Merge pull request #4474 from rust-lang/rustup-2025-07-18

Automatic Rustup

57 files changed, 225 insertions, 312 deletions

diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 28958b60fc3..22a75183404 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -697,7 +697,7 @@ impl Config {
         config.change_id = toml.change_id.inner;
 
         let Build {
-            mut description,
+            description,
             build,
             host,
             target,
@@ -749,7 +749,7 @@ impl Config {
             compiletest_diff_tool,
             compiletest_use_stage0_libtest,
             tidy_extra_checks,
-            mut ccache,
+            ccache,
             exclude,
         } = toml.build.unwrap_or_default();
 
@@ -942,7 +942,7 @@ impl Config {
         config.rust_profile_use = flags_rust_profile_use;
         config.rust_profile_generate = flags_rust_profile_generate;
 
-        config.apply_rust_config(toml.rust, flags_warnings, &mut description);
+        config.apply_rust_config(toml.rust, flags_warnings);
 
         config.reproducible_artifacts = flags_reproducible_artifact;
         config.description = description;
@@ -963,7 +963,7 @@ impl Config {
             config.channel = channel;
         }
 
-        config.apply_llvm_config(toml.llvm, &mut ccache);
+        config.apply_llvm_config(toml.llvm);
 
         config.apply_gcc_config(toml.gcc);
 
diff --git a/src/bootstrap/src/core/config/toml/llvm.rs b/src/bootstrap/src/core/config/toml/llvm.rs
index 4774e202bd8..1f0cecd145c 100644
--- a/src/bootstrap/src/core/config/toml/llvm.rs
+++ b/src/bootstrap/src/core/config/toml/llvm.rs
@@ -17,8 +17,6 @@ define_config! {
         tests: Option<bool> = "tests",
         enzyme: Option<bool> = "enzyme",
         plugins: Option<bool> = "plugins",
-        // FIXME: Remove this field at Q2 2025, it has been replaced by build.ccache
-        ccache: Option<StringOrBool> = "ccache",
         static_libstdcpp: Option<bool> = "static-libstdcpp",
         libzstd: Option<bool> = "libzstd",
         ninja: Option<bool> = "ninja",
@@ -97,7 +95,6 @@ pub fn check_incompatible_options_for_ci_llvm(
         assertions: _,
         tests: _,
         plugins,
-        ccache: _,
         static_libstdcpp: _,
         libzstd,
         ninja: _,
@@ -149,11 +146,7 @@ pub fn check_incompatible_options_for_ci_llvm(
 }
 
 impl Config {
-    pub fn apply_llvm_config(
-        &mut self,
-        toml_llvm: Option<Llvm>,
-        ccache: &mut Option<StringOrBool>,
-    ) {
+    pub fn apply_llvm_config(&mut self, toml_llvm: Option<Llvm>) {
         let mut llvm_tests = None;
         let mut llvm_enzyme = None;
         let mut llvm_offload = None;
@@ -168,7 +161,6 @@ impl Config {
                 tests,
                 enzyme,
                 plugins,
-                ccache: llvm_ccache,
                 static_libstdcpp,
                 libzstd,
                 ninja,
@@ -191,13 +183,7 @@ impl Config {
                 download_ci_llvm,
                 build_config,
             } = llvm;
-            if llvm_ccache.is_some() {
-                eprintln!("Warning: llvm.ccache is deprecated. Use build.ccache instead.");
-            }
 
-            if ccache.is_none() {
-                *ccache = llvm_ccache;
-            }
             set(&mut self.ninja_in_file, ninja);
             llvm_tests = tests;
             llvm_enzyme = enzyme;
diff --git a/src/bootstrap/src/core/config/toml/rust.rs b/src/bootstrap/src/core/config/toml/rust.rs
index 0fae235bb93..307aa52294b 100644
--- a/src/bootstrap/src/core/config/toml/rust.rs
+++ b/src/bootstrap/src/core/config/toml/rust.rs
@@ -36,8 +36,6 @@ define_config! {
         incremental: Option<bool> = "incremental",
         default_linker: Option<String> = "default-linker",
         channel: Option<String> = "channel",
-        // FIXME: Remove this field at Q2 2025, it has been replaced by build.description
-        description: Option<String> = "description",
         musl_root: Option<String> = "musl-root",
         rpath: Option<bool> = "rpath",
         strip: Option<bool> = "strip",
@@ -320,7 +318,6 @@ pub fn check_incompatible_options_for_ci_rustc(
         jemalloc,
         rpath,
         channel,
-        description,
         default_linker,
         std_features,
 
@@ -388,7 +385,6 @@ pub fn check_incompatible_options_for_ci_rustc(
     err!(current_rust_config.std_features, std_features, "rust");
 
     warn!(current_rust_config.channel, channel, "rust");
-    warn!(current_rust_config.description, description, "rust");
 
     Ok(())
 }
@@ -415,12 +411,7 @@ pub(crate) fn validate_codegen_backends(backends: Vec<String>, section: &str) ->
 }
 
 impl Config {
-    pub fn apply_rust_config(
-        &mut self,
-        toml_rust: Option<Rust>,
-        warnings: Warnings,
-        description: &mut Option<String>,
-    ) {
+    pub fn apply_rust_config(&mut self, toml_rust: Option<Rust>, warnings: Warnings) {
         let mut debug = None;
         let mut rustc_debug_assertions = None;
         let mut std_debug_assertions = None;
@@ -459,7 +450,6 @@ impl Config {
                 randomize_layout,
                 default_linker,
                 channel: _, // already handled above
-                description: rust_description,
                 musl_root,
                 rpath,
                 verbose_tests,
@@ -552,14 +542,6 @@ impl Config {
             set(&mut self.jemalloc, jemalloc);
             set(&mut self.test_compare_mode, test_compare_mode);
             set(&mut self.backtrace, backtrace);
-            if rust_description.is_some() {
-                eprintln!(
-                    "Warning: rust.description is deprecated. Use build.description instead."
-                );
-            }
-            if description.is_none() {
-                *description = rust_description;
-            }
             set(&mut self.rust_dist_src, dist_src);
             set(&mut self.verbose_tests, verbose_tests);
             // in the case "false" is set explicitly, do not overwrite the command line args
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index d888a7863bc..f802640a42d 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -481,4 +481,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Warning,
         summary: "The current `./x suggest` implementation has been removed due to it being quite broken and a lack of maintenance bandwidth, with no prejudice against re-implementing it in a more maintainable form.",
     },
+    ChangeInfo {
+        change_id: 143926,
+        severity: ChangeSeverity::Warning,
+        summary: "Removed `rust.description` and `llvm.ccache` as it was deprecated in #137723 and #136941 long time ago.",
+    },
 ];
diff --git a/src/build_helper/src/lib.rs b/src/build_helper/src/lib.rs
index 05de8fd2d42..266eedc6245 100644
--- a/src/build_helper/src/lib.rs
+++ b/src/build_helper/src/lib.rs
@@ -5,6 +5,7 @@ pub mod drop_bomb;
 pub mod fs;
 pub mod git;
 pub mod metrics;
+pub mod npm;
 pub mod stage0_parser;
 pub mod targets;
 pub mod util;
diff --git a/src/build_helper/src/npm.rs b/src/build_helper/src/npm.rs
new file mode 100644
index 00000000000..dedef40978d
--- /dev/null
+++ b/src/build_helper/src/npm.rs
@@ -0,0 +1,30 @@
+use std::error::Error;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::{fs, io};
+
+/// Install an exact package version, and return the path of `node_modules`.
+pub fn install_one(
+    out_dir: &Path,
+    npm_bin: &Path,
+    pkg_name: &str,
+    pkg_version: &str,
+) -> Result<PathBuf, io::Error> {
+    let nm_path = out_dir.join("node_modules");
+    let _ = fs::create_dir(&nm_path);
+    let mut child = Command::new(npm_bin)
+        .arg("install")
+        .arg("--audit=false")
+        .arg("--fund=false")
+        .arg(format!("{pkg_name}@{pkg_version}"))
+        .current_dir(out_dir)
+        .spawn()?;
+    let exit_status = child.wait()?;
+    if !exit_status.success() {
+        eprintln!("npm install did not exit successfully");
+        return Err(io::Error::other(Box::<dyn Error + Send + Sync>::from(format!(
+            "npm install returned exit code {exit_status}"
+        ))));
+    }
+    Ok(nm_path)
+}
diff --git a/src/ci/docker/host-aarch64/aarch64-gnu-llvm-19/Dockerfile b/src/ci/docker/host-aarch64/aarch64-gnu-llvm-19/Dockerfile
index 2f9d0010573..e73fbe506f7 100644
--- a/src/ci/docker/host-aarch64/aarch64-gnu-llvm-19/Dockerfile
+++ b/src/ci/docker/host-aarch64/aarch64-gnu-llvm-19/Dockerfile
@@ -50,9 +50,7 @@ ENV RUST_CONFIGURE_ARGS \
 
