Auto merge of #43800 - GuillaumeGomez:rollup, r=GuillaumeGomez

Rollup of 18 pull requests

- Successful merges: #43176, #43632, #43650, #43712, #43715, #43721, #43739, #43741, #43744, #43747, #43752, #43760, #43773, #43779, #43783, #43791, #43793, #43795
- Failed merges:

Author: bors

src/liballoc/arc.rs

@@ -95,7 +95,7 @@ const MAX_REFCOUNT: usize = (isize::MAX) as usize;
 /// # Cloning references
 ///
 /// Creating a new reference from an existing reference counted pointer is done using the
-/// `Clone` trait implemented for [`Arc<T>`][`arc`] and [`Weak<T>`][`weak`].
+/// `Clone` trait implemented for [`Arc<T>`][arc] and [`Weak<T>`][weak].
 ///
 /// ```
 /// use std::sync::Arc;

src/liballoc/string.rs

@@ -144,7 +144,7 @@ use boxed::Box;
 /// # Deref
 ///
 /// `String`s implement [`Deref`]`<Target=str>`, and so inherit all of [`str`]'s
-/// methods. In addition, this means that you can pass a `String` to any
+/// methods. In addition, this means that you can pass a `String` to a
 /// function which takes a [`&str`] by using an ampersand (`&`):
 ///
 /// ```
@@ -160,8 +160,38 @@ use boxed::Box;
 ///
 /// This will create a [`&str`] from the `String` and pass it in. This
 /// conversion is very inexpensive, and so generally, functions will accept
-/// [`&str`]s as arguments unless they need a `String` for some specific reason.
+/// [`&str`]s as arguments unless they need a `String` for some specific
+/// reason.
 ///
+/// In certain cases Rust doesn't have enough information to make this
+/// conversion, known as `Deref` coercion. In the following example a string
+/// slice `&'a str` implements the trait `TraitExample`, and the function
+/// `example_func` takes anything that implements the trait. In this case Rust
+/// would need to make two implicit conversions, which Rust doesn't have the
+/// means to do. For that reason, the following example will not compile.
+///
+/// ```compile_fail,E0277
+/// trait TraitExample {}
+///
+/// impl<'a> TraitExample for &'a str {}
+///
+/// fn example_func<A: TraitExample>(example_arg: A) {}
+///
+/// fn main() {
+///     let example_string = String::from("example_string");
+///     example_func(&example_string);
+/// }
+/// ```
+///
+/// There are two options that would work instead. The first would be to
+/// change the line `example_func(&example_string);` to
+/// `example_func(example_string.as_str());`, using the method `as_str()`
+/// to explicitly extract the string slice containing the string. The second
+/// way changes `example_func(&example_string);` to
+/// `example_func(&*example_string);`. In this case we are dereferencing a
+/// `String` to a `str`, then referencing the `str` back to `&str`. The
+/// second way is more idiomatic, however both work to do the conversion
+/// explicitly rather than relying on the implicit conversion.
 ///
 /// # Representation
 ///

src/librustc/ty/layout.rs

@@ -2197,8 +2197,8 @@ impl<'a, 'tcx> TyLayout<'tcx> {
         let tcx = cx.tcx();
 
         let ptr_field_type = |pointee: Ty<'tcx>| {
+            assert!(i < 2);
             let slice = |element: Ty<'tcx>| {
-                assert!(i < 2);
                 if i == 0 {
                     tcx.mk_mut_ptr(element)
                 } else {

src/librustc_metadata/encoder.rs

@@ -563,7 +563,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
         Entry {
             kind: EntryKind::Mod(self.lazy(&data)),
             visibility: self.lazy(&ty::Visibility::from_hir(vis, id, tcx)),
-            span: self.lazy(&md.inner),
+            span: self.lazy(&tcx.def_span(def_id)),
             attributes: self.encode_attributes(attrs),
             children: self.lazy_seq(md.item_ids.iter().map(|item_id| {
                 tcx.hir.local_def_id(item_id.id).index

src/librustc_typeck/diagnostics.rs

@@ -1525,9 +1525,9 @@ static BAR: _ = "test"; // error, explicitly write out the type instead
 "##,
 
