Rollup of 15 pull requests

README.md

@@ -1,7 +1,9 @@
-# The Rust Programming Language
+<a href = "https://www.rust-lang.org/"> 
+<img width = "90%" height = "auto" src = "https://img.shields.io/badge/Rust-Programming%20Language-black?style=flat&logo=rust" alt = "The Rust Programming Language">
+</a>
 
 This is the main source code repository for [Rust]. It contains the compiler,
-standard library, and documentation.
+standard library, and documentation. 
 
 [Rust]: https://www.rust-lang.org
 
@@ -17,9 +19,9 @@ Read ["Installation"] from [The Book].
 _Note: If you wish to contribute to the compiler, you should read [this
 chapter][rustcguidebuild] of the rustc-dev-guide instead of this section._
 
-The Rust build system has a Python script called `x.py` to bootstrap building
-the compiler. More information about it may be found by running `./x.py --help`
-or reading the [rustc dev guide][rustcguidebuild].
+The Rust build system uses a Python script called `x.py` to build the compiler,
+which manages the bootstrapping process. More information about it can be found 
+by running `./x.py --help` or reading the [rustc dev guide][rustcguidebuild].
 
 [rustcguidebuild]: https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html
 
@@ -54,9 +56,8 @@ or reading the [rustc dev guide][rustcguidebuild].
     $ cp config.toml.example config.toml
     ```
 
-    It is recommended that if you plan to use the Rust build system to create
-    an installation (using `./x.py install`) that you set the `prefix` value
-    in the `[install]` section to a directory that you have write permissions.
+    If you plan to use `x.py install` to create an installation, it is recommended
+    that you set the `prefix` value in the `[install]` section to a directory.
 
     Create install directory if you are not installing in default directory
 
@@ -143,8 +144,8 @@ shell with:
 ```
 
 Currently, building Rust only works with some known versions of Visual Studio. If
-you have a more recent version installed the build system doesn't understand
-then you may need to force rustbuild to use an older version. This can be done
+you have a more recent version installed and the build system doesn't understand,
+you may need to force rustbuild to use an older version. This can be done
 by manually calling the appropriate vcvars file before running the bootstrap.
 
 ```batch

src/liballoc/boxed.rs

@@ -384,7 +384,10 @@ impl<T: ?Sized> Box<T> {
     ///
     /// unsafe {
     ///     let ptr = alloc(Layout::new::<i32>()) as *mut i32;
-    ///     *ptr = 5;
+    ///     // In general .write is required to avoid attempting to destruct
+    ///     // the (uninitialized) previous contents of `ptr`, though for this
+    ///     // simple example `*ptr = 5` would have worked as well.
+    ///     ptr.write(5);
     ///     let x = Box::from_raw(ptr);
     /// }
     /// ```

src/liballoc/string.rs

@@ -2518,3 +2518,11 @@ impl DoubleEndedIterator for Drain<'_> {
 
 #[stable(feature = "fused", since = "1.26.0")]
 impl FusedIterator for Drain<'_> {}
+
+#[stable(feature = "from_char_for_string", since = "1.46.0")]
+impl From<char> for String {
+    #[inline]
+    fn from(c: char) -> Self {
+        c.to_string()
+    }
+}

src/liballoc/tests/string.rs

@@ -714,3 +714,10 @@ fn test_try_reserve_exact() {
         }
     }
 }
+
+#[test]
+fn test_from_char() {
+    assert_eq!(String::from('a'), 'a'.to_string());
+    let s: String = 'x'.into();
+    assert_eq!(s, 'x'.to_string());
+}

src/libcore/intrinsics.rs

@@ -952,6 +952,7 @@ extern "rust-intrinsic" {
     /// Any use other than with `if` statements will probably not have an effect.
     ///
     /// This intrinsic does not have a stable counterpart.
+    #[rustc_const_unstable(feature = "const_likely", issue = "none")]
     pub fn likely(b: bool) -> bool;
 
