Rollup of 11 pull requests

Cargo.lock

@@ -4267,6 +4267,7 @@ dependencies = [
  "rustc_parse_format",
  "rustc_session",
  "rustc_span",
+ "rustc_symbol_mangling",
  "rustc_target",
  "rustc_trait_selection",
  "smallvec",

compiler/rustc_ast/src/ast.rs

@@ -3867,6 +3867,19 @@ pub struct Fn {
     pub eii_impls: ThinVec<EiiImpl>,
 }
 
+impl Fn {
+    pub fn is_pin_drop_sugar(&self) -> bool {
+        self.ident.name == sym::drop
+            && self
+                .sig
+                .decl
+                .inputs
+                .first()
+                .and_then(|param| param.to_self())
+                .is_some_and(|eself| matches!(eself.node, SelfKind::Pinned(None, Mutability::Mut)))
+    }
+}
+
 #[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub struct EiiImpl {
     pub node_id: NodeId,

compiler/rustc_ast_lowering/src/item.rs

@@ -1192,6 +1192,52 @@ impl<'hir> LoweringContext<'_, 'hir> {
         })
     }
 
+    fn resolve_pin_drop_sugar_impl_item(
+        &self,
+        i: &AssocItem,
+        ident: Ident,
+        span: Span,
+    ) -> (Ident, Result<DefId, ErrorGuaranteed>) {
+        let trait_item_def_id = self
+            .get_partial_res(i.id)
+            .and_then(|r| r.expect_full_res().opt_def_id())
+            .ok_or_else(|| {
+                self.dcx().span_delayed_bug(span, "could not resolve trait item being implemented")
+            });
+
+        let is_pin_drop_sugar = match &i.kind {
+            AssocItemKind::Fn(fn_kind) => fn_kind.is_pin_drop_sugar(),
+            _ => false,
+        };
+        let def_id = match trait_item_def_id {
+            Ok(def_id) => def_id,
+            Err(guar) => return (ident, Err(guar)),
+        };
+        if !is_pin_drop_sugar {
+            return (ident, Ok(def_id));
+        }
+
+        let is_drop_pin_drop = self
+            .tcx
+            .lang_items()
+            .drop_trait()
+            .is_some_and(|drop_trait| self.tcx.parent(def_id) == drop_trait);
+        if is_drop_pin_drop {
+            // Associated item collection still derives the impl item's name from HIR.
+            return (Ident::new(sym::pin_drop, ident.span), Ok(def_id));
+        }
+
+        let guar = self
+            .dcx()
+            .struct_span_err(
+                i.span,
+                "method `drop` with `&pin mut self` is only supported for the `Drop` trait",
+            )
+            .with_span_label(i.span, "not a `Drop::pin_drop` implementation")
+            .emit();
+        (ident, Err(guar))
+    }
+
     fn lower_impl_item(
         &mut self,
         i: &AssocItem,
@@ -1309,26 +1355,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
 
         let span = self.lower_span(i.span);
+        let (effective_ident, impl_kind) = if is_in_trait_impl {
+            let (effective_ident, trait_item_def_id) =
+                self.resolve_pin_drop_sugar_impl_item(i, ident, span);
+            (effective_ident, ImplItemImplKind::Trait { defaultness, trait_item_def_id })
+        } else {
+            (ident, ImplItemImplKind::Inherent { vis_span: self.lower_span(i.vis.span) })
+        };
+
         let item = hir::ImplItem {
             owner_id: hir_id.expect_owner(),
-            ident: self.lower_ident(ident),
+            ident: self.lower_ident(effective_ident),
             generics,
-            impl_kind: if is_in_trait_impl {
-                ImplItemImplKind::Trait {
-                    defaultness,
-                    trait_item_def_id: self
-                        .get_partial_res(i.id)
-                        .and_then(|r| r.expect_full_res().opt_def_id())
-                        .ok_or_else(|| {
-                            self.dcx().span_delayed_bug(
-                                span,
-                                "could not resolve trait item being implemented",
-                            )
-                        }),
-                }
-            } else {
-                ImplItemImplKind::Inherent { vis_span: self.lower_span(i.vis.span) }
-            },
+            impl_kind,
             kind,
             span,
             has_delayed_lints: !self.delayed_lints.is_empty(),