 E0122: r##"
-An attempt was made to add a generic constraint to a type alias. While Rust will
-allow this with a warning, it will not currently enforce the constraint.
-Consider the example below:
+An attempt was made to add a generic constraint to a type alias. This constraint
+is entirely ignored. For backwards compatibility, Rust still allows this with a
+warning. Consider the example below:
 
 ```
 trait Foo{}

src/librustdoc/html/render.rs

@@ -2141,8 +2141,8 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
 
     if !types.is_empty() {
         write!(w, "
-            <h2 id='associated-types' class='section-header'>
-              <a href='#associated-types'>Associated Types</a>
+            <h2 id='associated-types' class='small-section-header'>
+              Associated Types<a href='#associated-types' class='anchor'></a>
             </h2>
             <div class='methods'>
         ")?;
@@ -2154,8 +2154,8 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
 
     if !consts.is_empty() {
         write!(w, "
-            <h2 id='associated-const' class='section-header'>
-              <a href='#associated-const'>Associated Constants</a>
+            <h2 id='associated-const' class='small-section-header'>
+              Associated Constants<a href='#associated-const' class='anchor'></a>
             </h2>
             <div class='methods'>
         ")?;
@@ -2168,8 +2168,8 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
     // Output the documentation for each function individually
     if !required.is_empty() {
         write!(w, "
-            <h2 id='required-methods' class='section-header'>
-              <a href='#required-methods'>Required Methods</a>
+            <h2 id='required-methods' class='small-section-header'>
+              Required Methods<a href='#required-methods' class='anchor'></a>
             </h2>
             <div class='methods'>
         ")?;
@@ -2180,8 +2180,8 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
     }
     if !provided.is_empty() {
         write!(w, "
-            <h2 id='provided-methods' class='section-header'>
-              <a href='#provided-methods'>Provided Methods</a>
+            <h2 id='provided-methods' class='small-section-header'>
+              Provided Methods<a href='#provided-methods' class='anchor'></a>
             </h2>
             <div class='methods'>
         ")?;
@@ -2196,8 +2196,8 @@ fn item_trait(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
 
     let cache = cache();
     write!(w, "
-        <h2 id='implementors' class='section-header'>
-          <a href='#implementors'>Implementors</a>
+        <h2 id='implementors' class='small-section-header'>
+          Implementors<a href='#implementors' class='anchor'></a>
         </h2>
         <ul class='item-list' id='implementors-list'>
     ")?;
@@ -2436,8 +2436,8 @@ fn item_struct(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
     }).peekable();
     if let doctree::Plain = s.struct_type {
         if fields.peek().is_some() {
-            write!(w, "<h2 id='fields' class='fields section-header'>
-                       <a href='#fields'>Fields</a></h2>")?;
+            write!(w, "<h2 id='fields' class='fields small-section-header'>
+                       Fields<a href='#fields' class='anchor'></a></h2>")?;
             for (field, ty) in fields {
                 let id = derive_id(format!("{}.{}",
                                            ItemType::StructField,
@@ -2485,8 +2485,8 @@ fn item_union(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
         }
     }).peekable();
     if fields.peek().is_some() {
-        write!(w, "<h2 id='fields' class='fields section-header'>
-                   <a href='#fields'>Fields</a></h2>")?;
+        write!(w, "<h2 id='fields' class='fields small-section-header'>
+                   Fields<a href='#fields' class='anchor'></a></h2>")?;
         for (field, ty) in fields {
             write!(w, "<span id='{shortty}.{name}' class=\"{shortty}\"><code>{name}: {ty}</code>
