Auto merge of rust-lang#102627 - matthiaskrgr:rollup-2xtrqkw, r=matth…

…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#102439 (rustdoc: re-sugar more cross-crate trait bounds)
 - rust-lang#102569 (Improve `FromStr` example)
 - rust-lang#102597 (Avoid ICE in printing RPITIT type)
 - rust-lang#102607 (Improve documentation of `slice::{from_ptr_range, from_ptr_range_mut}`)
 - rust-lang#102613 (Fix ICE rust-lang#101739)
 - rust-lang#102615 (Cleanup some error code explanations)
 - rust-lang#102617 (`HirId` for `deferred_transmute_checks`)
 - rust-lang#102620 (Migrate `.stab` elements style to CSS variables)

Failed merges:

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

compiler/rustc_error_codes/src/error_codes/E0045.md

@@ -3,9 +3,7 @@ Variadic parameters have been used on a non-C ABI function.
 Erroneous code example:
 
 ```compile_fail,E0045
-#![feature(unboxed_closures)]
-
-extern "rust-call" {
+extern "Rust" {
     fn foo(x: u8, ...); // error!
 }
 ```

compiler/rustc_error_codes/src/error_codes/E0092.md

@@ -19,6 +19,6 @@ functions are defined in `compiler/rustc_codegen_llvm/src/intrinsic.rs` and in
 #![feature(intrinsics)]
 
 extern "rust-intrinsic" {
-    fn atomic_fence(); // ok!
+    fn atomic_fence_seqcst(); // ok!
 }
 ```

compiler/rustc_error_codes/src/error_codes/E0161.md

@@ -3,7 +3,6 @@ A value was moved whose size was not known at compile time.
 Erroneous code example:
 
 ```compile_fail,E0161
-#![feature(box_syntax)]
 trait Bar {
     fn f(self);
 }
@@ -13,7 +12,7 @@ impl Bar for i32 {
 }
 
 fn main() {
-    let b: Box<dyn Bar> = box (0 as i32);
+    let b: Box<dyn Bar> = Box::new(0i32);
     b.f();
     // error: cannot move a value of type dyn Bar: the size of dyn Bar cannot
     //        be statically determined
@@ -27,8 +26,6 @@ either `&x` or `&mut x`. Since a reference has a fixed size, this lets you move
 it around as usual. Example:
 
 ```
-#![feature(box_syntax)]
-
 trait Bar {
     fn f(&self);
 }
@@ -38,7 +35,7 @@ impl Bar for i32 {
 }
 
 fn main() {
-    let b: Box<dyn Bar> = box (0 as i32);
+    let b: Box<dyn Bar> = Box::new(0i32);
     b.f();
     // ok!
 }

compiler/rustc_error_codes/src/error_codes/E0579.md

@@ -8,9 +8,9 @@ Erroneous code example:
 fn main() {
     match 5u32 {
         // This range is ok, albeit pointless.
-        1 .. 2 => {}
+        1..2 => {}
         // This range is empty, and the compiler can tell.
-        5 .. 5 => {} // error!
+        5..5 => {} // error!
     }
 }
 ```

compiler/rustc_error_codes/src/error_codes/E0622.md

@@ -5,7 +5,7 @@ Erroneous code example:
 ```compile_fail,E0622
 #![feature(intrinsics)]
 extern "rust-intrinsic" {
-    pub static breakpoint : fn(); // error: intrinsic must be a function
+    pub static breakpoint: fn(); // error: intrinsic must be a function
 }
 
 fn main() { unsafe { breakpoint(); } }

compiler/rustc_error_codes/src/error_codes/E0743.md

@@ -3,8 +3,6 @@ The C-variadic type `...` has been nested inside another type.
 Erroneous code example:
 
