Auto merge of #126540 - jhpratt:rollup-fzzz8j3, r=jhpratt

Rollup of 4 pull requests

Successful merges:

 - #125112 (Document behavior of `create_dir_all` wrt. empty path)
 - #126127 (Spell out other trait diagnostic)
 - #126309 (unify git command preperation)
 - #126539 (Update `Arc::try_unwrap()` docs)

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

Author: bors

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -2068,7 +2068,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     if all_traits_equal {
                         format!("\n  {}", c.self_ty())
                     } else {
-                        format!("\n  {c}")
+                        format!("\n  `{}` implements `{}`", c.self_ty(), c.print_only_trait_path())
                     }
                 })
                 .collect();

library/alloc/src/sync.rs

@@ -940,15 +940,18 @@ impl<T, A: Allocator> Arc<T, A> {
     /// This will succeed even if there are outstanding weak references.
     ///
     /// It is strongly recommended to use [`Arc::into_inner`] instead if you don't
-    /// want to keep the `Arc` in the [`Err`] case.
-    /// Immediately dropping the [`Err`] payload, like in the expression
-    /// `Arc::try_unwrap(this).ok()`, can still cause the strong count to
-    /// drop to zero and the inner value of the `Arc` to be dropped:
-    /// For instance if two threads each execute this expression in parallel, then
-    /// there is a race condition. The threads could first both check whether they
-    /// have the last clone of their `Arc` via `Arc::try_unwrap`, and then
-    /// both drop their `Arc` in the call to [`ok`][`Result::ok`],
-    /// taking the strong count from two down to zero.
+    /// keep the `Arc` in the [`Err`] case.
+    /// Immediately dropping the [`Err`]-value, as the expression
+    /// `Arc::try_unwrap(this).ok()` does, can cause the strong count to
+    /// drop to zero and the inner value of the `Arc` to be dropped.
+    /// For instance, if two threads execute such an expression in parallel,
+    /// there is a race condition without the possibility of unsafety:
+    /// The threads could first both check whether they own the last instance
+    /// in `Arc::try_unwrap`, determine that they both do not, and then both
+    /// discard and drop their instance in the call to [`ok`][`Result::ok`].
+    /// In this scenario, the value inside the `Arc` is safely destroyed
+    /// by exactly one of the threads, but neither thread will ever be able
+    /// to use the value.
     ///
     /// # Examples
     ///

library/std/src/fs.rs

@@ -2386,6 +2386,9 @@ pub fn create_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
 /// If this function returns an error, some of the parent components might have
 /// been created already.
 ///
+/// If the empty path is passed to this function, it always succeeds without
+/// creating any directories.
+///
 /// # Platform-specific behavior
 ///
 /// This function currently corresponds to multiple calls to the `mkdir`

src/bootstrap/src/core/build_steps/format.rs

@@ -1,7 +1,7 @@
 //! Runs rustfmt on the repository.
 
 use crate::core::builder::Builder;
-use crate::utils::helpers::{output, program_out_of_date, t};
+use crate::utils::helpers::{self, output, program_out_of_date, t};
 use build_helper::ci::CiEnv;
 use build_helper::git::get_git_modified_files;
 use ignore::WalkBuilder;
@@ -160,7 +160,7 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
             override_builder.add(&format!("!{ignore}")).expect(&ignore);
         }
     }
-    let git_available = match Command::new("git")
+    let git_available = match helpers::git(None)
         .arg("--version")
         .stdout(Stdio::null())
         .stderr(Stdio::null())
@@ -172,9 +172,7 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
 
     let mut adjective = None;
     if git_available {
-        let in_working_tree = match build
-            .config
-            .git()
+        let in_working_tree = match helpers::git(Some(&build.src))
             .arg("rev-parse")
             .arg("--is-inside-work-tree")
             .stdout(Stdio::null())
@@ -186,9 +184,7 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
         };
         if in_working_tree {
             let untracked_paths_output = output(
-                build
-                    .config
-                    .git()
+                helpers::git(Some(&build.src))
                     .arg("status")
                     .arg("--porcelain")
                     .arg("-z")

src/bootstrap/src/core/build_steps/llvm.rs

@@ -159,7 +159,7 @@ pub(crate) fn detect_llvm_sha(config: &Config, is_git: bool) -> String {
         // in that case.
         let closest_upstream = get_git_merge_base(&config.git_config(), Some(&config.src))
             .unwrap_or_else(|_| "HEAD".into());
-        let mut rev_list = config.git();
+        let mut rev_list = helpers::git(Some(&config.src));
         rev_list.args(&[
             PathBuf::from("rev-list"),
             format!("--author={}", config.stage0_metadata.config.git_merge_commit_email).into(),
@@ -252,7 +252,7 @@ pub(crate) fn is_ci_llvm_modified(config: &Config) -> bool {
         // We assume we have access to git, so it's okay to unconditionally pass
         // `true` here.
         let llvm_sha = detect_llvm_sha(config, true);
-        let head_sha = output(config.git().arg("rev-parse").arg("HEAD"));
+        let head_sha = output(helpers::git(Some(&config.src)).arg("rev-parse").arg("HEAD"));
         let head_sha = head_sha.trim();
         llvm_sha == head_sha
     }

src/bootstrap/src/core/build_steps/setup.rs

@@ -8,7 +8,7 @@
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::t;
 use crate::utils::change_tracker::CONFIG_CHANGE_HISTORY;
-use crate::utils::helpers::hex_encode;
+use crate::utils::helpers::{self, hex_encode};
 use crate::Config;
 use sha2::Digest;
 use std::env::consts::EXE_SUFFIX;
@@ -482,10 +482,13 @@ impl Step for Hook {
 
