Rollup of 11 pull requests

compiler/rustc_expand/src/lib.rs

@@ -1,6 +1,7 @@
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
 #![feature(destructuring_assignment)]
+#![feature(format_args_capture)]
 #![feature(iter_zip)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -85,6 +85,7 @@ use smallvec::{smallvec, SmallVec};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
+use rustc_span::symbol::Ident;
 use std::borrow::Cow;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::mem;
@@ -615,7 +616,11 @@ fn inner_parse_loop<'root, 'tt>(
 
 /// Use the given sequence of token trees (`ms`) as a matcher. Match the token
 /// stream from the given `parser` against it and return the match.
-pub(super) fn parse_tt(parser: &mut Cow<'_, Parser<'_>>, ms: &[TokenTree]) -> NamedParseResult {
+pub(super) fn parse_tt(
+    parser: &mut Cow<'_, Parser<'_>>,
+    ms: &[TokenTree],
+    macro_name: Ident,
+) -> NamedParseResult {
     // A queue of possible matcher positions. We initialize it with the matcher position in which
     // the "dot" is before the first token of the first token tree in `ms`. `inner_parse_loop` then
     // processes all of these possible matcher positions and produces possible next positions into
@@ -711,7 +716,7 @@ pub(super) fn parse_tt(parser: &mut Cow<'_, Parser<'_>>, ms: &[TokenTree]) -> Na
             return Error(
                 parser.token.span,
                 format!(
-                    "local ambiguity: multiple parsing options: {}",
+                    "local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}",
                     match next_items.len() {
                         0 => format!("built-in NTs {}.", nts),
                         1 => format!("built-in NTs {} or 1 other option.", nts),

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -245,7 +245,7 @@ fn generic_extension<'cx>(
         // are not recorded. On the first `Success(..)`ful matcher, the spans are merged.
         let mut gated_spans_snapshot = mem::take(&mut *sess.gated_spans.spans.borrow_mut());
 
-        match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt) {
+        match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt, name) {
             Success(named_matches) => {
                 // The matcher was `Success(..)`ful.
                 // Merge the gated spans from parsing the matcher with the pre-existing ones.
@@ -338,7 +338,7 @@ fn generic_extension<'cx>(
                 _ => continue,
             };
             if let Success(_) =
-                parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt)
+                parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt, name)
             {
                 if comma_span.is_dummy() {
                     err.note("you might be missing a comma");
@@ -432,7 +432,7 @@ pub fn compile_declarative_macro(
     ];
 
     let parser = Parser::new(&sess.parse_sess, body, true, rustc_parse::MACRO_ARGUMENTS);
-    let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram) {
+    let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram, def.ident) {
         Success(m) => m,
         Failure(token, msg) => {
             let s = parse_failure_msg(&token);

compiler/rustc_typeck/src/collect.rs

@@ -2771,7 +2771,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
             }
         } else if tcx.sess.check_name(attr, sym::target_feature) {
             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
-                if tcx.sess.target.is_like_wasm {
+                if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                     // The `#[target_feature]` attribute is allowed on
                     // WebAssembly targets on all functions, including safe
                     // ones. Other targets require that `#[target_feature]` is
@@ -2785,6 +2785,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
                     // deterministic trap. There is no undefined behavior when
                     // executing WebAssembly so `#[target_feature]` is allowed
                     // on safe functions (but again, only for WebAssembly)
+                    //
+                    // Note that this is also allowed if `actually_rustdoc` so
+                    // if a target is documenting some wasm-specific code then
+                    // it's not spuriously denied.
                 } else if !tcx.features().target_feature_11 {
                     let mut err = feature_err(
                         &tcx.sess.parse_sess,

