Auto merge of #77462 - jonas-schievink:rollup-m0rqdh5, r=jonas-schievink

Rollup of 12 pull requests

Successful merges:

 - #76101 (Update RELEASES.md for 1.47.0)
 - #76739 (resolve: prohibit anon const non-static lifetimes)
 - #76811 (Doc alias name restriction)
 - #77405 (Add tracking issue of iter_advance_by feature)
 - #77409 (Add example for iter chain struct)
 - #77415 (Better error message for `async` blocks in a const-context)
 - #77423 (Add `-Zprecise-enum-drop-elaboration`)
 - #77432 (Use posix_spawn on musl targets)
 - #77441 (Fix AVR stack corruption bug)
 - #77442 (Clean up on example doc fixes for ptr::copy)
 - #77444 (Fix span for incorrect pattern field and add label)
 - #77453 (Stop running macOS builds on Azure Pipelines)

Failed merges:

r? `@ghost`

Author: bors

Diff for: RELEASES.md

@@ -1,3 +1,138 @@
+Version 1.47.0 (2020-10-08)
+==========================
+
+Language
+--------
+- [Closures will now warn when not used.][74869]
+
+Compiler
+--------
+- [Stabilized the `-C control-flow-guard` codegen option][73893], which enables
+  [Control Flow Guard][1.47.0-cfg] for Windows platforms, and is ignored on other
+  platforms.
+- [Upgraded to LLVM 11.][73526]
+- [Added tier 3\* support for the `thumbv4t-none-eabi` target.][74419]
+- [Upgrade the FreeBSD toolchain to version 11.4][75204]
+- [`RUST_BACKTRACE`'s output is now more compact.][75048]
+
+\* Refer to Rust's [platform support page][forge-platform-support] for more
+information on Rust's tiered platform support.
+
+Libraries
+---------
+- [`CStr` now implements `Index<RangeFrom<usize>>`.][74021]
+- [Traits in `std`/`core` are now implemented for arrays of any length, not just
+  those of length less than 33.][74060]
+- [`ops::RangeFull` and `ops::Range` now implement Default.][73197]
+- [`panic::Location` now implements `Copy`, `Clone`, `Eq`, `Hash`, `Ord`,
+  `PartialEq`, and `PartialOrd`.][73583]
+
+Stabilized APIs
+---------------
+- [`Ident::new_raw`]
+- [`Range::is_empty`]
+- [`RangeInclusive::is_empty`]
+- [`Result::as_deref`]
+- [`Result::as_deref_mut`]
+- [`Vec::leak`]
+- [`pointer::offset_from`]
+- [`f32::TAU`]
+- [`f64::TAU`]
+
+The following previously stable APIs have now been made const.
+
+- [The `new` method for all `NonZero` integers.][73858]
+- [The `checked_add`,`checked_sub`,`checked_mul`,`checked_neg`, `checked_shl`,
+  `checked_shr`, `saturating_add`, `saturating_sub`, and `saturating_mul`
+  methods for all integers.][73858]
+- [The `checked_abs`, `saturating_abs`, `saturating_neg`, and `signum`  for all
+  signed integers.][73858]
+- [The `is_ascii_alphabetic`, `is_ascii_uppercase`, `is_ascii_lowercase`,
+  `is_ascii_alphanumeric`, `is_ascii_digit`, `is_ascii_hexdigit`,
+  `is_ascii_punctuation`, `is_ascii_graphic`, `is_ascii_whitespace`, and
+  `is_ascii_control` methods for `char` and `u8`.][73858]
+
+Cargo
+-----
+- [`build-dependencies` are now built with opt-level 0 by default.][cargo/8500]
+  You can override this by setting the following in your `Cargo.toml`.
+  ```toml
+  [profile.release.build-override]
+  opt-level = 3
+  ```
+- [`cargo-help` will now display man pages for commands rather just the
+  `--help` text.][cargo/8456]
+- [`cargo-metadata` now emits a `test` field indicating if a target has
+  tests enabled.][cargo/8478]
+- [`workspace.default-members` now respects `workspace.exclude`.][cargo/8485]
+- [`cargo-publish` will now use an alternative registry by default if it's the
+  only registry specified in `package.publish`.][cargo/8571]
+
+Misc
+----
+- [Added a help button beside Rustdoc's searchbar that explains rustdoc's
+  type based search.][75366]
+- [Added the Ayu theme to rustdoc.][71237]
+
+Compatibility Notes
+-------------------
+- [Bumped the minimum supported Emscripten version to 1.39.20.][75716]
+- [Fixed a regression parsing `{} && false` in tail expressions.][74650]
+- [Added changes to how proc-macros are expanded in `macro_rules!` that should