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -152,7 +152,20 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
         cx.size_and_align_of(Ty::new_mut_ptr(cx.tcx, pointee_type))
     );
 
-    let pointee_type_di_node = type_di_node(cx, pointee_type);
+    let pointee_type_di_node = match pointee_type.kind() {
+        // `&[T]` will look like `{ data_ptr: *const T, length: usize }`
+        ty::Slice(element_type) => type_di_node(cx, *element_type),
+        // `&str` will look like `{ data_ptr: *const u8, length: usize }`
+        ty::Str => type_di_node(cx, cx.tcx.types.u8),
+
+        // `&dyn K` will look like `{ pointer: _, vtable: _}`
+        // any Adt `Foo` containing an unsized type (eg `&[_]` or `&dyn _`)
+        //   will look like `{ data_ptr: *const Foo, length: usize }`
+        // and thin pointers `&Foo` will just look like `*const Foo`.
+        //
+        // in all those cases, we just use the pointee_type
+        _ => type_di_node(cx, pointee_type),
+    };
 
     return_if_di_node_created_in_meantime!(cx, unique_type_id);
 
@@ -389,26 +402,11 @@ fn build_dyn_type_di_node<'ll, 'tcx>(
 }
 
 /// Create debuginfo for `[T]` and `str`. These are unsized.
-///
-/// NOTE: We currently emit just emit the debuginfo for the element type here
-/// (i.e. `T` for slices and `u8` for `str`), so that we end up with
-/// `*const T` for the `data_ptr` field of the corresponding wide-pointer
-/// debuginfo of `&[T]`.
-///
-/// It would be preferable and more accurate if we emitted a DIArray of T
-/// without an upper bound instead. That is, LLVM already supports emitting
-/// debuginfo of arrays of unknown size. But GDB currently seems to end up
-/// in an infinite loop when confronted with such a type.
-///
-/// As a side effect of the current encoding every instance of a type like
-/// `struct Foo { unsized_field: [u8] }` will look like
-/// `struct Foo { unsized_field: u8 }` in debuginfo. If the length of the
-/// slice is zero, then accessing `unsized_field` in the debugger would
-/// result in an out-of-bounds access.
 fn build_slice_type_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     slice_type: Ty<'tcx>,
     unique_type_id: UniqueTypeId<'tcx>,
+    span: Span,
 ) -> DINodeCreationResult<'ll> {
     let element_type = match slice_type.kind() {
         ty::Slice(element_type) => *element_type,
@@ -423,7 +421,20 @@ fn build_slice_type_di_node<'ll, 'tcx>(
 
     let element_type_di_node = type_di_node(cx, element_type);
     return_if_di_node_created_in_meantime!(cx, unique_type_id);
-    DINodeCreationResult { di_node: element_type_di_node, already_stored_in_typemap: false }
+    let (size, align) = cx.spanned_size_and_align_of(slice_type, span);
+    let subrange = unsafe { llvm::LLVMDIBuilderGetOrCreateSubrange(DIB(cx), 0, -1) };
+    let subscripts = &[subrange];
+    let di_node = unsafe {
+        llvm::LLVMDIBuilderCreateArrayType(
+            DIB(cx),
+            size.bits(),
+            align.bits() as u32,
+            element_type_di_node,
+            subscripts.as_ptr(),
+            subscripts.len() as c_uint,
+        )
+    };
+    DINodeCreationResult { di_node, already_stored_in_typemap: false }
 }
 
