Auto merge of rust-lang#136002 - joboet:rollup-f7cf3xs, r=joboet

Rollup of 6 pull requests

Successful merges:

 - rust-lang#135728 (document order of items in iterator from drain)
 - rust-lang#135829 (Rustc dev guide subtree update)
 - rust-lang#135886 (Document purpose of closure in from_fn.rs more clearly)
 - rust-lang#135977 (Fix `FormattingOptions` instantiation with `Default`)
 - rust-lang#135983 (Doc difference between extend and extend_from_slice)
 - rust-lang#135985 (Rename test to `unresolvable-upvar-issue-87987.rs` and add some notes)

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

Author: bors

library/alloc/src/vec/mod.rs

@@ -2571,9 +2571,11 @@ impl<T, A: Allocator> Vec<T, A> {
         self.len += count;
     }
 
-    /// Removes the specified range from the vector in bulk, returning all
-    /// removed elements as an iterator. If the iterator is dropped before
-    /// being fully consumed, it drops the remaining removed elements.
+    /// Removes the subslice indicated by the given range from the vector,
+    /// returning a double-ended iterator over the removed subslice.
+    ///
+    /// If the iterator is dropped before being fully consumed,
+    /// it drops the remaining removed elements.
     ///
     /// The returned iterator keeps a mutable borrow on the vector to optimize
     /// its implementation.

library/core/src/fmt/mod.rs

@@ -288,7 +288,7 @@ pub enum DebugAsHex {
 ///
 /// `FormattingOptions` is a [`Formatter`] without an attached [`Write`] trait.
 /// It is mainly used to construct `Formatter` instances.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Default)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[unstable(feature = "formatting_options", issue = "118117")]
 pub struct FormattingOptions {
     flags: u32,
@@ -508,6 +508,15 @@ impl FormattingOptions {
     }
 }
 
+#[unstable(feature = "formatting_options", issue = "118117")]
+impl Default for FormattingOptions {
+    /// Same as [`FormattingOptions::new()`].
+    fn default() -> Self {
+        // The `#[derive(Default)]` implementation would set `fill` to `\0` instead of space.
+        Self::new()
+    }
+}
+
 /// Configuration for formatting.
 ///
 /// A `Formatter` represents various options related to formatting. Users do not

library/core/src/iter/sources/from_fn.rs

@@ -1,7 +1,7 @@
 use crate::fmt;
 
-/// Creates a new iterator where each iteration calls the provided closure
-/// `F: FnMut() -> Option<T>`.
+/// Creates an iterator with the provided closure
+/// `F: FnMut() -> Option<T>` as its `[next](Iterator::next)` method.
 ///
 /// The iterator will yield the `T`s returned from the closure.
 ///

library/core/tests/fmt/mod.rs

@@ -51,6 +51,12 @@ fn test_maybe_uninit_short() {
     assert_eq!(format!("{x:?}"), "MaybeUninit<u32>");
 }
 
+#[test]
+fn formatting_options_ctor() {
+    use core::fmt::FormattingOptions;
+    assert_eq!(FormattingOptions::new(), FormattingOptions::default());
+}
+
 #[test]
 fn formatting_options_flags() {
     use core::fmt::*;

src/doc/rustc-dev-guide/.github/workflows/ci.yml

@@ -35,12 +35,13 @@ jobs:
             ~/.cargo/bin
           key: ${{ runner.os }}-${{ env.MDBOOK_VERSION }}--${{ env.MDBOOK_LINKCHECK2_VERSION }}--${{ env.MDBOOK_TOC_VERSION }}--${{ env.MDBOOK_MERMAID_VERSION }}
 
-      - name: Cache linkcheck
-        uses: actions/cache@v4
+      - name: Restore cached Linkcheck
+        if: github.event_name == 'schedule'
+        id: cache-linkcheck-restore
+        uses: actions/cache/restore@v4
         with:
-          path: |
-            ~/book/linkcheck
-          key: ${{ runner.os }}-${{ hashFiles('./book/linkcheck') }}
+          path: book/linkcheck/cache.json
+          key: linkcheck--${{ env.MDBOOK_LINKCHECK2_VERSION }}
 
       - name: Install latest nightly Rust toolchain
         if: steps.mdbook-cache.outputs.cache-hit != 'true'
@@ -59,6 +60,14 @@ jobs:
       - name: Check build
         run: ENABLE_LINKCHECK=1 mdbook build
 
+      - name: Save cached Linkcheck
+        id: cache-linkcheck-save
+        if: ${{ !cancelled() && github.event_name == 'schedule' }}
+        uses: actions/cache/save@v4
+        with:
+          path: book/linkcheck/cache.json
+          key: linkcheck--${{ env.MDBOOK_LINKCHECK2_VERSION }}
+
       - name: Deploy to gh-pages
         if: github.event_name == 'push'
         run: |