 COPY scripts/shared.sh /scripts/
 
-ARG SCRIPT_ARG
+COPY scripts/stage_2_test_set1.sh /scripts/
+COPY scripts/stage_2_test_set2.sh /scripts/
 
-COPY scripts/stage_2_test_set1.sh /tmp/
-COPY scripts/stage_2_test_set2.sh /tmp/
-
-ENV SCRIPT "/tmp/${SCRIPT_ARG}"
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
index 44f6a8d2a15..01f19eac1d2 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
@@ -96,12 +96,10 @@ ENV RUST_CONFIGURE_ARGS \
       --set rust.lto=thin \
       --set rust.codegen-units=1
 
-ARG SCRIPT_ARG
-
 COPY host-x86_64/dist-x86_64-linux/dist.sh /scripts/
 COPY host-x86_64/dist-x86_64-linux/dist-alt.sh /scripts/
 
-ENV SCRIPT /scripts/${SCRIPT_ARG}
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
 
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
diff --git a/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile b/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
index 58e66fd637a..be3df9d4036 100644
--- a/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
+++ b/src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile
@@ -23,7 +23,7 @@ COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu --disable-optimize-tests
-ARG SCRIPT_ARG
 COPY scripts/stage_2_test_set1.sh /scripts/
 COPY scripts/stage_2_test_set2.sh /scripts/
-ENV SCRIPT ${SCRIPT_ARG}
+COPY scripts/i686-gnu-nopt-2.sh /scripts/
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
diff --git a/src/ci/docker/host-x86_64/i686-gnu/Dockerfile b/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
index a715f7182d2..00cd24b89db 100644
--- a/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
+++ b/src/ci/docker/host-x86_64/i686-gnu/Dockerfile
@@ -24,7 +24,6 @@ COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu
-ARG SCRIPT_ARG
 COPY scripts/stage_2_test_set1.sh /scripts/
 COPY scripts/stage_2_test_set2.sh /scripts/
-ENV SCRIPT /scripts/${SCRIPT_ARG}
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile
index c09be047c6a..5cba7c564f1 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile
@@ -57,12 +57,10 @@ ENV RUST_CONFIGURE_ARGS \
 
 COPY scripts/shared.sh /scripts/
 
-ARG SCRIPT_ARG
+COPY scripts/x86_64-gnu-llvm.sh /scripts/
+COPY scripts/x86_64-gnu-llvm2.sh /scripts/
+COPY scripts/x86_64-gnu-llvm3.sh /scripts/
+COPY scripts/stage_2_test_set1.sh /scripts/
+COPY scripts/stage_2_test_set2.sh /scripts/
 
-COPY scripts/x86_64-gnu-llvm.sh /tmp/
-COPY scripts/x86_64-gnu-llvm2.sh /tmp/
-COPY scripts/x86_64-gnu-llvm3.sh /tmp/
-COPY scripts/stage_2_test_set1.sh /tmp/
-COPY scripts/stage_2_test_set2.sh /tmp/
-
-ENV SCRIPT "/tmp/${SCRIPT_ARG}"
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-llvm-20/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-20/Dockerfile
index 83a3bfb37a5..92c2631000f 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-llvm-20/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-20/Dockerfile
@@ -57,12 +57,10 @@ ENV RUST_CONFIGURE_ARGS \
 
 COPY scripts/shared.sh /scripts/
 
-ARG SCRIPT_ARG
+COPY scripts/x86_64-gnu-llvm.sh /scripts/
+COPY scripts/x86_64-gnu-llvm2.sh /scripts/
+COPY scripts/x86_64-gnu-llvm3.sh /scripts/
+COPY scripts/stage_2_test_set1.sh /scripts/
+COPY scripts/stage_2_test_set2.sh /scripts/
 
-COPY scripts/x86_64-gnu-llvm.sh /tmp/
-COPY scripts/x86_64-gnu-llvm2.sh /tmp/
-COPY scripts/x86_64-gnu-llvm3.sh /tmp/
-COPY scripts/stage_2_test_set1.sh /tmp/
-COPY scripts/stage_2_test_set2.sh /tmp/
-
-ENV SCRIPT "/tmp/${SCRIPT_ARG}"
+ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-miri/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-miri/Dockerfile
index b937bc3e678..ad2ee85c7bb 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-miri/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-miri/Dockerfile
@@ -46,12 +46,4 @@ ENV HOST_TARGET x86_64-unknown-linux-gnu
 
 COPY scripts/shared.sh /scripts/
 
-# For now, we need to use `--unsafe-perm=true` to go around an issue when npm tries
-# to create a new folder. For reference:
-# https://github.com/puppeteer/puppeteer/issues/375
-#
-# We also specify the version in case we need to update it to go around cache limitations.
-#
-# The `browser-ui-test.version` file is also used by bootstrap to emit warnings in case
-# the local version of the package is different than the one used by the CI.
 ENV SCRIPT /tmp/check-miri.sh ../x.py
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
index e770c58bd9c..95357d22937 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
@@ -76,8 +76,6 @@ COPY scripts/nodejs.sh /scripts/
 RUN sh /scripts/nodejs.sh /node
 ENV PATH="/node/bin:${PATH}"
 
-COPY host-x86_64/x86_64-gnu-tools/browser-ui-test.version /tmp/
-
 ENV RUST_CONFIGURE_ARGS \
   --build=x86_64-unknown-linux-gnu \
   --save-toolstates=/tmp/toolstate/toolstates.json \
@@ -91,15 +89,6 @@ ENV HOST_TARGET x86_64-unknown-linux-gnu
 
 COPY scripts/shared.sh /scripts/
 
-# For now, we need to use `--unsafe-perm=true` to go around an issue when npm tries
-# to create a new folder. For reference:
-# https://github.com/puppeteer/puppeteer/issues/375
-#
-# We also specify the version in case we need to update it to go around cache limitations.
-#
-# The `browser-ui-test.version` file is also used by bootstrap to emit warnings in case
-# the local version of the package is different than the one used by the CI.
 ENV SCRIPT /tmp/checktools.sh ../x.py && \
-  npm install browser-ui-test@$(head -n 1 /tmp/browser-ui-test.version) --unsafe-perm=true && \
   python3 ../x.py check compiletest --set build.compiletest-use-stage0-libtest=true && \
   python3 ../x.py test tests/rustdoc-gui --stage 2 --test-args "'--jobs 1'"
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-tools/browser-ui-test.version b/src/ci/docker/host-x86_64/x86_64-gnu-tools/browser-ui-test.version
deleted file mode 100644
index b9f8e558df4..00000000000
--- a/src/ci/docker/host-x86_64/x86_64-gnu-tools/browser-ui-test.version
+++ /dev/null
@@ -1 +0,0 @@
-0.21.1
\ No newline at end of file
diff --git a/src/ci/docker/run.sh b/src/ci/docker/run.sh
index da7d084d48d..044f5a8fff3 100755
--- a/src/ci/docker/run.sh
+++ b/src/ci/docker/run.sh
@@ -114,14 +114,6 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
         "$context"
     )
 
-    # If the environment variable DOCKER_SCRIPT is defined,
-    # set the build argument SCRIPT_ARG to DOCKER_SCRIPT.
-    # In this way, we run the script defined in CI,
-    # instead of the one defined in the Dockerfile.
-    if [ -n "${DOCKER_SCRIPT+x}" ]; then
-      build_args+=("--build-arg" "SCRIPT_ARG=${DOCKER_SCRIPT}")
-    fi
-
     GHCR_BUILDKIT_IMAGE="ghcr.io/rust-lang/buildkit:buildx-stable-1"
     # On non-CI jobs, we try to download a pre-built image from the rust-lang-ci
     # ghcr.io registry. If it is not possible, we fall back to building the image
@@ -341,6 +333,10 @@ if [ "$ENABLE_GCC_CODEGEN" = "1" ]; then
   echo "Setting extra environment values for docker: $extra_env"
 fi
 