library/alloc/src/string.rs

@@ -2491,6 +2491,9 @@ impl AsRef<[u8]> for String {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl From<&str> for String {
+    /// Converts a `&str` into a [`String`].
+    ///
+    /// The result is allocated on the heap.
     #[inline]
     fn from(s: &str) -> String {
         s.to_owned()
@@ -2500,7 +2503,7 @@ impl From<&str> for String {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_mut_str_for_string", since = "1.44.0")]
 impl From<&mut str> for String {
-    /// Converts a `&mut str` into a `String`.
+    /// Converts a `&mut str` into a [`String`].
     ///
     /// The result is allocated on the heap.
     #[inline]
@@ -2512,6 +2515,9 @@ impl From<&mut str> for String {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_ref_string", since = "1.35.0")]
 impl From<&String> for String {
+    /// Converts a `&String` into a [`String`].
+    ///
+    /// This clones `s` and returns the clone.
     #[inline]
     fn from(s: &String) -> String {
         s.clone()
@@ -2522,7 +2528,7 @@ impl From<&String> for String {
 #[cfg(not(test))]
 #[stable(feature = "string_from_box", since = "1.18.0")]
 impl From<Box<str>> for String {
-    /// Converts the given boxed `str` slice to a `String`.
+    /// Converts the given boxed `str` slice to a [`String`].
     /// It is notable that the `str` slice is owned.
     ///
     /// # Examples
@@ -2544,7 +2550,7 @@ impl From<Box<str>> for String {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_str", since = "1.20.0")]
 impl From<String> for Box<str> {
-    /// Converts the given `String` to a boxed `str` slice that is owned.
+    /// Converts the given [`String`] to a boxed `str` slice that is owned.
     ///
     /// # Examples
     ///
@@ -2565,6 +2571,22 @@ impl From<String> for Box<str> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "string_from_cow_str", since = "1.14.0")]
 impl<'a> From<Cow<'a, str>> for String {
+    /// Converts a clone-on-write string to an owned
+    /// instance of [`String`].
+    ///
+    /// This extracts the owned string,
+    /// clones the string if it is not already owned.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use std::borrow::Cow;
+    /// // If the string is not owned...
+    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// // It will allocate on the heap and copy the string.
+    /// let owned: String = String::from(cow);
+    /// assert_eq!(&owned[..], "eggplant");
+    /// ```
     fn from(s: Cow<'a, str>) -> String {
         s.into_owned()
     }
@@ -2573,7 +2595,7 @@ impl<'a> From<Cow<'a, str>> for String {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> From<&'a str> for Cow<'a, str> {
-    /// Converts a string slice into a Borrowed variant.
+    /// Converts a string slice into a [`Borrowed`] variant.
     /// No heap allocation is performed, and the string
     /// is not copied.
     ///
@@ -2583,6 +2605,8 @@ impl<'a> From<&'a str> for Cow<'a, str> {
     /// # use std::borrow::Cow;
     /// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));
     /// ```
+    ///
+    /// [`Borrowed`]: crate::borrow::Cow::Borrowed
     #[inline]
     fn from(s: &'a str) -> Cow<'a, str> {
         Cow::Borrowed(s)
@@ -2592,7 +2616,7 @@ impl<'a> From<&'a str> for Cow<'a, str> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> From<String> for Cow<'a, str> {
-    /// Converts a String into an Owned variant.
+    /// Converts a [`String`] into an [`Owned`] variant.
     /// No heap allocation is performed, and the string
     /// is not copied.
     ///
@@ -2604,6 +2628,8 @@ impl<'a> From<String> for Cow<'a, str> {
     /// let s2 = "eggplant".to_string();
     /// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2));
     /// ```
+    ///
+    /// [`Owned`]: crate::borrow::Cow::Owned
     #[inline]
     fn from(s: String) -> Cow<'a, str> {
         Cow::Owned(s)
@@ -2613,7 +2639,7 @@ impl<'a> From<String> for Cow<'a, str> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "cow_from_string_ref", since = "1.28.0")]
 impl<'a> From<&'a String> for Cow<'a, str> {
-    /// Converts a String reference into a Borrowed variant.
+    /// Converts a [`String`] reference into a [`Borrowed`] variant.
     /// No heap allocation is performed, and the string
     /// is not copied.
     ///
@@ -2624,6 +2650,8 @@ impl<'a> From<&'a String> for Cow<'a, str> {
     /// let s = "eggplant".to_string();
     /// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant"));
     /// ```
+    ///
+    /// [`Borrowed`]: crate::borrow::Cow::Borrowed
     #[inline]
     fn from(s: &'a String) -> Cow<'a, str> {
         Cow::Borrowed(s.as_str())
@@ -2656,7 +2684,7 @@ impl<'a> FromIterator<String> for Cow<'a, str> {
 
 #[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
 impl From<String> for Vec<u8> {
-    /// Converts the given `String` to a vector `Vec` that holds values of type `u8`.
+    /// Converts the given [`String`] to a vector [`Vec`] that holds values of type [`u8`].
     ///
     /// # Examples
     ///
@@ -2802,6 +2830,14 @@ impl FusedIterator for Drain<'_> {}
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_char_for_string", since = "1.46.0")]
 impl From<char> for String {
+    /// Allocates an owned [`String`] from a single character.
+    ///
+    /// # Example
+    /// ```rust
+    /// let c: char = 'a';
+    /// let s: String = String::from(c);
+    /// assert_eq!("a", &s[..]);
+    /// ```
     #[inline]
     fn from(c: char) -> Self {
         c.to_string()

library/proc_macro/src/lib.rs

@@ -31,6 +31,7 @@
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
 #![feature(min_specialization)]
+#![feature(bound_cloned)]
 #![recursion_limit = "256"]
 
 #[unstable(feature = "proc_macro_internals", issue = "27812")]
@@ -43,7 +44,7 @@ mod diagnostic;
 pub use diagnostic::{Diagnostic, Level, MultiSpan};
 
 use std::cmp::Ordering;
-use std::ops::{Bound, RangeBounds};
+use std::ops::RangeBounds;
 use std::path::PathBuf;
 use std::str::FromStr;
 use std::{error, fmt, iter, mem};
@@ -1162,16 +1163,7 @@ impl Literal {
     // was 'c' or whether it was '\u{63}'.
     #[unstable(feature = "proc_macro_span", issue = "54725")]
     pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
-        // HACK(eddyb) something akin to `Option::cloned`, but for `Bound<&T>`.
-        fn cloned_bound<T: Clone>(bound: Bound<&T>) -> Bound<T> {
-            match bound {
-                Bound::Included(x) => Bound::Included(x.clone()),
-                Bound::Excluded(x) => Bound::Excluded(x.clone()),
-                Bound::Unbounded => Bound::Unbounded,
-            }
-        }
-
-        self.0.subspan(cloned_bound(range.start_bound()), cloned_bound(range.end_bound())).map(Span)
+        self.0.subspan(range.start_bound().cloned(), range.end_bound().cloned()).map(Span)
     }
 }
 

library/std/src/io/impls.rs

@@ -87,6 +87,11 @@ impl<S: Seek + ?Sized> Seek for &mut S {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (**self).seek(pos)
     }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for &mut B {
@@ -186,6 +191,11 @@ impl<S: Seek + ?Sized> Seek for Box<S> {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (**self).seek(pos)
     }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for Box<B> {