Auto merge of rust-lang#128142 - matthiaskrgr:rollup-rep8ofv, r=matth…

…iaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang#126152 (size_of_val_raw: for length 0 this is safe to call)
 - rust-lang#127252 (Add edge-case examples to `{count,leading,trailing}_{ones,zeros}` methods)
 - rust-lang#127374 (Tweak "wrong # of generics" suggestions)
 - rust-lang#127457 (Make tidy fast without compromising case alternation)
 - rust-lang#127480 (Fix build failure on vxworks rust-lang#127084 )
 - rust-lang#127733 (Replace some `mem::forget`'s with `ManuallyDrop`)
 - rust-lang#128120 (Gate `AsyncFn*` under `async_closure` feature)
 - rust-lang#128131 (Import `c_void` rather than using the full path)
 - rust-lang#128133 (Improve spans on evaluated `cfg_attr`s.)

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

compiler/rustc_ast_lowering/src/path.rs

@@ -44,13 +44,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut res = self.lower_res(base_res);
 
         // When we have an `async` kw on a bound, map the trait it resolves to.
-        let mut bound_modifier_allowed_features = None;
         if let Some(TraitBoundModifiers { asyncness: BoundAsyncness::Async(_), .. }) = modifiers {
             match res {
                 Res::Def(DefKind::Trait, def_id) => {
-                    if let Some((async_def_id, features)) = self.map_trait_to_async_trait(def_id) {
+                    if let Some(async_def_id) = self.map_trait_to_async_trait(def_id) {
                         res = Res::Def(DefKind::Trait, async_def_id);
-                        bound_modifier_allowed_features = Some(features);
                     } else {
                         self.dcx().emit_err(AsyncBoundOnlyForFnTraits { span: p.span });
                     }
@@ -67,6 +65,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
 
+        // Ungate the `async_fn_traits` feature in the path if the trait is
+        // named via either `async Fn*()` or `AsyncFn*()`.
+        let bound_modifier_allowed_features = if let Res::Def(DefKind::Trait, async_def_id) = res
+            && self.tcx.async_fn_trait_kind_from_def_id(async_def_id).is_some()
+        {
+            Some(self.allow_async_fn_traits.clone())
+        } else {
+            None
+        };
+
         let path_span_lo = p.span.shrink_to_lo();
         let proj_start = p.segments.len() - unresolved_segments;
         let path = self.arena.alloc(hir::Path {
@@ -506,14 +514,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// This only needs to be done until we unify `AsyncFn` and `Fn` traits into one
     /// that is generic over `async`ness, if that's ever possible, or modify the
     /// lowering of `async Fn()` bounds to desugar to another trait like `LendingFn`.
-    fn map_trait_to_async_trait(&self, def_id: DefId) -> Option<(DefId, Lrc<[Symbol]>)> {
+    fn map_trait_to_async_trait(&self, def_id: DefId) -> Option<DefId> {
         let lang_items = self.tcx.lang_items();
         if Some(def_id) == lang_items.fn_trait() {
-            Some((lang_items.async_fn_trait()?, self.allow_async_fn_traits.clone()))
+            lang_items.async_fn_trait()
         } else if Some(def_id) == lang_items.fn_mut_trait() {
-            Some((lang_items.async_fn_mut_trait()?, self.allow_async_fn_traits.clone()))
+            lang_items.async_fn_mut_trait()
         } else if Some(def_id) == lang_items.fn_once_trait() {
-            Some((lang_items.async_fn_once_trait()?, self.allow_async_fn_traits.clone()))
+            lang_items.async_fn_once_trait()
         } else {
             None
         }

compiler/rustc_expand/src/config.rs

@@ -6,7 +6,7 @@ use crate::errors::{
 };
 use rustc_ast::ptr::P;
 use rustc_ast::token::{Delimiter, Token, TokenKind};
-use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree, DelimSpacing, DelimSpan, Spacing};
+use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree, Spacing};
 use rustc_ast::tokenstream::{LazyAttrTokenStream, TokenTree};
 use rustc_ast::NodeId;
 use rustc_ast::{self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem};
@@ -298,47 +298,47 @@ impl<'a> StripUnconfigured<'a> {
         cfg_attr: &Attribute,
         (item, item_span): (ast::AttrItem, Span),
     ) -> Attribute {
-        // We are taking an attribute of the form `#[cfg_attr(pred, attr)]`
-        // and producing an attribute of the form `#[attr]`. We
-        // have captured tokens for `attr` itself, but we need to
-        // synthesize tokens for the wrapper `#` and `[]`, which
-        // we do below.
-
-        // Use the `#` in `#[cfg_attr(pred, attr)]` as the `#` token
-        // for `attr` when we expand it to `#[attr]`
+        // Convert `#[cfg_attr(pred, attr)]` to `#[attr]`.
+
+        // Use the `#` from `#[cfg_attr(pred, attr)]` in the result `#[attr]`.
         let mut orig_trees = cfg_attr.token_trees().into_iter();
-        let TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _) =
-            orig_trees.next().unwrap().clone()
+        let Some(TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _)) =
+            orig_trees.next()
         else {
             panic!("Bad tokens for attribute {cfg_attr:?}");
         };
 