+if [ -n "${DOCKER_SCRIPT}" ]; then
+  extra_env="$extra_env --env SCRIPT=\"/scripts/${DOCKER_SCRIPT}\""
+fi
+
 docker \
   run \
   --workdir /checkout/obj \
diff --git a/src/ci/docker/scripts/i686-gnu-nopt-2.sh b/src/ci/docker/scripts/i686-gnu-nopt-2.sh
new file mode 100755
index 00000000000..4c171739daf
--- /dev/null
+++ b/src/ci/docker/scripts/i686-gnu-nopt-2.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+
+set -ex
+
+python3 ../x.py test --stage 1 --set rust.optimize=false library/std &&
+/scripts/stage_2_test_set2.sh
diff --git a/src/ci/docker/scripts/x86_64-gnu-llvm2.sh b/src/ci/docker/scripts/x86_64-gnu-llvm2.sh
index fe5382aaa48..0060b9bfd23 100755
--- a/src/ci/docker/scripts/x86_64-gnu-llvm2.sh
+++ b/src/ci/docker/scripts/x86_64-gnu-llvm2.sh
@@ -4,7 +4,7 @@ set -ex
 
 ##### Test stage 2 #####
 
-/tmp/stage_2_test_set1.sh
+/scripts/stage_2_test_set1.sh
 
 # Run the `mir-opt` tests again but this time for a 32-bit target.
 # This enforces that tests using `// EMIT_MIR_FOR_EACH_BIT_WIDTH` have
diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index 445fc0dd018..6c5e37b51ef 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -315,16 +315,14 @@ auto:
   - name: i686-gnu-nopt-1
     env:
       IMAGE: i686-gnu-nopt
-      DOCKER_SCRIPT: /scripts/stage_2_test_set1.sh
+      DOCKER_SCRIPT: stage_2_test_set1.sh
     <<: *job-linux-4c
 
   # Skip tests that run in i686-gnu-nopt-1
   - name: i686-gnu-nopt-2
     env:
       IMAGE: i686-gnu-nopt
-      DOCKER_SCRIPT: >-
-        python3 ../x.py test --stage 1 --set rust.optimize=false library/std &&
-        /scripts/stage_2_test_set2.sh
+      DOCKER_SCRIPT: i686-gnu-nopt-2.sh
     <<: *job-linux-4c
 
   - name: pr-check-1
diff --git a/src/doc/rustc-dev-guide/src/effects.md b/src/doc/rustc-dev-guide/src/effects.md
index c7aa2714668..87b0103a7bc 100644
--- a/src/doc/rustc-dev-guide/src/effects.md
+++ b/src/doc/rustc-dev-guide/src/effects.md
@@ -67,10 +67,8 @@ in [`wfcheck::check_impl`].
 Here's an example:
 
 ```rust
-#[const_trait]
-trait Bar {}
-#[const_trait]
-trait Foo: ~const Bar {}
+const trait Bar {}
+const trait Foo: ~const Bar {}
 // `const_conditions` contains `HostEffect(Self: Bar, maybe)`
 
 impl const Bar for () {}
@@ -85,8 +83,7 @@ predicates of the trait method, and we attempt to prove the predicates of the
 impl method. We do the same for `const_conditions`:
 
 ```rust
-#[const_trait]
-trait Foo {
+const trait Foo {
     fn hi<T: ~const Default>();
 }
 
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index e7a1f4d8397..1265a39d27b 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -390,7 +390,8 @@ pub(crate) fn clean_predicate<'tcx>(
         ty::ClauseKind::ConstEvaluatable(..)
         | ty::ClauseKind::WellFormed(..)
         | ty::ClauseKind::ConstArgHasType(..)
-        // FIXME(const_trait_impl): We can probably use this `HostEffect` pred to render `[const]`.
+        | ty::ClauseKind::UnstableFeature(..)
+        // FIXME(const_trait_impl): We can probably use this `HostEffect` pred to render `~const`.
         | ty::ClauseKind::HostEffect(_) => None,
     }
 }
@@ -2864,7 +2865,7 @@ fn clean_maybe_renamed_item<'tcx>(
             ItemKind::Fn { ref sig, generics, body: body_id, .. } => {
                 clean_fn_or_proc_macro(item, sig, generics, body_id, &mut name, cx)
             }
-            ItemKind::Trait(_, _, _, generics, bounds, item_ids) => {
+            ItemKind::Trait(_, _, _, _, generics, bounds, item_ids) => {
                 let items = item_ids
                     .iter()
                     .map(|&ti| clean_trait_item(cx.tcx.hir_trait_item(ti), cx))
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 20babc6168b..09647492d93 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -648,7 +648,7 @@ impl Item {
             let sig = tcx.fn_sig(def_id).skip_binder();
             let constness = if tcx.is_const_fn(def_id) {
                 // rustc's `is_const_fn` returns `true` for associated functions that have an `impl const` parent
-                // or that have a `#[const_trait]` parent. Do not display those as `const` in rustdoc because we
+                // or that have a `const trait` parent. Do not display those as `const` in rustdoc because we
                 // won't be printing correct syntax plus the syntax is unstable.
                 match tcx.opt_associated_item(def_id) {
                     Some(ty::AssocItem {
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index bf3f7607274..fd1b17b6476 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -3,6 +3,7 @@ use std::fmt::{self, Display, Write as _};
 use std::sync::LazyLock as Lazy;
 use std::{ascii, mem};
 
+use rustc_ast::join_path_idents;
 use rustc_ast::tokenstream::TokenTree;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
@@ -24,7 +25,7 @@ use crate::clean::{
     clean_middle_ty, inline,
 };
 use crate::core::DocContext;
-use crate::display::{Joined as _, MaybeDisplay as _};
+use crate::display::Joined as _;
 
 #[cfg(test)]
 mod tests;
@@ -251,13 +252,7 @@ pub(crate) fn qpath_to_string(p: &hir::QPath<'_>) -> String {
         hir::QPath::LangItem(lang_item, ..) => return lang_item.name().to_string(),
     };
 
-    fmt::from_fn(|f| {
-        segments
-            .iter()
-            .map(|seg| (seg.ident.name != kw::PathRoot).then_some(seg.ident).maybe_display())
-            .joined("::", f)
-    })
-    .to_string()
+    join_path_idents(segments.iter().map(|seg| seg.ident))
 }
 
 pub(crate) fn build_deref_target_impls(
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
index 4989bd718c9..5191120ebdb 100644
--- a/src/librustdoc/formats/cache.rs
+++ b/src/librustdoc/formats/cache.rs
@@ -1,5 +1,6 @@
 use std::mem;
 
+use rustc_ast::join_path_syms;
 use rustc_attr_data_structures::StabilityLevel;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet};
@@ -13,7 +14,6 @@ use crate::core::DocContext;
 use crate::fold::DocFolder;
 use crate::formats::Impl;
 use crate::formats::item_type::ItemType;
-use crate::html::format::join_with_double_colon;
 use crate::html::markdown::short_markdown_summary;
 use crate::html::render::IndexItem;
 use crate::html::render::search_index::get_function_type_for_search;
@@ -558,7 +558,7 @@ fn add_item_to_search_index(tcx: TyCtxt<'_>, cache: &mut Cache, item: &clean::It
         clean::ItemKind::ImportItem(import) => import.source.did.unwrap_or(item_def_id),
         _ => item_def_id,
     };
-    let path = join_with_double_colon(parent_path);
+    let path = join_path_syms(parent_path);
     let impl_id = if let Some(ParentStackItem::Impl { item_id, .. }) = cache.parent_stack.last() {
         item_id.as_def_id()
     } else {
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index bcb3e57c844..b16485107a0 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -14,6 +14,7 @@ use std::slice;
 
 use itertools::{Either, Itertools};
 use rustc_abi::ExternAbi;
+use rustc_ast::join_path_syms;
 use rustc_attr_data_structures::{ConstStability, StabilityLevel, StableSince};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
@@ -25,7 +26,7 @@ use rustc_span::symbol::kw;
 use rustc_span::{Symbol, sym};
 use tracing::{debug, trace};
 
-use super::url_parts_builder::{UrlPartsBuilder, estimate_item_path_byte_length};
+use super::url_parts_builder::UrlPartsBuilder;
 use crate::clean::types::ExternalLocation;
 use crate::clean::utils::find_nearest_parent_module;
 use crate::clean::{self, ExternalCrate, PrimitiveType};
@@ -369,18 +370,6 @@ pub(crate) enum HrefError {
     NotInExternalCache,
 }
 