+  help to preserve more span information.][73084] These changes may cause
+  compiliation errors if your macro was unhygenic or didn't correctly handle
+  `Delimiter::None`.
+- [Moved support for the CloudABI target to tier 3.][75568]
+- [`linux-gnu` targets now require minimum kernel 2.6.32 and glibc 2.11.][74163]
+- [Added the `rustc-docs` component.][75560] This allows you to install
+  and read the documentation for the compiler internal APIs. (Currently only
+  available for `x86_64-unknown-linux-gnu`.)
+
+Internal Only
+--------
+- [Improved default settings for bootstrapping in `x.py`.][73964] You can read details about this change in the ["Changes To `x.py` Defaults"](https://blog.rust-lang.org/inside-rust/2020/08/30/changes-to-x-py-defaults.html) post on the Inside Rust blog.
+
+[1.47.0-cfg]: https://docs.microsoft.com/en-us/windows/win32/secbp/control-flow-guard
+[75048]: https://github.com/rust-lang/rust/pull/75048/
+[74163]: https://github.com/rust-lang/rust/pull/74163/
+[71237]: https://github.com/rust-lang/rust/pull/71237/
+[74869]: https://github.com/rust-lang/rust/pull/74869/
+[73858]: https://github.com/rust-lang/rust/pull/73858/
+[75716]: https://github.com/rust-lang/rust/pull/75716/
+[75908]: https://github.com/rust-lang/rust/pull/75908/
+[75516]: https://github.com/rust-lang/rust/pull/75516/
+[75560]: https://github.com/rust-lang/rust/pull/75560/
+[75568]: https://github.com/rust-lang/rust/pull/75568/
+[75366]: https://github.com/rust-lang/rust/pull/75366/
+[75204]: https://github.com/rust-lang/rust/pull/75204/
+[74650]: https://github.com/rust-lang/rust/pull/74650/
+[74419]: https://github.com/rust-lang/rust/pull/74419/
+[73964]: https://github.com/rust-lang/rust/pull/73964/
+[74021]: https://github.com/rust-lang/rust/pull/74021/
+[74060]: https://github.com/rust-lang/rust/pull/74060/
+[73893]: https://github.com/rust-lang/rust/pull/73893/
+[73526]: https://github.com/rust-lang/rust/pull/73526/
+[73583]: https://github.com/rust-lang/rust/pull/73583/
+[73084]: https://github.com/rust-lang/rust/pull/73084/
+[73197]: https://github.com/rust-lang/rust/pull/73197/
+[72488]: https://github.com/rust-lang/rust/pull/72488/
+[cargo/8456]: https://github.com/rust-lang/cargo/pull/8456/
+[cargo/8478]: https://github.com/rust-lang/cargo/pull/8478/
+[cargo/8485]: https://github.com/rust-lang/cargo/pull/8485/
+[cargo/8500]: https://github.com/rust-lang/cargo/pull/8500/
+[cargo/8571]: https://github.com/rust-lang/cargo/pull/8571/
+[`Ident::new_raw`]:  https://doc.rust-lang.org/nightly/proc_macro/struct.Ident.html#method.new_raw
+[`Range::is_empty`]: https://doc.rust-lang.org/nightly/std/ops/struct.Range.html#method.is_empty
+[`RangeInclusive::is_empty`]: https://doc.rust-lang.org/nightly/std/ops/struct.RangeInclusive.html#method.is_empty
+[`Result::as_deref_mut`]: https://doc.rust-lang.org/nightly/std/result/enum.Result.html#method.as_deref_mut
+[`Result::as_deref`]: https://doc.rust-lang.org/nightly/std/result/enum.Result.html#method.as_deref
+[`TypeId::of`]: https://doc.rust-lang.org/nightly/std/any/struct.TypeId.html#method.of
+[`Vec::leak`]: https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.leak
+[`f32::TAU`]: https://doc.rust-lang.org/nightly/std/f32/consts/constant.TAU.html
+[`f64::TAU`]: https://doc.rust-lang.org/nightly/std/f64/consts/constant.TAU.html
+[`pointer::offset_from`]: https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.offset_from
+
+
 Version 1.46.0 (2020-08-27)
 ==========================
 

Diff for: compiler/rustc_interface/src/tests.rs

@@ -568,6 +568,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(osx_rpath_install_name, true);
     tracked!(panic_abort_tests, true);
     tracked!(plt, Some(true));
+    tracked!(precise_enum_drop_elaboration, false);
     tracked!(print_fuel, Some("abc".to_string()));
     tracked!(profile, true);
     tracked!(profile_emit, Some(PathBuf::from("abc")));

