Rollup of 10 pull requests

CODE_OF_CONDUCT.md

@@ -33,7 +33,7 @@ In the Rust community we strive to go the extra step to look out for each other.
 
 And if someone takes issue with something you said or did, resist the urge to be defensive. Just stop doing what it was they complained about and apologize. Even if you feel you were misinterpreted or unfairly accused, chances are good there was something you could've communicated better — remember that it's your responsibility to make your fellow Rustaceans comfortable. Everyone wants to get along and we are all here first and foremost because we want to talk about cool technology. You will find that people will be eager to assume good intent and forgive as long as you earn their trust.
 
-The enforcement policies listed above apply to all official Rust venues; including official IRC channels (#rust, #rust-internals, #rust-tools, #rust-libs, #rustc, #rust-beginners, #rust-docs, #rust-community, #rust-lang, and #cargo); GitHub repositories under rust-lang, rust-lang-nursery, and rust-lang-deprecated; and all forums under rust-lang.org (users.rust-lang.org, internals.rust-lang.org). For other projects adopting the Rust Code of Conduct, please contact the maintainers of those projects for enforcement. If you wish to use this code of conduct for your own project, consider explicitly mentioning your moderation policy or making a copy with your own moderation policy so as to avoid confusion.
+The enforcement policies listed above apply to all official Rust venues; including all communication channels (Rust Discord server, Rust Zulip server); GitHub repositories under rust-lang, rust-lang-nursery, and rust-lang-deprecated; and all forums under rust-lang.org (users.rust-lang.org, internals.rust-lang.org). For other projects adopting the Rust Code of Conduct, please contact the maintainers of those projects for enforcement. If you wish to use this code of conduct for your own project, consider explicitly mentioning your moderation policy or making a copy with your own moderation policy so as to avoid confusion.
 
 *Adapted from the [Node.js Policy on Trolling](https://blog.izs.me/2012/08/policy-on-trolling) as well as the [Contributor Covenant v1.3.0](https://www.contributor-covenant.org/version/1/3/0/).*
 

CONTRIBUTING.md

@@ -15,7 +15,7 @@ links to the major sections:
 * [Helpful Links and Information](#helpful-links-and-information)
 
 If you have questions, please make a post on [internals.rust-lang.org][internals] or
-hop on the [Rust Discord server][rust-discord], [Rust Zulip server][rust-zulip] or [#rust-internals][pound-rust-internals].
+hop on the [Rust Discord server][rust-discord] or [Rust Zulip server][rust-zulip].
 
 As a reminder, all contributors are expected to follow our [Code of Conduct][coc].
 
@@ -25,7 +25,6 @@ to contribute to it in more detail than this document.
 If this is your first time contributing, the [walkthrough] chapter of the guide
 can give you a good example of how a typical contribution would go.
 
-[pound-rust-internals]: https://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust-internals
 [internals]: https://internals.rust-lang.org
 [rust-discord]: http://discord.gg/rust-lang
 [rust-zulip]: https://rust-lang.zulipchat.com
@@ -404,7 +403,7 @@ If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
 There are a number of other ways to contribute to Rust that don't deal with
 this repository.
 
-Answer questions in [#rust][pound-rust], or on [users.rust-lang.org][users],
+Answer questions in the _Get Help!_ channels from the [Rust Discord server][rust-discord], on [users.rust-lang.org][users],
 or on [StackOverflow][so].
 
 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
@@ -413,7 +412,7 @@ Find a [requested community library][community-library], build it, and publish
 it to [Crates.io](http://crates.io). Easier said than done, but very, very
 valuable!
 
-[pound-rust]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
+[rust-discord]: https://discord.gg/rust-lang
 [users]: https://users.rust-lang.org/
 [so]: http://stackoverflow.com/questions/tagged/rust
 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library

README.md

@@ -244,19 +244,17 @@ The Rust community congregates in a few places:
 
 To contribute to Rust, please see [CONTRIBUTING](CONTRIBUTING.md).
 
-Rust has an [IRC] culture and most real-time collaboration happens in a
-variety of channels on Mozilla's IRC network, irc.mozilla.org. The
-most popular channel is [#rust], a venue for general discussion about
-Rust. And a good place to ask for help would be [#rust-beginners].
+Most real-time collaboration happens in a variety of channels on the
+[Rust Discord server][rust-discord], with channels dedicated for getting help,
+community, documentation, and all major contribution areas in the Rust ecosystem.
+A good place to ask for help would be the #help channel.
 
 The [rustc guide] might be a good place to start if you want to find out how
 various parts of the compiler work.
 
 Also, you may find the [rustdocs for the compiler itself][rustdocs] useful.
 