     /// Hints to the compiler that branch condition is likely to be false.
@@ -960,6 +961,7 @@ extern "rust-intrinsic" {
     /// Any use other than with `if` statements will probably not have an effect.
     ///
     /// This intrinsic does not have a stable counterpart.
+    #[rustc_const_unstable(feature = "const_likely", issue = "none")]
     pub fn unlikely(b: bool) -> bool;
 
     /// Executes a breakpoint trap, for inspection by a debugger.

src/libcore/lib.rs

@@ -92,6 +92,7 @@
 #![feature(const_slice_from_raw_parts)]
 #![feature(const_slice_ptr_len)]
 #![feature(const_type_name)]
+#![feature(const_likely)]
 #![feature(custom_inner_attributes)]
 #![feature(decl_macro)]
 #![feature(doc_cfg)]
@@ -118,7 +119,7 @@
 #![feature(staged_api)]
 #![feature(std_internals)]
 #![feature(stmt_expr_attributes)]
-#![feature(track_caller)]
+#![cfg_attr(bootstrap, feature(track_caller))]
 #![feature(transparent_unions)]
 #![feature(unboxed_closures)]
 #![feature(unsized_locals)]

src/libcore/macros/mod.rs

@@ -1,6 +1,6 @@
 #[doc(include = "panic.md")]
 #[macro_export]
-#[allow_internal_unstable(core_panic, track_caller)]
+#[allow_internal_unstable(core_panic, const_caller_location)]
 #[stable(feature = "core", since = "1.6.0")]
 macro_rules! panic {
     () => (

src/libcore/panic.rs

@@ -190,7 +190,6 @@ impl<'a> Location<'a> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(track_caller)]
     /// use core::panic::Location;
     ///
     /// /// Returns the [`Location`] at which it is called.
@@ -206,7 +205,7 @@ impl<'a> Location<'a> {
     ///
     /// let fixed_location = get_just_one_location();
     /// assert_eq!(fixed_location.file(), file!());
-    /// assert_eq!(fixed_location.line(), 15);
+    /// assert_eq!(fixed_location.line(), 14);
     /// assert_eq!(fixed_location.column(), 5);
     ///
     /// // running the same untracked function in a different location gives us the same result
@@ -217,7 +216,7 @@ impl<'a> Location<'a> {
     ///
     /// let this_location = get_caller_location();
     /// assert_eq!(this_location.file(), file!());
-    /// assert_eq!(this_location.line(), 29);
+    /// assert_eq!(this_location.line(), 28);
     /// assert_eq!(this_location.column(), 21);
     ///
     /// // running the tracked function in a different location produces a different value
@@ -226,13 +225,8 @@ impl<'a> Location<'a> {
     /// assert_ne!(this_location.line(), another_location.line());
     /// assert_ne!(this_location.column(), another_location.column());
     /// ```
-    // FIXME: When stabilizing this method, please also update the documentation
-    // of `intrinsics::caller_location`.
-    #[unstable(
-        feature = "track_caller",
-        reason = "uses #[track_caller] which is not yet stable",
-        issue = "47809"
-    )]
+    #[stable(feature = "track_caller", since = "1.46.0")]
+    #[rustc_const_unstable(feature = "const_caller_location", issue = "47809")]
     #[track_caller]
     pub const fn caller() -> &'static Location<'static> {
         crate::intrinsics::caller_location()

src/librustc_ast_pretty/pprust.rs

@@ -9,7 +9,7 @@ use rustc_ast::ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_ast::attr;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, BinOpToken, DelimToken, Nonterminal, Token, TokenKind};
-use rustc_ast::tokenstream::{self, TokenStream, TokenTree};
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::util::parser::{self, AssocOp, Fixity};
 use rustc_ast::util::{classify, comments};
 use rustc_span::edition::Edition;
@@ -293,7 +293,7 @@ pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
         token::NtIdent(e, is_raw) => IdentPrinter::for_ast_ident(e, is_raw).to_string(),
         token::NtLifetime(e) => e.to_string(),
         token::NtLiteral(ref e) => expr_to_string(e),
-        token::NtTT(ref tree) => tt_to_string(tree.clone()),
+        token::NtTT(ref tree) => tt_to_string(tree),
         token::NtVis(ref e) => vis_to_string(e),
     }
 }
@@ -314,11 +314,11 @@ pub fn expr_to_string(e: &ast::Expr) -> String {
     to_string(|s| s.print_expr(e))
 }
 
