Auto merge of rust-lang#107021 - matthiaskrgr:rollup-0dzxfyi, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#106244 (Improve Markdown styling in README)
 - rust-lang#106747 (Add 'static lifetime suggestion when GAT implied 'static requirement from HRTB)
 - rust-lang#106873 (dont randomly use `_` to print out const generic arguments)
 - rust-lang#106992 (Remove unused `#![feature(box_syntax)]` in `alloc`)
 - rust-lang#106995 (bump failing assembly & codegen tests from LLVM 14 to LLVM 15)
 - rust-lang#106996 (rustdoc: instead of `.setting-name { width: 100% }`, use default div CSS)
 - rust-lang#106997 (Add heapsort fallback in `select_nth_unstable`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

README.md

@@ -3,10 +3,11 @@
 This is the main source code repository for [Rust]. It contains the compiler,
 standard library, and documentation.
 
-[Rust]: https://www.rust-lang.org
+[Rust]: https://www.rust-lang.org/
 
 **Note: this README is for _users_ rather than _contributors_.**
-If you wish to _contribute_ to the compiler, you should read [CONTRIBUTING.md](CONTRIBUTING.md) instead.
+If you wish to _contribute_ to the compiler, you should read
+[CONTRIBUTING.md](CONTRIBUTING.md) instead.
 
 ## Quick Start
 
@@ -20,13 +21,15 @@ Read ["Installation"] from [The Book].
 The Rust build system uses a Python script called `x.py` to build the compiler,
 which manages the bootstrapping process. It lives at the root of the project.
 
-The `x.py` command can be run directly on most Unix systems in the following format:
+The `x.py` command can be run directly on most Unix systems in the following
+format:
 
 ```sh
 ./x.py <subcommand> [flags]
 ```
 
-This is how the documentation and examples assume you are running `x.py`. Some alternative ways are:
+This is how the documentation and examples assume you are running `x.py`.
+Some alternative ways are:
 
 ```sh
 # On a Unix shell if you don't have the necessary `python3` command
@@ -39,8 +42,8 @@ x.py <subcommand> [flags]
 python x.py <subcommand> [flags]
 ```
 
-More information about `x.py` can be found
-by running it with the `--help` flag or reading the [rustc dev guide][rustcguidebuild].
+More information about `x.py` can be found by running it with the `--help` flag
+or reading the [rustc dev guide][rustcguidebuild].
 
 [gettingstarted]: https://rustc-dev-guide.rust-lang.org/getting-started.html
 [rustcguidebuild]: https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html
@@ -49,24 +52,29 @@ by running it with the `--help` flag or reading the [rustc dev guide][rustcguide
 
 Make sure you have installed the dependencies:
 
-   * `python` 3 or 2.7
-   * `git`
-   * A C compiler (when building for the host, `cc` is enough; cross-compiling may need additional compilers)
-   * `curl` (not needed on Windows)
-   * `pkg-config` if you are compiling on Linux and targeting Linux
-   * `libiconv` (already included with glibc on Debian-based distros)
+* `python` 3 or 2.7
+* `git`
+* A C compiler (when building for the host, `cc` is enough; cross-compiling may
+  need additional compilers)
+* `curl` (not needed on Windows)
+* `pkg-config` if you are compiling on Linux and targeting Linux
+* `libiconv` (already included with glibc on Debian-based distros)
 
-To build cargo, you'll also need OpenSSL (`libssl-dev` or `openssl-devel` on most Unix distros).
+To build Cargo, you'll also need OpenSSL (`libssl-dev` or `openssl-devel` on
+most Unix distros).
 
 If building LLVM from source, you'll need additional tools:
 
 * `g++`, `clang++`, or MSVC with versions listed on
   [LLVM's documentation](https://llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library)
-* `ninja`, or GNU `make` 3.81 or later (ninja is recommended, especially on Windows)
+* `ninja`, or GNU `make` 3.81 or later (Ninja is recommended, especially on
+  Windows)
 * `cmake` 3.13.4 or later
-* `libstdc++-static` may be required on some Linux distributions such as Fedora and Ubuntu
+* `libstdc++-static` may be required on some Linux distributions such as Fedora
+  and Ubuntu
 
-On tier 1 or tier 2 with host tools platforms, you can also choose to download LLVM by setting `llvm.download-ci-llvm = true`.
+On tier 1 or tier 2 with host tools platforms, you can also choose to download
+LLVM by setting `llvm.download-ci-llvm = true`.
 Otherwise, you'll need LLVM installed and `llvm-config` in your path.
 See [the rustc-dev-guide for more info][sysllvm].
 
@@ -86,52 +94,57 @@ See [the rustc-dev-guide for more info][sysllvm].
 