-[IRC]: https://en.wikipedia.org/wiki/Internet_Relay_Chat
-[#rust]: irc://irc.mozilla.org/rust
-[#rust-beginners]: irc://irc.mozilla.org/rust-beginners
+[rust-discord]: https://discord.gg/rust-lang
 [rustc guide]: https://rust-lang.github.io/rustc-guide/about-this-guide.html
 [rustdocs]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
 

src/bootstrap/README.md

@@ -328,6 +328,8 @@ are:
   `Config` struct.
 * Adding a sanity check? Take a look at `bootstrap/sanity.rs`.
 
-If you have any questions feel free to reach out on `#rust-infra` on IRC or ask on
-internals.rust-lang.org. When you encounter bugs, please file issues on the
-rust-lang/rust issue tracker.
+If you have any questions feel free to reach out on `#infra` channel in the
+[Rust Discord server][rust-discord] or ask on internals.rust-lang.org. When
+you encounter bugs, please file issues on the rust-lang/rust issue tracker.
+
+[rust-discord]: https://discord.gg/rust-lang

src/libcore/macros.rs

@@ -465,7 +465,7 @@ macro_rules! writeln {
 /// The unsafe counterpart of this macro is the [`unreachable_unchecked`] function, which
 /// will cause undefined behavior if the code is reached.
 ///
-/// [`panic!`]:  ../std/macro.panic.html
+/// [`panic!`]: ../std/macro.panic.html
 /// [`unreachable_unchecked`]: ../std/hint/fn.unreachable_unchecked.html
 /// [`std::hint`]: ../std/hint/index.html
 ///
@@ -474,6 +474,7 @@ macro_rules! writeln {
 /// This will always [`panic!`]
 ///
 /// [`panic!`]: ../std/macro.panic.html
+///
 /// # Examples
 ///
 /// Match arms:
@@ -525,6 +526,9 @@ macro_rules! unreachable {
 /// code type-check, or if you're implementing a trait that requires multiple
 /// methods, and you're only planning on using one of them.
 ///
+/// There is no difference between `unimplemented!` and `todo!` apart from the
+/// name.
+///
 /// # Panics
 ///
 /// This will always [panic!](macro.panic.html)
@@ -579,8 +583,10 @@ macro_rules! unimplemented {
 /// Indicates unfinished code.
 ///
 /// This can be useful if you are prototyping and are just looking to have your
-/// code typecheck. `todo!` works exactly like `unimplemented!`. The only
-/// difference between the two macros is the name.
+/// code typecheck.
+///
+/// There is no difference between `unimplemented!` and `todo!` apart from the
+/// name.
 ///
 /// # Panics
 ///
@@ -602,8 +608,6 @@ macro_rules! unimplemented {
 /// `baz()`, so we can use `todo!`:
 ///
 /// ```
-/// #![feature(todo_macro)]
-///
 /// # trait Foo {
 /// #     fn bar(&self);
 /// #     fn baz(&self);
@@ -629,7 +633,7 @@ macro_rules! unimplemented {
 /// }
 /// ```
 #[macro_export]
-#[unstable(feature = "todo_macro", issue = "59277")]
+#[stable(feature = "todo_macro", since = "1.39.0")]
 macro_rules! todo {
     () => (panic!("not yet implemented"));
     ($($arg:tt)+) => (panic!("not yet implemented: {}", $crate::format_args!($($arg)+)));

src/librustc/middle/cstore.rs

@@ -148,9 +148,7 @@ pub enum ExternCrateSource {
         /// such ids
         DefId,
     ),
-    // Crate is loaded by `use`.
-    Use,
-    /// Crate is implicitly loaded by an absolute path.
+    /// Crate is implicitly loaded by a path resolving through extern prelude.
     Path,
 }
 

src/librustc/mir/visit.rs

@@ -166,6 +166,15 @@ macro_rules! make_mir_visitor {
                 self.super_projection(base, projection, context, location);
             }
 
+            fn visit_projection_elem(&mut self,
+                                     base: & $($mutability)? PlaceBase<'tcx>,
+                                     proj_base: & $($mutability)? [PlaceElem<'tcx>],
+                                     elem: & $($mutability)? PlaceElem<'tcx>,
+                                     context: PlaceContext,
+                                     location: Location) {
+                self.super_projection_elem(base, proj_base, elem, context, location);
+            }
+
             fn visit_constant(&mut self,
                               constant: & $($mutability)? Constant<'tcx>,
                               location: Location) {
@@ -725,27 +734,36 @@ macro_rules! make_mir_visitor {
                                 projection: & $($mutability)? [PlaceElem<'tcx>],
                                 context: PlaceContext,
                                 location: Location) {
-                if let [proj_base @ .., elem] = projection {
-                    self.visit_projection(base, proj_base, context, location);
+                let mut cursor = projection;
+                while let [proj_base @ .., elem] = cursor {
+                    cursor = proj_base;
+                    self.visit_projection_elem(base, cursor, elem, context, location);
+                }
+            }
 
