Rollup of 6 pull requests

compiler/rustc_ast/src/ast.rs

@@ -2577,8 +2577,7 @@ pub enum TyPatKind {
 pub enum TraitObjectSyntax {
     // SAFETY: When adding new variants make sure to update the `Tag` impl.
     Dyn = 0,
-    DynStar = 1,
-    None = 2,
+    None = 1,
 }
 
 /// SAFETY: `TraitObjectSyntax` only has 3 data-less variants which means
@@ -2594,8 +2593,7 @@ unsafe impl Tag for TraitObjectSyntax {
     unsafe fn from_usize(tag: usize) -> Self {
         match tag {
             0 => TraitObjectSyntax::Dyn,
-            1 => TraitObjectSyntax::DynStar,
-            2 => TraitObjectSyntax::None,
+            1 => TraitObjectSyntax::None,
             _ => unreachable!(),
         }
     }

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -505,7 +505,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     );
     gate_all!(associated_const_equality, "associated const equality is incomplete");
     gate_all!(yeet_expr, "`do yeet` expression is experimental");
-    gate_all!(dyn_star, "`dyn*` trait objects are experimental");
     gate_all!(const_closures, "const closures are experimental");
     gate_all!(builtin_syntax, "`builtin #` syntax is unstable");
     gate_all!(ergonomic_clones, "ergonomic clones are experimental");

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1303,7 +1303,6 @@ impl<'a> State<'a> {
             ast::TyKind::TraitObject(bounds, syntax) => {
                 match syntax {
                     ast::TraitObjectSyntax::Dyn => self.word_nbsp("dyn"),
-                    ast::TraitObjectSyntax::DynStar => self.word_nbsp("dyn*"),
                     ast::TraitObjectSyntax::None => {}
                 }
                 self.print_type_bounds(bounds);

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -131,6 +131,17 @@ impl Deprecation {
     }
 }
 
+/// There are three valid forms of the attribute:
+/// `#[used]`, which is semantically equivalent to `#[used(linker)]` except that the latter is currently unstable.
+/// `#[used(compiler)]`
+/// `#[used(linker)]`
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic, PrintAttribute)]
+pub enum UsedBy {
+    Compiler,
+    Linker,
+}
+
 /// Represents parsed *built-in* inert attributes.
 ///
 /// ## Overview
@@ -285,5 +296,8 @@ pub enum AttributeKind {
 
     /// Represents `#[track_caller]`
     TrackCaller(Span),
+
+    /// Represents `#[used]`
+    Used { used_by: UsedBy, span: Span },
     // tidy-alphabetical-end
 }

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -38,6 +38,7 @@ impl AttributeKind {
             PubTransparent(..) => Yes,
             SkipDuringMethodDispatch { .. } => No,
             TrackCaller(..) => Yes,
+            Used { .. } => No,
         }
     }
 }

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::{AttributeKind, OptimizeAttr};
+use rustc_attr_data_structures::{AttributeKind, OptimizeAttr, UsedBy};
 use rustc_feature::{AttributeTemplate, template};
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
@@ -228,3 +228,84 @@ impl<S: Stage> SingleAttributeParser<S> for NoMangleParser {
         Some(AttributeKind::NoMangle(cx.attr_span))
     }
 }
+
+#[derive(Default)]
+pub(crate) struct UsedParser {
+    first_compiler: Option<Span>,
+    first_linker: Option<Span>,
+}
+
+// A custom `AttributeParser` is used rather than a Simple attribute parser because
+// - Specifying two `#[used]` attributes is a warning (but will be an error in the future)
+// - But specifying two conflicting attributes: `#[used(compiler)]` and `#[used(linker)]` is already an error today
+// We can change this to a Simple parser once the warning becomes an error
+impl<S: Stage> AttributeParser<S> for UsedParser {
+    const ATTRIBUTES: AcceptMapping<Self, S> = &[(
+        &[sym::used],
+        template!(Word, List: "compiler|linker"),
+        |group: &mut Self, cx, args| {
+            let used_by = match args {
+                ArgParser::NoArgs => UsedBy::Linker,
+                ArgParser::List(list) => {
+                    let Some(l) = list.single() else {
+                        cx.expected_single_argument(list.span);
+                        return;
+                    };
+
+                    match l.meta_item().and_then(|i| i.path().word_sym()) {
+                        Some(sym::compiler) => {
+                            if !cx.features().used_with_arg() {
+                                feature_err(
+                                    &cx.sess(),
+                                    sym::used_with_arg,
+                                    cx.attr_span,
+                                    "`#[used(compiler)]` is currently unstable",
+                                )
+                                .emit();
+                            }
+                            UsedBy::Compiler
+                        }
+                        Some(sym::linker) => {
+                            if !cx.features().used_with_arg() {
+                                feature_err(
+                                    &cx.sess(),
+                                    sym::used_with_arg,
+                                    cx.attr_span,
+                                    "`#[used(linker)]` is currently unstable",
+                                )
+                                .emit();
+                            }
+                            UsedBy::Linker
+                        }
+                        _ => {
+                            cx.expected_specific_argument(l.span(), vec!["compiler", "linker"]);
+                            return;
+                        }
+                    }
+                }
+                ArgParser::NameValue(_) => return,
+            };
+
+            let target = match used_by {
+                UsedBy::Compiler => &mut group.first_compiler,
+                UsedBy::Linker => &mut group.first_linker,
+            };
+
+            let attr_span = cx.attr_span;
+            if let Some(prev) = *target {
+                cx.warn_unused_duplicate(prev, attr_span);
+            } else {
+                *target = Some(attr_span);
+            }
+        },
+    )];
+
+    fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
+        // Ratcheting behaviour, if both `linker` and `compiler` are specified, use `linker`
+        Some(match (self.first_compiler, self.first_linker) {
+            (_, Some(span)) => AttributeKind::Used { used_by: UsedBy::Linker, span },
+            (Some(span), _) => AttributeKind::Used { used_by: UsedBy::Compiler, span },
+            (None, None) => return None,
+        })
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -17,6 +17,7 @@ use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInternalUnstableParser};
 use crate::attributes::codegen_attrs::{
     ColdParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser, TrackCallerParser,
+    UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
@@ -103,6 +104,7 @@ attribute_parsers!(
         ConstStabilityParser,
         NakedParser,
         StabilityParser,
+        UsedParser,
         // tidy-alphabetical-end
 