 ```compile_fail,E0743
-#![feature(c_variadic)]
-
 fn foo2(x: u8, y: &...) {} // error!
 ```
 

compiler/rustc_hir_analysis/src/check/expr.rs

@@ -542,7 +542,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // been resolved or we errored. This is important as we can only check transmute
                 // on concrete types, but the output type may not be known yet (it would only
                 // be known if explicitly specified via turbofish).
-                self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
+                self.deferred_transmute_checks.borrow_mut().push((from, to, expr.hir_id));
             }
             if !tcx.features().unsized_fn_params {
                 // We want to remove some Sized bounds from std functions,

compiler/rustc_hir_analysis/src/check/fn_ctxt/checks.rs

@@ -50,8 +50,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(in super::super) fn check_transmutes(&self) {
         let mut deferred_transmute_checks = self.deferred_transmute_checks.borrow_mut();
         debug!("FnCtxt::check_transmutes: {} deferred checks", deferred_transmute_checks.len());
-        for (from, to, span) in deferred_transmute_checks.drain(..) {
-            self.check_transmute(span, from, to);
+        for (from, to, hir_id) in deferred_transmute_checks.drain(..) {
+            self.check_transmute(from, to, hir_id);
         }
     }
 

compiler/rustc_hir_analysis/src/check/inherited.rs

@@ -55,7 +55,7 @@ pub struct Inherited<'a, 'tcx> {
 
     pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
 
-    pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, Span)>>,
+    pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, hir::HirId)>>,
 
     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
 

compiler/rustc_hir_analysis/src/check/intrinsicck.rs

@@ -1,3 +1,4 @@
+use hir::HirId;
 use rustc_ast::InlineAsmTemplatePiece;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::struct_span_err;
@@ -6,7 +7,7 @@ use rustc_index::vec::Idx;
 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
 use rustc_middle::ty::{self, Article, FloatTy, IntTy, Ty, TyCtxt, TypeVisitable, UintTy};
 use rustc_session::lint;
-use rustc_span::{Span, Symbol, DUMMY_SP};
+use rustc_span::{Symbol, DUMMY_SP};
 use rustc_target::abi::{Pointer, VariantIdx};
 use rustc_target::asm::{InlineAsmReg, InlineAsmRegClass, InlineAsmRegOrRegClass, InlineAsmType};
 
@@ -40,11 +41,13 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
 }
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
-    pub fn check_transmute(&self, span: Span, from: Ty<'tcx>, to: Ty<'tcx>) {
+    pub fn check_transmute(&self, from: Ty<'tcx>, to: Ty<'tcx>, hir_id: HirId) {
+        let tcx = self.tcx;
+        let span = tcx.hir().span(hir_id);
         let convert = |ty: Ty<'tcx>| {
             let ty = self.resolve_vars_if_possible(ty);
-            let ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
-            (SizeSkeleton::compute(ty, self.tcx, self.param_env), ty)
+            let ty = tcx.normalize_erasing_regions(self.param_env, ty);
+            (SizeSkeleton::compute(ty, tcx, self.param_env), ty)
         };
         let (sk_from, from) = convert(from);
         let (sk_to, to) = convert(to);
@@ -57,9 +60,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // Special-case transmuting from `typeof(function)` and
             // `Option<typeof(function)>` to present a clearer error.
-            let from = unpack_option_like(self.tcx, from);
-            if let (&ty::FnDef(..), SizeSkeleton::Known(size_to)) = (from.kind(), sk_to) && size_to == Pointer.size(&self.tcx) {
-                struct_span_err!(self.tcx.sess, span, E0591, "can't transmute zero-sized type")
+            let from = unpack_option_like(tcx, from);
+            if let (&ty::FnDef(..), SizeSkeleton::Known(size_to)) = (from.kind(), sk_to) && size_to == Pointer.size(&tcx) {
+                struct_span_err!(tcx.sess, span, E0591, "can't transmute zero-sized type")
                     .note(&format!("source type: {from}"))
