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

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.");

src/doc/rustc-dev-guide/rust-version

@@ -1 +1 @@
-dcfa38fe234de9304169afc6638e81d0dd222c06
+ecda83b30f0f68cf5692855dddc0bc38ee8863fc

src/doc/rustc-dev-guide/src/appendix/code-index.md

@@ -14,17 +14,16 @@ Item            |  Kind    | Short description           | Chapter            |
 `Diag` | struct | A struct for a compiler diagnostic, such as an error or lint | [Emitting Diagnostics] | [compiler/rustc_errors/src/diagnostic.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.Diag.html)
 `DocContext` | struct | A state container used by rustdoc when crawling through a crate to gather its documentation | [Rustdoc] | [src/librustdoc/core.rs](https://github.com/rust-lang/rust/blob/master/src/librustdoc/core.rs)
 `HirId` | struct | One of four types of HIR node identifiers | [Identifiers in the HIR] | [compiler/rustc_hir/src/hir_id.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir_id/struct.HirId.html)
+`Lexer` | struct | This is the lexer used during parsing. It consumes characters from the raw source code being compiled and produces a series of tokens for use by the rest of the parser | [The parser] |  [compiler/rustc_parse/src/lexer/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_parse/lexer/struct.Lexer.html)
 `NodeId` | struct | One of four types of HIR node identifiers. Being phased out | [Identifiers in the HIR] | [compiler/rustc_ast/src/ast.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/node_id/struct.NodeId.html)
 `P` | struct | An owned immutable smart pointer. By contrast, `&T` is not owned, and `Box<T>` is not immutable. | None | [compiler/rustc_ast/src/ptr.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/ptr/struct.P.html)
 `ParamEnv` | struct | Information about generic parameters or `Self`, useful for working with associated or generic items | [Parameter Environment] | [compiler/rustc_middle/src/ty/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.ParamEnv.html)
 `ParseSess` | struct | This struct contains information about a parsing session | [The parser] | [compiler/rustc_session/src/parse/parse.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_session/parse/struct.ParseSess.html)
-`Query` | struct | Represents the result of query to the `Compiler` interface and allows stealing, borrowing, and returning the results of compiler passes. | [The Rustc Driver and Interface] | [compiler/rustc_interface/src/queries.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/queries/struct.Query.html)
 `Rib` | struct | Represents a single scope of names | [Name resolution] | [compiler/rustc_resolve/src/lib.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_resolve/late/struct.Rib.html)
 `Session` | struct | The data associated with a compilation session | [The parser], [The Rustc Driver and Interface] | [compiler/rustc_session/src/session.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_session/struct.Session.html)
 `SourceFile` | struct | Part of the `SourceMap`. Maps AST nodes to their source code for a single source file. Was previously called FileMap | [The parser] | [compiler/rustc_span/src/lib.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_span/struct.SourceFile.html)
 `SourceMap` | struct | Maps AST nodes to their source code. It is composed of `SourceFile`s. Was previously called CodeMap | [The parser] | [compiler/rustc_span/src/source_map.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_span/source_map/struct.SourceMap.html)
 `Span` | struct  | A location in the user's source code, used for error reporting primarily | [Emitting Diagnostics] | [compiler/rustc_span/src/span_encoding.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_span/struct.Span.html)
-`StringReader` | struct | This is the lexer used during parsing. It consumes characters from the raw source code being compiled and produces a series of tokens for use by the rest of the parser | [The parser] |  [compiler/rustc_parse/src/lexer/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_parse/lexer/struct.StringReader.html)
 `rustc_ast::token_stream::TokenStream` | struct | An abstract sequence of tokens, organized into `TokenTree`s | [The parser], [Macro expansion] | [compiler/rustc_ast/src/tokenstream.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/tokenstream/struct.TokenStream.html)
 `TraitDef` | struct | This struct contains a trait's definition with type information | [The `ty` modules] |  [compiler/rustc_middle/src/ty/trait_def.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/trait_def/struct.TraitDef.html)
 `TraitRef` | struct | The combination of a trait and its input types (e.g. `P0: Trait<P1...Pn>`) | [Trait Solving: Goals and Clauses]  |  [compiler/rustc_middle/src/ty/sty.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/type.TraitRef.html)