 // install a git hook to automatically run tidy, if they want
 fn install_git_hook_maybe(config: &Config) -> io::Result<()> {
-    let git = config.git().args(["rev-parse", "--git-common-dir"]).output().map(|output| {
-        assert!(output.status.success(), "failed to run `git`");
-        PathBuf::from(t!(String::from_utf8(output.stdout)).trim())
-    })?;
+    let git = helpers::git(Some(&config.src))
+        .args(["rev-parse", "--git-common-dir"])
+        .output()
+        .map(|output| {
+            assert!(output.status.success(), "failed to run `git`");
+            PathBuf::from(t!(String::from_utf8(output.stdout)).trim())
+        })?;
     let hooks_dir = git.join("hooks");
     let dst = hooks_dir.join("pre-push");
     if dst.exists() {

src/bootstrap/src/core/build_steps/toolstate.rs

@@ -5,15 +5,14 @@
 //! [Toolstate]: https://forge.rust-lang.org/infra/toolstate.html
 
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
-use crate::utils::helpers::t;
+use crate::utils::helpers::{self, t};
 use serde_derive::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::env;
 use std::fmt;
 use std::fs;
 use std::io::{Seek, SeekFrom};
 use std::path::{Path, PathBuf};
-use std::process::Command;
 use std::time;
 
 // Each cycle is 42 days long (6 weeks); the last week is 35..=42 then.
@@ -102,12 +101,8 @@ fn print_error(tool: &str, submodule: &str) {
 
 fn check_changed_files(toolstates: &HashMap<Box<str>, ToolState>) {
     // Changed files
-    let output = std::process::Command::new("git")
-        .arg("diff")
-        .arg("--name-status")
-        .arg("HEAD")
-        .arg("HEAD^")
-        .output();
+    let output =
+        helpers::git(None).arg("diff").arg("--name-status").arg("HEAD").arg("HEAD^").output();
     let output = match output {
         Ok(o) => o,
         Err(e) => {
@@ -324,7 +319,7 @@ fn checkout_toolstate_repo() {
         t!(fs::remove_dir_all(TOOLSTATE_DIR));
     }
 
-    let status = Command::new("git")
+    let status = helpers::git(None)
         .arg("clone")
         .arg("--depth=1")
         .arg(toolstate_repo())
@@ -342,7 +337,7 @@ fn checkout_toolstate_repo() {
 /// Sets up config and authentication for modifying the toolstate repo.
 fn prepare_toolstate_config(token: &str) {
     fn git_config(key: &str, value: &str) {
-        let status = Command::new("git").arg("config").arg("--global").arg(key).arg(value).status();
+        let status = helpers::git(None).arg("config").arg("--global").arg(key).arg(value).status();
         let success = match status {
             Ok(s) => s.success(),
             Err(_) => false,
@@ -406,8 +401,7 @@ fn commit_toolstate_change(current_toolstate: &ToolstateData) {
         publish_test_results(current_toolstate);
 
         // `git commit` failing means nothing to commit.
-        let status = t!(Command::new("git")
-            .current_dir(TOOLSTATE_DIR)
+        let status = t!(helpers::git(Some(Path::new(TOOLSTATE_DIR)))
             .arg("commit")
             .arg("-a")
             .arg("-m")
@@ -418,8 +412,7 @@ fn commit_toolstate_change(current_toolstate: &ToolstateData) {
             break;
         }
 
-        let status = t!(Command::new("git")
-            .current_dir(TOOLSTATE_DIR)
+        let status = t!(helpers::git(Some(Path::new(TOOLSTATE_DIR)))
             .arg("push")
             .arg("origin")
             .arg("master")
@@ -431,15 +424,13 @@ fn commit_toolstate_change(current_toolstate: &ToolstateData) {
         }
         eprintln!("Sleeping for 3 seconds before retrying push");
         std::thread::sleep(std::time::Duration::from_secs(3));
-        let status = t!(Command::new("git")
-            .current_dir(TOOLSTATE_DIR)
+        let status = t!(helpers::git(Some(Path::new(TOOLSTATE_DIR)))
             .arg("fetch")
             .arg("origin")
             .arg("master")
             .status());
         assert!(status.success());
-        let status = t!(Command::new("git")
-            .current_dir(TOOLSTATE_DIR)
+        let status = t!(helpers::git(Some(Path::new(TOOLSTATE_DIR)))
             .arg("reset")
             .arg("--hard")
             .arg("origin/master")
@@ -458,7 +449,7 @@ fn commit_toolstate_change(current_toolstate: &ToolstateData) {
 /// `publish_toolstate.py` script if the PR passes all tests and is merged to
 /// master.
 fn publish_test_results(current_toolstate: &ToolstateData) {
-    let commit = t!(std::process::Command::new("git").arg("rev-parse").arg("HEAD").output());
+    let commit = t!(helpers::git(None).arg("rev-parse").arg("HEAD").output());
     let commit = t!(String::from_utf8(commit.stdout));
 