                        </span>",
@@ -2558,8 +2558,8 @@ fn item_enum(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
 
     document(w, cx, it)?;
     if !e.variants.is_empty() {
-        write!(w, "<h2 id='variants' class='variants section-header'>
-                   <a href='#variants'>Variants</a></h2>\n")?;
+        write!(w, "<h2 id='variants' class='variants small-section-header'>
+                   Variants<a href='#variants' class='anchor'></a></h2>\n")?;
         for variant in &e.variants {
             let id = derive_id(format!("{}.{}",
                                        ItemType::Variant,
@@ -2831,16 +2831,16 @@ fn render_assoc_items(w: &mut fmt::Formatter,
         let render_mode = match what {
             AssocItemRender::All => {
                 write!(w, "
-                    <h2 id='methods' class='section-header'>
-                      <a href='#methods'>Methods</a>
+                    <h2 id='methods' class='small-section-header'>
+                      Methods<a href='#methods' class='anchor'></a>
                     </h2>
                 ")?;
                 RenderMode::Normal
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
                 write!(w, "
-                    <h2 id='deref-methods' class='section-header'>
-                      <a href='#deref-methods'>Methods from {}&lt;Target = {}&gt;</a>
+                    <h2 id='deref-methods' class='small-section-header'>
+                      Methods from {}&lt;Target = {}&gt;<a href='#deref-methods' class='anchor'></a>
                     </h2>
                 ", trait_, type_)?;
                 RenderMode::ForDeref { mut_: deref_mut_ }
@@ -2865,8 +2865,8 @@ fn render_assoc_items(w: &mut fmt::Formatter,
             render_deref_methods(w, cx, impl_, containing_item, has_deref_mut)?;
         }
         write!(w, "
-            <h2 id='implementations' class='section-header'>
-              <a href='#implementations'>Trait Implementations</a>
+            <h2 id='implementations' class='small-section-header'>
+              Trait Implementations<a href='#implementations' class='anchor'></a>
             </h2>
         ")?;
         for i in &traits {

src/librustdoc/html/static/rustdoc.css

@@ -438,6 +438,16 @@ a {
 	background: transparent;
 }
 
+.small-section-header:hover > .anchor {
+	display: initial;
+}
+.anchor {
+	display: none;
+}
+.anchor:after {
+	content: '\2002\00a7\2002';
+}
+
 .docblock a:hover, .docblock-short a:hover, .stability a {
 	text-decoration: underline;
 }
@@ -677,6 +687,10 @@ span.since {
 	left: 0;
 }
 
+.variant + .toggle-wrapper + .docblock > p {
+	margin-top: 5px;
+}
+
 .variant + .toggle-wrapper > a {
 	margin-top: 5px;
 }
@@ -695,7 +709,7 @@ span.since {
 	margin-bottom: 25px;
 }
 
-.enum .variant, .struct .structfield, .union .structfield {
+#main > .variant, #main > .structfield {
 	display: block;
 }
 

src/libstd/fs.rs

@@ -28,7 +28,7 @@ use time::SystemTime;
 /// A reference to an open file on the filesystem.
 ///
 /// An instance of a `File` can be read and/or written depending on what options
-/// it was opened with. Files also implement `Seek` to alter the logical cursor
+/// it was opened with. Files also implement [`Seek`] to alter the logical cursor
 /// that the file contains internally.
 ///
 /// Files are automatically closed when they go out of scope.
@@ -48,7 +48,7 @@ use time::SystemTime;
 /// # }
 /// ```
 ///
-/// Read the contents of a file into a `String`:
+/// Read the contents of a file into a [`String`]:
 ///
 /// ```no_run
 /// use std::fs::File;
@@ -81,6 +81,8 @@ use time::SystemTime;
 /// # }
 /// ```
 ///
+/// [`Seek`]: ../io/trait.Seek.html
+/// [`String`]: ../string/struct.String.html
 /// [`Read`]: ../io/trait.Read.html
 /// [`BufReader<R>`]: ../io/struct.BufReader.html
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -104,19 +106,19 @@ pub struct Metadata(fs_imp::FileAttr);
 /// Iterator over the entries in a directory.
 ///
 /// This iterator is returned from the [`read_dir`] function of this module and