src/doc/rustc-dev-guide/src/appendix/glossary.md

@@ -69,7 +69,7 @@ Term                                                  | Meaning
 <span id="rib">rib</span>                      |  A data structure in the name resolver that keeps track of a single scope for names. ([see more](../name-resolution.md))
 <span id="rpit">RPIT</span>                    |  A return-position `impl Trait`. ([see the reference](https://doc.rust-lang.org/reference/types/impl-trait.html#abstract-return-types)).
 <span id="rpitit">RPITIT</span>                |  A return-position `impl Trait` in trait. Unlike RPIT, this is desugared to a generic associated type (GAT). Introduced in [RFC 3425](https://rust-lang.github.io/rfcs/3425-return-position-impl-trait-in-traits.html). ([see more](../return-position-impl-trait-in-trait.md))
-<span id="scrutinee">scrutinee</div>           |  A scrutinee is the expression that is matched on in `match` expressions and similar pattern matching constructs. For example, in `match x { A => 1, B => 2 }`, the expression `x` is the scrutinee.
+<span id="scrutinee">scrutinee</span>          |  A scrutinee is the expression that is matched on in `match` expressions and similar pattern matching constructs. For example, in `match x { A => 1, B => 2 }`, the expression `x` is the scrutinee.
 <span id="sess">`sess`</span>                  |  The compiler _session_, which stores global data used throughout compilation
 <span id="side-tables">side tables</span>      |  Because the [AST](#ast) and HIR are immutable once created, we often carry extra information about them in the form of hashtables, indexed by the id of a particular node.
 <span id="sigil">sigil</span>                  |  Like a keyword but composed entirely of non-alphanumeric tokens. For example, `&` is a sigil for references.

src/doc/rustc-dev-guide/src/backend/backend-agnostic.md

@@ -45,7 +45,7 @@ heavily on other parts of the crate. The separation of the code must not affect
 the logic of the code nor its performance.
 
 For these reasons, the separation process involves two transformations that
-have to be done at the same time for the resulting code to compile :
+have to be done at the same time for the resulting code to compile:
 
 1. replace all the LLVM-specific types by generics inside function signatures
    and structure definitions;

src/doc/rustc-dev-guide/src/borrow_check/region_inference/closure_constraints.md

@@ -31,9 +31,9 @@ It starts by calling `fn try_promote_type_test_subject`. This function takes the
 
 We then promote the `lower_bound` into the context of the caller. If the lower bound is equal to a placeholder, we replace it with `'static`
 
-We then look at all universal regions `uv` which are required to outlive `lower_bound`, i.e. for which borrow checking adding region constraints. For each of these we then emit a `ClosureOutlivesRequirement` for non-local universal regions which are known to outlive `uv`.
+We then look at all universal regions `uv` which are required to be outlived by `lower_bound`, i.e. for which borrow checking added region constraints. For each of these we then emit a `ClosureOutlivesRequirement` for all non-local universal regions which are known to outlive `uv`.
 
-As we've already built the region graph of the closure at this point and emitted errors if that one is inconsistent, we are also able to assume that the outlive constraints `uv: lower_bound` hold.
+As we've already built the region graph of the closure at this point and separately check that it is consistent, we are also able to assume the outlive constraints `uv: lower_bound` here.
 
 So if we have a type-outlives bounds we can't prove, e.g. `T: 'local_infer`, we use the region graph to go to universal variables `'a` with `'a: local_infer`. In case `'a` are local, we then use the assumed outlived constraints to go to non-local ones.
 

src/doc/rustc-dev-guide/src/bug-fix-procedure.md

@@ -227,7 +227,7 @@ that we use for unstable features:
 Ideally, breaking changes should have landed on the **stable branch** of the
 compiler before they are finalized.
 
-<a id="guide">
+<a id="guide"></a>
 
 ### Removing a lint
 

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

@@ -157,7 +157,7 @@ The other option is to step through the code using lldb or gdb.
 
 1. `rust-lldb build/host/stage1/bin/rustc test.rs`
 2. In lldb:
-    1. `b upvar.rs:134`  // Setting the breakpoint on a certain line in the upvar.rs file`
+    1. `b upvar.rs:134`  // Setting the breakpoint on a certain line in the upvar.rs file
     2. `r`  // Run the program until it hits the breakpoint
 
 Let's start with [`upvar.rs`][upvar]. This file has something called

src/doc/rustc-dev-guide/src/const-eval.md

@@ -17,7 +17,7 @@ Prominent examples are:
     * need to be known to check for overlapping patterns
 
 Additionally constant evaluation can be used to reduce the workload or binary
-size at runtime by precomputing complex operations at compiletime and only
+size at runtime by precomputing complex operations at compile time and only
 storing the result.
 
 All uses of constant evaluation can either be categorized as "influencing the type system"