 /// Get the debuginfo node for the given type.
@@ -454,7 +465,7 @@ pub(crate) fn spanned_type_di_node<'ll, 'tcx>(
         }
         ty::Tuple(elements) if elements.is_empty() => build_basic_type_di_node(cx, t),
         ty::Array(..) => build_fixed_size_array_di_node(cx, unique_type_id, t, span),
-        ty::Slice(_) | ty::Str => build_slice_type_di_node(cx, t, unique_type_id),
+        ty::Slice(_) | ty::Str => build_slice_type_di_node(cx, t, unique_type_id, span),
         ty::Dynamic(..) => build_dyn_type_di_node(cx, t, unique_type_id),
         ty::Foreign(..) => build_foreign_type_di_node(cx, t, unique_type_id),
         ty::RawPtr(pointee_type, _) | ty::Ref(_, pointee_type, _) => {

compiler/rustc_error_codes/src/error_codes/E0755.md

@@ -20,7 +20,7 @@ side effects or infinite loops:
 
 extern "C" {
     #[unsafe(ffi_pure)] // ok!
-    pub fn strlen(s: *const i8) -> isize;
+    pub fn strlen(s: *const std::ffi::c_char) -> usize;
 }
 # fn main() {}
 ```

compiler/rustc_error_codes/src/error_codes/E0756.md

@@ -21,7 +21,7 @@ which have no side effects except for their return value:
 
 extern "C" {
     #[unsafe(ffi_const)] // ok!
-    pub fn strlen(s: *const i8) -> i32;
+    pub fn strlen(s: *const std::ffi::c_char) -> usize;
 }
 # fn main() {}
 ```

compiler/rustc_hir/src/hir.rs

@@ -1088,6 +1088,93 @@ impl<'hir> Generics<'hir> {
             bound_span.with_lo(bounds[bound_pos - 1].span().hi())
         }
     }
+
+    /// Computes the span representing the removal of a generic parameter at `param_index`.
+    ///
+    /// This function identifies the correct slice of source code to delete so that the
+    /// remaining generic list remains syntactically valid (handling commas and brackets).
+    ///
+    /// ### Examples
+    ///
+    /// 1. **With a following parameter:** (Includes the trailing comma)
+    ///    - Input: `<T, U>` (index 0)
+    ///    - Produces span for: `T, `
+    ///
+    /// 2. **With a previous parameter:** (Includes the leading comma and bounds)
+    ///    - Input: `<T: Clone, U>` (index 1)
+    ///    - Produces span for: `, U`
+    ///
+    /// 3. **The only parameter:** (Includes the angle brackets)
+    ///    - Input: `<T>` (index 0)
+    ///    - Produces span for: `<T>`
+    ///
+    /// 4. **Parameter with where-clause bounds:**
+    ///    - Input: `fn foo<T, U>() where T: Copy` (index 0)
+    ///    - Produces span for: `T, ` (The where-clause remains for other logic to handle).
+    pub fn span_for_param_removal(&self, param_index: usize) -> Span {
+        if param_index >= self.params.len() {
+            return self.span.shrink_to_hi();
+        }
+
+        let is_param_explicit = |par: &&GenericParam<'_>| match par.kind {
+            GenericParamKind::Type { .. }
+            | GenericParamKind::Const { .. }
+            | GenericParamKind::Lifetime { kind: LifetimeParamKind::Explicit } => true,
+            _ => false,
+        };
+
+        // Find the span of the type parameter.
+        if let Some(next) = self.params[param_index + 1..].iter().find(is_param_explicit) {
+            self.params[param_index].span.until(next.span)
+        } else if let Some(prev) = self.params[..param_index].iter().rfind(is_param_explicit) {
+            let mut prev_span = prev.span;
+            // Consider the span of the bounds with the previous generic parameter when there is.
+            if let Some(prev_bounds_span) = self.span_for_param_bounds(prev) {
+                prev_span = prev_span.to(prev_bounds_span);
+            }
+
+            // Consider the span of the bounds with the current generic parameter when there is.
+            prev_span.shrink_to_hi().to(
+                if let Some(cur_bounds_span) = self.span_for_param_bounds(&self.params[param_index])
+                {
+                    cur_bounds_span
+                } else {
+                    self.params[param_index].span
+                },
+            )
+        } else {
+            // Remove also angle brackets <> when there is just ONE generic parameter.
+            self.span
+        }
+    }
+
+    /// Returns the span of the `WherePredicate` associated with the given `GenericParam`, if any.
+    ///
+    /// This looks specifically for predicates in the `where` clause that were generated
+    /// from the parameter definition (e.g., `T` in `where T: Bound`).
+    ///
+    /// ### Example
+    ///
+    /// - Input: `param` representing `T`
+    /// - Context: `where T: Clone + Default, U: Copy`
+    /// - Returns: Span of `T: Clone + Default`
+    fn span_for_param_bounds(&self, param: &GenericParam<'hir>) -> Option<Span> {
+        self.predicates
+            .iter()
+            .find(|pred| {
+                if let WherePredicateKind::BoundPredicate(WhereBoundPredicate {
+                    origin: PredicateOrigin::GenericParam,
+                    bounded_ty,
+                    ..
+                }) = pred.kind
+                {
+                    bounded_ty.span == param.span
+                } else {
+                    false
+                }
+            })
+            .map(|pred| pred.span)
+    }
 }
 