     let toolstate_serialized = t!(serde_json::to_string(&current_toolstate));

src/bootstrap/src/core/config/config.rs

@@ -20,7 +20,7 @@ use crate::core::build_steps::llvm;
 use crate::core::config::flags::{Color, Flags, Warnings};
 use crate::utils::cache::{Interned, INTERNER};
 use crate::utils::channel::{self, GitInfo};
-use crate::utils::helpers::{exe, output, t};
+use crate::utils::helpers::{self, exe, output, t};
 use build_helper::exit;
 use serde::{Deserialize, Deserializer};
 use serde_derive::Deserialize;
@@ -1248,7 +1248,7 @@ impl Config {
 
         // Infer the source directory. This is non-trivial because we want to support a downloaded bootstrap binary,
         // running on a completely different machine from where it was compiled.
-        let mut cmd = Command::new("git");
+        let mut cmd = helpers::git(None);
         // NOTE: we cannot support running from outside the repository because the only other path we have available
         // is set at compile time, which can be wrong if bootstrap was downloaded rather than compiled locally.
         // We still support running outside the repository if we find we aren't in a git directory.
@@ -2090,15 +2090,6 @@ impl Config {
         build_helper::util::try_run(cmd, self.is_verbose())
     }
 
-    /// A git invocation which runs inside the source directory.
-    ///
-    /// Use this rather than `Command::new("git")` in order to support out-of-tree builds.
-    pub(crate) fn git(&self) -> Command {
-        let mut git = Command::new("git");
-        git.current_dir(&self.src);
-        git
-    }
-
     pub(crate) fn test_args(&self) -> Vec<&str> {
         let mut test_args = match self.cmd {
             Subcommand::Test { ref test_args, .. }
@@ -2130,7 +2121,7 @@ impl Config {
             "`Config::read_file_by_commit` is not supported in non-git sources."
         );
 
-        let mut git = self.git();
+        let mut git = helpers::git(Some(&self.src));
         git.arg("show").arg(format!("{commit}:{}", file.to_str().unwrap()));
         output(&mut git)
     }
@@ -2436,15 +2427,16 @@ impl Config {
         };
 
         // Handle running from a directory other than the top level
-        let top_level = output(self.git().args(["rev-parse", "--show-toplevel"]));
+        let top_level =
+            output(helpers::git(Some(&self.src)).args(["rev-parse", "--show-toplevel"]));
         let top_level = top_level.trim_end();
         let compiler = format!("{top_level}/compiler/");
         let library = format!("{top_level}/library/");
 
         // Look for a version to compare to based on the current commit.
         // Only commits merged by bors will have CI artifacts.
         let merge_base = output(
-            self.git()
+            helpers::git(Some(&self.src))
                 .arg("rev-list")
                 .arg(format!("--author={}", self.stage0_metadata.config.git_merge_commit_email))
                 .args(["-n1", "--first-parent", "HEAD"]),
@@ -2459,8 +2451,7 @@ impl Config {
         }
 
         // Warn if there were changes to the compiler or standard library since the ancestor commit.
-        let has_changes = !t!(self
-            .git()
+        let has_changes = !t!(helpers::git(Some(&self.src))
             .args(["diff-index", "--quiet", commit, "--", &compiler, &library])
             .status())
         .success();
@@ -2533,13 +2524,14 @@ impl Config {
         if_unchanged: bool,
     ) -> Option<String> {
         // Handle running from a directory other than the top level
-        let top_level = output(self.git().args(["rev-parse", "--show-toplevel"]));
+        let top_level =
+            output(helpers::git(Some(&self.src)).args(["rev-parse", "--show-toplevel"]));
         let top_level = top_level.trim_end();
 
         // Look for a version to compare to based on the current commit.
         // Only commits merged by bors will have CI artifacts.
         let merge_base = output(
-            self.git()
+            helpers::git(Some(&self.src))
                 .arg("rev-list")
                 .arg(format!("--author={}", self.stage0_metadata.config.git_merge_commit_email))
                 .args(["-n1", "--first-parent", "HEAD"]),
@@ -2554,7 +2546,7 @@ impl Config {
         }
 
         // Warn if there were changes to the compiler or standard library since the ancestor commit.
-        let mut git = self.git();
+        let mut git = helpers::git(Some(&self.src));
         git.args(["diff-index", "--quiet", commit, "--"]);
 
         for path in modified_paths {