Diff for: compiler/rustc_mir/src/dataflow/impls/mod.rs

@@ -358,6 +358,10 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
         discr: &mir::Operand<'tcx>,
         edge_effects: &mut impl SwitchIntEdgeEffects<G>,
     ) {
+        if !self.tcx.sess.opts.debugging_opts.precise_enum_drop_elaboration {
+            return;
+        }
+
         let enum_ = discr.place().and_then(|discr| {
             switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
         });
@@ -469,6 +473,10 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
         discr: &mir::Operand<'tcx>,
         edge_effects: &mut impl SwitchIntEdgeEffects<G>,
     ) {
+        if !self.tcx.sess.opts.debugging_opts.precise_enum_drop_elaboration {
+            return;
+        }
+
         if !self.mark_inactive_variants_as_uninit {
             return;
         }

Diff for: compiler/rustc_mir/src/transform/check_consts/ops.rs

@@ -151,14 +151,15 @@ impl NonConstOp for FnPtrCast {
 }
 
 #[derive(Debug)]
-pub struct Generator;
+pub struct Generator(pub hir::GeneratorKind);
 impl NonConstOp for Generator {
     fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status {
         Status::Forbidden
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
-        ccx.tcx.sess.struct_span_err(span, "Generators and `async` functions cannot be `const`")
+        let msg = format!("{}s are not allowed in {}s", self.0, ccx.const_kind());
+        ccx.tcx.sess.struct_span_err(span, &msg)
     }
 }
 

Diff for: compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -770,6 +770,14 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
                     return;
                 }
 
+                // `async` blocks get lowered to `std::future::from_generator(/* a closure */)`.
+                let is_async_block = Some(callee) == tcx.lang_items().from_generator_fn();
+                if is_async_block {
+                    let kind = hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block);
+                    self.check_op(ops::Generator(kind));
+                    return;
+                }
+
                 // HACK: This is to "unstabilize" the `transmute` intrinsic
                 // within const fns. `transmute` is allowed in all other const contexts.
                 // This won't really scale to more intrinsics or functions. Let's allow const
@@ -869,7 +877,7 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
             TerminatorKind::Abort => self.check_op(ops::Abort),
 
             TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
-                self.check_op(ops::Generator)
+                self.check_op(ops::Generator(hir::GeneratorKind::Gen))
             }
 
             TerminatorKind::Assert { .. }

Diff for: compiler/rustc_parse/src/parser/pat.rs

@@ -795,6 +795,7 @@ impl<'a> Parser<'a> {
         }
         self.bump();
         let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
+            e.span_label(path.span, "while parsing the fields for this pattern");
             e.emit();
             self.recover_stmt();
             (vec![], true)
@@ -844,7 +845,7 @@ impl<'a> Parser<'a> {
 
             // check that a comma comes after every field
             if !ate_comma {
-                let err = self.struct_span_err(self.prev_token.span, "expected `,`");
+                let err = self.struct_span_err(self.token.span, "expected `,`");
                 if let Some(mut delayed) = delayed_err {
                     delayed.emit();
                 }

Diff for: compiler/rustc_passes/src/check_attr.rs

@@ -260,23 +260,42 @@ impl CheckAttrVisitor<'tcx> {
         }
     }
 
+    fn doc_alias_str_error(&self, meta: &NestedMetaItem) {
+        self.tcx
+            .sess
+            .struct_span_err(
+                meta.span(),
+                "doc alias attribute expects a string: #[doc(alias = \"0\")]",
+            )
+            .emit();
+    }
+
     fn check_doc_alias(&self, attr: &Attribute, hir_id: HirId, target: Target) -> bool {
         if let Some(mi) = attr.meta() {
             if let Some(list) = mi.meta_item_list() {
                 for meta in list {
                     if meta.has_name(sym::alias) {
-                        if !meta.is_value_str()
-                            || meta
-                                .value_str()
-                                .map(|s| s.to_string())
-                                .unwrap_or_else(String::new)
-                                .is_empty()
+                        if !meta.is_value_str() {
+                            self.doc_alias_str_error(meta);
+                            return false;
+                        }
+                        let doc_alias =
+                            meta.value_str().map(|s| s.to_string()).unwrap_or_else(String::new);
+                        if doc_alias.is_empty() {
+                            self.doc_alias_str_error(meta);
+                            return false;
+                        }
+                        if let Some(c) =
+                            doc_alias.chars().find(|&c| c == '"' || c == '\'' || c.is_whitespace())
                         {
                             self.tcx
                                 .sess
                                 .struct_span_err(
                                     meta.span(),
-                                    "doc alias attribute expects a string: #[doc(alias = \"0\")]",
+                                    &format!(
+                                        "{:?} character isn't allowed in `#[doc(alias = \"...\")]`",
+                                        c,
+                                    ),
                                 )
                                 .emit();
                             return false;
@@ -312,6 +331,7 @@ impl CheckAttrVisitor<'tcx> {
                                     &format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err),
                                 )
                                 .emit();
+                            return false;
                         }
                     }
                 }