-                    match elem {
-                        ProjectionElem::Field(_field, ty) => {
-                            self.visit_ty(ty, TyContext::Location(location));
-                        }
-                        ProjectionElem::Index(local) => {
-                            self.visit_local(
-                                local,
-                                PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
-                                location
-                            );
-                        }
-                        ProjectionElem::Deref |
-                        ProjectionElem::Subslice { from: _, to: _ } |
-                        ProjectionElem::ConstantIndex { offset: _,
-                                                        min_length: _,
-                                                        from_end: _ } |
-                        ProjectionElem::Downcast(_, _) => {
-                        }
+            fn super_projection_elem(&mut self,
+                                     _base: & $($mutability)? PlaceBase<'tcx>,
+                                     _proj_base: & $($mutability)? [PlaceElem<'tcx>],
+                                     elem: & $($mutability)? PlaceElem<'tcx>,
+                                     _context: PlaceContext,
+                                     location: Location) {
+                match elem {
+                    ProjectionElem::Field(_field, ty) => {
+                        self.visit_ty(ty, TyContext::Location(location));
+                    }
+                    ProjectionElem::Index(local) => {
+                        self.visit_local(
+                            local,
+                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
+                            location
+                        );
+                    }
+                    ProjectionElem::Deref |
+                    ProjectionElem::Subslice { from: _, to: _ } |
+                    ProjectionElem::ConstantIndex { offset: _,
+                                                    min_length: _,
+                                                    from_end: _ } |
+                    ProjectionElem::Downcast(_, _) => {
                     }
                 }
             }

src/librustc_codegen_llvm/attributes.rs

@@ -273,25 +273,51 @@ pub fn from_fn_attrs(
     } else if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND) {
         // Special attribute for allocator functions, which can't unwind
         false
-    } else if let Some(id) = id {
+    } else if let Some(_) = id {
+        // rust-lang/rust#64655, rust-lang/rust#63909: to minimize
+        // risk associated with changing cases where nounwind
+        // attribute is attached, this code is deliberately mimicking
+        // old control flow based on whether `id` is `Some` or `None`.
+        //
+        // However, in the long term we should either:
+        // - fold this into final else (i.e. stop inspecting `id`)
+        // - or, adopt Rust PR #63909.
+        //
+        // see also Rust RFC 2753.
+
         let sig = cx.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
-        if cx.tcx.is_foreign_item(id) {
-            // Foreign items like `extern "C" { fn foo(); }` are assumed not to
-            // unwind
-            false
-        } else if sig.abi != Abi::Rust && sig.abi != Abi::RustCall {
-            // Any items defined in Rust that *don't* have the `extern` ABI are
-            // defined to not unwind. We insert shims to abort if an unwind
-            // happens to enforce this.
-            false
-        } else {
-            // Anything else defined in Rust is assumed that it can possibly
-            // unwind
+        if sig.abi == Abi::Rust || sig.abi == Abi::RustCall {
+            // Any Rust method (or `extern "Rust" fn` or `extern
+            // "rust-call" fn`) is explicitly allowed to unwind
+            // (unless it has no-unwind attribute, handled above).
             true
+        } else {
+            // Anything else is either:
+            //
+            //  1. A foreign item using a non-Rust ABI (like `extern "C" { fn foo(); }`), or
+            //
+            //  2. A Rust item using a non-Rust ABI (like `extern "C" fn foo() { ... }`).
+            //
+            // Foreign items (case 1) are assumed to not unwind; it is
+            // UB otherwise. (At least for now; see also
+            // rust-lang/rust#63909 and Rust RFC 2753.)
+            //
+            // Items defined in Rust with non-Rust ABIs (case 2) are also
+            // not supposed to unwind. Whether this should be enforced
+            // (versus stating it is UB) and *how* it would be enforced
+            // is currently under discussion; see rust-lang/rust#58794.
+            //
+            // In either case, we mark item as explicitly nounwind.
+            false
         }
     } else {
         // assume this can possibly unwind, avoiding the application of a
         // `nounwind` attribute below.
+        //
+        // (But: See comments in previous branch. Specifically, it is
+        // unclear whether there is real value in the assumption this
+        // can unwind. The conservatism here may just be papering over
+        // a real problem by making some UB a bit harder to hit.)
         true
     });