         // tidy-alphabetical-start

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -25,9 +25,9 @@ use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::{
-    self, Binder, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, CoroutineArgsExt,
-    Dynamic, GenericArgsRef, OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt,
-    TypeVisitableExt, UserArgs, UserTypeAnnotationIndex, fold_regions,
+    self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, CoroutineArgsExt,
+    GenericArgsRef, OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt, TypeVisitableExt,
+    UserArgs, UserTypeAnnotationIndex, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::move_paths::MoveData;
@@ -1233,38 +1233,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         );
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::DynStar, coercion_source) => {
-                        // get the constraints from the target type (`dyn* Clone`)
-                        //
-                        // apply them to prove that the source type `Foo` implements `Clone` etc
-                        let (existential_predicates, region) = match ty.kind() {
-                            Dynamic(predicates, region, ty::DynStar) => (predicates, region),
-                            _ => panic!("Invalid dyn* cast_ty"),
-                        };
-
-                        let self_ty = op.ty(self.body, tcx);
-
-                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
-                        self.prove_predicates(
-                            existential_predicates
-                                .iter()
-                                .map(|predicate| predicate.with_self_ty(tcx, self_ty)),
-                            location.to_locations(),
-                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
-                        );
-
-                        let outlives_predicate = tcx.mk_predicate(Binder::dummy(
-                            ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(
-                                ty::OutlivesPredicate(self_ty, *region),
-                            )),
-                        ));
-                        self.prove_predicate(
-                            outlives_predicate,
-                            location.to_locations(),
-                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
-                        );
-                    }
-
                     CastKind::PointerCoercion(
                         PointerCoercion::MutToConstPointer,
                         coercion_source,

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -753,51 +753,6 @@ pub(crate) fn codegen_drop<'tcx>(
                 fx.bcx.ins().call_indirect(sig, drop_fn, &[ptr]);
                 fx.bcx.ins().jump(ret_block, &[]);
             }
-            ty::Dynamic(_, _, ty::DynStar) => {
-                // IN THIS ARM, WE HAVE:
-                // ty = *mut (dyn* Trait)
-                // which is: *mut exists<T: sizeof(T) == sizeof(usize)> (T, Vtable<T: Trait>)
-                //
-                // args = [ * ]
-                //          |
-                //          v
-                //      ( Data, Vtable )
-                //                |
-                //                v
-                //              /-------\
-                //              | ...   |
-                //              \-------/
-                //
-                //
-                // WE CAN CONVERT THIS INTO THE ABOVE LOGIC BY DOING
-                //
-                // data = &(*args[0]).0    // gives a pointer to Data above (really the same pointer)
-                // vtable = (*args[0]).1   // loads the vtable out
-                // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
-                //
-                // SO THEN WE CAN USE THE ABOVE CODE.
-                let (data, vtable) = drop_place.to_cvalue(fx).dyn_star_force_data_on_stack(fx);
-                let drop_fn = crate::vtable::drop_fn_of_obj(fx, vtable);
-
-                let is_null = fx.bcx.ins().icmp_imm(IntCC::Equal, drop_fn, 0);
-                let target_block = fx.get_block(target);
-                let continued = fx.bcx.create_block();
-                fx.bcx.ins().brif(is_null, target_block, &[], continued, &[]);
-                fx.bcx.switch_to_block(continued);
-
-                let virtual_drop = Instance {
-                    def: ty::InstanceKind::Virtual(drop_instance.def_id(), 0),
-                    args: drop_instance.args,
-                };
-                let fn_abi = FullyMonomorphizedLayoutCx(fx.tcx)
-                    .fn_abi_of_instance(virtual_drop, ty::List::empty());
-
-                let sig = clif_sig_from_fn_abi(fx.tcx, fx.target_config.default_call_conv, &fn_abi);
-                let sig = fx.bcx.import_signature(sig);
-                fx.bcx.ins().call_indirect(sig, drop_fn, &[data]);
-                // FIXME implement cleanup on exceptions
-                fx.bcx.ins().jump(ret_block, &[]);
-            }
             _ => {
                 assert!(!matches!(drop_instance.def, InstanceKind::Virtual(_, _)));
 