src/doc/rustc-dev-guide/.github/workflows/rustc-pull.yml

@@ -0,0 +1,85 @@
+name: rustc-pull
+
+on:
+  workflow_dispatch:
+  schedule:
+    # Run at 04:00 UTC every Monday
+    - cron: '0 4 * * 1'
+
+jobs:
+  pull:
+    if: github.repository == 'rust-lang/rustc-dev-guide'
+    runs-on: ubuntu-latest
+    outputs:
+      pr_url: ${{ steps.update-pr.outputs.pr_url }}
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          # We need the full history for josh to work
+          fetch-depth: '0'
+      - name: Install stable Rust toolchain
+        run: rustup update stable
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: "josh-sync"
+          # Cache the josh directory with checked out rustc
+          cache-directories: "/home/runner/.cache/rustc-dev-guide-josh"
+      - name: Install josh
+        run: RUSTFLAGS="--cap-lints warn" cargo +stable install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04
+      - name: Setup bot git name and email
+        run: |
+          git config --global user.name 'The rustc-dev-guide Cronjob Bot'
+          git config --global user.email 'github-actions@github.com'
+      - name: Perform rustc-pull
+        run: cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull
+      - name: Push changes to a branch
+        run: |
+          # Update a sticky branch that is used only for rustc pulls
+          BRANCH="rustc-pull"
+          git switch -c $BRANCH
+          git push -u origin $BRANCH --force
+      - name: Create pull request
+        id: update-pr
+        run: |
+          # Check if an open pull request for an rustc pull update already exists
+          # If it does, the previous push has just updated it
+          # If not, we create it now
+          RESULT=`gh pr list --author github-actions[bot] --state open -q 'map(select(.title=="Rustc pull update")) | length' --json title`
+          if [[ "$RESULT" -eq 0 ]]; then
+            echo "Creating new pull request"
+            PR_URL=gh pr create -B master --title 'Rustc pull update' --body 'Latest update from rustc.'
+            echo "pr_url=$PR_URL" >> $GITHUB_OUTPUT
+          else
+            PR_URL=gh pr list --author github-actions[bot] --state open -q 'map(select(.title=="Rustc pull update")) | .[0].url' --json url,title
+            echo "pr_url=$PR_URL" >> $GITHUB_OUTPUT
+          fi
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  send-zulip-message:
+    needs: [pull]
+    if: ${{ !cancelled() }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Compute message
+        id: message
+        run: |
+          if [ "${{ needs.pull.result }}" == "failure" ];
+          then
+            WORKFLOW_URL="${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
+            echo "message=Rustc pull sync failed. Check out the [workflow URL]($WORKFLOW_URL)." >> $GITHUB_OUTPUT
+          else
+            echo "message=Rustc pull sync succeeded. Check out the [PR](${{ needs.pull.outputs.pr_url }})." >> $GITHUB_OUTPUT
+          fi
+      - name: Send a Zulip message about updated PR
+        uses: zulip/github-actions-zulip/send-message@e4c8f27c732ba9bd98ac6be0583096dea82feea5
+        with:
+          api-key: ${{ secrets.ZULIP_API_TOKEN }}
+          email: "rustc-dev-guide-gha-notif-bot@rust-lang.zulipchat.com"
+          organization-url: "https://rust-lang.zulipchat.com"
+          to: 196385
+          type: "stream"
+          topic: "Subtree sync automation"
+          content: ${{ steps.message.outputs.message }}

src/doc/rustc-dev-guide/.gitignore

@@ -4,3 +4,5 @@ ci/date-check/target/
 
 # Generated by check-in.sh
 pulls.json
+
+josh-sync/target

src/doc/rustc-dev-guide/README.md

@@ -74,6 +74,13 @@ including the `<!-- toc -->` marker at the place where you want the TOC.
 
 This repository is linked to `rust-lang/rust` as a [josh](https://josh-project.github.io/josh/intro.html) subtree. You can use the following commands to synchronize the subtree in both directions.
 
+You'll need to install `josh-proxy` locally via
+
+```
+cargo +stable install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04
+```
+Older versions of `josh-proxy` may not round trip commits losslessly so it is important to install this exact version.
+
 ### Pull changes from `rust-lang/rust` into this repository
 1) Checkout a new branch that will be used to create a PR into `rust-lang/rustc-dev-guide`
 2) Run the pull command

src/doc/rustc-dev-guide/book.toml

@@ -52,7 +52,9 @@ exclude = [
     # 500 is returned for HEAD request
     "code\\.visualstudio\\.com/docs/editor/tasks",
 ]
-cache-timeout = 86400
+# The scheduled CI runs every day and so we need to reuse a part of the cache
+# in order to face "Server returned 429 Too Many Requests" errors for github.com.
+cache-timeout = 90000
 warning-policy = "error"
 
 [output.html.redirect]

src/doc/rustc-dev-guide/josh-sync/src/sync.rs

@@ -45,6 +45,11 @@ impl GitSync {
         let josh_url =
             format!("http://localhost:{JOSH_PORT}/{UPSTREAM_REPO}.git@{commit}{JOSH_FILTER}.git");
 
+        let previous_base_commit = sh.read_file("rust-version")?.trim().to_string();
+        if previous_base_commit == commit {
+            return Err(anyhow::anyhow!("No changes since last pull"));
+        }
+
         // Update rust-version file. As a separate commit, since making it part of
         // the merge has confused the heck out of josh in the past.
         // We pass `--no-verify` to avoid running git hooks.
@@ -76,12 +81,22 @@ impl GitSync {
         };
         let num_roots_before = num_roots()?;
 
+        let sha = cmd!(sh, "git rev-parse HEAD").output().context("FAILED to get current commit")?.stdout;
+
         // Merge the fetched commit.
         const MERGE_COMMIT_MESSAGE: &str = "Merge from rustc";
         cmd!(sh, "git merge FETCH_HEAD --no-verify --no-ff -m {MERGE_COMMIT_MESSAGE}")
             .run()
             .context("FAILED to merge new commits, something went wrong")?;
 
+        let current_sha = cmd!(sh, "git rev-parse HEAD").output().context("FAILED to get current commit")?.stdout;
+        if current_sha == sha {
+            cmd!(sh, "git reset --hard HEAD^")
+                .run()
+                .expect("FAILED to clean up after creating the preparation commit");
+            return Err(anyhow::anyhow!("No merge was performed, nothing to pull. Rolled back the preparation commit."));
+        }
+
         // Check that the number of roots did not increase.
         if num_roots()? != num_roots_before {
             bail!("Josh created a new root commit. This is probably not the history you want.");