-// Panics if `syms` is empty.
-pub(crate) fn join_with_double_colon(syms: &[Symbol]) -> String {
-    let mut s = String::with_capacity(estimate_item_path_byte_length(syms.len()));
-    // NOTE: using `Joined::joined` here causes a noticeable perf regression
-    s.push_str(syms[0].as_str());
-    for sym in &syms[1..] {
-        s.push_str("::");
-        s.push_str(sym.as_str());
-    }
-    s
-}
-
 /// This function is to get the external macro path because they are not in the cache used in
 /// `href_with_root_path`.
 fn generate_macro_def_id_path(
@@ -672,7 +661,7 @@ pub(crate) fn link_tooltip(
             write!(f, "{}", cx.tcx().item_name(id))?;
         } else if !fqp.is_empty() {
             write!(f, "{shortty} ")?;
-            fqp.iter().joined("::", f)?;
+            write!(f, "{}", join_path_syms(fqp))?;
         }
         Ok(())
     })
@@ -703,7 +692,7 @@ fn resolved_path(
                     write!(
                         f,
                         "{path}::{anchor}",
-                        path = join_with_double_colon(&fqp[..fqp.len() - 1]),
+                        path = join_path_syms(&fqp[..fqp.len() - 1]),
                         anchor = print_anchor(did, *fqp.last().unwrap(), cx)
                     )
                 } else {
@@ -835,7 +824,7 @@ pub(crate) fn print_anchor(did: DefId, text: Symbol, cx: &Context<'_>) -> impl D
             write!(
                 f,
                 r#"<a class="{short_ty}" href="{url}" title="{short_ty} {path}">{text}</a>"#,
-                path = join_with_double_colon(&fqp),
+                path = join_path_syms(fqp),
                 text = EscapeBodyText(text.as_str()),
             )
         } else {
@@ -1095,7 +1084,7 @@ impl clean::QPathData {
                                     title=\"type {path}::{name}\">{name}</a>",
                         shortty = ItemType::AssocType,
                         name = assoc.name,
-                        path = join_with_double_colon(&path),
+                        path = join_path_syms(path),
                     )
                 } else {
                     write!(f, "{}", assoc.name)
diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index 3b4dae841ee..7b814701a73 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -6,6 +6,7 @@ use std::path::{Path, PathBuf};
 use std::sync::mpsc::{Receiver, channel};
 
 use askama::Template;
+use rustc_ast::join_path_syms;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_hir::def_id::{DefIdMap, LOCAL_CRATE};
 use rustc_middle::ty::TyCtxt;
@@ -27,7 +28,6 @@ use crate::formats::FormatRenderer;
 use crate::formats::cache::Cache;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::Escape;
-use crate::html::format::join_with_double_colon;
 use crate::html::markdown::{self, ErrorCodes, IdMap, plain_text_summary};
 use crate::html::render::write_shared::write_shared;
 use crate::html::url_parts_builder::UrlPartsBuilder;
@@ -211,7 +211,7 @@ impl<'tcx> Context<'tcx> {
                 title.push_str(" in ");
             }
             // No need to include the namespace for primitive types and keywords
-            title.push_str(&join_with_double_colon(&self.current));
+            title.push_str(&join_path_syms(&self.current));
         };
         title.push_str(" - Rust");
         let tyname = it.type_();
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 06de4944d97..d8c37137bbc 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -49,6 +49,7 @@ use std::{fs, str};
 
 use askama::Template;
 use itertools::Either;
+use rustc_ast::join_path_syms;
 use rustc_attr_data_structures::{
     ConstStability, DeprecatedSince, Deprecation, RustcVersion, StabilityLevel, StableSince,
 };
@@ -74,9 +75,9 @@ use crate::formats::cache::Cache;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::Escape;
 use crate::html::format::{
-    Ending, HrefError, PrintWithSpace, href, join_with_double_colon, print_abi_with_space,
-    print_constness_with_space, print_default_space, print_generic_bounds, print_where_clause,
-    visibility_print_with_space, write_str,
+    Ending, HrefError, PrintWithSpace, href, print_abi_with_space, print_constness_with_space,
+    print_default_space, print_generic_bounds, print_where_clause, visibility_print_with_space,
+    write_str,
 };
 use crate::html::markdown::{
     HeadingOffset, IdMap, Markdown, MarkdownItemInfo, MarkdownSummaryLine,
@@ -2555,7 +2556,7 @@ fn collect_paths_for_type(first_ty: &clean::Type, cache: &Cache) -> Vec<String>
         let fqp = cache.exact_paths.get(&did).or_else(get_extern);
 
         if let Some(path) = fqp {
-            out.push(join_with_double_colon(path));
+            out.push(join_path_syms(path));
         }
     };
 
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 667d39e9bc2..5fbda4797cc 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -4,6 +4,7 @@ use std::iter;
 
 use askama::Template;
 use rustc_abi::VariantIdx;
+use rustc_ast::join_path_syms;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_hir as hir;
 use rustc_hir::def::CtorKind;
@@ -30,8 +31,8 @@ use crate::formats::Impl;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::{Escape, EscapeBodyTextWithWbr};
 use crate::html::format::{
-    Ending, PrintWithSpace, join_with_double_colon, print_abi_with_space,
-    print_constness_with_space, print_where_clause, visibility_print_with_space,
+    Ending, PrintWithSpace, print_abi_with_space, print_constness_with_space, print_where_clause,
+    visibility_print_with_space,
 };
 use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
 use crate::html::render::{document_full, document_item_info};
@@ -1424,7 +1425,7 @@ fn item_type_alias(cx: &Context<'_>, it: &clean::Item, t: &clean::TypeAlias) ->
                 iter::repeat_n("..", cx.current.len()).chain(iter::once("type.impl")).collect();
             js_src_path.extend(target_fqp[..target_fqp.len() - 1].iter().copied());
             js_src_path.push_fmt(format_args!("{target_type}.{}.js", target_fqp.last().unwrap()));
-            let self_path = fmt::from_fn(|f| self_fqp.iter().joined("::", f));
+            let self_path = join_path_syms(self_fqp);
             write!(
                 w,
                 "<script src=\"{src}\" data-self-path=\"{self_path}\" async></script>",
@@ -2256,7 +2257,7 @@ pub(crate) fn compare_names(left: &str, right: &str) -> Ordering {
 }
 
 pub(super) fn full_path(cx: &Context<'_>, item: &clean::Item) -> String {
-    let mut s = join_with_double_colon(&cx.current);
+    let mut s = join_path_syms(&cx.current);
     s.push_str("::");
     s.push_str(item.name.unwrap().as_str());
     s
diff --git a/src/librustdoc/html/render/search_index.rs b/src/librustdoc/html/render/search_index.rs
index aff8684ee3a..80a59fa218c 100644
--- a/src/librustdoc/html/render/search_index.rs
+++ b/src/librustdoc/html/render/search_index.rs
@@ -4,6 +4,7 @@ use std::collections::hash_map::Entry;
 use std::collections::{BTreeMap, VecDeque};
 
 use encode::{bitmap_to_string, write_vlqhex_to_string};
+use rustc_ast::join_path_syms;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::DefId;
@@ -17,7 +18,6 @@ use crate::clean::types::{Function, Generics, ItemId, Type, WherePredicate};
 use crate::clean::{self, utils};
 use crate::formats::cache::{Cache, OrphanImplItem};
 use crate::formats::item_type::ItemType;
-use crate::html::format::join_with_double_colon;
 use crate::html::markdown::short_markdown_summary;
 use crate::html::render::ordered_json::OrderedJson;
 use crate::html::render::{self, IndexItem, IndexItemFunctionType, RenderType, RenderTypeId};
@@ -78,7 +78,7 @@ pub(crate) fn build_index(
                 ty: item.type_(),
                 defid: item.item_id.as_def_id(),
                 name: item.name.unwrap(),
-                path: join_with_double_colon(&fqp[..fqp.len() - 1]),
+                path: join_path_syms(&fqp[..fqp.len() - 1]),
                 desc,
                 parent: Some(parent),
                 parent_idx: None,
@@ -416,7 +416,7 @@ pub(crate) fn build_index(
                             if fqp.len() < 2 {
                                 return None;
                             }
-                            join_with_double_colon(&fqp[..fqp.len() - 1])
+                            join_path_syms(&fqp[..fqp.len() - 1])
                         };
                     if path == item.path {
                         return None;
@@ -427,10 +427,10 @@ pub(crate) fn build_index(
                 let i = <isize as TryInto<usize>>::try_into(parent_idx).unwrap();
                 item.path = {
                     let p = &crate_paths[i].1;
-                    join_with_double_colon(&p[..p.len() - 1])
+                    join_path_syms(&p[..p.len() - 1])
                 };
                 item.exact_path =
-                    crate_paths[i].2.as_ref().map(|xp| join_with_double_colon(&xp[..xp.len() - 1]));
+                    crate_paths[i].2.as_ref().map(|xp| join_path_syms(&xp[..xp.len() - 1]));
             }
 