-pub fn tt_to_string(tt: tokenstream::TokenTree) -> String {
+pub fn tt_to_string(tt: &TokenTree) -> String {
     to_string(|s| s.print_tt(tt, false))
 }
 
-pub fn tts_to_string(tokens: TokenStream) -> String {
+pub fn tts_to_string(tokens: &TokenStream) -> String {
     to_string(|s| s.print_tts(tokens, false))
 }
 
@@ -585,7 +585,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 false,
                 None,
                 delim.to_token(),
-                tokens.clone(),
+                tokens,
                 true,
                 span,
             ),
@@ -594,7 +594,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 if let MacArgs::Eq(_, tokens) = &item.args {
                     self.space();
                     self.word_space("=");
-                    self.print_tts(tokens.clone(), true);
+                    self.print_tts(tokens, true);
                 }
             }
         }
@@ -635,9 +635,9 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     /// appropriate macro, transcribe back into the grammar we just parsed from,
     /// and then pretty-print the resulting AST nodes (so, e.g., we print
     /// expression arguments as expressions). It can be done! I think.
-    fn print_tt(&mut self, tt: tokenstream::TokenTree, convert_dollar_crate: bool) {
+    fn print_tt(&mut self, tt: &TokenTree, convert_dollar_crate: bool) {
         match tt {
-            TokenTree::Token(ref token) => {
+            TokenTree::Token(token) => {
                 self.word(token_to_string_ext(&token, convert_dollar_crate));
                 if let token::DocComment(..) = token.kind {
                     self.hardbreak()
@@ -648,7 +648,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                     None,
                     false,
                     None,
-                    delim,
+                    *delim,
                     tts,
                     convert_dollar_crate,
                     dspan.entire(),
@@ -657,14 +657,14 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         }
     }
 
-    fn print_tts(&mut self, tts: tokenstream::TokenStream, convert_dollar_crate: bool) {
-        let mut iter = tts.into_trees().peekable();
+    fn print_tts(&mut self, tts: &TokenStream, convert_dollar_crate: bool) {
+        let mut iter = tts.trees().peekable();
         while let Some(tt) = iter.next() {
-            let show_space =
-                if let Some(next) = iter.peek() { tt_prepend_space(next, &tt) } else { false };
-            self.print_tt(tt, convert_dollar_crate);
-            if show_space {
-                self.space();
+            self.print_tt(&tt, convert_dollar_crate);
+            if let Some(next) = iter.peek() {
+                if tt_prepend_space(next, &tt) {
+                    self.space();
+                }
             }
         }
     }
@@ -675,7 +675,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         has_bang: bool,
         ident: Option<Ident>,
         delim: DelimToken,
-        tts: TokenStream,
+        tts: &TokenStream,
         convert_dollar_crate: bool,
         span: Span,
     ) {
@@ -1253,7 +1253,7 @@ impl<'a> State<'a> {
                     has_bang,
                     Some(item.ident),
                     macro_def.body.delim(),
-                    macro_def.body.inner_tokens(),
+                    &macro_def.body.inner_tokens(),
                     true,
                     item.span,
                 );
@@ -1577,7 +1577,7 @@ impl<'a> State<'a> {
             true,
             None,
             m.args.delim(),
-            m.args.inner_tokens(),
+            &m.args.inner_tokens(),
             true,
             m.span(),
         );

src/librustc_builtin_macros/log_syntax.rs

@@ -7,7 +7,7 @@ pub fn expand_log_syntax<'cx>(
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
-    println!("{}", pprust::tts_to_string(tts));
+    println!("{}", pprust::tts_to_string(&tts));
 