-/// will yield instances of `io::Result<DirEntry>`. Through a [`DirEntry`]
+/// will yield instances of [`io::Result`]`<`[`DirEntry`]`>`. Through a [`DirEntry`]
 /// information like the entry's path and possibly other metadata can be
 /// learned.
 ///
-/// [`read_dir`]: fn.read_dir.html
-/// [`DirEntry`]: struct.DirEntry.html
-///
 /// # Errors
 ///
-/// This [`io::Result`] will be an `Err` if there's some sort of intermittent
+/// This [`io::Result`] will be an [`Err`] if there's some sort of intermittent
 /// IO error during iteration.
 ///
+/// [`read_dir`]: fn.read_dir.html
+/// [`DirEntry`]: struct.DirEntry.html
 /// [`io::Result`]: ../io/type.Result.html
+/// [`Err`]: ../result/enum.Result.html#variant.Err
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct ReadDir(fs_imp::ReadDir);

src/libstd/io/error.rs

@@ -17,17 +17,21 @@ use convert::From;
 /// A specialized [`Result`](../result/enum.Result.html) type for I/O
 /// operations.
 ///
-/// This type is broadly used across `std::io` for any operation which may
+/// This type is broadly used across [`std::io`] for any operation which may
 /// produce an error.
 ///
-/// This typedef is generally used to avoid writing out `io::Error` directly and
-/// is otherwise a direct mapping to `Result`.
+/// This typedef is generally used to avoid writing out [`io::Error`] directly and
+/// is otherwise a direct mapping to [`Result`].
 ///
-/// While usual Rust style is to import types directly, aliases of `Result`
-/// often are not, to make it easier to distinguish between them. `Result` is
-/// generally assumed to be `std::result::Result`, and so users of this alias
+/// While usual Rust style is to import types directly, aliases of [`Result`]
+/// often are not, to make it easier to distinguish between them. [`Result`] is
+/// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
 /// will generally use `io::Result` instead of shadowing the prelude's import
-/// of `std::result::Result`.
+/// of [`std::result::Result`][`Result`].
+///
+/// [`std::io`]: ../io/index.html
+/// [`io::Error`]: ../io/struct.Error.html
+/// [`Result`]: ../result/enum.Result.html
 ///
 /// # Examples
 ///
@@ -47,13 +51,16 @@ use convert::From;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub type Result<T> = result::Result<T, Error>;
 
-/// The error type for I/O operations of the `Read`, `Write`, `Seek`, and
+/// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
 /// associated traits.
 ///
 /// Errors mostly originate from the underlying OS, but custom instances of
 /// `Error` can be created with crafted error messages and a particular value of
 /// [`ErrorKind`].
 ///
+/// [`Read`]: ../io/trait.Read.html
+/// [`Write`]: ../io/trait.Write.html
+/// [`Seek`]: ../io/trait.Seek.html
 /// [`ErrorKind`]: enum.ErrorKind.html
 #[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]

src/libstd/io/mod.rs

@@ -22,7 +22,7 @@
 //! you'll see a few different types of I/O throughout the documentation in
 //! this module: [`File`]s, [`TcpStream`]s, and sometimes even [`Vec<T>`]s. For
 //! example, [`Read`] adds a [`read`][`Read::read`] method, which we can use on
-//! `File`s:
+//! [`File`]s:
 //!
 //! ```
 //! use std::io;
@@ -146,9 +146,9 @@
 //! # }
 //! ```
 //!
-//! Note that you cannot use the `?` operator in functions that do not return
-//! a `Result<T, E>` (e.g. `main`). Instead, you can call `.unwrap()` or `match`
-//! on the return value to catch any possible errors:
+//! Note that you cannot use the [`?` operator] in functions that do not return
+//! a [`Result<T, E>`][`Result`] (e.g. `main`). Instead, you can call [`.unwrap()`]
+//! or `match` on the return value to catch any possible errors:
 //!
 //! ```
 //! use std::io;
@@ -265,6 +265,8 @@
 //! [`io::Result`]: type.Result.html
 //! [`?` operator]: ../../book/first-edition/syntax-index.html
 //! [`Read::read`]: trait.Read.html#tymethod.read
+//! [`Result`]: ../result/enum.Result.html
+//! [`.unwrap()`]: ../result/enum.Result.html#method.unwrap
 
 #![stable(feature = "rust1", since = "1.0.0")]