             // Omit the parent path if it is same to that of the prior item.
@@ -549,11 +549,11 @@ pub(crate) fn build_index(
                     });
                     continue;
                 }
-                let full_path = join_with_double_colon(&path[..path.len() - 1]);
+                let full_path = join_path_syms(&path[..path.len() - 1]);
                 let full_exact_path = exact
                     .as_ref()
                     .filter(|exact| exact.last() == path.last() && exact.len() >= 2)
-                    .map(|exact| join_with_double_colon(&exact[..exact.len() - 1]));
+                    .map(|exact| join_path_syms(&exact[..exact.len() - 1]));
                 let exact_path = extra_paths.len() + self.items.len();
                 let exact_path = full_exact_path.as_ref().map(|full_exact_path| match extra_paths
                     .entry(full_exact_path.clone())
diff --git a/src/librustdoc/html/render/write_shared.rs b/src/librustdoc/html/render/write_shared.rs
index 0078671fcc5..1f691392b17 100644
--- a/src/librustdoc/html/render/write_shared.rs
+++ b/src/librustdoc/html/render/write_shared.rs
@@ -26,6 +26,7 @@ use std::{fmt, fs};
 
 use indexmap::IndexMap;
 use regex::Regex;
+use rustc_ast::join_path_syms;
 use rustc_data_structures::flock;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_middle::ty::TyCtxt;
@@ -43,7 +44,6 @@ use crate::docfs::PathError;
 use crate::error::Error;
 use crate::formats::Impl;
 use crate::formats::item_type::ItemType;
-use crate::html::format::join_with_double_colon;
 use crate::html::layout;
 use crate::html::render::ordered_json::{EscapedJson, OrderedJson};
 use crate::html::render::search_index::{SerializedSearchIndex, build_index};
@@ -608,7 +608,7 @@ impl TypeAliasPart {
                     for &(type_alias_fqp, type_alias_item) in type_aliases {
                         cx.id_map.borrow_mut().clear();
                         cx.deref_id_map.borrow_mut().clear();
-                        let type_alias_fqp = join_with_double_colon(&type_alias_fqp);
+                        let type_alias_fqp = join_path_syms(type_alias_fqp);
                         if let Some(ret) = &mut ret {
                             ret.aliases.push(type_alias_fqp);
                         } else {
diff --git a/src/librustdoc/html/url_parts_builder.rs b/src/librustdoc/html/url_parts_builder.rs
index 9a533827441..705fa498e8d 100644
--- a/src/librustdoc/html/url_parts_builder.rs
+++ b/src/librustdoc/html/url_parts_builder.rs
@@ -117,7 +117,7 @@ impl UrlPartsBuilder {
 
 /// This is just a guess at the average length of a URL part,
 /// used for [`String::with_capacity`] calls in the [`FromIterator`]
-/// and [`Extend`] impls, and for [estimating item path lengths].
+/// and [`Extend`] impls.
 ///
 /// The value `8` was chosen for two main reasons:
 ///
@@ -125,18 +125,8 @@ impl UrlPartsBuilder {
 /// * jemalloc's size classes are all multiples of eight,
 ///   which means that the amount of memory it allocates will often match
 ///   the amount requested, avoiding wasted bytes.
-///
-/// [estimating item path lengths]: estimate_item_path_byte_length
 const AVG_PART_LENGTH: usize = 8;
 
-/// Estimate the number of bytes in an item's path, based on how many segments it has.
-///
-/// **Note:** This is only to be used with, e.g., [`String::with_capacity()`];
-/// the return value is just a rough estimate.
-pub(crate) const fn estimate_item_path_byte_length(segment_count: usize) -> usize {
-    AVG_PART_LENGTH * segment_count
-}
-
 impl<'a> FromIterator<&'a str> for UrlPartsBuilder {
     fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
         let iter = iter.into_iter();
diff --git a/src/tools/clippy/clippy_lints/src/arbitrary_source_item_ordering.rs b/src/tools/clippy/clippy_lints/src/arbitrary_source_item_ordering.rs
index 07df893ae3c..a9d3015ce5c 100644
--- a/src/tools/clippy/clippy_lints/src/arbitrary_source_item_ordering.rs
+++ b/src/tools/clippy/clippy_lints/src/arbitrary_source_item_ordering.rs
@@ -306,7 +306,7 @@ impl<'tcx> LateLintPass<'tcx> for ArbitrarySourceItemOrdering {
                     cur_f = Some(field);
                 }
             },
-            ItemKind::Trait(is_auto, _safety, _ident, _generics, _generic_bounds, item_ref)
+            ItemKind::Trait(_constness, is_auto, _safety, _ident, _generics, _generic_bounds, item_ref)
                 if self.enable_ordering_for_trait && *is_auto == IsAuto::No =>
             {
                 let mut cur_t: Option<(TraitItemId, Ident)> = None;
diff --git a/src/tools/clippy/clippy_lints/src/doc/mod.rs b/src/tools/clippy/clippy_lints/src/doc/mod.rs
index 2bf52216b83..22b781b8929 100644
--- a/src/tools/clippy/clippy_lints/src/doc/mod.rs
+++ b/src/tools/clippy/clippy_lints/src/doc/mod.rs
@@ -740,7 +740,7 @@ impl<'tcx> LateLintPass<'tcx> for Documentation {
                             );
                         }
                     },
-                    ItemKind::Trait(_, unsafety, ..) => match (headers.safety, unsafety) {
+                    ItemKind::Trait(_, _, unsafety, ..) => match (headers.safety, unsafety) {
                         (false, Safety::Unsafe) => span_lint(
                             cx,
                             MISSING_SAFETY_DOC,
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index d32017a8b41..1bf03480c82 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -125,7 +125,7 @@ declare_lint_pass!(LenZero => [LEN_ZERO, LEN_WITHOUT_IS_EMPTY, COMPARISON_TO_EMP
 