-        // We don't really have a good span to use for the synthesized `[]`
-        // in `#[attr]`, so just use the span of the `#` token.
-        let bracket_group = AttrTokenTree::Delimited(
-            DelimSpan::from_single(pound_token.span),
-            DelimSpacing::new(Spacing::JointHidden, Spacing::Alone),
-            Delimiter::Bracket,
-            item.tokens
-                .as_ref()
-                .unwrap_or_else(|| panic!("Missing tokens for {item:?}"))
-                .to_attr_token_stream(),
-        );
-        let trees = if cfg_attr.style == AttrStyle::Inner {
-            // For inner attributes, we do the same thing for the `!` in `#![some_attr]`
-            let TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }, _) =
-                orig_trees.next().unwrap().clone()
+        // For inner attributes, we do the same thing for the `!` in `#![attr]`.
+        let mut trees = if cfg_attr.style == AttrStyle::Inner {
+            let Some(TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }, _)) =
+                orig_trees.next()
             else {
                 panic!("Bad tokens for attribute {cfg_attr:?}");
             };
             vec![
                 AttrTokenTree::Token(pound_token, Spacing::Joint),
                 AttrTokenTree::Token(bang_token, Spacing::JointHidden),
-                bracket_group,
             ]
         } else {
-            vec![AttrTokenTree::Token(pound_token, Spacing::JointHidden), bracket_group]
+            vec![AttrTokenTree::Token(pound_token, Spacing::JointHidden)]
         };
+
+        // And the same thing for the `[`/`]` delimiters in `#[attr]`.
+        let Some(TokenTree::Delimited(delim_span, delim_spacing, Delimiter::Bracket, _)) =
+            orig_trees.next()
+        else {
+            panic!("Bad tokens for attribute {cfg_attr:?}");
+        };
+        trees.push(AttrTokenTree::Delimited(
+            delim_span,
+            delim_spacing,
+            Delimiter::Bracket,
+            item.tokens
+                .as_ref()
+                .unwrap_or_else(|| panic!("Missing tokens for {item:?}"))
+                .to_attr_token_stream(),
+        ));
+
         let tokens = Some(LazyAttrTokenStream::new(AttrTokenStream::new(trees)));
         let attr = attr::mk_attr_from_item(
             &self.sess.psess.attr_id_generator,

compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs

@@ -888,7 +888,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         let comma = if args.len() > 0 { ", " } else { "" };
         let trait_path = self.tcx.def_path_str(trait_def_id);
         let method_name = self.tcx.item_name(self.def_id);
-        err.span_suggestion(
+        err.span_suggestion_verbose(
             expr.span,
             msg,
             format!("{trait_path}::{generics}::{method_name}({rcvr}{comma}{rest})"),
@@ -939,18 +939,20 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
                 }
             }
 
-            let span_lo_redundant_lt_args = lt_arg_spans[self.num_expected_lifetime_args()];
+            let span_lo_redundant_lt_args = if self.num_expected_lifetime_args() == 0 {
+                lt_arg_spans[0]
+            } else {
+                lt_arg_spans[self.num_expected_lifetime_args() - 1]
+            };
             let span_hi_redundant_lt_args = lt_arg_spans[lt_arg_spans.len() - 1];
 
-            let span_redundant_lt_args = span_lo_redundant_lt_args.to(span_hi_redundant_lt_args);
+            let span_redundant_lt_args =
+                span_lo_redundant_lt_args.shrink_to_hi().to(span_hi_redundant_lt_args);
             debug!("span_redundant_lt_args: {:?}", span_redundant_lt_args);
 
             let num_redundant_lt_args = lt_arg_spans.len() - self.num_expected_lifetime_args();
-            let msg_lifetimes = format!(
-                "remove {these} lifetime argument{s}",
-                these = pluralize!("this", num_redundant_lt_args),
-                s = pluralize!(num_redundant_lt_args),
-            );
+            let msg_lifetimes =
+                format!("remove the lifetime argument{s}", s = pluralize!(num_redundant_lt_args));
 