                     .note(&format!("target type: {to}"))
                     .help("cast with `as` to a pointer instead")
@@ -83,7 +86,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let mut err = struct_span_err!(
-            self.tcx.sess,
+            tcx.sess,
             span,
             E0512,
             "cannot transmute between types of different sizes, \

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -927,7 +927,7 @@ pub trait PrettyPrinter<'tcx>:
                         // unless we can find out what generator return type it comes from.
                         let term = if let Some(ty) = term.skip_binder().ty()
                             && let ty::Projection(proj) = ty.kind()
-                            && let assoc = tcx.associated_item(proj.item_def_id)
+                            && let Some(assoc) = tcx.opt_associated_item(proj.item_def_id)
                             && assoc.trait_container(tcx) == tcx.lang_items().gen_trait()
                             && assoc.name == rustc_span::sym::Return
                         {

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -11,9 +11,10 @@ use rustc_hir::lang_items::LangItem;
 use rustc_index::bit_set::GrowableBitSet;
 use rustc_infer::infer::InferOk;
 use rustc_infer::infer::LateBoundRegionConversionTime::HigherRankedType;
-use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt};
-use rustc_middle::ty::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
-use rustc_middle::ty::{ToPolyTraitRef, ToPredicate};
+use rustc_middle::ty::{
+    self, GenericArg, GenericArgKind, GenericParamDefKind, InternalSubsts, SubstsRef,
+    ToPolyTraitRef, ToPredicate, Ty, TyCtxt,
+};
 use rustc_span::def_id::DefId;
 
 use crate::traits::project::{normalize_with_depth, normalize_with_depth_to};
@@ -289,8 +290,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         let scope = type_at(2).skip_binder();
 
-        let assume =
-            rustc_transmute::Assume::from_const(self.infcx.tcx, obligation.param_env, const_at(3));
+        let Some(assume) =
+            rustc_transmute::Assume::from_const(self.infcx.tcx, obligation.param_env, const_at(3)) else {
+                return Err(Unimplemented);
+            };
 
         let cause = obligation.cause.clone();
 

compiler/rustc_transmute/src/lib.rs

@@ -115,18 +115,23 @@ mod rustc {
             tcx: TyCtxt<'tcx>,
             param_env: ParamEnv<'tcx>,
             c: Const<'tcx>,
-        ) -> Self {
+        ) -> Option<Self> {
             use rustc_middle::ty::ScalarInt;
             use rustc_middle::ty::TypeVisitable;
             use rustc_span::symbol::sym;
 
             let c = c.eval(tcx, param_env);
 
             if let Some(err) = c.error_reported() {
-                return Self { alignment: true, lifetimes: true, safety: true, validity: true };
+                return Some(Self {
+                    alignment: true,
+                    lifetimes: true,
+                    safety: true,
+                    validity: true,
+                });
             }
 
-            let adt_def = c.ty().ty_adt_def().expect("The given `Const` must be an ADT.");
+            let adt_def = c.ty().ty_adt_def()?;
 
             assert_eq!(
                 tcx.require_lang_item(LangItem::TransmuteOpts, None),
@@ -148,12 +153,12 @@ mod rustc {
                 fields[field_idx].unwrap_leaf() == ScalarInt::TRUE
             };
 
-            Self {
+            Some(Self {
                 alignment: get_field(sym::alignment),
                 lifetimes: get_field(sym::lifetimes),
                 safety: get_field(sym::safety),
                 validity: get_field(sym::validity),
-            }
+            })
         }
     }
 }

library/core/src/slice/raw.rs

@@ -188,6 +188,10 @@ pub const fn from_mut<T>(s: &mut T) -> &mut [T] {
 ///
 /// Note that a range created from [`slice::as_ptr_range`] fulfills these requirements.
 ///
+/// # Panics
+///
+/// This function panics if `T` is a Zero-Sized Type (“ZST”).
+///