     // any so that `log_syntax` can be invoked as an expression and item.
     base::DummyResult::any_valid(sp)

src/librustc_builtin_macros/source_util.rs

@@ -71,7 +71,7 @@ pub fn expand_stringify(
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
     let sp = cx.with_def_site_ctxt(sp);
-    let s = pprust::tts_to_string(tts);
+    let s = pprust::tts_to_string(&tts);
     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&s)))
 }
 

src/librustc_error_codes/error_codes/E0736.md

@@ -3,8 +3,6 @@
 Erroneous code example:
 
 ```compile_fail,E0736
-#![feature(track_caller)]
-
 #[naked]
 #[track_caller]
 fn foo() {}

src/librustc_error_codes/error_codes/E0737.md

@@ -5,8 +5,6 @@ restrictions.
 Erroneous code example:
 
 ```compile_fail,E0737
-#![feature(track_caller)]
-
 #[track_caller]
 extern "C" fn foo() {}
 ```

src/librustc_error_codes/error_codes/E0739.md

@@ -3,7 +3,6 @@
 Erroneous code example:
 
 ```compile_fail,E0739
-#![feature(track_caller)]
 #[track_caller]
 struct Bar {
     a: u8,

src/librustc_errors/lib.rs

@@ -5,7 +5,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(crate_visibility_modifier)]
 #![feature(nll)]
-#![feature(track_caller)]
+#![cfg_attr(bootstrap, feature(track_caller))]
 
 pub use emitter::ColorConfig;
 

src/librustc_expand/mbe/macro_rules.rs

@@ -224,7 +224,7 @@ fn generic_extension<'cx>(
     let sess = cx.parse_sess;
 
     if cx.trace_macros() {
-        let msg = format!("expanding `{}! {{ {} }}`", name, pprust::tts_to_string(arg.clone()));
+        let msg = format!("expanding `{}! {{ {} }}`", name, pprust::tts_to_string(&arg));
         trace_macros_note(&mut cx.expansions, sp, msg);
     }
 
@@ -300,7 +300,7 @@ fn generic_extension<'cx>(
                 }
 
                 if cx.trace_macros() {
-                    let msg = format!("to `{}`", pprust::tts_to_string(tts.clone()));
+                    let msg = format!("to `{}`", pprust::tts_to_string(&tts));
                     trace_macros_note(&mut cx.expansions, sp, msg);
                 }
 

src/librustc_expand/proc_macro_server.rs

@@ -413,7 +413,7 @@ impl server::TokenStream for Rustc<'_> {
         )
     }
     fn to_string(&mut self, stream: &Self::TokenStream) -> String {
-        pprust::tts_to_string(stream.clone())
+        pprust::tts_to_string(stream)
     }
     fn from_token_tree(
         &mut self,

src/librustc_feature/accepted.rs

@@ -265,6 +265,9 @@ declare_features! (
     (accepted, const_if_match, "1.45.0", Some(49146), None),
     /// Allows the use of `loop` and `while` in constants.
     (accepted, const_loop, "1.45.0", Some(52000), None),
+    /// Allows `#[track_caller]` to be used which provides
+    /// accurate caller location reporting during panic (RFC 2091).
+    (accepted, track_caller, "1.46.0", Some(47809), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

src/librustc_feature/active.rs

@@ -494,10 +494,6 @@ declare_features! (
     /// Allows the use of raw-dylibs (RFC 2627).
     (active, raw_dylib, "1.40.0", Some(58713), None),
 
-    /// Allows `#[track_caller]` to be used which provides
-    /// accurate caller location reporting during panic (RFC 2091).
-    (active, track_caller, "1.40.0", Some(47809), None),
-
     /// Allows making `dyn Trait` well-formed even if `Trait` is not object safe.
     /// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
     /// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.