 2. Configure the build settings:
 
-    The Rust build system uses a file named `config.toml` in the root of the
-    source tree to determine various configuration settings for the build.
-    Set up the defaults intended for distros to get started. You can see a full list of options
-    in `config.toml.example`.
+   The Rust build system uses a file named `config.toml` in the root of the
+   source tree to determine various configuration settings for the build.
+   Set up the defaults intended for distros to get started. You can see a full
+   list of options in `config.toml.example`.
 
-    ```sh
-    printf 'profile = "user" \nchangelog-seen = 2 \n' > config.toml
-    ```
+   ```sh
+   printf 'profile = "user" \nchangelog-seen = 2 \n' > config.toml
+   ```
 
-    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.
+   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.
 
 3. Build and install:
 
-    ```sh
-    ./x.py build && ./x.py install
-    ```
+   ```sh
+   ./x.py build && ./x.py install
+   ```
 
-    When complete, `./x.py install` will place several programs into
-    `$PREFIX/bin`: `rustc`, the Rust compiler, and `rustdoc`, the
-    API-documentation tool. If you've set `profile = "user"` or `build.extended = true`, it will
-    also include [Cargo], Rust's package manager.
+   When complete, `./x.py install` will place several programs into
+   `$PREFIX/bin`: `rustc`, the Rust compiler, and `rustdoc`, the
+   API-documentation tool. If you've set `profile = "user"` or
+   `build.extended = true`, it will also include [Cargo], Rust's package
+   manager.
 
 [Cargo]: https://github.com/rust-lang/cargo
 
 ### Building on Windows
 
-On Windows, we suggest using [winget] to install dependencies by running the following in a terminal:
+On Windows, we suggest using [winget] to install dependencies by running the
+following in a terminal:
 
 ```powershell
 winget install -e Python.Python.3
 winget install -e Kitware.CMake
 winget install -e Git.Git
 ```
 
-Then edit your system's `PATH` variable and add: `C:\Program Files\CMake\bin`. See
-[this guide on editing the system `PATH`](https://www.java.com/en/download/help/path.html) from the
-Java documentation.
+Then edit your system's `PATH` variable and add: `C:\Program Files\CMake\bin`.
+See
+[this guide on editing the system `PATH`](https://www.java.com/en/download/help/path.html)
+from the Java documentation.
 
 [winget]: https://github.com/microsoft/winget-cli
 
 There are two prominent ABIs in use on Windows: the native (MSVC) ABI used by
 Visual Studio and the GNU ABI used by the GCC toolchain. Which version of Rust
 you need depends largely on what C/C++ libraries you want to interoperate with.
-Use the MSVC build of Rust to interop with software produced by Visual Studio and
-the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain.
+Use the MSVC build of Rust to interop with software produced by Visual Studio
+and the GNU build to interop with GNU software built using the MinGW/MSYS2
+toolchain.
 
 #### MinGW
 
@@ -144,7 +157,7 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
 2. Run `mingw32_shell.bat` or `mingw64_shell.bat` from the MSYS2 installation
    directory (e.g. `C:\msys64`), depending on whether you want 32-bit or 64-bit
    Rust. (As of the latest version of MSYS2 you have to run `msys2_shell.cmd
-   -mingw32` or `msys2_shell.cmd -mingw64` from the command line instead)
+   -mingw32` or `msys2_shell.cmd -mingw64` from the command line instead.)
 
 3. From this terminal, install the required tools:
 
@@ -153,11 +166,11 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
    pacman -Sy pacman-mirrors
 
    # Install build tools needed for Rust. If you're building a 32-bit compiler,
-   # then replace "x86_64" below with "i686". If you've already got git, python,
-   # or CMake installed and in PATH you can remove them from this list. Note
-   # that it is important that you do **not** use the 'python2', 'cmake' and 'ninja'
-   # packages from the 'msys2' subsystem. The build has historically been known
-   # to fail with these packages.
+   # then replace "x86_64" below with "i686". If you've already got Git, Python,
+   # or CMake installed and in PATH you can remove them from this list.
+   # Note that it is important that you do **not** use the 'python2', 'cmake',
+   # and 'ninja' packages from the 'msys2' subsystem.
+   # The build has historically been known to fail with these packages.
    pacman -S git \
                make \
                diffutils \
@@ -178,12 +191,12 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
 
 MSVC builds of Rust additionally require an installation of Visual Studio 2017
 (or later) so `rustc` can use its linker.  The simplest way is to get
-[Visual Studio], check the “C++ build tools” and “Windows 10 SDK” workload.
+[Visual Studio], check the "C++ build tools" and "Windows 10 SDK" workload.
 
 [Visual Studio]: https://visualstudio.microsoft.com/downloads/
 
-(If you're installing cmake yourself, be careful that “C++ CMake tools for
-Windows” doesn't get included under “Individual components”.)
+(If you're installing CMake yourself, be careful that "C++ CMake tools for
+Windows" doesn't get included under "Individual components".)
 
