Rollup merge of #125637 - nnethercote:rustfmt-fixes, r=GuillaumeGomez

rustfmt fixes

The `rmake.rs` entries in `rustfmt.toml` are causing major problems for `x fmt`. This PR removes them and does some minor related cleanups.

r? ``@GuillaumeGomez``

5 files changed, 37 insertions, 40 deletions

diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index 5e70b300f33..a54332b6f25 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -219,10 +219,8 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
                     for (i, field) in variant.fields.iter_enumerated() {
                         let field_ty = field.ty(self.tcx, args);
                         if field_ty == *cast_ty {
-                            let place = place.project_deeper(
-                                &[ProjectionElem::Field(i, *cast_ty)],
-                                self.tcx,
-                            );
+                            let place = place
+                                .project_deeper(&[ProjectionElem::Field(i, *cast_ty)], self.tcx);
                             let operand = if operand.is_move() {
                                 Operand::Move(place)
                             } else {
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index 6df32169eec..8d7547d03e8 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -691,7 +691,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                                 location,
                                 format!(
                                     "You can't project to field {f:?} of `DynMetadata` because \
-                                         layout is weird and thinks it doesn't have fields."
+                                     layout is weird and thinks it doesn't have fields."
                                 ),
                             );
                         }
diff --git a/library/core/src/ptr/metadata.rs b/library/core/src/ptr/metadata.rs
index e501970b580..6dfeb66694d 100644
--- a/library/core/src/ptr/metadata.rs
+++ b/library/core/src/ptr/metadata.rs
@@ -209,18 +209,14 @@ impl<Dyn: ?Sized> DynMetadata<Dyn> {
         // Consider a reference like `&(i32, dyn Send)`: the vtable will only store the size of the
         // `Send` part!
         // SAFETY: DynMetadata always contains a valid vtable pointer
-        return unsafe {
-            crate::intrinsics::vtable_size(self.vtable_ptr() as *const ())
-        };
+        return unsafe { crate::intrinsics::vtable_size(self.vtable_ptr() as *const ()) };
     }
 
     /// Returns the alignment of the type associated with this vtable.
     #[inline]
     pub fn align_of(self) -> usize {
         // SAFETY: DynMetadata always contains a valid vtable pointer
-        return unsafe {
-            crate::intrinsics::vtable_align(self.vtable_ptr() as *const ())
-        };
+        return unsafe { crate::intrinsics::vtable_align(self.vtable_ptr() as *const ()) };
     }
 
     /// Returns the size and alignment together as a `Layout`
diff --git a/rustfmt.toml b/rustfmt.toml
index ef56059feb1..b78e96d5872 100644
--- a/rustfmt.toml
+++ b/rustfmt.toml
@@ -3,25 +3,18 @@ version = "Two"
 use_small_heuristics = "Max"
 merge_derives = false
 
-# by default we ignore everything in the repository
-# tidy only checks files which are not ignored, each entry follows gitignore style
+# Files to ignore. Each entry uses gitignore syntax, but `!` prefixes aren't allowed.
 ignore = [
     "/build/",
     "/*-build/",
     "/build-*/",
     "/vendor/",
 
-    # tests for now are not formatted, as they are sometimes pretty-printing constrained
-    # (and generally rustfmt can move around comments in UI-testing incompatible ways)
-    "/tests/*",
+    # Tests for now are not formatted, as they are sometimes pretty-printing constrained
+    # (and generally rustfmt can move around comments in UI-testing incompatible ways).
+    "/tests/",
 
-    # but we still want to format rmake.rs files in tests/run-make/ so we need to do this
-    # dance to avoid the parent directory from being excluded
-    "!/tests/run-make/",
-    "/tests/run-make/*/*.rs",
-    "!/tests/run-make/*/rmake.rs",
-
-    # do not format submodules
+    # Do not format submodules.
     # FIXME: sync submodule list with tidy/bootstrap/etc
     # tidy/src/walk.rs:filter_dirs
     "library/backtrace",
@@ -43,7 +36,7 @@ ignore = [
     "src/tools/rustc-perf",
     "src/tools/rustfmt",
 
-    # these are ignored by a standard cargo fmt run
+    # These are ignored by a standard cargo fmt run.
     "compiler/rustc_codegen_cranelift/scripts",
     "compiler/rustc_codegen_cranelift/example/gen_block_iterate.rs", # uses edition 2024
 ]
diff --git a/src/bootstrap/src/core/build_steps/format.rs b/src/bootstrap/src/core/build_steps/format.rs
index d9dc34c0137..44f575b51da 100644
--- a/src/bootstrap/src/core/build_steps/format.rs
+++ b/src/bootstrap/src/core/build_steps/format.rs
@@ -12,8 +12,8 @@ use std::sync::mpsc::SyncSender;
 
 fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl FnMut(bool) -> bool {
     let mut cmd = Command::new(rustfmt);
-    // avoid the submodule config paths from coming into play,
-    // we only allow a single global config for the workspace for now
+    // Avoid the submodule config paths from coming into play. We only allow a single global config
+    // for the workspace for now.
     cmd.arg("--config-path").arg(&src.canonicalize().unwrap());
     cmd.arg("--edition").arg("2021");
     cmd.arg("--unstable-features");
@@ -24,7 +24,7 @@ fn rustfmt(src: &Path, rustfmt: &Path, paths: &[PathBuf], check: bool) -> impl F
     cmd.args(paths);
     let cmd_debug = format!("{cmd:?}");
     let mut cmd = cmd.spawn().expect("running rustfmt");
-    // poor man's async: return a closure that'll wait for rustfmt's completion
+    // Poor man's async: return a closure that'll wait for rustfmt's completion.
     move |block: bool| -> bool {
         if !block {
             match cmd.try_wait() {
@@ -72,7 +72,7 @@ fn verify_rustfmt_version(build: &Builder<'_>) -> bool {
     !program_out_of_date(&stamp_file, &version)
 }
 
-/// Updates the last rustfmt version used
+/// Updates the last rustfmt version used.
 fn update_rustfmt_version(build: &Builder<'_>) {
     let Some((version, stamp_file)) = get_rustfmt_version(build) else {
         return;
@@ -115,8 +115,15 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
     let rustfmt_config: RustfmtConfig = t!(toml::from_str(&rustfmt_config));
     let mut fmt_override = ignore::overrides::OverrideBuilder::new(&build.src);
     for ignore in rustfmt_config.ignore {
-        if let Some(ignore) = ignore.strip_prefix('!') {
-            fmt_override.add(ignore).expect(ignore);
+        if ignore.starts_with('!') {
+            // A `!`-prefixed entry could be added as a whitelisted entry in `fmt_override`, i.e.
+            // strip the `!` prefix. But as soon as whitelisted entries are added, an
+            // `OverrideBuilder` will only traverse those whitelisted entries, and won't traverse
+            // any files that aren't explicitly mentioned. No bueno! Maybe there's a way to combine
+            // explicit whitelisted entries and traversal of unmentioned files, but for now just
+            // forbid such entries.
+            eprintln!("`!`-prefixed entries are not supported in rustfmt.toml, sorry");
+            crate::exit!(1);
         } else {
             fmt_override.add(&format!("!{ignore}")).expect(&ignore);
         }
@@ -168,9 +175,10 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
                 untracked_count += 1;
                 fmt_override.add(&format!("!/{untracked_path}")).expect(untracked_path);
             }
-            // Only check modified files locally to speed up runtime.
-            // We still check all files in CI to avoid bugs in `get_modified_rs_files` letting regressions slip through;
-            // we also care about CI time less since this is still very fast compared to building the compiler.
+            // Only check modified files locally to speed up runtime. We still check all files in
+            // CI to avoid bugs in `get_modified_rs_files` letting regressions slip through; we
+            // also care about CI time less since this is still very fast compared to building the
+            // compiler.
             if !CiEnv::is_ci() && paths.is_empty() {
                 match get_modified_rs_files(build) {
                     Ok(Some(files)) => {
@@ -275,21 +283,23 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
     .overrides(fmt_override)
     .build_parallel();
 
-    // there is a lot of blocking involved in spawning a child process and reading files to format.
-    // spawn more processes than available concurrency to keep the CPU busy
+    // There is a lot of blocking involved in spawning a child process and reading files to format.
+    // Spawn more processes than available concurrency to keep the CPU busy.
     let max_processes = build.jobs() as usize * 2;
 
-    // spawn child processes on a separate thread so we can batch entries we have received from ignore
+    // Spawn child processes on a separate thread so we can batch entries we have received from
+    // ignore.
     let thread = std::thread::spawn(move || {
         let mut children = VecDeque::new();
         while let Ok(path) = rx.recv() {
-            // try getting more paths from the channel to amortize the overhead of spawning processes
+            // Try getting more paths from the channel to amortize the overhead of spawning
+            // processes.
             let paths: Vec<_> = rx.try_iter().take(63).chain(std::iter::once(path)).collect();
 
             let child = rustfmt(&src, &rustfmt_path, paths.as_slice(), check);
             children.push_back(child);
 
-            // poll completion before waiting
+            // Poll completion before waiting.
             for i in (0..children.len()).rev() {
                 if children[i](false) {
                     children.swap_remove_back(i);
@@ -298,12 +308,12 @@ pub fn format(build: &Builder<'_>, check: bool, paths: &[PathBuf]) {
             }
 
             if children.len() >= max_processes {
-                // await oldest child
+                // Await oldest child.
                 children.pop_front().unwrap()(true);
             }
         }
 
-        // await remaining children
+        // Await remaining children.
         for mut child in children {
             child(true);
         }