compiler/rustc_codegen_cranelift/src/base.rs

@@ -778,14 +778,6 @@ fn codegen_stmt<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, cur_block: Block, stmt:
                     let operand = codegen_operand(fx, operand);
                     crate::unsize::coerce_unsized_into(fx, operand, lval);
                 }
-                Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::DynStar, _),
-                    ref operand,
-                    _,
-                ) => {
-                    let operand = codegen_operand(fx, operand);
-                    crate::unsize::coerce_dyn_star(fx, operand, lval);
-                }
                 Rvalue::Cast(CastKind::Transmute, ref operand, _to_ty) => {
                     let operand = codegen_operand(fx, operand);
                     lval.write_cvalue_transmute(fx, operand);

compiler/rustc_codegen_cranelift/src/unsize.rs

@@ -112,21 +112,6 @@ fn unsize_ptr<'tcx>(
     }
 }
 
-/// Coerces `src` to `dst_ty` which is guaranteed to be a `dyn*` type.
-pub(crate) fn cast_to_dyn_star<'tcx>(
-    fx: &mut FunctionCx<'_, '_, 'tcx>,
-    src: Value,
-    src_ty_and_layout: TyAndLayout<'tcx>,
-    dst_ty: Ty<'tcx>,
-    old_info: Option<Value>,
-) -> (Value, Value) {
-    assert!(
-        matches!(dst_ty.kind(), ty::Dynamic(_, _, ty::DynStar)),
-        "destination type must be a dyn*"
-    );
-    (src, unsized_info(fx, src_ty_and_layout.ty, dst_ty, old_info))
-}
-
 /// Coerce `src`, which is a reference to a value of type `src_ty`,
 /// to a value of type `dst_ty` and store the result in `dst`
 pub(crate) fn coerce_unsized_into<'tcx>(
@@ -174,24 +159,6 @@ pub(crate) fn coerce_unsized_into<'tcx>(
     }
 }
 
-pub(crate) fn coerce_dyn_star<'tcx>(
-    fx: &mut FunctionCx<'_, '_, 'tcx>,
-    src: CValue<'tcx>,
-    dst: CPlace<'tcx>,
-) {
-    let (data, extra) = if let ty::Dynamic(_, _, ty::DynStar) = src.layout().ty.kind() {
-        let (data, vtable) = src.load_scalar_pair(fx);
-        (data, Some(vtable))
-    } else {
-        let data = src.load_scalar(fx);
-        (data, None)
-    };
-
-    let (data, vtable) = cast_to_dyn_star(fx, data, src.layout(), dst.layout().ty, extra);
-
-    dst.write_cvalue(fx, CValue::by_val_pair(data, vtable, dst.layout()));
-}
-
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
 
 pub(crate) fn size_and_align_of<'tcx>(

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -121,43 +121,6 @@ impl<'tcx> CValue<'tcx> {
         }
     }
 
-    // FIXME remove
-    /// Forces the data value of a dyn* value to the stack and returns a pointer to it as well as the
-    /// vtable pointer.
-    pub(crate) fn dyn_star_force_data_on_stack(
-        self,
-        fx: &mut FunctionCx<'_, '_, 'tcx>,
-    ) -> (Value, Value) {
-        assert!(self.1.ty.is_dyn_star());
-
-        match self.0 {
-            CValueInner::ByRef(ptr, None) => {
-                let (a_scalar, b_scalar) = match self.1.backend_repr {
-                    BackendRepr::ScalarPair(a, b) => (a, b),
-                    _ => unreachable!("dyn_star_force_data_on_stack({:?})", self),
-                };
-                let b_offset = scalar_pair_calculate_b_offset(fx.tcx, a_scalar, b_scalar);
-                let clif_ty2 = scalar_to_clif_type(fx.tcx, b_scalar);
-                let mut flags = MemFlags::new();
-                flags.set_notrap();
-                let vtable = ptr.offset(fx, b_offset).load(fx, clif_ty2, flags);
-                (ptr.get_addr(fx), vtable)
-            }
-            CValueInner::ByValPair(data, vtable) => {
-                let data_ptr = fx.create_stack_slot(
-                    u32::try_from(fx.target_config.pointer_type().bytes()).unwrap(),
-                    u32::try_from(fx.target_config.pointer_type().bytes()).unwrap(),
-                );
-                data_ptr.store(fx, data, MemFlags::trusted());
-
-                (data_ptr.get_addr(fx), vtable)
-            }
-            CValueInner::ByRef(_, Some(_)) | CValueInner::ByVal(_) => {
-                unreachable!("dyn_star_force_data_on_stack({:?})", self)
-            }
-        }
-    }
-
     pub(crate) fn try_to_ptr(self) -> Option<(Pointer, Option<Value>)> {
         match self.0 {
             CValueInner::ByRef(ptr, meta) => Some((ptr, meta)),