 /// # Caveat
 ///
 /// The lifetime for the returned slice is inferred from its usage. To
@@ -219,9 +223,15 @@ pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T] {
     unsafe { from_raw_parts(range.start, range.end.sub_ptr(range.start)) }
 }
 
-/// Performs the same functionality as [`from_ptr_range`], except that a
+/// Forms a mutable slice from a pointer range.
+///
+/// This is the same functionality as [`from_ptr_range`], except that a
 /// mutable slice is returned.
 ///
+/// This function is useful for interacting with foreign interfaces which
+/// use two pointers to refer to a range of elements in memory, as is
+/// common in C++.
+///
 /// # Safety
 ///
 /// Behavior is undefined if any of the following conditions are violated:
@@ -247,6 +257,18 @@ pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T] {
 ///
 /// Note that a range created from [`slice::as_mut_ptr_range`] fulfills these requirements.
 ///
+/// # Panics
+///
+/// This function panics if `T` is a Zero-Sized Type (“ZST”).
+///
+/// # Caveat
+///
+/// The lifetime for the returned slice is inferred from its usage. To
+/// prevent accidental misuse, it's suggested to tie the lifetime to whichever
+/// source lifetime is safe in the context, such as by providing a helper
+/// function taking the lifetime of a host value for the slice, or by explicit
+/// annotation.
+///
 /// # Examples
 ///
 /// ```

library/core/src/str/traits.rs

@@ -507,26 +507,28 @@ unsafe impl const SliceIndex<str> for ops::RangeToInclusive<usize> {
 ///
 /// ```
 /// use std::str::FromStr;
-/// use std::num::ParseIntError;
 ///
 /// #[derive(Debug, PartialEq)]
 /// struct Point {
 ///     x: i32,
 ///     y: i32
 /// }
 ///
+/// #[derive(Debug, PartialEq, Eq)]
+/// struct ParsePointError;
+///
 /// impl FromStr for Point {
-///     type Err = ParseIntError;
+///     type Err = ParsePointError;
 ///
 ///     fn from_str(s: &str) -> Result<Self, Self::Err> {
 ///         let (x, y) = s
 ///             .strip_prefix('(')
 ///             .and_then(|s| s.strip_suffix(')'))
 ///             .and_then(|s| s.split_once(','))
-///             .unwrap();
+///             .ok_or(ParsePointError)?;
 ///
-///         let x_fromstr = x.parse::<i32>()?;
-///         let y_fromstr = y.parse::<i32>()?;
+///         let x_fromstr = x.parse::<i32>().map_err(|_| ParsePointError)?;
+///         let y_fromstr = y.parse::<i32>().map_err(|_| ParsePointError)?;
 ///
 ///         Ok(Point { x: x_fromstr, y: y_fromstr })
 ///     }
@@ -538,6 +540,8 @@ unsafe impl const SliceIndex<str> for ops::RangeToInclusive<usize> {
 /// // Implicit calls, through parse
 /// assert_eq!("(1,2)".parse(), expected);
 /// assert_eq!("(1,2)".parse::<Point>(), expected);
+/// // Invalid input string
+/// assert!(Point::from_str("(1 2)").is_err());
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait FromStr: Sized {

src/librustdoc/clean/mod.rs

@@ -1176,6 +1176,15 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
             }
 
             if let ty::TraitContainer = assoc_item.container {
+                // FIXME(fmease): `tcx.explicit_item_bounds` does not contain the bounds of GATs,
+                //                e.g. the bounds `Copy`, `Display` & (implicitly) `Sized` in
+                //                `type Assoc<T: Copy> where T: Display`. This also means that we
+                //                later incorrectly render `where T: ?Sized`.
+                //
+                //                The result of `tcx.explicit_predicates_of` *does* contain them but
+                //                it does not contain the other bounds / predicates we need.
+                //                Either merge those two interned lists somehow or refactor
+                //                `clean_ty_generics` to call `explicit_item_bounds` by itself.
                 let bounds = tcx.explicit_item_bounds(assoc_item.def_id);
                 let predicates = ty::GenericPredicates { parent: None, predicates: bounds };
                 let mut generics =