 impl<'tcx> LateLintPass<'tcx> for LenZero {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
-        if let ItemKind::Trait(_, _, ident, _, _, trait_items) = item.kind
+        if let ItemKind::Trait(_, _, _, ident, _, _, trait_items) = item.kind
             && !item.span.from_expansion()
         {
             check_trait_items(cx, item, ident, trait_items);
diff --git a/src/tools/clippy/clippy_lints/src/methods/from_iter_instead_of_collect.rs b/src/tools/clippy/clippy_lints/src/methods/from_iter_instead_of_collect.rs
index 045363058d1..d664eaaac70 100644
--- a/src/tools/clippy/clippy_lints/src/methods/from_iter_instead_of_collect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/from_iter_instead_of_collect.rs
@@ -4,6 +4,7 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::implements_trait;
 use clippy_utils::{is_path_diagnostic_item, sugg};
+use rustc_ast::join_path_idents;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
 use rustc_hir::{self as hir, Expr, ExprKind, GenericArg, QPath, TyKind};
@@ -47,7 +48,7 @@ fn build_full_type(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, app: &mut Applica
         && let QPath::Resolved(None, ty_path) = &ty_qpath
         && let Res::Def(_, ty_did) = ty_path.res
     {
-        let mut ty_str = itertools::join(ty_path.segments.iter().map(|s| s.ident), "::");
+        let mut ty_str = join_path_idents(ty_path.segments.iter().map(|seg| seg.ident));
         let mut first = true;
         let mut append = |arg: &str| {
             write!(&mut ty_str, "{}{arg}", [", ", "<"][usize::from(first)]).unwrap();
diff --git a/src/tools/clippy/clippy_lints/src/missing_inline.rs b/src/tools/clippy/clippy_lints/src/missing_inline.rs
index 329f7193437..c4a3d10299b 100644
--- a/src/tools/clippy/clippy_lints/src/missing_inline.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_inline.rs
@@ -101,7 +101,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
                 let attrs = cx.tcx.hir_attrs(it.hir_id());
                 check_missing_inline_attrs(cx, attrs, it.span, desc);
             },
-            hir::ItemKind::Trait(ref _is_auto, ref _unsafe, _ident, _generics, _bounds, trait_items) => {
+            hir::ItemKind::Trait(ref _constness, ref _is_auto, ref _unsafe, _ident, _generics, _bounds, trait_items) => {
                 // note: we need to check if the trait is exported so we can't use
                 // `LateLintPass::check_trait_item` here.
                 for &tit in trait_items {
diff --git a/src/tools/clippy/clippy_lints/src/trait_bounds.rs b/src/tools/clippy/clippy_lints/src/trait_bounds.rs
index 45e54302e32..9182a55081f 100644
--- a/src/tools/clippy/clippy_lints/src/trait_bounds.rs
+++ b/src/tools/clippy/clippy_lints/src/trait_bounds.rs
@@ -112,7 +112,7 @@ impl<'tcx> LateLintPass<'tcx> for TraitBounds {
         // special handling for self trait bounds as these are not considered generics
         // ie. trait Foo: Display {}
         if let Item {
-            kind: ItemKind::Trait(_, _, _, _, bounds, ..),
+            kind: ItemKind::Trait(_, _, _, _, _, bounds, ..),
             ..
         } = item
         {
@@ -133,7 +133,7 @@ impl<'tcx> LateLintPass<'tcx> for TraitBounds {
                     ..
                 }) = segments.first()
                 && let Some(Node::Item(Item {
-                    kind: ItemKind::Trait(_, _, _, _, self_bounds, _),
+                    kind: ItemKind::Trait(_, _, _, _, _, self_bounds, _),
                     ..
                 })) = cx.tcx.hir_get_if_local(*def_id)
             {
diff --git a/src/tools/clippy/clippy_lints/src/upper_case_acronyms.rs b/src/tools/clippy/clippy_lints/src/upper_case_acronyms.rs
index 02281b9e922..944cd91a7fd 100644
--- a/src/tools/clippy/clippy_lints/src/upper_case_acronyms.rs
+++ b/src/tools/clippy/clippy_lints/src/upper_case_acronyms.rs
@@ -131,7 +131,7 @@ impl LateLintPass<'_> for UpperCaseAcronyms {
             return;
         }
         match it.kind {
-            ItemKind::TyAlias(ident, ..) | ItemKind::Struct(ident, ..) | ItemKind::Trait(_, _, ident, ..) => {
+            ItemKind::TyAlias(ident, ..) | ItemKind::Struct(ident, ..) | ItemKind::Trait(_, _, _, ident, ..) => {
                 check_ident(cx, &ident, it.hir_id(), self.upper_case_acronyms_aggressive);
             },
             ItemKind::Enum(ident, _, ref enumdef) => {
diff --git a/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs b/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs
index 42254ec8e92..96f0273c439 100644
--- a/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs
+++ b/src/tools/clippy/clippy_utils/src/ast_utils/mod.rs
@@ -444,6 +444,7 @@ pub fn eq_item_kind(l: &ItemKind, r: &ItemKind) -> bool {
         },
         (
             Trait(box ast::Trait {
+                constness: lc,
                 is_auto: la,
                 safety: lu,
                 ident: li,
@@ -452,6 +453,7 @@ pub fn eq_item_kind(l: &ItemKind, r: &ItemKind) -> bool {
                 items: lis,
             }),
             Trait(box ast::Trait {
+                constness: rc,
                 is_auto: ra,
                 safety: ru,
                 ident: ri,
@@ -460,7 +462,8 @@ pub fn eq_item_kind(l: &ItemKind, r: &ItemKind) -> bool {
                 items: ris,
             }),
         ) => {
-            la == ra
+            matches!(lc, ast::Const::No) == matches!(rc, ast::Const::No)
+                && la == ra
                 && matches!(lu, Safety::Default) == matches!(ru, Safety::Default)
                 && eq_id(*li, *ri)
                 && eq_generics(lg, rg)
diff --git a/src/tools/clippy/clippy_utils/src/check_proc_macro.rs b/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
index ce61fffe0de..dc31ed08fb7 100644
--- a/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
+++ b/src/tools/clippy/clippy_utils/src/check_proc_macro.rs
@@ -252,11 +252,11 @@ fn item_search_pat(item: &Item<'_>) -> (Pat, Pat) {
         ItemKind::Struct(_, _, VariantData::Struct { .. }) => (Pat::Str("struct"), Pat::Str("}")),
         ItemKind::Struct(..) => (Pat::Str("struct"), Pat::Str(";")),
         ItemKind::Union(..) => (Pat::Str("union"), Pat::Str("}")),
-        ItemKind::Trait(_, Safety::Unsafe, ..)
+        ItemKind::Trait(_, _, Safety::Unsafe, ..)
         | ItemKind::Impl(Impl {
             safety: Safety::Unsafe, ..
         }) => (Pat::Str("unsafe"), Pat::Str("}")),
-        ItemKind::Trait(IsAuto::Yes, ..) => (Pat::Str("auto"), Pat::Str("}")),
+        ItemKind::Trait(_, IsAuto::Yes, ..) => (Pat::Str("auto"), Pat::Str("}")),
         ItemKind::Trait(..) => (Pat::Str("trait"), Pat::Str("}")),
         ItemKind::Impl(_) => (Pat::Str("impl"), Pat::Str("}")),
         _ => return (Pat::Str(""), Pat::Str("")),
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index ad8c816e204..ff1ee663f9b 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -89,6 +89,7 @@ use std::sync::{Mutex, MutexGuard, OnceLock};
 
 use itertools::Itertools;
 use rustc_abi::Integer;
+use rustc_ast::join_path_syms;
 use rustc_ast::ast::{self, LitKind, RangeLimits};
 use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashMap;
@@ -3245,8 +3246,8 @@ fn maybe_get_relative_path(from: &DefPath, to: &DefPath, max_super: usize) -> St
                 // a::b::c  ::d::sym refers to
                 // e::f::sym:: ::
                 // result should be super::super::super::super::e::f
-                if let DefPathData::TypeNs(s) = l {
-                    path.push(s.to_string());
+                if let DefPathData::TypeNs(sym) = l {
+                    path.push(sym);
                 }
                 if let DefPathData::TypeNs(_) = r {
                     go_up_by += 1;
@@ -3256,7 +3257,7 @@ fn maybe_get_relative_path(from: &DefPath, to: &DefPath, max_super: usize) -> St
             // a::b::sym:: ::    refers to
             // c::d::e  ::f::sym
             // when looking at `f`
-            Left(DefPathData::TypeNs(sym)) => path.push(sym.to_string()),
+            Left(DefPathData::TypeNs(sym)) => path.push(sym),
             // consider:
             // a::b::c  ::d::sym refers to
             // e::f::sym:: ::
@@ -3268,17 +3269,17 @@ fn maybe_get_relative_path(from: &DefPath, to: &DefPath, max_super: usize) -> St
 
     if go_up_by > max_super {
         // `super` chain would be too long, just use the absolute path instead
-        once(String::from("crate"))
-            .chain(to.data.iter().filter_map(|el| {
+        join_path_syms(
+            once(kw::Crate).chain(to.data.iter().filter_map(|el| {
                 if let DefPathData::TypeNs(sym) = el.data {
-                    Some(sym.to_string())
+                    Some(sym)
                 } else {
                     None
                 }
             }))
-            .join("::")
+        )
     } else {
-        repeat_n(String::from("super"), go_up_by).chain(path).join("::")
+        join_path_syms(repeat_n(kw::Super, go_up_by).chain(path))
     }
 }
 
diff --git a/src/tools/clippy/tests/ui/assign_ops.fixed b/src/tools/clippy/tests/ui/assign_ops.fixed
index 99beea850a2..eee61f949e7 100644
--- a/src/tools/clippy/tests/ui/assign_ops.fixed
+++ b/src/tools/clippy/tests/ui/assign_ops.fixed
@@ -84,8 +84,7 @@ mod issue14871 {
         const ONE: Self;
     }
 
-    #[const_trait]
-    pub trait NumberConstants {
+    pub const trait NumberConstants {
         fn constant(value: usize) -> Self;
     }
 
diff --git a/src/tools/clippy/tests/ui/assign_ops.rs b/src/tools/clippy/tests/ui/assign_ops.rs
index 900d5ad38e0..13ffcee0a3c 100644
--- a/src/tools/clippy/tests/ui/assign_ops.rs
+++ b/src/tools/clippy/tests/ui/assign_ops.rs
@@ -84,8 +84,7 @@ mod issue14871 {
         const ONE: Self;
     }
 
-    #[const_trait]
-    pub trait NumberConstants {
+    pub const trait NumberConstants {
         fn constant(value: usize) -> Self;
     }
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.fixed b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.fixed
index f1d5579a723..c113c1caaa6 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.fixed
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.fixed
@@ -3,8 +3,7 @@
 
 // Reduced test case from https://github.com/rust-lang/rust-clippy/issues/14658
 
-#[const_trait]
-trait ConstTrait {
+const trait ConstTrait {
     fn method(self);
 }
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.rs b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.rs
index d495759526d..69248bc52d5 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.rs
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.rs
@@ -3,8 +3,7 @@
 
