[beta] Backports

.github/workflows/ci.yml

@@ -41,15 +41,15 @@ jobs:
       matrix:
         include:
           - name: mingw-check
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-llvm-12
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-tools
             env:
               CI_ONLY_WHEN_SUBMODULES_CHANGED: 1
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
     timeout-minutes: 600
     runs-on: "${{ matrix.os }}"
     steps:
@@ -166,128 +166,128 @@ jobs:
               - ARM64
               - linux
           - name: arm-android
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: armhf-gnu
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-aarch64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-android
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-arm-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-armhf-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-armv7-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-i586-gnu-i586-i686-musl
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-i686-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-mips-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-mips64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-mips64el-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-mipsel-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-powerpc-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-powerpc64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-powerpc64le-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-riscv64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-s390x-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-various-1
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-various-2
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-x86_64-freebsd
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-x86_64-illumos
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-x86_64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-x86_64-linux-alt
             env:
               IMAGE: dist-x86_64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
           - name: dist-x86_64-musl
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: dist-x86_64-netbsd
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: i686-gnu
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: i686-gnu-nopt
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: mingw-check
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: test-various
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: wasm32
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-stable
             env:
               IMAGE: x86_64-gnu
               RUST_CI_OVERRIDE_RELEASE_CHANNEL: stable
               CI_ONLY_WHEN_CHANNEL: nightly
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
           - name: x86_64-gnu-aux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-debug
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-distcheck
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-llvm-12
             env:
               RUST_BACKTRACE: 1
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
           - name: x86_64-gnu-nopt
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
           - name: x86_64-gnu-tools
             env:
               DEPLOY_TOOLSTATES_JSON: toolstates-linux.json
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
           - name: dist-x86_64-apple
             env:
               SCRIPT: "./x.py dist --exclude rust-docs --exclude extended && ./x.py dist --target=x86_64-apple-darwin rust-docs && ./x.py dist extended"
@@ -538,7 +538,7 @@ jobs:
       matrix:
         include:
           - name: dist-x86_64-linux
-            os: ubuntu-latest-xl
+            os: ubuntu-20.04-xl
             env: {}
     timeout-minutes: 600
     runs-on: "${{ matrix.os }}"

compiler/rustc_builtin_macros/src/format.rs

@@ -23,6 +23,7 @@ enum ArgumentType {
 
 enum Position {
     Exact(usize),
+    Capture(usize),
     Named(Symbol),
 }
 
@@ -47,6 +48,8 @@ struct Context<'a, 'b> {
     /// * `arg_unique_types` (in simplified JSON): `[["o", "x"], ["o", "x"], ["o", "x"]]`
     /// * `names` (in JSON): `{"foo": 2}`
     args: Vec<P<ast::Expr>>,
+    /// The number of arguments that were added by implicit capturing.
+    num_captured_args: usize,
     /// Placeholder slot numbers indexed by argument.
     arg_types: Vec<Vec<usize>>,
     /// Unique format specs seen for each argument.
@@ -229,6 +232,11 @@ fn parse_args<'a>(
 }
 
 impl<'a, 'b> Context<'a, 'b> {
+    /// The number of arguments that were explicitly given.
+    fn num_args(&self) -> usize {
+        self.args.len() - self.num_captured_args
+    }
+
     fn resolve_name_inplace(&self, p: &mut parse::Piece<'_>) {
         // NOTE: the `unwrap_or` branch is needed in case of invalid format
         // arguments, e.g., `format_args!("{foo}")`.
@@ -343,7 +351,7 @@ impl<'a, 'b> Context<'a, 'b> {
     }
 
     fn describe_num_args(&self) -> Cow<'_, str> {
-        match self.args.len() {
+        match self.num_args() {
             0 => "no arguments were given".into(),
             1 => "there is 1 argument".into(),
             x => format!("there are {} arguments", x).into(),
@@ -369,7 +377,7 @@ impl<'a, 'b> Context<'a, 'b> {
 