 With these dependencies installed, you can build the compiler in a `cmd.exe`
 shell with:
@@ -192,10 +205,11 @@ shell with:
 python x.py build
 ```
 
-Right now, building Rust only works with some known versions of Visual Studio. If
-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.
+Right now, building Rust only works with some known versions of Visual Studio.
+If 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
 CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
@@ -215,9 +229,9 @@ Windows build triples are:
     - `x86_64-pc-windows-msvc`
 
 The build triple can be specified by either specifying `--build=<triple>` when
-invoking `x.py` commands, or by creating a `config.toml` file (as described
-in [Installing From Source](#installing-from-source)), and modifying the
-`build` option under the `[build]` section.
+invoking `x.py` commands, or by creating a `config.toml` file (as described in
+[Installing from Source](#installing-from-source)), and modifying the `build`
+option under the `[build]` section.
 
 ### Configure and Make
 
@@ -229,33 +243,35 @@ configure script and makefile (the latter of which just invokes `x.py`).
 make && sudo make install
 ```
 
-`configure` generates a `config.toml` which can also be used with normal `x.py` invocations.
+`configure` generates a `config.toml` which can also be used with normal `x.py`
+invocations.
 
 ## Building Documentation
 
-If you’d like to build the documentation, it’s almost the same:
+If you'd like to build the documentation, it's almost the same:
 
 ```sh
 ./x.py doc
 ```
 
 The generated documentation will appear under `doc` in the `build` directory for
-the ABI used. I.e., if the ABI was `x86_64-pc-windows-msvc`, the directory will be
-`build\x86_64-pc-windows-msvc\doc`.
+the ABI used. That is, if the ABI was `x86_64-pc-windows-msvc`, the directory
+will be `build\x86_64-pc-windows-msvc\doc`.
 
 ## Notes
 
-Since the Rust compiler is written in Rust, it must be built by a
-precompiled "snapshot" version of itself (made in an earlier stage of
-development). As such, source builds require an Internet connection to
-fetch snapshots, and an OS that can execute the available snapshot binaries.
+Since the Rust compiler is written in Rust, it must be built by a precompiled
+"snapshot" version of itself (made in an earlier stage of development).
+As such, source builds require an Internet connection to fetch snapshots, and an
+OS that can execute the available snapshot binaries.
 
-See https://doc.rust-lang.org/nightly/rustc/platform-support.html for a list of supported platforms.
-Only "host tools" platforms have a pre-compiled snapshot binary available; to compile for a platform
-without host tools you must cross-compile.
+See https://doc.rust-lang.org/nightly/rustc/platform-support.html for a list of
+supported platforms.
+Only "host tools" platforms have a pre-compiled snapshot binary available; to
+compile for a platform without host tools you must cross-compile.
 
-You may find that other platforms work, but these are our officially
-supported build environments that are most likely to work.
+You may find that other platforms work, but these are our officially supported
+build environments that are most likely to work.
 
 ## Getting Help
 
@@ -267,23 +283,24 @@ See [CONTRIBUTING.md](CONTRIBUTING.md).
 
 ## License
 
-Rust is primarily distributed under the terms of both the MIT license
-and the Apache License (Version 2.0), with portions covered by various
-BSD-like licenses.
+Rust is primarily distributed under the terms of both the MIT license and the
+Apache License (Version 2.0), with portions covered by various BSD-like
+licenses.
 
 See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
 [COPYRIGHT](COPYRIGHT) for details.
 
 ## Trademark
 
 [The Rust Foundation][rust-foundation] owns and protects the Rust and Cargo
-trademarks and logos (the “Rust Trademarks”).
+trademarks and logos (the "Rust Trademarks").
 
-If you want to use these names or brands, please read the [media guide][media-guide].
+If you want to use these names or brands, please read the
+[media guide][media-guide].
 
 Third-party logos may be subject to third-party copyrights and trademarks. See
 [Licenses][policies-licenses] for details.
 
 [rust-foundation]: https://foundation.rust-lang.org/
-[media-guide]: https://www.rust-lang.org/policies/media-guide
+[media-guide]: https://foundation.rust-lang.org/policies/logo-policy-and-media-guide/
 [policies-licenses]: https://www.rust-lang.org/policies/licenses

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -5,8 +5,13 @@
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
 use rustc_hir as hir;
+use rustc_hir::def::Res::Def;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
+use rustc_hir::GenericBound::Trait;
+use rustc_hir::QPath::Resolved;
+use rustc_hir::WherePredicate::BoundPredicate;
+use rustc_hir::{PolyTraitRef, TyKind, WhereBoundPredicate};
 use rustc_infer::infer::{
     error_reporting::nice_region_error::{
         self, find_anon_type, find_param_with_region, suggest_adding_lifetime_params,
@@ -186,6 +191,101 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         false
     }
 