 // Reduced test case from https://github.com/rust-lang/rust-clippy/issues/14658
 
-#[const_trait]
-trait ConstTrait {
+const trait ConstTrait {
     fn method(self);
 }
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.stderr b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.stderr
index b994b88fac6..7ea009cfc9b 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.stderr
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/const_trait.stderr
@@ -1,5 +1,5 @@
 error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/const_trait.rs:24:1
+  --> tests/ui/missing_const_for_fn/const_trait.rs:23:1
    |
 LL | / fn can_be_const() {
 LL | |     0u64.method();
diff --git a/src/tools/clippy/tests/ui/ptr_arg.rs b/src/tools/clippy/tests/ui/ptr_arg.rs
index 65f3f05d6cb..578641e910d 100644
--- a/src/tools/clippy/tests/ui/ptr_arg.rs
+++ b/src/tools/clippy/tests/ui/ptr_arg.rs
@@ -312,7 +312,7 @@ mod issue_9218 {
 
     // Inferred to be `&'a str`, afaik.
     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
-        //~^ ERROR: lifetime flowing from input to output with different syntax
+        //~^ ERROR: eliding a lifetime that's named elsewhere is confusing
         todo!()
     }
 }
diff --git a/src/tools/clippy/tests/ui/ptr_arg.stderr b/src/tools/clippy/tests/ui/ptr_arg.stderr
index 600343754e1..fd9ceddfe11 100644
--- a/src/tools/clippy/tests/ui/ptr_arg.stderr
+++ b/src/tools/clippy/tests/ui/ptr_arg.stderr
@@ -231,18 +231,19 @@ error: writing `&String` instead of `&str` involves a new object where a slice w
 LL |     fn good(v1: &String, v2: &String) {
    |                              ^^^^^^^ help: change this to: `&str`
 
-error: lifetime flowing from input to output with different syntax can be confusing
+error: eliding a lifetime that's named elsewhere is confusing
   --> tests/ui/ptr_arg.rs:314:36
    |
 LL |     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
-   |                                    ^^     ^^           ---- the lifetime gets resolved as `'a`
+   |                                    ^^     ^^           ---- the same lifetime is elided here
    |                                    |      |
-   |                                    |      these lifetimes flow to the output
-   |                                    these lifetimes flow to the output
+   |                                    |      the lifetime is named here
+   |                                    the lifetime is named here
    |
+   = help: the same lifetime is referred to in inconsistent ways, making the signature confusing
    = note: `-D mismatched-lifetime-syntaxes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(mismatched_lifetime_syntaxes)]`
-help: one option is to consistently use `'a`
+help: consistently use `'a`
    |
 LL |     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &'a str {
    |                                                         ++
diff --git a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.fixed b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.fixed
index cf52ecf2f03..88ba5f810b4 100644
--- a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.fixed
+++ b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.fixed
@@ -167,8 +167,7 @@ where
 }
 
 // #13476
-#[const_trait]
-trait ConstTrait {}
+const trait ConstTrait {}
 const fn const_trait_bounds_good<T: ConstTrait + [const] ConstTrait>() {}
 
 const fn const_trait_bounds_bad<T: [const] ConstTrait>() {}
diff --git a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.rs b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.rs
index 955562f08dc..19a4e70e294 100644
--- a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.rs
+++ b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.rs
@@ -167,8 +167,7 @@ where
 }
 
 // #13476
-#[const_trait]
-trait ConstTrait {}
+const trait ConstTrait {}
 const fn const_trait_bounds_good<T: ConstTrait + [const] ConstTrait>() {}
 
 const fn const_trait_bounds_bad<T: [const] ConstTrait + [const] ConstTrait>() {}
diff --git a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.stderr b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.stderr
index ab31721ef51..a56a683de97 100644
--- a/src/tools/clippy/tests/ui/trait_duplication_in_bounds.stderr
+++ b/src/tools/clippy/tests/ui/trait_duplication_in_bounds.stderr
@@ -59,19 +59,19 @@ LL | fn bad_trait_object(arg0: &(dyn Any + Send + Send)) {
    |                                 ^^^^^^^^^^^^^^^^^ help: try: `Any + Send`
 
 error: these bounds contain repeated elements
-  --> tests/ui/trait_duplication_in_bounds.rs:174:36
+  --> tests/ui/trait_duplication_in_bounds.rs:173:36
    |
 LL | const fn const_trait_bounds_bad<T: [const] ConstTrait + [const] ConstTrait>() {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `[const] ConstTrait`
 
 error: these where clauses contain repeated elements
-  --> tests/ui/trait_duplication_in_bounds.rs:181:8
+  --> tests/ui/trait_duplication_in_bounds.rs:180:8
    |
 LL |     T: IntoIterator<Item = U::Owned> + IntoIterator<Item = U::Owned>,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `IntoIterator<Item = U::Owned>`
 
 error: these where clauses contain repeated elements
-  --> tests/ui/trait_duplication_in_bounds.rs:203:8
+  --> tests/ui/trait_duplication_in_bounds.rs:202:8
    |
 LL |     T: AssocConstTrait<ASSOC = 0> + AssocConstTrait<ASSOC = 0>,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `AssocConstTrait<ASSOC = 0>`
diff --git a/src/tools/lint-docs/Cargo.toml b/src/tools/lint-docs/Cargo.toml
index e914a2df2ba..6e1ab84ed18 100644
--- a/src/tools/lint-docs/Cargo.toml
+++ b/src/tools/lint-docs/Cargo.toml
@@ -7,7 +7,7 @@ description = "A script to extract the lint documentation for the rustc book."
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-rustc-literal-escaper = "0.0.4"
+rustc-literal-escaper = "0.0.5"
 serde_json = "1.0.57"
 tempfile = "3.1.0"
 walkdir = "2.3.1"
diff --git a/src/tools/miri/rust-version b/src/tools/miri/rust-version
index 3f10132b684..f9457b3e447 100644
--- a/src/tools/miri/rust-version
+++ b/src/tools/miri/rust-version
@@ -1 +1 @@
-fd2eb391d032181459773f3498c17b198513e0d0
+e4662966273ed58b51f9ff8d682accc202aa1210
diff --git a/src/tools/miri/src/bin/log/tracing_chrome.rs b/src/tools/miri/src/bin/log/tracing_chrome.rs
index 459acea6f0b..5a96633c99e 100644
--- a/src/tools/miri/src/bin/log/tracing_chrome.rs
+++ b/src/tools/miri/src/bin/log/tracing_chrome.rs
@@ -1,8 +1,18 @@
 // SPDX-License-Identifier: MIT
 // SPDX-FileCopyrightText: Copyright (c) 2020 Thoren Paulson
-//! This file is taken unmodified from the following link, except for file attributes and
-//! `extern crate` at the top.
-//! https://github.com/thoren-d/tracing-chrome/blob/7e2625ab4aeeef2f0ef9bde9d6258dd181c04472/src/lib.rs
+//! This file was initially taken from the following link:
+//! <https://github.com/thoren-d/tracing-chrome/blob/7e2625ab4aeeef2f0ef9bde9d6258dd181c04472/src/lib.rs>
+//!
+//! The precise changes that were made to the original file can be found in git history
+//! (`git log -- path/to/tracing_chrome.rs`), but in summary:
+//! - the file attributes were changed and `extern crate` was added at the top
+//! - if a tracing span has a field called "tracing_separate_thread", it will be given a separate
+//! span ID even in [TraceStyle::Threaded] mode, to make it appear on a separate line when viewing
+//! the trace in <https://ui.perfetto.dev>. This is the syntax to trigger this behavior:
+//!   ```rust
+//!   tracing::info_span!("my_span", tracing_separate_thread = tracing::field::Empty, /* ... */)
+//!   ```
+//!
 //! Depending on the tracing-chrome crate from crates.io is unfortunately not possible, since it
 //! depends on `tracing_core` which conflicts with rustc_private's `tracing_core` (meaning it would
 //! not be possible to use the [ChromeLayer] in a context that expects a [Layer] from
@@ -79,14 +89,26 @@ where
 }
 
 /// Decides how traces will be recorded.
+/// Also see <https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview#heading=h.jh64i9l3vwa1>
 #[derive(Default)]
 pub enum TraceStyle {
-    /// Traces will be recorded as a group of threads.
+    /// Traces will be recorded as a group of threads, and all spans on the same thread will appear
+    /// on a single trace line in <https://ui.perfetto.dev>.
     /// In this style, spans should be entered and exited on the same thread.
+    ///
+    /// If a tracing span has a field called "tracing_separate_thread", it will be given a separate
+    /// span ID even in this mode, to make it appear on a separate line when viewing the trace in
+    /// <https://ui.perfetto.dev>. This is the syntax to trigger this behavior:
+    /// ```rust
+    /// tracing::info_span!("my_span", tracing_separate_thread = tracing::field::Empty, /* ... */)
+    /// ```
+    /// [tracing::field::Empty] is used so that other tracing layers (e.g. the logger) will ignore
+    /// the "tracing_separate_thread" argument and not print out anything for it.
     #[default]
     Threaded,
 