 /// A single predicate in a where-clause.

compiler/rustc_hir/src/lang_items.rs

@@ -448,6 +448,14 @@ language_item_table! {
 
     // Used to fallback `{float}` to `f32` when `f32: From<{float}>`
     From,                    sym::From,                from_trait,                 Target::Trait,          GenericRequirement::Exact(1);
+
+    // Runtime symbols
+    MemCpy,                  sym::memcpy_fn,           memcpy_fn,                  Target::Fn,             GenericRequirement::None;
+    MemMove,                 sym::memmove_fn,          memmove_fn,                 Target::Fn,             GenericRequirement::None;
+    MemSet,                  sym::memset_fn,           memset_fn,                  Target::Fn,             GenericRequirement::None;
+    MemCmp,                  sym::memcmp_fn,           memcmp_fn,                  Target::Fn,             GenericRequirement::None;
+    Bcmp,                    sym::bcmp_fn,             bcmp_fn,                    Target::Fn,             GenericRequirement::None;
+    StrLen,                  sym::strlen_fn,           strlen_fn,                  Target::Fn,             GenericRequirement::None;
 }
 
 /// The requirement imposed on the generics of a lang item

compiler/rustc_hir/src/weak_lang_items.rs

@@ -23,8 +23,29 @@ macro_rules! weak_lang_items {
     }
 }
 
+macro_rules! weak_only_lang_items {
+    ($($item:ident,)*) => {
+        pub static WEAK_ONLY_LANG_ITEMS: &[LangItem] = &[$(LangItem::$item,)*];
+
+        impl LangItem {
+            pub fn is_weak_only(self) -> bool {
+                matches!(self, $(LangItem::$item)|*)
+            }
+        }
+    }
+}
+
 weak_lang_items! {
     PanicImpl,          rust_begin_unwind;
     EhPersonality,      rust_eh_personality;
     EhCatchTypeinfo,    rust_eh_catch_typeinfo;
 }
+
+weak_only_lang_items! {
+    MemCpy,
+    MemMove,
+    MemSet,
+    MemCmp,
+    Bcmp,
+    StrLen,
+}

compiler/rustc_hir_analysis/src/delegation.rs

@@ -14,6 +14,7 @@ use rustc_middle::ty::{
 use rustc_span::{ErrorGuaranteed, Span, kw};
 
 use crate::collect::ItemCtxt;
+use crate::errors::DelegationSelfTypeNotSpecified;
 use crate::hir_ty_lowering::HirTyLowerer;
 
 type RemapTable = FxHashMap<u32, u32>;
@@ -284,6 +285,12 @@ fn get_delegation_self_ty_or_err(tcx: TyCtxt<'_>, delegation_id: LocalDefId) ->
             ctx.lower_ty(tcx.hir_node(id).expect_ty())
         })
         .unwrap_or_else(|| {
+            // It is possible to attempt to get self type when it is used in signature
+            // (i.e., `fn default() -> Self`), so emit error here in addition to possible
+            // `mismatched types` error (see #156388).
+            let err = DelegationSelfTypeNotSpecified { span: tcx.def_span(delegation_id) };
+            tcx.dcx().emit_err(err);
+
             Ty::new_error_with_message(
                 tcx,
                 tcx.def_span(delegation_id),