unwrap();
+    /// let bytes = c_string.as_bytes_with_nul();
+    /// assert_eq!(bytes, &[b'f', b'o', b'o', b'\0']);
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn as_bytes_with_nul(&self) -> &[u8] {
         &self.inner

src/libstd/ffi/c_str.rs

@@ -112,7 +112,7 @@ pub trait UnwindSafe {}
 /// This is a "helper marker trait" used to provide impl blocks for the
 /// `UnwindSafe` trait, for more information see that documentation.
 #[stable(feature = "catch_unwind", since = "1.9.0")]
-#[rustc_on_unimplemented = "the type {Self} contains interior mutability \
+#[rustc_on_unimplemented = "the type {Self} may contain interior mutability \
                             and a reference may not be safely transferrable \
                             across a catch_unwind boundary"]
 pub trait RefUnwindSafe {}

src/libstd/panic.rs

@@ -1249,10 +1249,7 @@ impl<'a> Parser<'a> {
             let mac = respan(lo.to(self.prev_span), Mac_ { path: pth, tts: tts });
             (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac))
         } else {
-            let (constness, unsafety, abi) = match self.parse_fn_front_matter() {
-                Ok(cua) => cua,
-                Err(e) => return Err(e),
-            };
+            let (constness, unsafety, abi) = self.parse_fn_front_matter()?;
 
             let ident = self.parse_ident()?;
             let mut generics = self.parse_generics()?;

src/libsyntax/parse/parser.rs

@@ -211,10 +211,7 @@ impl<T: Encodable> Encodable for P<[T]> {
 
 impl<T: Decodable> Decodable for P<[T]> {
     fn decode<D: Decoder>(d: &mut D) -> Result<P<[T]>, D::Error> {
-        Ok(P::from_vec(match Decodable::decode(d) {
-            Ok(t) => t,
-            Err(e) => return Err(e)
-        }))
+        Ok(P::from_vec(Decodable::decode(d)?))
     }
 }
 

src/libsyntax/ptr.rs

@@ -14,13 +14,13 @@ use std::cell::UnsafeCell;
 
 const A: UnsafeCell<usize> = UnsafeCell::new(1);
 const B: &'static UnsafeCell<usize> = &A;
-//~^ ERROR: cannot borrow a constant which contains interior mutability
+//~^ ERROR: cannot borrow a constant which may contain interior mutability
 
 struct C { a: UnsafeCell<usize> }
 const D: C = C { a: UnsafeCell::new(1) };
 const E: &'static UnsafeCell<usize> = &D.a;
-//~^ ERROR: cannot borrow a constant which contains interior mutability
+//~^ ERROR: cannot borrow a constant which may contain interior mutability
 const F: &'static C = &D;
-//~^ ERROR: cannot borrow a constant which contains interior mutability
+//~^ ERROR: cannot borrow a constant which may contain interior mutability
 
 fn main() {}

src/test/compile-fail/issue-17718-const-borrow.rs

@@ -0,0 +1,16 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::cell::Cell;
+use std::panic::catch_unwind;
+fn main() {
+    let mut x = Cell::new(22);
+    catch_unwind(|| { x.set(23); });
+}

src/test/ui/interior-mutability/interior-mutability.rs

@@ -0,0 +1,14 @@
+error[E0277]: the trait bound `std::cell::UnsafeCell<i32>: std::panic::RefUnwindSafe` is not satisfied in `std::cell::Cell<i32>`
+  --> $DIR/interior-mutability.rs:15:5
+   |
+15 |     catch_unwind(|| { x.set(23); });
+   |     ^^^^^^^^^^^^ the type std::cell::UnsafeCell<i32> may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+   |
+   = help: within `std::cell::Cell<i32>`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<i32>`
+   = note: required because it appears within the type `std::cell::Cell<i32>`
+   = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&std::cell::Cell<i32>`
+   = note: required because it appears within the type `[closure@$DIR/interior-mutability.rs:15:18: 15:35 x:&std::cell::Cell<i32>]`
+   = note: required by `std::panic::catch_unwind`
+
+error: aborting due to previous error(s)
+