-    /// Traces will recorded as a group of asynchronous operations.
+    /// Traces will recorded as a group of asynchronous operations. All spans will be given separate
+    /// span IDs and will appear on separate trace lines in <https://ui.perfetto.dev>.
     Async,
 }
 
@@ -497,31 +519,39 @@ where
         }
     }
 
-    fn get_root_id(span: SpanRef<S>) -> u64 {
-        span.scope()
-            .from_root()
-            .take(1)
-            .next()
-            .unwrap_or(span)
-            .id()
-            .into_u64()
+    fn get_root_id(&self, span: SpanRef<S>) -> Option<u64> {
+        match self.trace_style {
+            TraceStyle::Threaded => {
+                if span.fields().field("tracing_separate_thread").is_some() {
+                    // assign an independent "id" to spans with argument "tracing_separate_thread",
+                    // so they appear a separate trace line in trace visualization tools, see
+                    // https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview#heading=h.jh64i9l3vwa1
+                    Some(span.id().into_u64())
+                } else {
+                    None
+                }
+            },
+            TraceStyle::Async => Some(
+                span.scope()
+                    .from_root()
+                    .take(1)
+                    .next()
+                    .unwrap_or(span)
+                    .id()
+                    .into_u64()
+            ),
+        }
     }
 
     fn enter_span(&self, span: SpanRef<S>, ts: f64) {
         let callsite = self.get_callsite(EventOrSpan::Span(&span));
-        let root_id = match self.trace_style {
-            TraceStyle::Async => Some(ChromeLayer::get_root_id(span)),
-            _ => None,
-        };
+        let root_id = self.get_root_id(span);
         self.send_message(Message::Enter(ts, callsite, root_id));
     }
 
     fn exit_span(&self, span: SpanRef<S>, ts: f64) {
         let callsite = self.get_callsite(EventOrSpan::Span(&span));
-        let root_id = match self.trace_style {
-            TraceStyle::Async => Some(ChromeLayer::get_root_id(span)),
-            _ => None,
-        };
+        let root_id = self.get_root_id(span);
         self.send_message(Message::Exit(ts, callsite, root_id));
     }
 
diff --git a/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs b/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
index dc1eba1a1ab..e5d8f78d948 100644
--- a/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
+++ b/src/tools/rust-analyzer/crates/test-utils/src/minicore.rs
@@ -1011,8 +1011,7 @@ pub mod ops {
     }
 
     #[lang = "add_assign"]
-    #[const_trait]
-    pub trait AddAssign<Rhs = Self> {
+    pub const trait AddAssign<Rhs = Self> {
         fn add_assign(&mut self, rhs: Rhs);
     }
 
diff --git a/src/tools/rustdoc-gui-test/src/main.rs b/src/tools/rustdoc-gui-test/src/main.rs
index 0e35861fbf7..5b86bea8932 100644
--- a/src/tools/rustdoc-gui-test/src/main.rs
+++ b/src/tools/rustdoc-gui-test/src/main.rs
@@ -1,63 +1,15 @@
+use std::env;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::sync::Arc;
-use std::{env, fs};
 
+use build_helper::npm;
 use build_helper::util::try_run;
 use compiletest::directives::TestProps;
 use config::Config;
 
 mod config;
 
-fn get_browser_ui_test_version_inner(npm: &Path, global: bool) -> Option<String> {
-    let mut command = Command::new(&npm);
-    command.arg("list").arg("--parseable").arg("--long").arg("--depth=0");
-    if global {
-        command.arg("--global");
-    }
-    let lines = match command.output() {
-        Ok(output) => String::from_utf8_lossy(&output.stdout).into_owned(),
-        Err(e) => {
-            eprintln!(
-                "path to npm can be wrong, provided path: {npm:?}. Try to set npm path \
-            in bootstrap.toml in [build.npm]",
-            );
-            panic!("{:?}", e)
-        }
-    };
-    lines
-        .lines()
-        .find_map(|l| l.rsplit(':').next()?.strip_prefix("browser-ui-test@"))
-        .map(|v| v.to_owned())
-}
-
-fn get_browser_ui_test_version(npm: &Path) -> Option<String> {
-    get_browser_ui_test_version_inner(npm, false)
-        .or_else(|| get_browser_ui_test_version_inner(npm, true))
-}
-
-fn compare_browser_ui_test_version(installed_version: &str, src: &Path) {
-    match fs::read_to_string(
-        src.join("src/ci/docker/host-x86_64/x86_64-gnu-tools/browser-ui-test.version"),
-    ) {
-        Ok(v) => {
-            if v.trim() != installed_version {
-                eprintln!(
-                    "⚠️ Installed version of browser-ui-test (`{}`) is different than the \
-                     one used in the CI (`{}`)",
-                    installed_version, v
-                );
-                eprintln!(
-                    "You can install this version using `npm update browser-ui-test` or by using \
-                     `npm install browser-ui-test@{}`",
-                    v,
-                );
-            }
-        }
-        Err(e) => eprintln!("Couldn't find the CI browser-ui-test version: {:?}", e),
-    }
-}
-
 fn find_librs<P: AsRef<Path>>(path: P) -> Option<PathBuf> {
     for entry in walkdir::WalkDir::new(path) {
         let entry = entry.ok()?;
@@ -71,27 +23,6 @@ fn find_librs<P: AsRef<Path>>(path: P) -> Option<PathBuf> {
 fn main() -> Result<(), ()> {
     let config = Arc::new(Config::from_args(env::args().collect()));
 
-    // The goal here is to check if the necessary packages are installed, and if not, we
-    // panic.
-    match get_browser_ui_test_version(&config.npm) {
-        Some(version) => {
-            // We also check the version currently used in CI and emit a warning if it's not the
-            // same one.
-            compare_browser_ui_test_version(&version, &config.rust_src);
-        }
-        None => {
-            eprintln!(
-                r#"
-error: rustdoc-gui test suite cannot be run because npm `browser-ui-test` dependency is missing.
-
-If you want to install the `browser-ui-test` dependency, run `npm install browser-ui-test`
-"#,
-            );
-
-            panic!("Cannot run rustdoc-gui tests");
-        }
-    }
-
     let src_path = config.rust_src.join("tests/rustdoc-gui/src");
     for entry in src_path.read_dir().expect("read_dir call failed") {
         if let Ok(entry) = entry {
@@ -134,16 +65,12 @@ If you want to install the `browser-ui-test` dependency, run `npm install browse
         }
     }
 
-    let mut command = Command::new(&config.nodejs);
+    // FIXME(binarycat): once we get package.json in version control, this should be updated to install via that instead
+    let local_node_modules =
+        npm::install_one(&config.out_dir, &config.npm, "browser-ui-test", "0.21.1")
+            .expect("unable to install browser-ui-test");
 
-    if let Ok(current_dir) = env::current_dir() {
-        let local_node_modules = current_dir.join("node_modules");
-        if local_node_modules.exists() {
-            // Link the local node_modules if exists.
-            // This is useful when we run rustdoc-gui-test from outside of the source root.
-            env::set_var("NODE_PATH", local_node_modules);
-        }
-    }
+    let mut command = Command::new(&config.nodejs);
 
     command
         .arg(config.rust_src.join("src/tools/rustdoc-gui/tester.js"))
@@ -154,6 +81,12 @@ If you want to install the `browser-ui-test` dependency, run `npm install browse
         .arg("--tests-folder")
         .arg(config.rust_src.join("tests/rustdoc-gui"));
 
+    if local_node_modules.exists() {
+        // Link the local node_modules if exists.
+        // This is useful when we run rustdoc-gui-test from outside of the source root.
+        command.env("NODE_PATH", local_node_modules);
+    }
+
     for file in &config.goml_files {
         command.arg("--file").arg(file);
     }
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
index 1a3897b51cb..7084639aca9 100644
--- a/src/tools/rustfmt/src/items.rs
+++ b/src/tools/rustfmt/src/items.rs
@@ -1172,6 +1172,7 @@ pub(crate) fn format_trait(
         unreachable!();
     };
     let ast::Trait {
+        constness,
         is_auto,
         safety,
         ident,
@@ -1182,7 +1183,8 @@ pub(crate) fn format_trait(
 
     let mut result = String::with_capacity(128);
     let header = format!(
-        "{}{}{}trait ",
+        "{}{}{}{}trait ",
+        format_constness(constness),
         format_visibility(context, &item.vis),
         format_safety(safety),
         format_auto(is_auto),