         let count = self.pieces.len()
             + self.arg_with_formatting.iter().filter(|fmt| fmt.precision_span.is_some()).count();
-        if self.names.is_empty() && !numbered_position_args && count != self.args.len() {
+        if self.names.is_empty() && !numbered_position_args && count != self.num_args() {
             e = self.ecx.struct_span_err(
                 sp,
                 &format!(
@@ -417,7 +425,7 @@ impl<'a, 'b> Context<'a, 'b> {
             if let Some(span) = fmt.precision_span {
                 let span = self.fmtsp.from_inner(span);
                 match fmt.precision {
-                    parse::CountIsParam(pos) if pos > self.args.len() => {
+                    parse::CountIsParam(pos) if pos > self.num_args() => {
                         e.span_label(
                             span,
                             &format!(
@@ -460,7 +468,7 @@ impl<'a, 'b> Context<'a, 'b> {
             if let Some(span) = fmt.width_span {
                 let span = self.fmtsp.from_inner(span);
                 match fmt.width {
-                    parse::CountIsParam(pos) if pos > self.args.len() => {
+                    parse::CountIsParam(pos) if pos > self.num_args() => {
                         e.span_label(
                             span,
                             &format!(
@@ -492,12 +500,15 @@ impl<'a, 'b> Context<'a, 'b> {
     /// Actually verifies and tracks a given format placeholder
     /// (a.k.a. argument).
     fn verify_arg_type(&mut self, arg: Position, ty: ArgumentType) {
+        if let Exact(arg) = arg {
+            if arg >= self.num_args() {
+                self.invalid_refs.push((arg, self.curpiece));
+                return;
+            }
+        }
+
         match arg {
-            Exact(arg) => {
-                if self.args.len() <= arg {
-                    self.invalid_refs.push((arg, self.curpiece));
-                    return;
-                }
+            Exact(arg) | Capture(arg) => {
                 match ty {
                     Placeholder(_) => {
                         // record every (position, type) combination only once
@@ -524,7 +535,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 match self.names.get(&name) {
                     Some(&idx) => {
                         // Treat as positional arg.
-                        self.verify_arg_type(Exact(idx), ty)
+                        self.verify_arg_type(Capture(idx), ty)
                     }
                     None => {
                         // For the moment capturing variables from format strings expanded from macros is
@@ -539,9 +550,10 @@ impl<'a, 'b> Context<'a, 'b> {
                             } else {
                                 self.fmtsp
                             };
+                            self.num_captured_args += 1;
                             self.args.push(self.ecx.expr_ident(span, Ident::new(name, span)));
                             self.names.insert(name, idx);
-                            self.verify_arg_type(Exact(idx), ty)
+                            self.verify_arg_type(Capture(idx), ty)
                         } else {
                             let msg = format!("there is no argument named `{}`", name);
                             let sp = if self.is_literal {
@@ -1010,6 +1022,7 @@ pub fn expand_preparsed_format_args(
     let mut cx = Context {
         ecx,
         args,
+        num_captured_args: 0,
         arg_types,
         arg_unique_types,
         names,

compiler/rustc_lint/src/builtin.rs

@@ -3165,7 +3165,10 @@ declare_lint! {
     /// of this, GNU assembler [local labels] *must* be used instead of labels
     /// with a name. Using named labels might cause assembler or linker errors.
     ///
+    /// See the explanation in [Rust By Example] for more details.
+    ///
     /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
+    /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
     pub NAMED_ASM_LABELS,
     Deny,
     "named labels in inline assembly",

compiler/rustc_lint/src/context.rs

@@ -770,6 +770,7 @@ pub trait LintContext: Sized {
                 }
                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
                     db.help(&help);
+                    db.note("see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information");
                 }
             }
             // Rewrap `db`, and pass control to the user.

compiler/rustc_lint_defs/src/builtin.rs

@@ -2444,6 +2444,10 @@ declare_lint! {
     /// register size, to alert you of possibly using the incorrect width. To
     /// fix this, add the suggested modifier to the template, or cast the
     /// value to the correct size.
+    ///
+    /// See [register template modifiers] in the reference for more details.
+    ///
+    /// [register template modifiers]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html#template-modifiers
     pub ASM_SUB_REGISTER,
     Warn,
     "using only a subset of a register for inline asm inputs",

library/core/src/lib.rs

@@ -375,13 +375,25 @@ pub mod arch {
     pub use crate::core_arch::arch::*;
 
     /// Inline assembly.
+    ///
+    /// Refer to [rust by example] for a usage guide and the [reference] for
+    /// detailed information about the syntax and available options.
+    ///
+    /// [rust by example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
     #[stable(feature = "asm", since = "1.59.0")]
     #[rustc_builtin_macro]
     pub macro asm("assembly template", $(operands,)* $(options($(option),*))?) {
         /* compiler built-in */
     }
 
     /// Module-level inline assembly.
+    ///
+    /// Refer to [rust by example] for a usage guide and the [reference] for
+    /// detailed information about the syntax and available options.
+    ///
+    /// [rust by example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
     #[stable(feature = "global_asm", since = "1.59.0")]
     #[rustc_builtin_macro]
     pub macro global_asm("assembly template", $(operands,)* $(options($(option),*))?) {

src/ci/github-actions/ci.yml

@@ -73,7 +73,7 @@ x--expand-yaml-anchors--remove:
     env: {}
 
   - &job-linux-xl
-    os: ubuntu-latest-xl
+    os: ubuntu-20.04-xl
     <<: *base-job
 
   - &job-macos-xl