             err.span_suggestion(
                 span_redundant_lt_args,
@@ -979,18 +981,22 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             }
 
             let span_lo_redundant_type_or_const_args =
-                gen_arg_spans[self.num_expected_type_or_const_args()];
+                if self.num_expected_type_or_const_args() == 0 {
+                    gen_arg_spans[0]
+                } else {
+                    gen_arg_spans[self.num_expected_type_or_const_args() - 1]
+                };
             let span_hi_redundant_type_or_const_args = gen_arg_spans[gen_arg_spans.len() - 1];
+            let span_redundant_type_or_const_args = span_lo_redundant_type_or_const_args
+                .shrink_to_hi()
+                .to(span_hi_redundant_type_or_const_args);
 
-            let span_redundant_type_or_const_args =
-                span_lo_redundant_type_or_const_args.to(span_hi_redundant_type_or_const_args);
             debug!("span_redundant_type_or_const_args: {:?}", span_redundant_type_or_const_args);
 
             let num_redundant_gen_args =
                 gen_arg_spans.len() - self.num_expected_type_or_const_args();
             let msg_types_or_consts = format!(
-                "remove {these} generic argument{s}",
-                these = pluralize!("this", num_redundant_gen_args),
+                "remove the unnecessary generic argument{s}",
                 s = pluralize!(num_redundant_gen_args),
             );
 
@@ -1036,7 +1042,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
                 .with_lo(self.path_segment.ident.span.hi());
 
             let msg = format!(
-                "remove these {}generics",
+                "remove the unnecessary {}generics",
                 if self.gen_args.parenthesized == hir::GenericArgsParentheses::ParenSugar {
                     "parenthetical "
                 } else {

library/alloc/src/lib.rs

@@ -101,6 +101,7 @@
 #![feature(array_windows)]
 #![feature(ascii_char)]
 #![feature(assert_matches)]
+#![feature(async_closure)]
 #![feature(async_fn_traits)]
 #![feature(async_iterator)]
 #![feature(clone_to_uninit)]

library/alloc/src/rc.rs

@@ -259,7 +259,7 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-use core::mem::{self, align_of_val_raw, forget, ManuallyDrop};
+use core::mem::{self, align_of_val_raw, ManuallyDrop};
 use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 #[cfg(not(no_global_oom_handling))]
@@ -908,19 +908,18 @@ impl<T, A: Allocator> Rc<T, A> {
     #[stable(feature = "rc_unique", since = "1.4.0")]
     pub fn try_unwrap(this: Self) -> Result<T, Self> {
         if Rc::strong_count(&this) == 1 {
-            unsafe {
-                let val = ptr::read(&*this); // copy the contained object
-                let alloc = ptr::read(&this.alloc); // copy the allocator
-
-                // Indicate to Weaks that they can't be promoted by decrementing
-                // the strong count, and then remove the implicit "strong weak"
-                // pointer while also handling drop logic by just crafting a
-                // fake Weak.
-                this.inner().dec_strong();
-                let _weak = Weak { ptr: this.ptr, alloc };
-                forget(this);
-                Ok(val)
-            }
+            let this = ManuallyDrop::new(this);
+
+            let val: T = unsafe { ptr::read(&**this) }; // copy the contained object
+            let alloc: A = unsafe { ptr::read(&this.alloc) }; // copy the allocator
+
+            // Indicate to Weaks that they can't be promoted by decrementing
+            // the strong count, and then remove the implicit "strong weak"
+            // pointer while also handling drop logic by just crafting a
+            // fake Weak.
+            this.inner().dec_strong();
+            let _weak = Weak { ptr: this.ptr, alloc };
+            Ok(val)
         } else {
             Err(this)
         }
@@ -1354,9 +1353,8 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     #[stable(feature = "rc_raw", since = "1.17.0")]
     #[rustc_never_returns_null_ptr]
     pub fn into_raw(this: Self) -> *const T {
-        let ptr = Self::as_ptr(&this);
-        mem::forget(this);
-        ptr
+        let this = ManuallyDrop::new(this);
+        Self::as_ptr(&*this)
     }
 
     /// Consumes the `Rc`, returning the wrapped pointer and allocator.
@@ -2127,7 +2125,7 @@ impl<T> Rc<[T]> {
             }
 
             // All clear. Forget the guard so it doesn't free the new RcBox.
-            forget(guard);
+            mem::forget(guard);
 