+    // For generic associated types (GATs) which implied 'static requirement
+    // from higher-ranked trait bounds (HRTB). Try to locate span of the trait
+    // and the span which bounded to the trait for adding 'static lifetime suggestion
+    fn suggest_static_lifetime_for_gat_from_hrtb(
+        &self,
+        diag: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        lower_bound: RegionVid,
+    ) {
+        let mut suggestions = vec![];
+        let hir = self.infcx.tcx.hir();
+
+        // find generic associated types in the given region 'lower_bound'
+        let gat_id_and_generics = self
+            .regioncx
+            .placeholders_contained_in(lower_bound)
+            .map(|placeholder| {
+                if let Some(id) = placeholder.name.get_id()
+                    && let Some(placeholder_id) = id.as_local()
+                    && let gat_hir_id = hir.local_def_id_to_hir_id(placeholder_id)
+                    && let Some(generics_impl) = hir.get_parent(gat_hir_id).generics()
+                {
+                    Some((gat_hir_id, generics_impl))
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>();
+        debug!(?gat_id_and_generics);
+
+        // find higher-ranked trait bounds bounded to the generic associated types
+        let mut hrtb_bounds = vec![];
+        gat_id_and_generics.iter().flatten().for_each(|(gat_hir_id, generics)| {
+            for pred in generics.predicates {
+                let BoundPredicate(
+                        WhereBoundPredicate {
+                            bound_generic_params,
+                            bounds,
+                            ..
+                        }) = pred else { continue; };
+                if bound_generic_params
+                    .iter()
+                    .rfind(|bgp| hir.local_def_id_to_hir_id(bgp.def_id) == *gat_hir_id)
+                    .is_some()
+                {
+                    for bound in *bounds {
+                        hrtb_bounds.push(bound);
+                    }
+                }
+            }
+        });
+        debug!(?hrtb_bounds);
+
+        hrtb_bounds.iter().for_each(|bound| {
+            let Trait(PolyTraitRef { trait_ref, span: trait_span, .. }, _) = bound else { return; };
+            diag.span_note(
+                *trait_span,
+                format!("due to current limitations in the borrow checker, this implies a `'static` lifetime")
+            );
+            let Some(generics_fn) = hir.get_generics(self.body.source.def_id().expect_local()) else { return; };
+            let Def(_, trait_res_defid) = trait_ref.path.res else { return; };
+            debug!(?generics_fn);
+            generics_fn.predicates.iter().for_each(|predicate| {
+                let BoundPredicate(
+                    WhereBoundPredicate {
+                        span: bounded_span,
+                        bounded_ty,
+                        bounds,
+                        ..
+                    }
+                ) = predicate else { return; };
+                bounds.iter().for_each(|bd| {
+                    if let Trait(PolyTraitRef { trait_ref: tr_ref, .. }, _) = bd
+                        && let Def(_, res_defid) = tr_ref.path.res
+                        && res_defid == trait_res_defid // trait id matches
+                        && let TyKind::Path(Resolved(_, path)) = bounded_ty.kind
+                        && let Def(_, defid) = path.res
+                        && generics_fn.params
+                            .iter()
+                            .rfind(|param| param.def_id.to_def_id() == defid)
+                            .is_some() {
+                            suggestions.push((bounded_span.shrink_to_hi(), format!(" + 'static")));
+                        }
+                });
+            });
+        });
+        if suggestions.len() > 0 {
+            suggestions.dedup();
+            diag.multipart_suggestion_verbose(
+                format!("consider restricting the type parameter to the `'static` lifetime"),
+                suggestions,
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
     /// Produces nice borrowck error diagnostics for all the errors collected in `nll_errors`.
     pub(crate) fn report_region_errors(&mut self, nll_errors: RegionErrors<'tcx>) {
         // Iterate through all the errors, producing a diagnostic for each one. The diagnostics are
@@ -223,12 +323,21 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         // to report it; we could probably handle it by
                         // iterating over the universal regions and reporting
                         // an error that multiple bounds are required.
-                        self.buffer_error(self.infcx.tcx.sess.create_err(
-                            GenericDoesNotLiveLongEnough {
+                        let mut diag =
+                            self.infcx.tcx.sess.create_err(GenericDoesNotLiveLongEnough {
                                 kind: type_test.generic_kind.to_string(),
                                 span: type_test_span,
-                            },
-                        ));
+                            });
+
+                        // Add notes and suggestions for the case of 'static lifetime
+                        // implied but not specified when a generic associated types
+                        // are from higher-ranked trait bounds
+                        self.suggest_static_lifetime_for_gat_from_hrtb(
+                            &mut diag,
+                            type_test.lower_bound,
+                        );
+
+                        self.buffer_error(diag);
                     }
                 }