Diff for: compiler/rustc_resolve/src/late/diagnostics.rs

@@ -16,6 +16,7 @@ use rustc_hir::def::{self, CtorKind, DefKind};
 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::PrimTy;
 use rustc_session::config::nightly_options;
+use rustc_session::parse::feature_err;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, Span, DUMMY_SP};
@@ -1599,4 +1600,32 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
             _ => {}
         }
     }
+
+    /// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics` so
+    /// this function will emit an error if `min_const_generics` is enabled, the body identified by
+    /// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
+    crate fn maybe_emit_forbidden_non_static_lifetime_error(
+        &self,
+        body_id: hir::BodyId,
+        lifetime_ref: &'tcx hir::Lifetime,
+    ) {
+        let is_anon_const = matches!(
+            self.tcx.def_kind(self.tcx.hir().body_owner_def_id(body_id)),
+            hir::def::DefKind::AnonConst
+        );
+        let is_allowed_lifetime = matches!(
+            lifetime_ref.name,
+            hir::LifetimeName::Implicit | hir::LifetimeName::Static | hir::LifetimeName::Underscore
+        );
+
+        if self.tcx.features().min_const_generics && is_anon_const && !is_allowed_lifetime {
+            feature_err(
+                &self.tcx.sess.parse_sess,
+                sym::const_generics,
+                lifetime_ref.span,
+                "a non-static lifetime is not allowed in a `const`",
+            )
+            .emit();
+        }
+    }
 }

Diff for: compiler/rustc_resolve/src/late/lifetimes.rs

@@ -1777,6 +1777,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         let result = loop {
             match *scope {
                 Scope::Body { id, s } => {
+                    // Non-static lifetimes are prohibited in anonymous constants under
+                    // `min_const_generics`.
+                    self.maybe_emit_forbidden_non_static_lifetime_error(id, lifetime_ref);
+
                     outermost_body = Some(id);
                     scope = s;
                 }

Diff for: compiler/rustc_session/src/options.rs

@@ -1008,6 +1008,10 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "a single extra argument to prepend the linker invocation (can be used several times)"),
     pre_link_args: Vec<String> = (Vec::new(), parse_list, [UNTRACKED],
         "extra arguments to prepend to the linker invocation (space separated)"),
+    precise_enum_drop_elaboration: bool = (true, parse_bool, [TRACKED],
+        "use a more precise version of drop elaboration for matches on enums (default: yes). \
+        This results in better codegen, but has caused miscompilations on some tier 2 platforms. \
+        See #77382 and #74551."),
     print_fuel: Option<String> = (None, parse_opt_string, [TRACKED],
         "make rustc print the total optimization fuel used by a crate"),
     print_link_args: bool = (false, parse_bool, [UNTRACKED],

Diff for: library/core/src/intrinsics.rs

@@ -1901,9 +1901,10 @@ pub unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
 /// ```
 /// use std::ptr;
 ///
-/// /// # Safety:
+/// /// # Safety
+/// ///
 /// /// * `ptr` must be correctly aligned for its type and non-zero.
-/// /// * `ptr` must be valid for reads of `elts` contiguous objects of type `T`.
+/// /// * `ptr` must be valid for reads of `elts` contiguous elements of type `T`.
 /// /// * Those elements must not be used after calling this function unless `T: Copy`.
 /// # #[allow(dead_code)]
 /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {

Diff for: library/core/src/iter/adapters/chain.rs

@@ -6,6 +6,17 @@ use crate::usize;
 ///
 /// This `struct` is created by [`Iterator::chain`]. See its documentation
 /// for more.
+///
+/// # Examples
+///
+/// ```
+/// use std::iter::Chain;
+/// use std::slice::Iter;
+///
+/// let a1 = [1, 2, 3];
+/// let a2 = [4, 5, 6];
+/// let iter: Chain<Iter<_>, Iter<_>> = a1.iter().chain(a2.iter());
+/// ```
 #[derive(Clone, Debug)]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]

Diff for: library/core/src/iter/traits/double_ended.rs

@@ -123,7 +123,7 @@ pub trait DoubleEndedIterator: Iterator {
     /// assert_eq!(iter.advance_back_by(100), Err(1)); // only `&3` was skipped
     /// ```
     #[inline]
-    #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "none")]
+    #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "77404")]
     fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
         for i in 0..n {
             self.next_back().ok_or(i)?;

Diff for: library/core/src/iter/traits/iterator.rs

@@ -314,7 +314,7 @@ pub trait Iterator {
     /// assert_eq!(iter.advance_by(100), Err(1)); // only `&4` was skipped
     /// ```
     #[inline]
-    #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "none")]
+    #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "77404")]
     fn advance_by(&mut self, n: usize) -> Result<(), usize> {
         for i in 0..n {
             self.next().ok_or(i)?;