             Self::from_ptr(ptr)
         }
@@ -3080,9 +3078,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
-        let result = self.as_ptr();
-        mem::forget(self);
-        result
+        mem::ManuallyDrop::new(self).as_ptr()
     }
 
     /// Consumes the `Weak<T>`, returning the wrapped pointer and allocator.
@@ -3762,10 +3758,11 @@ impl<T: ?Sized, A: Allocator> UniqueRcUninit<T, A> {
     /// # Safety
     ///
     /// The data must have been initialized (by writing to [`Self::data_ptr()`]).
-    unsafe fn into_rc(mut self) -> Rc<T, A> {
-        let ptr = self.ptr;
-        let alloc = self.alloc.take().unwrap();
-        mem::forget(self);
+    unsafe fn into_rc(self) -> Rc<T, A> {
+        let mut this = ManuallyDrop::new(self);
+        let ptr = this.ptr;
+        let alloc = this.alloc.take().unwrap();
+
         // SAFETY: The pointer is valid as per `UniqueRcUninit::new`, and the caller is responsible
         // for having initialized the data.
         unsafe { Rc::from_ptr_in(ptr.as_ptr(), alloc) }

library/alloc/src/sync.rs

@@ -20,7 +20,7 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-use core::mem::{self, align_of_val_raw};
+use core::mem::{self, align_of_val_raw, ManuallyDrop};
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::pin::Pin;
@@ -960,16 +960,14 @@ impl<T, A: Allocator> Arc<T, A> {
 
         acquire!(this.inner().strong);
 
-        unsafe {
-            let elem = ptr::read(&this.ptr.as_ref().data);
-            let alloc = ptr::read(&this.alloc); // copy the allocator
+        let this = ManuallyDrop::new(this);
+        let elem: T = unsafe { ptr::read(&this.ptr.as_ref().data) };
+        let alloc: A = unsafe { ptr::read(&this.alloc) }; // copy the allocator
 
-            // Make a weak pointer to clean up the implicit strong-weak reference
-            let _weak = Weak { ptr: this.ptr, alloc };
-            mem::forget(this);
+        // Make a weak pointer to clean up the implicit strong-weak reference
+        let _weak = Weak { ptr: this.ptr, alloc };
 
-            Ok(elem)
-        }
+        Ok(elem)
     }
 
     /// Returns the inner value, if the `Arc` has exactly one strong reference.
@@ -1493,9 +1491,8 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     #[stable(feature = "rc_raw", since = "1.17.0")]
     #[rustc_never_returns_null_ptr]
     pub fn into_raw(this: Self) -> *const T {
-        let ptr = Self::as_ptr(&this);
-        mem::forget(this);
-        ptr
+        let this = ManuallyDrop::new(this);
+        Self::as_ptr(&*this)
     }
 
     /// Consumes the `Arc`, returning the wrapped pointer and allocator.
@@ -2801,9 +2798,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
-        let result = self.as_ptr();
-        mem::forget(self);
-        result
+        ManuallyDrop::new(self).as_ptr()
     }
 
     /// Consumes the `Weak<T>`, returning the wrapped pointer and allocator.
@@ -3875,13 +3870,14 @@ impl<T: ?Sized, A: Allocator> UniqueArcUninit<T, A> {
     /// # Safety
     ///
     /// The data must have been initialized (by writing to [`Self::data_ptr()`]).
-    unsafe fn into_arc(mut self) -> Arc<T, A> {
-        let ptr = self.ptr;
-        let alloc = self.alloc.take().unwrap();
-        mem::forget(self);
+    unsafe fn into_arc(self) -> Arc<T, A> {
+        let mut this = ManuallyDrop::new(self);
+        let ptr = this.ptr.as_ptr();
+        let alloc = this.alloc.take().unwrap();
+
         // SAFETY: The pointer is valid as per `UniqueArcUninit::new`, and the caller is responsible
         // for having initialized the data.
-        unsafe { Arc::from_ptr_in(ptr.as_ptr(), alloc) }
+        unsafe { Arc::from_ptr_in(ptr, alloc) }
     }
 }
 

library/core/src/alloc/layout.rs

@@ -183,6 +183,8 @@ impl Layout {
     ///     - a [slice], then the length of the slice tail must be an initialized
     ///       integer, and the size of the *entire value*
     ///       (dynamic tail length + statically sized prefix) must fit in `isize`.
+    ///       For the special case where the dynamic tail length is 0, this function
+    ///       is safe to call.
     ///     - a [trait object], then the vtable part of the pointer must point
     ///       to a valid vtable for the type `T` acquired by an unsizing coercion,
     ///       and the size of the *entire value*